Case Study

Soil Health, Tree Health Veale Gardens/Walyu Yarta – (Park 21) – Part 3

This case study examines the application of advanced tree management techniques to rehabilitate a population of trees experiencing decline in Urban Forestry.

These management techniques focus on enhancing soil health by improving soil physical structure, chemistry and biology. The efficacy of this approach was evaluated using innovative sensing technologies to better understand the links between soil health and tree health and to quantify the productivity of trees in Urban Forestry.

Following up to PART 2 of this Case Study, which ran in The Australian Arbor Age April/May 2019 issue, we are now evaluating the results in terms of soil chemistry, soil biology, mycorrhizal colonization, soil respiration and compaction and wildlife predation.

Results

Soil Chemistry

Independent laboratory assessment of eight trees was conducted throughout the three years of the project. In 2015, Trees #6 and #31 were the focus with Tree #31 providing healthy a control throughout the PHC intervention period.

Soil chemistry is complex and shifts in one nutrient will affect other nutrient concentrations. In the initial investigations in 2015 and 2016 there were multiple issues associated with the chemistry at Veale Gardens ranging from nutrient deficiencies to nutrient toxicities based on desired levels.

Trees receiving PHC treatment displayed large increases in chemical properties compared with the untreated baseline

(Fig. 11). For example, the amount of total C, total N, exchangeable Mg, and exchangeable K increased by an average of two or three-fold (100 – 230%) in trees receiving treatment while in the baseline the increases were 8%, 44%, 20%, and 21%, respectively. Available P increased by a factor of ten 2 years after treatment, but only increased 33% in the untreated baseline. There was also an increase in plant available N over time compared with the baseline tree in teated trees (Fig. 12).

In an ever-changing soil environment it is important to understand all these nutrient pools and not just available soluble nutrient that is a common soil agronomic method. The shift in soil chemistry of the trees treated can be explained in some cases although it is important to understand this is a snap shot in time and additional adjustments will occur seasonally and over time. Another important factor is the interaction between soil biology and soil chemistry which is difficult to quantify.

Table 2 provides an in-depth analysis of the shifts in soil chemistry in 2016. In 2017, soil chemical parameters were shifting in many directions (Table 3). However, there appears to be a clear shift in total nutrient status between the treated trees and the untreated control tree. To date, these shifting patterns are positive and further monitoring is required to establish if it will result in more sustainable soil health for the trees treated at Veale Gardens/Waylu Yarta (Park 21).

Further analysis is required to determine the extent of the issues presented although as the soil physical status and soil microbiology improves so will the chemistry. The use of recycled water and mulch may present further issues in understanding the variation of soil chemistry results and requires further investigation to determine the long-term effects and management outcomes.

Further analysis and soil testing are required to determine true patterns.

The PHC treatments used in this study did not have a noticeable impact on soil pH, which remained elevated (> 7.5) in all of the tested trees, regardless of treatment (Fig. 13).

In summary, there were noticeable positive shifts in soil chemistry in the treated trees, suggesting that PHC # 1 and 2 increased soil nutrition, which should lead to greater nutrient uptake in treated trees and better tree health outcomes. The reduction in sodium (salt) from the recycled water is most likely a result of rainfall leaching, although increased soil carbon and humus from organic amendments and the resulting increase in microbial activity provides a buffer to sodium related issues because it is attracted to the humic and fulvic acid molecules.

Increased Root Zone Activity Due To Improved Soil Fertility

The root zone area of each tree had the sod removed prior to the application of compost and mulch.

The addition of organic materials and liquid amendments stimulated a significant amount of new healthy root growth and activity. This new root development was observed growing beneath the mulch layer and can be declared as new root mass (Fig.14), which increases the trees Root: Shoot ratio significantly.

Soil Biology

Soil biological activity is very sensitive to soil moisture content, compaction and soil chemistry. For this reason, there was a high degree of variability in the soil biological activity data. However, despite this variability, there were some very positive shifts in biological activity compared to the baseline (prior to PHC treatment) to note. In 2017, after the first application treatments, the soil biology of the treated trees increased 1741% compared with the increase of 273% of the control tree.

