Stephanie Adams, The Morton Arboretum, Lisle, Illinois, United States

Fine root health is paramount for healthy and vigorous trees. These roots, which are smaller than 1 cm in diameter, are responsible for the absorption and transport of water and nutrients from the soil into the tree. Without these resources, the tree is unable to grow, defend itself, and perform to its genetic potential and it makes the tree susceptible to secondary disease and insect pest problems. In order to identify whether a tree has a fine root rot one first needs to be able to identify what fine roots look like for their species. Being able to identify whether all orders of fine roots are present during the investigation will contribute to faster identification and management of root rots. This hands-on workshop will introduce attendees to healthy and diseased root systems of different woody plant species. There will be demonstrations on how to dissect root balls and how to find roots in the landscape to assess their health.

Andrew Hirons, Lancaster Environment Centre, Lancaster University, United Kingdom and University Centre Myerscough, United Kingdom

This preconference workshop is designed to allow delegates to gain hands-on experience with the latest sap flow sensors, dendrometers and soil sensors. As well as discussing the theoretical background of sensor measurement, we will explore the potential value of data from these sensors. Delegates will have the opportunity to install a range of sensors and learn how to best visualize the data in ways that support tree management. There will be opportunities to use the latest online dashboards for tree sensor analysis and opportunity to discuss a range of use cases. The workshop will be led by Dr. Andrew Hirons who has spent a number of years pioneering the use of IoT sensors in tree management.

Jason Miesbauer, The Morton Arboretum, United States; Brian Kane, University of Massachusetts, United States

This workshop will offer a look into the theory and applied research of assessing tree root anchorage. We will start with an indoor session discussing the forces that act on trees, and how root morphology and site conditions affect tree stability. Following the indoor session, we will go out into the field to look at different instruments that researchers and practitioners utilize to measure stability. This will be followed by static pull demonstrations that show methods that have been developed to non-destructively assess the stability of landscape trees. You will come away with a better understanding of methods you can use to better assess trees in your area.

Bryant C. Scharenbroch, University of Wisconsin–Stevens Point, United States, and The Morton Arboretum, Lisle, Illinois, United States

Soil assessment is a critical component of soil management for urban trees. The goal of this presentation is to provide an overview of soil assessment for urban trees. Soil quality will be

Methodologies and interpretations for each soil property will be presented. This presentation will also provide an overview of the soil quality indices used in urban tree management. Research on the development and efficacy of soil quality indices will be presented. This presentation will discuss the application of soil quality indices in the management of urban tree trees and forests highlighting a few case studies. This presentation will include research findings and provide applicable information for arborists, urban foresters, and other urban tree managers. This presentation will feature findings from research that has been funded by the TREE fund, The Morton Arboretum, University of Wisconsin–Stevens Point, and industry partners.

Arboretum Staff

Experience the beauty of the Arboretum’s 1,700 acres on a guided tram tour. This one-hour ride winds you through the Arboretum’s woodlands, wetlands, and prairie while listening to a narrated tour. This tour is subject to weather conditions (refunds for this tour will be issued if severely inclement weather prevents the tram from running).

Michael A. Arnold, Texas A&M University / Texas A&M AgriLife, College Station, Texas, United States

Planting a tree sounds like a simple undertaking, however our often less than perfect success rates would suggest otherwise. Decisions made anywhere in the production and transplant establishment processes can have lasting impacts on not only initial success but long-term value of urban trees. Lessons learned from over thirty years of experiences with tree transplanting experiments will be presented emphasizing a few critical decision junctures in producing and establishing trees in the built environment. As with most production processes the quality of inputs and attention to process details dictate the durability and resilience of the final product. Such is the same with nursery grown trees transplanted to modern built environments. Quality of inputs begins with appropriate genotypic selection and propagation methods. Nursery growing conditions and production techniques can add or detract to the quality of the final product. Proper handling and transportation preserve tree quality. Transplanting techniques and post-harvest conditions dictate the final post-harvest transition to the consumer and longer-term contributions to ecosystem services. Impending climate changes will require the best in genetic potential from our urban forests and heighten the importance of maximizing transplant survival through science-based decision-making during nursery production and the transplant process.

Jim Barborinas, Urban Forest Nursery, Inc., Anacortes, Washington, United States

The unintentional development of circling, kinked and deformed roots is a significant weakness during production of new plants in the nursery industry. These deformed roots are created when plants are left to grow and harden off in containers for too long. Roots planted in this condition prevent the vigorous and natural root growth of a plant, limiting proper establishment and anchorage. Correcting these conditions includes scarifying, slicing, and significant root removal. These work at the expense of plant stress and labor costs, but only if root manipulation happens in the first place.

Correcting deformed roots takes crew training and time, all at a higher cost to the contractor, contributing to poor establishment and eventually high mortality. Why not avoid these circling, kinked and deformed roots during production in the first place?

Higher costs are the first reason that production methods are slow to change. Second, the nursery industry does not seem to realize the problem these malformed roots create. There is a disconnect between manufacturers making the containers, nurseries growing the plants, the landscape companies who install the plants, and then finally the consumer, who has to live with and diagnose the reason why so many plants struggle to survive.  We can and should do better.

Different production methods have been developed and implemented, such as copper-lined containers, air-pots, root-catching fabric, and some fabric grow bags. All are definite improvements. This presentation will focus on one of those methods, fabric grow bags.

Fabric grow bags are a viable and attractive method of growing nursery stock for many reasons.  Most importantly certain grow bags stop or limit circling roots. Fabrics that allow ‘restricted’ and broad root penetration are most desirable. Some fabrics allow root penetration, and some do not. Those fabrics that allow root penetration reduce or eliminate the potential for deformed roots.

Our 25 years of grow bag history have illuminated the many advantages that certain fabric grow bags provide not only for root development but also for many other important aspects of nursery production and landscape plant installation. Benefits will be highlighted, and more questions will be raised.

Jon Banks, UK Bartlett Tree Research Laboratory, Reading, United Kingdom

The root collar, the area between root system and stem is a highly active part of a tree, where fluid translocation is concentrated. Tree root collars can become buried when trees are planted too deep, soil settles, or with poor nursery production and harvesting methods. Burial of this region is common occurring in over a half of all urban trees and widely reported to be a significant stress of trees in the urban environment. Dramatic impacts are described in online resources such as shortening tree life expectancy, poor establishment, trunk damage, tree decline, chronic drought stress and tree death. Even historic documents identify that “profound burying very frequently destroys a tree”. Research studies have found significant negative impacts on establishment and growth from a wide range of tree families. Despite the apparent broad agreement on the negative impacts of root collar burial other studies have found positive or no negative impacts of deep planting on tree survival and growth. Direct mechanistic explanation for the reported dramatic impacts of root collar burial are sparse and mostly based on research from cereal crops not trees, oxygen transport from shoot to root is significant in young plants but later, adventitious roots can act as a main route for internal oxygen diffusion burial of the root crown may therefore reduce oxygen diffusion deeper into roots. We therefore hypothesize that trees tolerant to waterlogging may be more tolerant to deep planting and this could be an explanation for the variable results found in deep planting studies. This has been suggested previously, but not empirically demonstrated. Early data from a study evaluating 11 species from 9 genera representing waterlogging sensitive to waterlogging tolerant genotypes has found generally positive growth and vitality impacts when root collars were buried with a negative correlation found between waterlogging tolerant species and deep planting response. These unexpected results will be discussed. With tree age and soil texture thought to be a primary cause for unexpected results.

Claudia Bashian-Victoroff, The Holden Arboretum, Mentor, Ohio, United States; Chad Rigsby, The Center for Tree Science, The Morton Arboretum, Lisle, Illinois, United States; David Burke, The Bartlett Tree Research Laboratories, Charlotte, North Carolina, United States

Mycorrhiza refers to the exchange of resources at the interface of fungal hyphae and plant roots. Beyond this exchange, mycorrhizal fungi may aid in plant drought tolerance, and improve plant defense against soil pathogens. It has become increasingly clear to researchers that mycorrhizal fungi can benefit restoration efforts. While research has indicated that restoring the soil microbiome (including mycorrhizal fungi) improves plant growth and influences plant recruitment, few restoration efforts apply these findings. Our laboratory group is investigating mechanisms to integrate mycorrhizal fungi into urban canopy restoration using whole soil inoculum. In 2021 we added soil inoculum from Holden Arboretum natural areas to urban plantings throughout the greater Cleveland area to determine if whole soil inoculation is viable, effective, and sustainable in large-scale restoration. In the first year of the project, we planted 155 trees across 12 different species in three urbanized sites. We added whole soil inoculum to half of the trees and left half as control. Upon planting, we measured each tree’s diameter and height. We remeasured the trees and recorded mortality after one year post planting. At this time scale we did not see differences in relative growth rate or mortality with soil treatment. We observed differences in growth rate according to site (P = 0.03) and in mortality (P = 0.03) and growth rate (P < 0.001) according to species. Species responses occurred in one site, suggesting some species may fair better in urbanized sites. Within this location Carya ovata grew faster than other species, and Nyssa sylvatica and Hamamelis virginiana experienced higher mortality after one year. In addition to the 155 trees planted in fall 2021, 450 trees were planted in fall 2022 and 344 trees were planted in spring of 2023. This effort has created a robust dataset to measure the effect of whole soil inoculation on the growth and survival of trees in urban soils. In coming years, these data will elucidate the effect of whole soil inoculation on urban tree survivorship and growth and will also provide restoration practitioners with guidance on species selection as well as planting and aftercare specificities.