The amount of total and active fungi and bacteria did not consistently increase over the three years of monitoring results (Fig. 15). On the other hand, there was a noticeable increase in protozoa under the treated trees over time compared with the non-treated baseline (Fig. 16).

While the laboratory analysis may have been a mixed bag of results, the visual indicators of soil microbial activity were astonishing. In January 2017 there was a fungal bloom and production of fruiting bodies (mushrooms) during the summer months and on consecutive days above 38 degrees Celsius. This is an unusual yet positive event and can only be explained because of the rapid increase to fungal activity caused by the intensive PHC works (Fig. 17,18).

Mycorrhizae

During PHC mobilizations in 2017 and 2018, 146 Kg of Mycorrhizae spores were applied between 30 trees. The methodology used for mycorrhizal colonization laboratory assessment is direct microscopy fluoresces staining. Based on this method, Endo-Mycorrhizae colonization does not appear to have increased, and in some instances, it decreased (Fig. 19A). Ecto- Mycorrhizae colonisation was only observed in Tree 2 (Fig. 19B). This is not of major concern as the sampling methodology is random and the mycorrhizae spores that were applied during PHC # 1 may have been dormant in the soil profile and are yet to infect the increasing root mass that has been observed and documented.

As with the soil biological activity presented above, there was a disconnect between the laboratory data and visual observations made in the field. In this case, Mycorrhizal activity was observed during data collection in September 2017 (Fig. 20).

It is important to understand which species of trees have relationships with which mycorrhizae group.

As per Figure 20, Scleroderma cepa ectomycorrhizal fruiting bodies were observed on tree number # 2. Tree 2 is an Ulmus sp and not an and it is assumed that the root of this tree was collected as the root systems overlap.

There have been recent statements by some leading experts in the Arboriculture industry that Mycorrhizal inoculums are not effective. This is problematic as mycorrhizal inoculums are a complex soil remediation concept. One component that makes mycorrhizal inoculums different from the use of chemical or organic fertilizers is that they are biological based and require a symbiotic connection with the plant root. Fertilizers provide available nutrients for root uptake or microbial food for microbial stimulation in soil. The Veale Gardens/Walyu Yarta PHC Project has identified that although some mycorrhizal activity was measured there was not a significant increase overall. There are multiple reasons for this in this case study.

  • Elevated Soil Compaction Levels
  • Highly Elevated Copper And Sodium Levels In Soil
  • Low Root Shoot Ratios Of Established Trees
  • Extreme Heat Events

Establishing mycorrhizal connections in some cases has been successful, the nursery industry is an example. Because nursery soil medium and plant roots are accessible, applying spores directly to active root mass is highly effective. Another important reason nursery tree’s develop mycorrhizal associations effectively is the age of the tree. Applying inoculums to established declining trees is difficult for two main reasons.

  • Determining Active Root Zones Of Trees Is Subjective
  • High soil compaction levels prevent healthy root activity and inoculation of microbial spores
  • Extreme heat events reduce soil moisture rapidly and increase soil temperature to levels difficult for beneficial soil microbes to flourish

The science of soil health focusing on soil microbiomes including mycorrhizae associations is relatively recent and evolving at a rapid rate. Those who have assisted in the development of these biological sciences are highly specialized, dedicated and experienced professionals. It is important for the industry to acknowledge their message that mycorrhizal associations are crucial to healthy plant growth although key soil health parameters will limit the effectiveness of developing the biological activity. The use of inoculums such as mycorrhizae should not be discouraged. It is important to inform the industry of the required soil health parameters that enable the effective use of mycorrhizal inoculums to provide better outcomes. Knowledge of how to define, investigate and measure soil health will assist industry to use these inputs successfully.

Soil Respiration

Soil respiration was measured from a subset of eight trees and cross-referenced with laboratory assessments and direct microscopy to determine if it is a viable methodology to use in determining soil biological activity. The advantage of this approach is that it is low-cost, requiring very few tools or laboratory experience to conduct the tests. One disadvantage of the test is that it is non-specific, meaning that it is measuring the CO2 mineralized by all the micro-organisms in the soil and does not allow the user to differentiate between bacteria, fungi or protozoa.

Soils collected in 2018 were analyzed and those results are presented in Figure 21. The lowest soil respiration was recorded in tree #31, which was the untreated control. Therefore, it appears that the addition of compost, mulch, AACT and microbial stimulants did result in an overall increase in soil respiration. Likewise, comparing soil respiration to protozoa from laboratory tests (Fig. 22), there appears to be a correlation between soil respiration and protozoa populations in this case study.

There may be modifications to this method that can allow for more targeted analysis of certain microbial groups. For example, adding a substrate specific to a specific group (e.g. fungi or bacteria) and measuring the CO2 burst may offer a low-cost way to estimate the activity of soil micro-organisms.

These methodologies need to be tested in future case studies.

Soil Compaction – A Physical Parameter

In addition to soil chemical and biological parameters, a penetrometer was used to measure soil compaction as an indicator of soil physical structure. Soil compaction decreased over time in all the treated trees that were measured, while compaction remained much higher in the untreated baseline (Fig. 23). Penetrometers are an indication device and the measures can be affected by the users-familiarity with the tool and measurement protocol, making interpretation of penetrometer data subjective. In this case study, all penetrometer measurements were taken by Matthew Daniel, reducing measurement variability. The development of more user-friendly penetrometers that standardize measurement processes and data capture would increase the value of compaction measurements in Urban Forestry.

Wildlife Predation on Soil Microarthropods

Local bird life had a noticeable impact on the soil in the TPZ. Ibis appeared to be the most effective soil aerators as they had longer beaks than the local ducks. Hundreds of aeration holes from microarthropod predation by local birdlife was observed in the TPZ of the 30 trees. Worms were observed in the new improved soil conditions and are an indication of increased soil microbiology.

Disclaimer

Note: Any soil analysis or observation taken and recorded in this report will only ever capture the status of the soil and vegetation on that day. It must be emphasized that changes of sometimes considerable magnitude can be expected in response to normal seasonal and extreme weather responses and some management actions. This means that outcomes, as anticipated with the available evidence collated, may be unpredictable, so the regular recording of the soil and vegetation using a Soil Health Card or VSA and VTA or TREE HEALTH CALCULATOR 1.0 is essential, with the taking of photos always encouraged to record a history of change. G.U.F warrant that the methods adopted in its programs are largely a practical application of many years of experience in Plant Health Care together with scientifically verified management directives and measures through numerous sensors which are continually improved as new research findings come to hand.

For more information visit http://globalurbanforest.com.au

July 3, 2019 / by / in ,
Soil Health, Tree Health

Veale Gardens/Walyu Yarta – (Park 21) – Part 2

This case study examines the application of advanced tree management techniques to rehabilitate a population of trees experiencing decline in Urban Forestry. These management techniques focus on enhancing soil health by improving soil physical structure, chemistry and biology. The efficacy of this approach was evaluated using innovative sensing technologies to better understand the links between soil health and tree health and to quantify the productivity of trees in Urban Forestry.

Following up to PART 1 of this Case Study, which ran in The Australian Arbor Age February/March 2019 issue, we are taking a further step ahead with this project, focusing on the evaluation of the tree and soil response.

Section 2: Plant Health Care and Evaluating Tree and Soil Response

2.1 Plant Health Care (PHC) Applications

In 2016, a soil remediation plant health care plan was designed for 30 trees in the northwest corner of Veale Gardens/Walyu Yarta. This plan included a mixture of compost, mulch, compost tea and microbial stimulants applied from 2016 – 2018 (Table 1). The first step was to calculate individual Tree Protection Zones (TPZ) and remove grass (sod) from within the treatment areas (Figure 6). One healthy tree, Tree #31, was left untreated and used as a healthy control tree throughout the course of the project.