Andrew Benson, The Tree Consultancy Company, Rosedale, Auckland, New Zealand

There are costs associated with maintaining urban trees. Some indirect costs of maintaining trees in the urban landscape are linked to the way in which tree roots interact with hard surfaces such as footpaths (sidewalks), which can result in expensive repairs and in some instances, tree removal. There is a need to understand the complex interactions between tree roots and infrastructure, to inform strategic planting and balance the needs of all stakeholders. A simple, cost-effective Arduino-based robot was designed and built to measure footpath displacement. Using an ultrasonic sensor, the robot generates a 2.1 m long, two-dimensional profile of a given surface. The accuracy of the robot was validated with objects of known size before deploying it to the field. Auckland City, in New Zealand, is stratified into geopolitical areas of wards and suburbs. Three suburbs were randomly selected from each ward, one street was selected from each suburb, and 15 trees were randomly selected from each street giving a total of 450 trees. The dimensions (height, trunk diameter at 30 cm) of each tree were recorded as well as species and the growing location type (lawn strip, tree pit, garden bed) and size. The type (concrete, asphalt) and size of the footpath, and the distance between the tree and the footpath were also recorded. Footpaths were scanned 1.05 m either side of each tree and the vertical profiles were recorded by the robot. Analysis of the two-dimensional profiles reveals that asphalt surfaces are significantly (p < 0.01) more prone to surface displacement than concrete surfaces. The type of growing environment did not significantly affect footpath displacement. Maximum and total displacements were significantly affected by species and trunk diameter as well as the interaction between species and growing environment type (p < 0.01), and the distance between the tree and footpath (p <0.05). Understanding which combinations of growing conditions result in the greatest infrastructure conflicts can help to better inform strategic planting, maximize footpath longevity, and minimize the need to cut roots or remove urban trees.

Andrew Benson, The Tree Consultancy Company, Rosedale, Auckland, New Zealand; Justin Morgenroth, The New Zealand School of Forestry, The University of Canterbury, Christchurch, New Zealand

Knowledge of when and how to correctly prune tree branches is one of the fundamental aspects of arboriculture that practicing arborists must understand. The CODIT model has helped to inform arboricultural practitioners of correct tree branch pruning to achieve the optimal biological response, e.g., to limit decay and optimize compartmentalization / occlusion. Research has also shown that the compartmentalization response of wounded trees is optimized when wounds are inflicted during periods of active growth, as opposed to periods of dormancy. Furthermore, internodal branch pruning which leaves short stubs, inherently produces epicormic shoots and sub-optimizes the compartmentalization process. Selecting branches and correctly positioning pruning cuts is therefore critical to optimizing compartmentalization and regrowth responses. Much attention has been given to this aspect of tree care, yet we know very little about these same responses when roots are removed. Roots are important tree structures and have a key biological function in tree health and survival. The roots of trees are sometimes damaged or removed, usually for buried utility maintenance, sidewalk repairs or other civil construction projects. When roots are damaged, or removed, the wound sites can become points of entry for decay-causing organisms such as fungi, which can lead to secondary tree health problems. Similarly, the removal of roots, particularly large roots, affects tree function by reducing the surface area of water-absorbing area. New roots need to be grown by the tree for healthy tree function to continue. It is necessary to understand how to optimize tree responses to root injury, by applying correct pruning techniques in the same way as branches are pruned from the crown. To achieve this, we undertook different root pruning regimes on mature trees to see their response to pruning position (internodal versus lateral root branch) and seasonality (pruning in summer versus winter). Three years after imposing treatments, the investigated responses are new root growth (root dry weight (g) / root cross-sectional area (cm2); and wood discoloration (wood discoloration (cm2) / root cross sectional area (cm2)). This presentation will introduce the research which is still ongoing.

Daniel Burcham, Colorado State University, Fort Collins, Colorado, United States

Largely obscured belowground, soil-root systems are essential to the life of trees. Together with the surrounding soil, tree root systems sustain the entire plant body by acquiring resources and carrying loads from the environment. In cities, tree roots are often damaged by excavation and construction work or infected by wood decay fungi, and it is regularly difficult for arborists to assess the condition of root systems during their work. Given the difficulty of inspecting roots, some have developed methods to indirectly assess the strength of root systems by monitoring their response to controlled or stochastic natural loading. However, root system load testing and deformation monitoring remains limited in arboricultural practice, likely due to concerns, in part, about the cost, feasibility, and reliability of available methods. Some devices are commercially marketed for evaluating the structural integrity of root systems, but the underlying analysis procedures have not been comprehensively disclosed or rigorously tested. This presentation will review a novel non-destructive load testing method for trees using computer vision to monitor time-varying stem deformation and root plate rotation. Combined with information about stem geometry and the applied load, the measured tree response was used to estimate the local bending and rotational stiffness of the trunk and root system, respectively, using the moment-curvature relationship. The accuracy and sensitivity of the method was evaluated in a series of controlled tests, including measuring trees with part of the lower stem or root system removed. The potential practical and scientific applications of the method will be reviewed, especially to improve tree risk assessments and related management decisions.

Josh Caplan, Temple University, Philadelphia, Pennsylvania, United States

Trees growing in urban environments can experience severe water limitation. Although this typically occurs during periods of hot and dry weather, design(able) factors like soil physical properties and unusual belowground hydrology can exacerbate or mitigate their effects substantially. To understand how urban soil conditions interact with other factors like weather and tree type (i.e., taxon identity), we investigated the physiological responses of multiple tree taxa to summer drought. We conducted one study in the context of green infrastructure tree trenches and the other in the context of urban lawns and landscaping beds. In tree trenches, stormwater was directed to soil pits from below but trenches were oversized such that water only contacted the soil pits during a hydrant release. Further, minimal water was retained in the soil media due to its hydraulic properties. Nonetheless, trees’ willingness to lose water (i.e., stomatal conductance) varied widely across taxa as did the responsiveness of stomatal conductance to increasing vapor pressure deficit. We attribute these contrasting responses to roots being largely confined to the soil pits vs. reaching a deeper water source, respectively. For trees growing in lawns and landscaping beds, there were multiple signs of physiological stress during a period of drought, though the magnitude differed by tree type and depended on local environmental conditions such as soil water availability and surrounding impervious cover. Moreover, these patterns were detectable both directly and using thermal imaging from a drone. These case studies highlight the risks of overlooking how trees will access water during project planning stages, instead suggesting that alternative or additional design strategies should be used to ensure water is available during dry summer periods. Additionally, they show that some taxa are better able to access water than others and underscore the importance of selecting such trees where conditions may be challenging.

Sebastien Comin, Università di Milano, Milano, Italy; Irene Vigevani, Università di Firenze, Sesto Fiorentino, Italy; Denise Corsini, Università di Milano, Milano, Italy; Noemi Valsecchi, Università di Milano, Milano, Italy; Gloria Brocca, Università di Milano, Milano, Italy; Simone Fumagalli, Università di Milano, Milano, Italy; Francesco Ferrini, Università di Firenze, Sesto Fiorentino, Italy; Giovanni Ravanelli, Ente Regionale per i Servizi all’Agricoltura e alle Foreste, Curno, Bergamo, Italy; Alessio Fini, Università di Milano, Milano, Italy

The demand for saplings has risen in the last years as a consequence of massive planting campaigns targeted at increasing canopy cover. To test the hypothesis that algae extract can improve root growth and morphology, an experiment was carried out at the Ersaf forest nursery (Curno, BG, Italy). Seeds of Amelanchier ovalis, Carpinus betulus, Crataegus monogyna, Fagus sylvatica and Ligustrum vulgare were seeded in trays using a substrate amended with 0x, 1x, 2x or 3x the label dose (1 kg/m3) of a pure Ascophyllum nodosum extract. After germination, 6400 seedlings were arranged according to a randomized complete block design with 10 blocks and grown under nursery conditions for 1 year. Thereafter, plants were transplanted into 1.7 L forest containers for one additional growing season. To measure biomass production, plants were cut at the flare and roots cleaned with a flush of air. Roots, stems, and leaves were oven-dried and weighed separately. Total plant leaf area was measured after scanning all leaves with an A3 scanner. Total root length was measured using the root line intersect method. Specific root length was calculated as root length/root dry biomass. Biomass and leaf area were measured 2, 6, 12, 24 and 72 weeks after germination. Leaf gas exchange was measured 2, 6, 12, 24, 48, and 72 weeks after germination using an infra-red gas analyzer (Ciras-2, PP-System, USA). Chlorophyll content was measured using a spad-meter, on the same days as leaf gas exchange. Species differed for growth rate, biomass allocation to roots and specific root length. Biostimulants increased stem and whole plant dry weights for 1 year only when applied at 3x label dose. Similarly, significant effects on leaf gas exchange were found only at the highest dose, and were mostly due to higher chlorophyll content than to lower stomatal limitations to photosynthesis. Results suggest that substrate amendment with Ascophyllum extracts may have short-term positive effects on plant and root growth, likely due to a nutritional boost. However, they did not trigger structural changes in plant traits that can enhance transplant tolerance in the long run.