Compost Application

100mm of compost material was applied to each designated TPZ. Compost was recommended because it’s a good source of plant nutrients and organic carbon, which provides an important food source for soil microorganisms early in the remediation process. Unfortunately, the standards for producing compost (Australian Standard AS 4454 – 2012 Compost, Soil Conditioners and Mulch) do not put an emphasis on quality, such that compost quality varies widely. Increasing the minimum standards for compost to promote material that is fit for soil remediation, meaning it can improve soil biological, chemical and physical status in soil would help improve compost quality.

Mulch Application

150 mm of course green waste mulch material was supplied by the ACC Green waste facility and was applied to each trees unique Tree Protection Zone (TPZ) area.

Actively Aerated Compost Tea (AACT)

AACT is a liquid soil amendment produced with specialised equipment that contains bacteria, fungi, protozoa, nematodes and soluble nutrients sourced from high-quality compost.

Over a 24-hour period the liquid amendment is brewed with food additives to grow bacteria and fungi and aerated with dissolved oxygen to grow the aerobic organisms derived from the compost inoculum. The outcome is a liquid product containing a concentrate of beneficial microorganisms including bacteria, fungi, protozoa and nematodes. Figures 7A, B and C show the processes used by G.U.F. for producing and applying AACT.

Microbial Stimulants

Microbial stimulants are organic liquid amendments that provide a strong food source for soil microbes. The types of products used are for specific microbial

Microbial Inoculums

Microbial inoculums provide dormant spores of species of Mycorrhizae and were applied as part of each batch of AACT, then drenched onto the tree root zone area covered by compost and mulch.

2.2 Measuring Photosynthesis – Canopy Function Data

The photosynthesis data collected in this study was collected using a sophisticated but inexpensive hand-held photosynthesis meter called the MultispeQ which was connected to the PhotosynQ open data platform (Figure 8A). PhotosynQ is a collaborative online plant research platform, which enables users to create, share and collaborate worldwide to analyse detailed sophisticated environmental scientific information. The PhotosynQ project was developed at Michigan State University in the Kramer Laboratory. The device and platform allow for intensive data collection to unlock nature’s secrets and develop a greater understanding of how the natural world functions in its innumerable complexities. In 2015, Matthew Daniel of Global Urban Forest Pty Ltd was invited by the PhotosynQ team to beta test the platform and join the Experts Program. This initial small group hailed from diverse fields of science and industry which included agricultural research scientists from Malawi (East Africa), science educators from Ukraine, Great Barrier Reef marine science researchers from Australia and plant scientists from across the USA.

Each member of the initial ‘Experts Program’ were supplied with a 3D printed MultispeQ prototype to conduct research in their chosen fields and support the development of the MultispeQ version 1.0. Matthew Daniel’s focus was the Arboriculture and Urban Forest industry. He developed the Tree Health Calculator 1.0 project to better understand the link between soil health and canopy function.

MultisepQ, photosynthesis data was collected from 2015 – 2018, intensively during the PHC # 1 and # 2 program mobilizations. The primary photosynthesis parameters that were measured with the MultispeQ are as follows:

  • SPAD – Relative chlorophyll content, measures leaf” greenness”
  • Phi2 – Quantum yield of Photosystem II. This measurement is essentially the percentage of incoming light (excited electrons) that go into Photosystem II. Photosystem II is where most light energy is converted into food
  • PhiNPQ – Estimate of non-photochemical quenching. The amount of incoming light that is regulated away from photosynthetic processes to reduce damage to the plan
  • PhiNO – Ratio of incoming light that is lost via non-regulated processes. PhiNO is the combination of several unregulated processes whose by-products can inhibit photosynthesis or be harmful to the plant
  • LEF – Linear Electron Flux. The total flow of electrons from antennae complexes (were light is captured) into Photosystem II, taking the leaf absorptivity into account. Calculated as LEF = Phi2 x PAR x 0.42

2.3: Measuring Soil Compaction and Moisture Content

Soil compaction was measured using a penetrometer (Figure 9A). Penetrometers measure the force of pushing a spike into the soil and then note the depth at which the pressure is recorded. For example, 600 psi @ 5cm would indicate high soil compaction at a shallow depth that would restrict healthy tree root growth.