Els Couenberg, Natura Ingenium, Diemen, The Netherlands

It has been a discussion for decennia: How large should a growing site be to give a street tree sufficient chance to survive and grow? Several methods have been developed to try to predict this. With increasing urbanization, available space for tree root growth is getting less and less, especially in high rise built up areas. In this paper we review 5 sites that have been established for 16 years to answer the question how much rooting space a tree actually needs.

In Amsterdam, 3 sites where groundwater was available, and two where ground water was not available with a fixed soil volume are compared. One of these sites had (computer) managed irrigation and drainage. The trees grown on these sites were mostly Ulmus and Tilia, but on the managed site grew multiple species. Tree growth data of trees after over 16 year after installation were taken: tree height, tree condition, tree circumference and tree crown projection of the trees at the sites.

The predicted growth data with the different methods were calculated for each site and compared with the actual growth data. No strong correlation between tree growth data in general and rooting volumes were shown. If separated for tree species, even with limited data, some tree species growth data showed a strong correlation with rooting volume, while others did not show any correlation at all. The data suggest differences in rooting volume need per species. The study indicates that some tree species can grow on relatively small large soil volumes in practice for at least 16 years, provided enough water was available for the roots. Most predicting formulas do not take tree species into account but the data suggest that this is necessary.

In a few of these sites the trees did not survive more than 20 years after installment. This was not due to tree decline, but changes in design. Site redesign or redevelopment may cause tree removal before the possibilities of the rooting space have been exhausted. In those places preparing sites for longevity may be unnecessary.

Bert Cregg, Horticulture, Michigan State University, East Lansing, Michigan, United States; Riley Johnson, Horticulture, Michigan State University, East Lansing, Michigan, United States

Circling roots have long been a concern when planting container-grown trees. Researchers and practitioners have proposed an array of techniques to remediate circling roots associated with container-grown trees including vertical slicing, teasing (pulling apart and straightening circling roots), shaving (removing the outer periphery of root systems with a saw or sharp spade), and bare-rooting (removing container substrate to expose and correct root defects). A major concern with techniques that remove significant amounts of root surface area, such as shaving and bare-rooting, is that treatments may increase tree water stress after transplanting, resulting in decreased survival or growth. Moreover, the long-term effects on root architecture and variation among species in response to root remediation are largely unknown. For the past ten years, we have conducted a series of studies to determine the impacts of root remediation at planting on plant water relations, growth, and root development of container-grown trees. We have also excavated roots systems on a subsample of trees in each trial in order to evaluate the effect of remediation on subsequent root development and root egress into backfill soil. Shaving root systems before planting did not reduce survival or growth of London plane tree (Platanus × acerifolia (Aiton) Willd.), red maple (Acer rubrum L.), tulip tree (Liriodendron tulipifera L.), American hornbeam (Carpinus caroliniana Walt.), and American hophornbeam (Ostrya virginiana (Mill.) K. Koch). Bare-rooting, in contrast, decreased pre-dawn and midday leaf water potential immediately after planting, resulting in increased leaf scorch and crown dieback and decreased survival of tulip tree, hornbeam, and hophornbeam. Root harvests of a subsample of trees from our studies indicate that shaving, teasing, and bare-rooting can reduce circling roots and improve root system quality compared to trees that were not treated. Shaving provides a rapid and effective means to remove circling roots and promote root egress into surrounding soil without adverse effects on tree survival or growth. Arborists and landscapers interested in bare-rooting container trees to remediate root defects are urged to use caution when applying the technique to trees that are reported to be difficult to transplant as bare-root nursery stock.

Christopher W. Fields-Johnson, The Davey Tree Expert Company, Gainesville, Virginia, United States

Urban development and redevelopment often destroy valuable urban forest resources both during and following the construction process, but this does not have to be the case. When existing trees are carefully considered from the beginning of projects and treated as full design features, they can often be retained in place or moved to a safe location. Modification of grading plans, installation of tree protection fencing, use of aeration matting to protect critical root zones, proper soil care and irrigation, root zone reclamation, and attention to pests and diseases caused by stress will be presented. Strategies for engaging stakeholders and enforcing preservation plans will be discussed. Methods of recycling urban green waste to enhance soil-water-plant relationships with biochar, compost, and mulch will also be discussed. Preserved trees make an instant, striking improvement to finished projects while generating good will with neighbors and the public. The right strategies and methods will lead to success in protecting and conserving trees.

Alessio Fini, Università di Milano, Milano, Italy; Sebastien Comin, Università di Milano, Milano, Italy; Irene Vigevani, Università di Firenze, Sesto Fiorentino, Italy; Denise Corsini, Università di Milano, Milano, Italy; Irene Pagliarini, Università di Pisa, Pisa, Italy; Alessandra Turrini, Università di Pisa, Pisa, Italy; Monica Agnolucci,Università di Pisa, Pisa, Italy; Francesco Ferrini, Università di Firenze, Sesto Fiorentino, Italy; Piero Frangi, Fondazione Minoprio, Vertemate con Minoprio, CO, Italy

This research investigated the effects of pavements on growth, physiology, and root mycorrhizal colonization in Celtis australis and Fraxinus ornus plants over a 9-year period. In March 2012, 48 trees were planted into 1 m2 planting pit, and assigned to one of the four pavement treatments: 1) impermeable pavement; 2) permeable pavers; 3) permeable concrete; 4) unpaved control. The experimental design was a randomized complete block with 6 blocks. Soil moisture and temperature were monitored using FDR and temperature probes, respectively. CO2 efflux from soil and soil O2 concentration were measured using a soil respiration chamber. Stem DBH, tree height, crown radius, and shoot growth were measured using a diameter tape and a graduated post. Leaf gas exchange and water relations were measured using an infra-red gas analyzer and a pressure chamber, respectively. Root density and rooting depth were estimated using a ground-penetrating-radar. The diversity and composition of arbuscular mycorrhizal fungal communities were assessed by PCR denaturating gradient gel electrophoresis of partial 18S rRNA gene, AMF taxa were identified by amplicon sequencing and mycorrhizal colonization was evaluated after root clearing and staining. Impermeable pavements and permeable pavers increased soil temperature and CO2, compared to permeable concrete and control. Before tree establishment, which occurred in 2015, soil moisture was higher under all types of pavements than in bare soil. After tree establishment, impermeable pavements delayed both soil dehydration during summer and soil rehydration during winter and early spring. Leaf gas exchange, water relation, and above-ground growth were unaffected by pavement treatments. Conversely, impermeable pavements affected root system characteristics and mycorrhizal fungal communities associated with the roots. The evidence that some fungal symbionts were only found under impermeable pavements suggests the opportunity to develop specific mycorrhizal inocula for trees growing in sealed soils. Overall, results of this research show that the quality of the soil beneath the pavements is far more important to tree health than the pavement itself. Authors are grateful to the Tree Fund for funding this research with Grants 13-JK-01 and 14-RF-01.

Jason Grabosky, Rutgers University, NJ Agricultural Experiment Station, Cazenovia, New Jersey, United States; Jason Miesbauer, The Morton Arboretum, Lisle, Illinois, United States; Andrew Koeser, University of Florida, Wimauma, Florida, United States

Tree care professionals are called to provide informed perspective on tree protection and appraisal of tree damage, often specific to segments of partial root systems. We also understand that tree root systems cannot be assumed to be uniformly symmetrical in their occurrence within the soil around a tree. For these reasons, it would be useful to make rapid inferences of root area as a ratio of expected total root system area in the assessment and protection delineation of larger trees. When delineating tree protection zones, or assessing root damages in the field, there is a challenge in making any inference or gauging the extent of impacted roots as a component of the total system; the dose of the impact. Whether for risk consideration or protection, it would be helpful to have an expectation of the total root system presence at varied distances from the tree in question from which to gauge observations of specific zone impacted by construction or conservation. Toward that end, we have initiated a series of studies to test a mass hydraulic balance approach. We deployed the Modified Pipe Model onto a series of 30 digitally mapped root systems of Fraxinus pennsylvanica ‘Patmore’ which were developed by Miesbauer and Koeser (LBG IV, 2020) 3 years post transplanting. We developed a code to section the root systems into hemispheric planes and determine the transverse root radii and variously derived variables based on radius, radius^2 and radius^4 criteria. We develop an allometric relationship series to link these variables to trunk DBH (1.37m). Findings are TBD as of this writing. From these findings we can hopefully develop guidance to field processes in tree appraisal, and move to larger trees and more varied species.

Andrew Hirons, University Centre Myerscough, Bilsborrow, Preston, Lancashire, United Kingdom, and Lancaster Environment Centre, Lancaster University, Lancaster, Lancashire, LA1 4YQ, United Kingdom

Tree nurseries use substantial volumes of water to produce high-quality plant material. However, most irrigation scheduling decisions are based on manager experience without considering relevant data on soil, tree or atmospheric water status.

High irrigation volumes promote individual tree size but are inefficient; they may also limit overall nursery production as irrigation licenses are capped at fixed volumes. Adopting more water-use-efficient irrigation techniques allows more trees to be produced without increasing current irrigation volumes.

As tree water demand increases in response to climate change, knowledge of tree water use in the nursery must become more precise to ensure that tree production is sustainable and resilient to scenarios characterized by reduced water availability.

It is now possible to assess tree water-use in real time using internet of things (IoT) sap flow sensors; data from these sensors can increase grower understanding of water demand and help refine irrigation protocols across the nursery. IoT dendrometers can also help monitor tree stress trajectories; this is particularly valuable for growers monitoring rain-fed trees that may require ad-hoc irrigation to maintain tree vitality during periods of water deficit.

This presentation will share findings from a research project based in the UK. As well as sharing experience on the integration of IoT sensors into nursery practice, it will address questions such as: how much water do young trees use; can I predict tree water use; do species vary in their water use and what difference does stock size make to tree water use? The talk will also help delegates understand the role of IoT sensors in modern nursery practices and discuss how experience from a nursery could be translated to landscape tree management.

Thibaut Houette, Department of Biology, The University of Akron, Akron, Ohio, United States; Elena Stachew, Department of Biology, The University of Akron, Akron, Ohio, United States; Claudia Naményi, Department of Biology, The University of Akron, Akron, Ohio, United States; Jason Miesbauer, The Morton Arboretum, Lisle, Illinois, United States; Petra Gruber, Transarch – Office for Transdisciplinary Research in Architecture, Ybbs, Austria

The lack of a standard method to analyze tree root systems considerably hinders knowledge production about root principles responsible for the adaptation of various tree species to diverse environments. Most methods measuring root morphology are time-consuming, conducted with semi-automated techniques, limited to specific environments, and often focus on one key characteristic without reporting the entirety of morphological traits, making comparisons between studies difficult. Beyond biology, root knowledge can benefit engineering for the design of root-inspired infrastructures, but also benefit from it by utilizing tools from such discipline. To extract comparable root traits, there is a need for a systematic way of representing and analyzing the morphology of tree root systems in the field integrating novel digital technology. Imaging tree roots in the field allows access to more specimens while reducing deformation caused by transportation. Our team combined photogrammetry and parametric algorithms to generate 3D models of coarse root systems and extract their morphological traits. First, pictures of a root system are taken in the field with a camera and uploaded into a photogrammetry software to produce its corresponding 3D model. Then, a skeletonization algorithm produces the skeleton of the 3D model to access the system’s topology and root traits. A parametric algorithm runs through the 3D model to extract morphological traits relating to the overall root system (e.g., volume and surface area) and individual roots segments (e.g., radius and curvature). Finally, the traits are statistically analyzed for a variety of purposes including biological research and biomimicry. For instance, comparing the traits across topological orders, quadrants, depth and distance from trunk, but also between species serves to study biological diversity and identify key strategies and principles of root adaptation to various environments. To go further, traits are also abstracted and transferred to the design of bio-inspired infrastructure, such as multifunctional building foundations. Producing a 3D model saves the data in a format which can be further analyzed in the future by teams with other research questions. Results from ten root systems of four species showcase the benefits of such a systematic method and its potential for biology and bioinspiration.

Albert Key, DeepRoot Green Infrastructure, Inc, San Francisco, California, United States; Ryan Winston, Department of Food, Agriculture and Biological Engineering, Ohio State University, Columbus, Ohio, United States

This presentation will provide an overview of integrating large urban trees and their associated soil volumes into stormwater management solutions, particularly in the densest urban areas, utilizing suspended pavement with load bearing modules. Suspended pavement has been recognized in research as an effective method for healthy urban tree growth, but might provide better return on investment if paired as a solution to urban stormwater management. Separate research studies from North Carolina State University and University of Tennessee demonstrate the effectiveness of specially designed suspended pavement urban tree / soil systems for stormwater volume reduction and water-quality benefits. These research papers have demonstrated that runoff from small events is often completely captured by these practices and often produces no drainage to downstream waters because of soil porosity, exfiltration, and temporary storage, akin to traditional bioretention practices. When drainage-producing events do occur, the studies have shown that suspended pavement practices are effectively equivalent to traditional bioretention practices and can achieve significant volume reductions within a similar range of values. In addition to the relative volume equivalency, the two studies show that water quality in suspended pavement systems are also comparable to traditional bioretention. Reductions of common stormwater pollutants including total suspended solids (TSS), nitrogen, phosphorus, and heavy metals are roughly equivalent among bioretention and suspended pavement systems and will be reviewed. Case studies of these systems at various scales (including as examples Uptown Normal Streetscape, CSO 14 & 15 in Spokane Washington, and Marriott Headquarters in Bethesda, MD) will be presented as well.

Andrew Koeser, University of Florida, United States

As long-living organisms, urban trees may find themselves in close proximity to construction activities during their lifespan. These activities can cause damage to tree roots through methods like root severing during trenching or excavation. In 2017, we conducted a simulation of trenching damage on mature Quercus virginiana Mill. trees at three different distances from the base (3x, 6x, and 12x stem diameter). After five years, we revisited these trees to assess root regrowth based on the cut root cross-sectional area and distance from the base. Regrowth was observed in all but 38 (6.7%) of the 557 cut roots revisited. The lack of regrowth observed in some roots was not associated with our original treatments or the cross-sectional area of the roots at the time of trenching. On average, the observed cross-sectional area of the regrowth was 22.3% of the original root’s cross-sectional area. There was a slight increase in regrowth percentage as the trenching distance from the base increased (min P-value = 0.003), and a slight decrease as the cross-sectional area of the cut root increased (P-value = 0.032). However, our model had low predictability (Adjusted R2 = 0.03). Our findings indicate that root systems require many years to recover from trenching damage. Increasing the distance between trenching activities and trees may have a minor effect on root regrowth but primarily helps reduce initial stress on the tree.

Luke McCormack, The Morton Arboretum, Lisle, Illinois, United States; Marvin Lo, The Morton Arboretum, Lisle, Illinois, United States; Newton Tran, The Morton Arboretum, Lisle, Illinois, United States

Drought and waterlogging both cause tree stress and dieback. Most observations of tree water stress focus on aboveground responses. While often ignored, fine roots also play important roles mediating tree responses to water stress. Indeed, the capacity of fine roots to acquire more water during drought or to tolerate low oxygen conditions during waterlogging may even be the most important features defining tree responses to both too much and too little water. In this talk we will discuss some of the causes and consequences of water stress from a belowground perspective as well as features of fine-root systems that may make them more functional or resilient in the face of water stress. Our preliminary work suggests aspects of root morphology may be important for water uptake during mild summer droughts. Importantly, these morphological features are usually easy and inexpensive to measure which may enable more rapid species selection and screening in the future. In contrast, morphological traits seem less important for how trees respond to waterlogging. Instead, strategies to maintain or rapidly shed fine roots may be important indicators of tree responses to waterlogging. Both maintaining fine roots and shedding, then subsequently regrowing fine roots provide potentially viable strategies to tolerate some waterlogging conditions. However, each likely has distinct advantages for either repeated, pulsed waterlogging events vs. single, but longer events. We are continuing field trials to better identify belowground strategies that enable trees to better cope with waterlogging and drought stress with our ultimate goal being to better select and site a wider diversity of tree species for planting in the urban environment.

Meghan Midgley, The Morton Arboretum, Lisle, Illinois, United States; Allyson Salisbury, The Morton Arboretum, Lisle, Illinois, United States; Brian Wagner, The Morton Arboretum, Lisle, Illinois, United States, and Illinois Math and Science Academy, Aurora, Illinois, and Notre Dame, South Bend, Indiana; Sav Henderson, The Morton Arboretum, Lisle, Illinois, United States; Marvin Lo, The Morton Arboretum, Lisle, Illinois, United States; Andrew Muñoz, The Morton Arboretum, Lisle, Illinois, United States and Chicago Botanic Garden, Glencoe, Illinois; Charles Cannon, The Morton Arboretum, Lisle, Illinois, United States; Jason Miesbauer, The Morton Arboretum, Lisle, Illinois, United States

Highway right-of-ways offer valuable opportunities for increasing forest cover and mitigating the negative environmental impacts of roadways. However, despite large planting areas available in right-of-ways, soils along highways are often poorly suited for trees – compacted and low in nutrients owing to road construction practices; and polluted, particularly by deicing salts at high latitudes. Biochar may improve tree performance in urban soils by decreasing soil bulk density, facilitating the slow release of nutrients, and retaining pollutants. Given the high cost of biochar, it is critical to identify the situations in which it most benefits trees and ecosystems. In fall 2018, we established a roadside experiment to test the effects of soil amendments (control, biosolids, or a biosolid-biochar mix) and planting strategies (single tree pits or 15-tree beds) on tree survival, growth, and physiology and soil properties. We found that amendments had no impact on tree survival (P≥0.22); tree species with high roadside tolerance (Catalpa speciosa and Gleditsia triacanthos) fared best in this experiment (P<0.001). Both biosolids alone and the biosolid-biochar mix increased nutrient availability, decreased bulk density, and increased SPAD (P≤0.03). In contrast, growth was greatest in the biosolid-biochar mix (P≤0.03), though growth responses to amendments varied among species and between planting types. To complement our roadside experiment, we conducted a four-month greenhouse experiment to test if biochar (top-dressed or incorporated into soil) enhanced tree seedling growth & physiology and decreased sodium leaching. When applied as a top dressing, biochar decreased sodium leaching (P<0.001) and increased tree seedling growth (P=0.009). These growth effects were largely driven by Catalpa speciosa, a salt-tolerant species with the highest growth rates in our experiment (P<0.001). Specifically, top-dressed biochar increased Catalpa speciosa stem and coarse root growth and SPAD (P≤0.03). Collectively, our results show that biochar effects on trees and soils are measurement- and context-dependent. Biochar does not improve the survival or growth of roadside-intolerant or slow-growing species but may increase tree growth and decrease sodium leaching – particularly when top dressed and applied to fast-growing, robust species like Catalpa speciosa. Given its high cost, biochar should be used sparingly to improve urban soils.