Soil moisture was measured using a moisture probe that provides moisture content as volumetric water content percentage (Figure 9B). Moisture was recorded at three depths – 10 cm, 20cm, 40cm

2.4: Laboratory Analysis of Soil Samples

Soil samples were collected from a subset of eight trees every year starting in 2015. Soil samples were collected from each tree in 2016, 2017 and 2018 to determine the shift in soil chemistry and allow for adjustments in the PHC program applications. These samples were then sent to Environmental Analysis Laboratories, Southern Cross University, Lismore NSW for analysis The chemistry assessments conducted were to understand three essential components of soil nutrients:

  1. Total Nutrients
  2. Available Nutrients
  3. Exchangeable Nutrients

2.5: Measuring Soil Respiration

Soil respiration was measured for a subset of eight trees using a Carbon Mineralization Sensor developed by Dr Dan TerAvest of Our Sci, LLC, a start-up from Michigan, USA. This method adds water to an air-dry soil sample and measures the resulting “burst” of CO2 after 24 hours by using a syringe to push air over a pass-through CO2 sensor. This methodology can be easily conducted by Urban Forest tree survey professionals in soil health investigations and can assist in the specification of input materials such as composts and mulches

Disclaimer

Note: Any soil analysis or observation taken and recorded in this report will only ever capture the status of the soil and vegetation on that day. It must be emphasized that changes of sometimes considerable magnitude can be expected in response to normal seasonal and extreme weather responses and some management actions. This means that outcomes, as anticipated with the available evidence collated, may be  unpredictable, so regular recording of the soil and vegetation using a Soil Health Card or VSA and VTA or TREE HEALTH CALCULATOR 1.0 is essential, with the taking of photos always encouraged to record a history of change. G.U.F warrants that the methods adopted in its programs are largely a practical application of many years of experience in Plant Health Care together with scientifically verified management directives and measures through numerous sensors which are continually improved as new research findings come to hand.

For more information visit http://globalurbanforest.com.au

May 6, 2019 / by / in
Soil Health, Tree Health Veale Gardens/Walyu Yarta – (Park 21) – Part 1

This case study examines the application of advanced tree management techniques to rehabilitate a population of trees experiencing decline in Urban Forestry.

These management techniques focus on enhancing soil health by improving soil physical structure, chemistry and biology. The efficacy of this approach was evaluated using innovative sensing technologies to better understand the links between soil health and tree health and to quantify the productivity of trees in Urban Forestry.

Summary

A four-year case study in remediating tree decline in Veale Gardens/Walyu Yarta (Park 21), Adelaide Park Lands.

Urban Forestry is currently experiencing unprecedented growth around the globe. By emulating a healthy natural system, urban forestry endeavours to provide multiple benefits including improving human health, increasing ecological sustainability, mitigating storm water and sequestering carbon. However, one of the most important goals of modern Urban Forestry is mitigating the Urban Heat Island Effect (UHIE) through the natural process of transpiration. This cooling effect from evapotranspiration comes from both plants and soil. Healthy plants and soil produce a microclimate that reduces air temperatures day and night during extreme heat conditions. This microclimate productivity is essential to the viability of cities and urbanised areas around the globe.

Extreme temperatures and the constraints of urbanisation have a relatively unknown effect on plant and soil health and present an ongoing issue to the effective use and sustainability of urban forests as mitigation tools. The complexities that drive urban forestry’s ability to provide sustainable ecosystem functions are currently underdefined and oversimplified.

The current standard approach to define tree health in Arboriculture is based on a Visual Tree Assessment (VTA). This approach uses few objective measures and instead relies on a complex set of observed tree health indicators that vary widely depending on the applicator’s education and experience. This small range of measures does little to define overall tree health and rarely considers below ground factors such as soil health.