Jason Miesbauer, The Morton Arboretum, Lisle, Illinois, United States; Andrew Koeser, University of Florida, Wimauma, Florida, United States;Brian Kane, University of Massachusetts, Amherst, Massachusetts, United States

Soil trenching is a common practice for installation and maintenance of underground utilities, as well as other types of urban infrastructure work. Although often necessary, trenching in close proximity to urban trees can lead to significant severance of tree root systems, thereby potentially reducing tree anchorage and stability. There have been a handful of studies over the past quarter-century investigating questions regarding root severance and stability. Each of these projects was a significant undertaking, yet represent only a few of the many possible combinations of species, size class, and level of root severance. More research is needed to cross-validate these findings and add additional information for use in industry BMPs. However, the current rate of research is slow and our use of trees is inefficient as researchers only get one opportunity to trench any given tree in a study. However, model scale testing has been utilized in various forestry-related disciplines for decades. Furthermore, to help aid in this endeavor, 3D printing has become an effective means of rapid prototyping, and 3D scans of real trees and tree roots can be easily and accurately created using low cost software. For this project, we conducted non-destructive static pull tests on thirty Acer rubrum ‘Florida Flame’ trees. After initial static pull tests were completed, trenches were cut at one of three distances (1, 3, or 5 times DBH) from the trunk. Pull tests were repeated to the same inclination. After the completion of pull tests, the root systems were excavated, and all soil and small roots (< 1cm) were removed. Severed roots from trenching were reattached. We then utilized structure from motion (SfM) photogrammetry to create 3D models of the root systems. These models were then subjected to wind tunnel testing, utilizing the same severance treatments outlined above. Results from this project, detailing the effects of trenching at different distances from the trunk on tree anchorage, as well as the results from wind tunnel testing will be presented. Additionally, the potential application of utilizing root system models for further research will also be discussed.

Michiel A.M. Mol, Terra Nostra, Bleskensgraaf, Zuid-Holland, Netherlands; Wendy W. Batenburg, Terra Nostra, Bleskensgraaf, Zuid-Holland, Netherlands; Jean-François J.F. Gauthier, SYLVA Landscape Architecture & Urban Forestry, Rotterdam, Zuid-Holland, Netherlands

This conference contribution will introduce the ‘Trees First’ overall vision as an integral solution for urban forest implementation. Next, selected cases of implementing the approach are also presented, followed by a set of design principles for the Forest City. The design methodology entails the following aspects: the city as a potential forest territory, trees as a starting point for a better design of public space, invent new public space typologies around tree communities, and ecological succession to bring health and well-being to our densely populated cities.

In the ‘Trees First’ methodology, climate adaptation of the urban environment is designed from the habitat of trees. The degree of sunlight, shade, soil moisture characteristics. and soil type determines which natural habitat and its corresponding planting type is applicable for a specific urban location. By matching urban typologies (streets, parks, squares, buildings, and urban infrastructures) with natural habitats (canyons, valleys, hills, mountains, etc.) we look at urbanization as an opportunity for a new nature to settle in the very heart of our city. There is increasing awareness of the importance of urban trees for ecosystem services. If we want to benefit from trees, we need to understand that trees growing in a forest-like system are more robust and contribute more to our well-being. When given time and space, a forest will grow strong and will self-sustain itself. By defining specific design strategies, ecological succession can happen within our various and constrained urban spaces. Citizens will then connect back with the slow-paced growth of trees, enhancing a sense of belonging to a place and social inclusiveness around the maintenance and care of urban forest. As an illustration of the design methodology, three ‘Trees First’ pilot projects in The Hague will be presented, including the design principles, the experimental aspects from the projects, the lessons learned and the results from the on-going monitoring. The methods for soil improvement will be explained in detail. In these pilots a flexible collective of participants was also organized to make tailor fit solutions for every project (design contractors, arborists, botanists, maintenance parties and inhabitants).

Kristin KM Moldestad, COWI AS, Oslo, Norway; Olve OL Lundetræ, Aker Trepleie AS, Oslo, Norway

Methods of identification of trees by leaf and bark are well known. This is not the case for tree roots. The aim of our project has been to create a field guide for arborists to the identification of roots. We are often outside on construction sites to control that the correct procedures are followed on site to protect existing trees. When digging works has revealed tree roots it is not always obvious which tree the roots belong to. Roots can expand far beyond the tree crown, and they are covered in soil and dirt. This reoccurring challenge, and our arborist inclination to save trees sparked us to study roots we came across through our work more closely. We began to assess roots as they appeared in ditches and on building sites more systematically. Through the studies we learned that the roots are almost as different as the branches and the leaves. We found roots with beautiful colors, amazing patterns, strange bark, and structure, and some with a distinct smell. So far, we have identified roots from around forty different tree species in Norway, and twenty species in New Jersey, US. We have described the roots with words and photos. We found this knowledge useful in our work as arborists, and we hope that this information can help other arborists on site, and maybe give them the evidence they need to change the direction of a ditch or move a building some meters. When this abstract is produced, we are in the final process of finalizing a field guide in Norwegian. We have given lectures at the Annual Conference of ISA in Malmö 2022 and the ISA Norwegian chapter and the ISA New Jersey chapter. We have been invited to talk about the project at the annual conference of the ISA Latvia chapter and the ISA annual conference in Albuquerque. So far we have not come across anyone else who has studied exactly this topic and we would like to present the study to you and look forward to discussing the topic with other professionals.

Gregory M Moore, University of Melbourne, Melbourne, Victoria, Australia; Timothy P Johnson, Board, TREENET, Adelaide, South Australia, Australia; Chris Brien, UniSA STEM, University of South Australia, Adelaide, South Australia, Australia

Sustainable cities require water sensitive urban design (WSUD) that integrates street trees, urban soils and engineering infrastructure. These systems can achieve synergies between civil engineering and urban vegetation that benefit ecosystems, stormwater management and human populations. However, there can be a perception that these systems can contribute to ground/soil movement that can be problematic for hard infrastructure. Reactive clays can shrink and heave as their water content changes, and there is concern that diverting water into curbside harvesting systems for street trees may exacerbate ground movement. Twenty-eight, small curbside stormwater harvesting systems that diverted storm runoff into roadside soakage wells were dispersed along a residential street in an inner suburb of the City of Adelaide, South Australia. The wells can be utilized with or without the presence of street trees, but greater utility and environmental benefits could be achieved with vegetation. Adelaide with an average annual rainfall of 540 mm is described as semi-arid and with impending climate change there is an imperative for more efficient water use and greater street tree canopy cover. Regular measurements of ground level were undertaken to determine ground movement over a period of nearly two years, comparing sites with and without soakage wells. Results showed that stormwater harvesting and infiltration into the site’s reactive clay did not increase ground movement at the curb or at the road surface during periods of above and below average rainfall. Ground movement was of similar amplitude near and further from infiltration points and was unaffected by stormwater harvesting. The use of trees within WSUD, particularly in fine clay soils in which root growth increases water harvesting and storage, can substantially contribute to urban hydrology through canopy rainfall interception, hydraulic redistribution, enhanced soil conductance through biopore creation and preferential flow along root channels. Further research is likely to reveal that opportunities exist to harvest and store larger volumes of stormwater in the soil for passive irrigation of urban vegetation. Research is needed to investigate the effects of point infiltration of larger volumes of stormwater into all soil types in different climates and in combination with different street tree species.

Ryan Munroe , NVK Nurseries, Dundas, Ontario, Canada

Poor root quality negatively affects the transplant success of tree liners. In field nurseries that grow balled and burlap stock, the survival, health and growth of these liners in the first year is critical. If bare root liners lack enough fine, absorptive roots, or if traditional container liners have become pot-bound and deformed, consequences are experienced in the field in terms of decreased ability to uptake water and nutrients, form associations with beneficial microorganisms and access available rooting volume for anchorage and access to resources.

NVK Nurseries is conducting a research trial, led by their internal Plant Health Team, to test the effectiveness of several leading commercial air-pruning and fabric containers on several species that are known to be tough-to-transplant bare root. Both 3 and 7 gallon containers of RediRoot, Pioneer and Root Pouch containers will be used to grow out species such as Abies fraserii, Carpinus betulus, Fagus sylvatica and Quercus spp. in an effort to stimulate well branched, fibrous root balls, relatively free of defects. These species will be transplanted bare root into these alternative containers and grown on for an additional 4-12 months using drip irrigation and then planted.

Chad M Rigsby, The Bartlett Tree Research Laboratories, Charlotte, North Carolina, United States, and Center for Tree Science, The Morton Arboretum, Lisle, Illinois, United States; Angelina Harley, Center for Tree Science, The Morton Arboretum, Lisle, Illinois, United States; Kelby L Fite, The Bartlett Tree Research Laboratories, Charlotte, North Carolina, United States; Shealyn C Malone, Department of Entomology, University of Wisconsin–Madison, Madison, Wisconsin, United States; Amy M Trowbridge, Department of Entomology, University of Wisconsin–Madison, Madison,Wisconsin, United States; Andrew L Loyd, The Bartlett Tree Research Laboratories, Charlotte, North Carolina, United States, and Botanical Research Institute of Texas, Fort Worth, Texas, United States

In plants, induced defenses are hypothesized to be a cost-saving strategy that allows for optimal growth during relatively ideal conditions with defense responses that can activate suddenly and be catered to specific challenges. Defense elicitors are substances such as hormones or analogues, fungal or arthropod proteins, lipids, or cell wall components, or other substances that induce molecular and biochemical changes to plant tissues such as alterations in gene expression, secondary metabolite accumulation, and increases in stress-response enzymatic activities. Defense elicitors are commonly used in the green industry as a pest management tool, and a significant amount of research has occurred on their aboveground effects, but relatively little research has addressed their effects on belowground tissues. In a potted greenhouse experiment, eastern white pine (Pinus strobus) saplings were drenched with a defense elicitor solution (potassium phosphite, chitosan, potassium silicate, or curdlan) or a carrier solution control, and plants were harvested at three, seven, and twenty days post-treatment to assess fine root chemical and enzyme-associated defenses. Fine root monoterpenes, soluble phenolics, and major diterpene resins showed only minor responses to treatments. Defensive enzyme activities (β-1,3-glucanase, chitinase, and peroxidase) were altered depending on the elicitor applied as well as the sampling date, with some eliciting a large, rapid increase in enzyme activity followed by a rapid return to decreased levels. Alternatively, some elicitors caused a slower, but still large increase in enzymatic activity over time. We hypothesize that, for the most part, we observed a “priming” response of pine saplings to these elicitors, where a physiological state is induced in which a plant is conditioned for the rapid activation of defenses upon further challenge. However, more research is needed to elucidate responses of belowground tissues to defense elicitors, which will allow for better recommendations in the field and the design/discovery of more effective elicitors.

Bryant C. Scharenbroch, University of Wisconsin–Stevens Point, Stevens Point, Wisconsin, United States, and The Morton Arboretum, Lisle, Illinois, United States

Urban tree growth may be reduced due to poor urban soil conditions. Soil management to alleviate poor urban soil conditions often includes organic amendments. Biochar is one type of organic amendment with great potential for soil improvement for urban trees. This presentation will discuss: 1) what biochar is, 2) research findings on its efficacy, and 3) its pros and cons for use in urban forestry and arboriculture. The presentation will highlight research from the speaker and others who have been working to assess the efficacy of biochar for urban tree management. The presentation will also focus on the application of this information for urban tree management. This presentation will feature findings from research that has been funded by the TREE fund, The Morton Arboretum, University of Wisconsin–Stevens Point, and industry partners.

Huib Sneep, H. Sneep Holding and GreenWaveSystems, The Netherlands

Different approaches have been published about the amount of soil trees need to thrive, with groundwater or without reachable groundwater. It is not easy to prepare a trial where the determining factors are completely under control. Roots are very smart in escaping from the plant pit. I was lucky to be able to make a project in spring 2004 with 70 trees of 19 species, both conifers and deciduous species, like Tilia, Prunus, Ulmus, Metasequoia, Liriodendron, Malus sp, Carpinus v. betulus and Pinus nigra. The trees were planted in half-submerged containers in the roof of an underground bikepark for 2500 bikes between the two World Trade Center buildings at Zuidplein (Southsquare) in Amsterdam-Zuidas, which is the high-rise business district of Amsterdam. Both the containers and the roof are made of concrete, which gives full control for the rooting possibilities, no root can escape! The plot is irrigated and the trees grow in 6-10 m3 of enriched Amsterdam treesoil, some of them as a solitary tree and others in a linear group. There is a lot of wind load from the building, and according to a test, trees would deliver the best results controlling wind hindrance. In the beginning the trees were anchored, and no tree failed by wind. In the design period everybody expected that the trees would not survive longer than 10 years. With good care and maintenance, the trees are still doing very well today, and have to be pruned regularly.

Conclusion:

• Trees can thrive on less substrate and under wind hindrance as ever estimated.
• Controlled irrigation and regular care are important to reach an expected life span of 30-45 years.
• The good development of length and diameter have generated a lot of information for fellow professionals.

Gary Watson, The Morton Arboretum, Lisle, Illinois, United States

Mature oaks have been declining unusually rapidly across the Chicago region in recent years. Declining trees tend to be confined to relatively small areas, even if part of a much larger stand of oaks. Many oak species are affected. Decline has occurred on a wide range of properties, including forest preserves, parks, street trees, and private properties. The symptoms are different than more typical gradual decline, oak wilt, Armillaria root rot, and bur oak blight. The decline symptoms suggest root rot. Phytophthora root rot is a widespread, but often overlooked, disease of landscape plants. Root infection can occur months, or years, ahead of first visible symptoms. Plants with Phytophthora root rot show aboveground symptoms in summer, because the plant does not have enough functional roots left to keep up with transpiration. It is generally accepted that when Phytophthora is found on a declining plant, it is likely to be a significant contributing factor. Fine roots of over 150 oaks, from 22 sites, were tested with DAS-ELISA (Double Antibody Sandwich-Enzyme Linked ImmunoSorbent Assay) and ImmunoStrip® ELISA (Lateral Flow ELISA) were are used to test for Phytophthora infection in the lab and field, respectively in 2021 and 2022. Ninety percent of the trees tested positive with ELISA, including trees without symptoms near declining trees. The pattern of declining trees in groups suggests a localized environmental influence. Sites where oaks have been rapidly declining all have soils with marginal to poor drainage naturally. The four spring seasons of 2017-2020 had much above normal precipitation. This would increase the already normally high spring soil moisture, and for a longer period, creating soil moisture conditions that would be extremely stressful for the trees, and very favorable for development of Phytophthora root rot. That the decline developed on multiple sites over a wide region, and even symptomless trees tested positive with ELISA, suggests that the pathogen occurs naturally in many soils, and is ‘lying in wait’ for a time when environmental conditions favor the pathogen over the tree. Whether it has a role in normal root activity, such as turnover, is unknown.

Matthew Werle, BlueGreen Urban, Knoxville, Tennessee, United States

This contribution introduces three European case studies demonstrating the practical integration of blue and green, where trees were planted with the help of suitable infrastructure, to deliver nature-based solutions within the urban environment.

An English case study is an example of how alterations to the road network in and around a historical town center, driven by a municipality’s desire to alleviate traffic congestion, can achieve additional benefits with the help of blue and green infrastructure.  A new tree planting scheme along a redesigned section of a road not only contributes to greening of the town but the trees play an important role in reducing air pollution. Faced with a combined sewer at capacity, the tree planting is concurrently utilized as a multi-functioning system for storm water attenuation and as treatment pits for road runoff pollution.

A Dutch case study, delivered as part of an EU-funded Interreg project, demonstrates how retrofitting a road by planting trees in hard surfaces using a suitable infrastructure not only aids future temperature regulation as a primary objective, but also addresses public health issues and improves a city’s climate change resilience. Having the foresight means the blue-green infrastructure installed as part of this intervention can simultaneously act as an effective stormwater management solution during periods of high rainfall.

A Welsh case study shows how retrofitting high-density residential areas with suitable blue and green infrastructure not only reduced pressure on an aging sewer network but delivered a myriad of benefits for its local communities including new cycle friendly routes. Implementation of innovative sustainable urban drainage solutions benefited the natural environment too, significantly improving water quality of nearby watercourses. This ground-breaking project involved the water company with several partners including the municipality which has an ambition to be the lead City in Europe for Sustainable Urban Drainage, positioning itself as a Water Capital.

The case studies show that blue and green infrastructure – water and trees – are not mutually exclusive but can complement each other. In our towns and cities where available space is limited, turning blue and green ideas into blue-green realities not only resolves the common lack of space issue but enables delivery of nature-based solutions, maximizing benefits for nature and for local communities.

Tyler Wilcox, NYC Department of Parks and Recreation, New York City, New York, United States; Henry Torres, NYC Department of Parks and Recreation, New York City, New York, United States

Urban trees in conflict with surrounding infrastructure has been a long-standing issue in New York City; sidewalk conflicts in conflict with city trees have received particular attention due to the shared maintenance responsibility and liability between the property owner and the city.

In 2005, the New York City Department of Parks and Recreation Trees & Sidewalks Program was established as a mayoral program funded to address sidewalks damaged by city owned trees abutting owner occupied, 1-3 family residential properties. In addition to addressing the existing damage/liability for constituents, the program’s goals are guided by the principles of tree preservation and extending the serviceable life of sidewalks around urban trees, a critical relationship between arboricultural best practices and engineering.

Through its almost 20-year history, on average, the program receives over 9,000 requests for repairs annually. Our team of foresters, managers, and consulting resident engineers respond to these requests by performing detailed inspections, which evaluates the severity of the sidewalk damage, the volume of pedestrian usage, and the condition and risk of the tree using an ISA-level 2 inspection method. For sites that qualify for the program, a prescriptive repair plan unique to each individual tree is designed and added to site listings that are sent to our contractors.

Repairs are made utilizing a number of methods and techniques to avoid or minimize damage to tree roots. These include hand and/or pneumatic excavation, expansion of tree beds, ramping sidewalks over and curving sidewalks around roots, and reinforcing cement to improve longevity of the sidewalk above tree roots. Topsoil and mulch are furnished within new tree beds to improve moisture retention and conditions for root growth. As a tree preservation program, tree health and preservation take priority during repairs. To assist with our preservation efforts, tree protection language and payable items specific to excavation and construction within the critical root zone have been included within our general contracts.

The sheer scale of this program is remarkable. In this presentation, NYC Parks intends to share best practices, lessons learned, insight on the development of inspection and repair methodology, and connect with other practitioners.

Wei Zhang, TreeDiaper/Zynnovation LLC, Ashland, Virginia, United States; Lawrence Alberty, Deep Roots Microbiome Company, Fordland, Missouri; Gordon Mann, Mann Made Resources, Auburn, California, United States

Why do most trees not have deep roots? Why are compacted soils bad for your landscape? At the same time, why do trees love to grow roots under sidewalks in between concrete and compacted soils? We all know overwatering creates an anaerobic condition that is bad for roots. But how long does it take for the process to start? When your plants are overwatered, you have two options: drain the water to save the plants with water being wasted OR save the water with the plants being wasted. Can you save both the water and the plants? Not typically. It is the reason why we have to water our plants with frequent, but little water each time. What makes Plant Available Water different from the irrigation water? Why is volcano mulching bad for your trees while foot-deep leaf litter in natural forests is good for the trees? What is the difference between double/triple shredded mulch versus arborist chips? Stockpiling topsoil is common in the construction industry and it is sold to the landscaping industry. What is the difference between a stockpiled topsoil versus actual top soil? After stockpiling for months or years, is it still soil or just dirt? What is the one thing in common for all of these questions? Soil Oxygen. It is the real limiting factor! We will use live demonstrations (when possible) to show the differences of soil oxygen in some situations.

Marie V Ambusk, TreesROI, Hinesburg, Vermont, United States; Jason Grabosky, Rutgers University,  NJ Agricultural Experiment Station, Cazenovia, New Jersey,, United States; Gordon Mann, Mann Made Resources, Auburn, California, United States

The widespread practice of growing nursery stock trees in containers is known to cause severe root system defects during the production process. If not corrected by planting (or if not correctable), those root system problems continue to proliferate – out of sight. At best the result is stunted trees failing to thrive; at worst the result is early tree mortality and removal prior to maturity. While this problem is unintended, it is unacceptable. It’s hard to fix what you can’t see! Our ongoing study supports the Overarching Vision for 2043. Ground penetrating radar (GPR) is among the currently accepted, reliable non-destructive testing technologies for mapping tree roots and for tree inspection. Tree roots in soil/substrate have a strong dielectric contrast, sufficient for GPR to resolve complex root structures to about 1cm in diameter. The power of GPR technology is the foundation of this R&D effort. The successful outcome is a tool and method to assess the root system quality of nursery stock trees above ground, with a peer reviewed quality grading metric to provide objective evidence of serious root problems. If correctable, guidance will be provided to locate and remediate the problems. The intention is to increase the lifespan of nursery stock trees to grow to maturity in the urban landscape and thus maximize their benefits to people and the environment. We discuss the development of a GPR-Tree-CT system that delivers real-time 3D root system image reconstruction with further analysis for the complete root system architecture assessment. Modeling for our experiments is based on the #15 size container. This novel method of GPR imaging is analogous to low resolution X-ray CT scanning, but without the radiation risk, the high cost or the deployment issues. We discuss empirical findings in the development of the tool as a proof of concept and share our research progress with a video demo of our current data set, some lessons learned and the research objectives to overcome many technical and industry challenges.

Josh Caplan, Landscape Architecture, Temple University, Ambler, Pennsylvania, United States; Allyson Salisbury, Landscape Architecture, Temple University, Ambler, Pennsylvania, United States

Plants in stormwater management systems contend with many challenges – extreme wetting and drying cycles, exposure to potentially toxic elements, and elevated salinity from deicing salts. The effects of deicing salts on plants in stormwater management systems such as bioretention basins are not well studied, despite the widespread usage of sodium chloride deicers in cold-weather climates. To further our understanding of this topic, we studied deicing salt impacts on Cornus sericea, a woody shrub commonly recommended for bioretention basins (also called rain gardens). We conducted our research at a set of bioretention basins in Philadelphia, United States, which receive stormwater runoff from an adjacent six-lane highway. At this site, the bioretention basins are shielded from most aerial spray generated by the highway, which allows us to focus on salt impacts via the soil system. We documented seasonal changes in basin soil electrical conductivity (EC), C. sericea sodium tissue concentrations, plant size, and survival. We observed a high degree of spatial and temporal variability in soil EC (a proxy for deicing salt concentration) within the basin. Notably, soil EC remained elevated into the start of the growing season after the cessation of winter deicing salt application. Na+ concentrations were elevated in the aboveground tissue of C. sericea which had died following a colder-than-average winter. This observation suggests that C. sericea may be unable to limit Na+ uptake and its toxic impacts above a certain threshold of Na+. Our research demonstrates how deicing salts can negatively impact bioretention basin C. sericea well into the growing season. It highlights the need to better understand the ability of common woody landscaping plants to tolerate deicing salts and to adjust planting plans in order to reduce plant exposure to deicers.

Els Couenberg, Natura Ingenium, Diemen, The Netherlands

During an experiment with Platanus x hispanica, designed to differentiate between several growth media, site construction issues caused one part of the site to be planted in June, while the other part was planted in August. Early frost caused much frost damage with the late planted trees. Differences in tree growth one year after planting (tree height, three length and tree circumference) were best explained by planting date, not soil type. Even three years after planting, while the differences in tree growth were much less than after one year, they still were explained best by planting date.

Riley Johnson, Horticulture, Michigan State University, East Lansing, Michigan, United States; Bert Cregg, Horticulture, Michigan State University, East Lansing, Michigan, United States

Recent trials in our lab indicate that bare-rooting container-grown trees before planting can be an effective means to remediate circling roots and other root defects. However, trees that have been subjected to bare-rooting may experience water stress due to an imbalance of root and shoot area, resulting in leaf scorch, crown dieback, and tree mortality. In a current trial we are evaluating methods to remediate circling roots (shaving, vertical slicing, and bare-rooting) on four common landscape species (London planetree (Platanus × acerifolia (Aiton) Willd.), tulip tree (Liriodendron tulipifera L.), American hornbeam (Carpinus caroliniana Walt.), and American hophornbeam (Ostrya virginiana (Mill.) K. Koch)) grown in #25 (100 L) containers. For a subsample of trees in the bare-root and control groups, we reduced crown leaf area by one-third (compensatory prune) prior to planting. For each tree in the compensatory prune group, we adjusted crown leaf area through a series of selective thinning cuts, which removed one-third of the cross-sectional branch area of that tree. Except for the bare-root treatment, root remediation treatments did not affect tree survival, growth, or crown dieback rating after transplanting relative to the untreated control trees. In contrast, bare-rooting reduced caliper growth and increased mortality and crown die-back of tulip tree, hornbeam, and hophornbeam trees. Among trees in the bare-root treatment, compensatory pruning improved survival and dieback rating, though these parameters were still below those in the other root treatments. Compensatory pruning has long been a controversial topic and is typically discouraged in the arboricultural literature. However, some of the studies on which the prohibition of compensatory pruning is based included indiscriminate pruning methods (i.e., heading cuts) or faulty experimental designs. Considerable literature exists that indicates improving root-shoot ratio can reduce plant water stress after transplanting. Moreover, increased application of root pruning techniques such as shaving and bare-rooting to remediate root systems of container-grown trees warrants a reexamination of the dogma against compensatory pruning.

Kelsey Patrick, Center for Tree Science, The Morton Arboretum, Lisle, Illinois, United States; Marvin Lo, Center for Tree Science, The Morton Arboretum, Lisle, Illinois, United States; Luke McCormack, Center for Tree Science, The Morton Arboretum, Lisle, Illinois, United States; Carla Rosenfeld, Section of Minerals & Earth Sciences, Carnegie Museum of Natural History, Pittsburgh, Pennsylvania, United States; Chad Rigsby, Center for Tree Science , The Morton Arboretum, Lisle, Illinois, United States, and The Bartlett Tree Research Laboratories, Bartlett Tree Experts , Charlotte, North Carolina, United States

Urban trees provide many environmental benefits, but often face challenging growing conditions. One of these challenges is waterlogged soils often caused by soil compaction and poor drainage. These issues are likely to be exacerbated by the projected increase in flooding events due to climate change. Root responses to waterlogging contribute to how trees respond to waterlogging stress, yet are not well understood. Our goal was to identify how root responses to waterlogging influence tree tolerance levels and possible recovery strategies. We assessed the effects of a two-week waterlogging period on saplings using two congeneric contrasts of species previously identified as tolerant and intolerant based solely on aboveground responses. Sugar maple and saucer magnolia are reported to be intolerant to waterlogging, whereas silver maple and star magnolia are reported to have moderate or high tolerance, respectively. Saplings were grown in rhizo-pots, with windows that allowed us to monitor root production, mortality, and enabled periodic sampling of root tissues for analysis of peroxidase activity and lipid oxidative damage. High root mortality and low photosynthesis rates were recorded for waterlogged individuals in all species except silver maple. No significant difference was found between peroxidase activity in maple species, making peroxidase scavenging an unlikely strategy explaining silver maple waterlogging tolerance, though other scavengers may still be involved and could account for silver maple’s tolerance levels. Sugar maples were the only species that showed significant increases in lipid oxidative damage post-waterlogging. Sugar maples did not recover post-waterlogging, possibly due to an excess of stress at the root level or insufficient energy reserves to enable post-stress recovery. Future research should investigate how timing and length of waterlogging impact the natural cycles of tree nonstructural carbohydrate storage and use, as the ability to catabolize energy reserves to drive new flushes of fine-root growth post-waterlogging may be an important strategy for some tolerant species. How these strategies respond to varying frequencies and durations of flooding events is another important question worth considering. This would better inform urban tree selection by determining mechanisms that assist tolerant species in performing well in repeatedly flooded and/or completely inundated soils.

Rosalind C Remsen, University of Wisconsin–Stevens Point, Stevens Point, Wisconsin, United States; Bryant C Scharenbroch, University of Wisconsin–Stevens Point, Stevens Point, Wisconsin, United States

A widespread trend of mature oak decline and mortality has been observed in the Chicago region in recent years. Declining members of the white oak group (Quercus alba, Q. macrocarpa, and Q. bicolor in the region) are often diagnosed and treated for inciting and contributing factors for oak decline, including Phytophthora spp, twolined chestnut borers, and other pests and diseases. While there have been studies on the stress physiology of white oaks and the pathology of decline diseases, there have not been any studies focusing on the relationship between tree’s abiotic site and soil characteristics and white oak decline in the Chicago metro area. The objective of this study is to determine which site and soil characteristics are significantly related to white oak decline in the Chicago region by comparing the characteristics present between both healthy and declining trees. I hypothesize that predisposing abiotic factors, such as fine textured poorly structured soils and shallow depths to water table, will have a significant relationship with white oak decline. Potential sites with both healthy and declining white oaks present have been identified through arborists, urban foresters, and forest preserves throughout the Chicago region. These sites will be visited throughout the growing season of 2023 to collect a representative deep pedon sample, composite soil samples, fine surface roots for oomycete detection, site characteristics, tree health assessments, and site management information. We expect to find that abiotic site (e.g., slope and profile position) and soil characteristics (e.g., texture, EC, and depth to redoximorphic features) will be found to be significantly different between healthy and declining white oaks. Results from this study may help arborists and urban foresters prioritize treatment and management of white oaks, improve our understanding of the processes that are influencing the health of managed trees, and improve future planting guidelines.

Hongbing Wang, Shanghai Normal University, Shanghai Engineering Research Center of Plant Germplasm Resources, Shanghai, China; Jun Qin, Shanghai Chenshan Botanical Garden, Shanghai, China; Yonghong Hu, Shanghai Chenshan Botanical Garden, Shanghai Chenshan Plant Science Research Center, Chinese Academy of Sciences, Shanghai, China

The issue of forest trees biologically designed to sustain wind and slope stresses for improving tree anchorage and stability has been of interest to many forest ecologists for over 200 years. Biomechanical design of the below- and above-ground organs should be systematically understood under asymmetric environments. This review tried to find the architectural connectivity between below- and above-ground organs of a tree based on the systematic summary of the asymmetric growth of crown, trunk, and root system. The asymmetrical aboveground growth is influenced by a complex interaction of tree species, age, neighborhood competition, wind, lighting, slope, and altitudes, showing twelve scenarios. The asymmetrical belowground development is dependent on tree species, age, trunk leaning, wind, soil, and slope. Uneven water conduction, nutrient allocation, hormone content, and photosynthesis rate can reveal the relationship of architectural mechanisms between the below- and above-ground organs. The contradictory observations on the directional deformations of the root system (buttresses) reveal the particular prominence of combined effects of multiple factors. Future research should focus on the comprehensive understanding of the below- and above-ground architectural relationships of different tree species. Our review provides novel insights into the connotations of root-shoot balance in biomass distribution of the individual plant organs.

Hongbing Wang, Shanghai Normal University, Shanghai Engineering Research Center of Plant Germplasm Resources, Shanghai, China; Jun Qin, Shanghai Chenshan Botanical Garden, Shanghai, China; Yonghong Hu, Shanghai Chenshan Botanical Garden, Shanghai Chenshan Plant Science Research Center, Chinese Academy of Sciences, Shanghai, China

Plant root and shoot growth are closely interrelated, which architecture is of great importance in studying plant growth and stability. Their directional distribution of mass in architecture and the resulting root–shoot interactions are the keys to understanding the dynamic balance of the below- and above-ground organs related to tree anchorage. Studying the stability mechanism of trees under asymmetric situations is very important for the cultivation of urban forest. However, the horizontal spatial relationship between root architecture and shoot architecture is not yet clear. This study focuses on the camphor tree (Cinnamomum camphora L.) to observe architectural responses to the asymmetric treatments of biased root (BRT), inclined trunk (ITT), and half-crown (HCT) in a controlled cultivation experiment using the minirhizotron method. We found an inverse architectural relationship of crowns to roots in BRT and opposite asymmetries of roots with crowns in response to the ITT and HCT treatments. We also observed higher net photosynthesis rate (Pn), water use efficiency, and chlorophyll content in the leaves on the side opposite the lean in ITT, and higher Pn, transpiration rate, and chlorophyll content on the root-bias side in BRT, which is consistent with the nutrient allocation strategies of allocating nutrients across plant organs in an optimal way to obtain ‘functional equilibrium’ and adapt to the stressed environment. Furthermore, the asymmetrical growth transformation of first-level branch length from the root-bias side to the opposite side in BRT, and a similar transformation of root length from the crown-bias side to the opposite side in HCT, imbues further theoretical support of the nutrient allocation strategy and the biomechanical stability principle, respectively. In summary, this study is the first to identify opposite architectural interaction between below- and above-ground organs of the camphor tree. The findings enrich the connotation of root-shoot balance and help to realize root design for the silviculture management of urban forests.

Qiang Xing, Shanghai Chenshan Botanical Garden, Shanghai, China; Jun Qin, Shanghai Chenshan Botanical Garden, Shanghai, China; Hongbing Wang, Shanghai Normal University, Shanghai Engineering Research Center of Plant Germplasm Resources, Shanghai, China; Yonghong Hu, Shanghai Chenshan Botanical Garden, Shanghai Chenshan Plant Science Research Center, Chinese Academy of Sciences, Shanghai, China

The study of the variation of plant root structure and the relationship with root traits can help to understand the adaptation strategies of plants in the limited growth space. In this study, two vine species of overhanging Vinca major ‘Variegata’ (VMV) and climbing Trachelospermum jasminoides ‘Variegatum’ (TJV) were selected for vertical green wall container cultivation. The dynamics in the biomass distribution and structural characteristics of the root system were observed over 5 years. The biomass and morphological characteristics of the root system showed the same pattern of evolution, but the variation of VMV was larger than that of TJV, showing the bimodal curve of root diameter of VMV and the decreasing trend of root diameter of TJV. Among the 4 diameter levels of the fine roots of the two plants, D1-1 (0<d ≤ 0.5 mm) are greater than D1-2 (0.5 < d ≤ 1.0 mm), while D1-3 (1.0 < d ≤ 1.5 mm) and D1-4 (1.5 < d ≤ 2.0 mm) could be combined into one unit for analysis because of small and similar values; and the multiple diameter levels of roots contributed differently to the average root diameter, in which D1-2 and D1-3 mainly contributed to VMV, and D1-1 and D1-2 contributed the most to TJV in 4th year. (3) The different growth forms of the two plants showed different adaptation strategies to the limited root space, of which VMV adapted to constrained environments through the variation of roots between diameter levels, while TJV adapted to the environment with the diameter variation of main roots and breeding developed adventitious roots. This study clarifies the root adaptability of two vine plants to limit growth environments, which is important for improving and maintaining biodiversity in special urban habitats and developing ecological community construction techniques.

Wei Zhang, Zynnovation LLC, Ashland, Virginia

Sodium Chloride, the most predominant salt used on streets for melting snow and ice, is the lubricant of the modern lifestyle in northern climates during wintry weather conditions. These same streets and parking lots are also the battleground where urban foresters and public workers strive to build green infrastructure for canopy coverage, stormwater management and aesthetics. It is all too common to observe damages and casualties on roadsides in spring when plants begin to display the impacts of salt through discoloration and canopy loss. At this stage, it is often too late to remedy and correct the damaged plants. The urban forestry community is keenly aware of the issue. Many landscape professionals have snow removal as part of their responsibility. Spreading salts is a big part of their standard operating procedures for winter weather. This scenario is magnified in areas with high population density and minimal tree canopy coverage. The potential for trees to experience road salt damage is likely in these communities.

Other than educating snow removal professionals about reducing the volume of salt and using alternatives (which often creates other environmental issues), there hasn’t been a viable solution. As a simple compound, sodium chloride doesn’t decompose, evaporate, or disappear magically. It has to be rinsed out of the soil and be washed away. Unfortunately, the irrigation systems are not available when the salts are applied. They are winterized either by people or by Mother Nature. The presence of salt degrades the quality of the soil, killing the beneficial organisms that keep soil alive. The same compound makes the Dead Sea “dead”.

Interestingly, the regions that need large amounts of road salts are also the regions with abundant amounts of precipitation. This presentation will present methods of catching/storing the abundant stormwater on site. When salt is introduced to the system, it triggers the release of the stored water to wash off the salt OR at least dilutes the salt concentration.