This scenario presents a major opportunity to improve the current standards in tree assessment in managing the urban forest. Global Urban Forest (G.U.F) have been investigating and remediating tree decline in urban environments for over a decade. The common denominators of tree decline are extreme weather events and poor soil health. These are interlinked and compounding and often lead to tree decline events. Despite the importance of soil health in tree decline, it is rarely considered nor currently defined in horticulture.

In this case study, soil health is defined as a framework of physical structure, biological activity and soil chemistry. All of which are interrelated, so increasing soil biological activity can improve soil chemical and physical parameters and vice versa. Measuring all three components provides a detailed understanding to apply evidence-based management practices to improve soil fertility in the Urban Forest.

This study utilised a variety of advanced techniques, methodologies and unique equipment to determine plant and soil health, remediate the issues and capture shifts in critical parameters. This study aimed to draw attention to the importance of soil health, how it is linked intrinsically to plant health and how it drives overall Urban Forest health and function.

“This Study Aimed To Draw Attention To The Importance Of Soil Health.”

In brief the outcomes of the four-year case study were:

  • Application of organic amendments increased soil organic matter and increased the availability of macro and micro nutrients including: Nitrogen, Potassium, Phosphorous, Calcium, etc
  • Soil biology can be increased rapidly with the combination of products such as compost, mulch and liquid biological soil amendments such as Actively Aerated Compost Tea
  • Soil biological activity could be measured easily and affordably using the Our-Sci Carbon Mineralization Sensor
  • The Plant Health Care treatments used in this study reduced soil compaction compared to an untreated control
  • Relative chlorophyll content and Visual Tree Assessments both showed tree health increasing over the four years of the case study, but the chlorophyll measurements were more consistent
  • Photosynthesis measurements were effective in identifying severe tree stress, but were too complex to be useful as an everyday management tool
  • Urban forest soil health can be damaged by long term compounding extreme heat conditions that leads to tree decline events
  • Improving soil health can arrest tree decline if implemented within a key threshold timeline
  • The use of recycled water and its impacts on soil health need to be monitored over time

Based on these results it is clear that soil health is crucial to tree health and long-term viability. Therefore, tree health assessments need to be improved to include additional, objective parameters such as relative chlorophyll and soil health indicators. The development of data-driven tree health assessments would provide Urban Forest managers with the tools they need to understand the effects of extreme climate events and management decisions. These tools can further provide managers with the ability to accurately assess the efficacy of remediation methods in urban forestry. This document lays out the process of developing such a data-driven process and provides insights into the lessons learned in the development process.

Section 1: Introduction

Statement of the Problem

In 2015, City of Adelaide parks management staff noticed a severe tree decline event affecting a large portion of the northwest corner of Veale Gardens/ Walyu Yarta (Park 21) Adelaide Park Lands, one of Adelaide’s most premier and historic open space parks.

In October 2015, Matthew Daniel, Director of Global Urban Forest Pty Ltd (formerly Director of Tree Preservation Australia), conducted site inspections and soil testing at various sites throughout Adelaide. These investigations uncovered various plant and soil health issues around the Adelaide Park Lands from a variety of stressors (Box 1). Common stressors across the sites were compaction, poor soil nutrition and biological activity, water quality and encroachment of the tree protection zone (Fig. 1, 2). It is common in Urban Forestry that plant and soil health stressors originate from management, environmental conditions and urbanisation impacts. Veale Gardens was an example of this and chosen by the City of Adelaide as a site to investigate advanced management principles.

The Veale Gardens/Walyu Yarta Plant Health Care (PHC) Project 2015-2018, was developed as an extensive study into rapid tree decline throughout the park, led by Matthew Daniel. The study was designed to take a holistic approach of measuring multiple tree and soil health factors extensively on an annual basis. Over a four-year period, the response of 30 trees, each showing signs of decline, to Plant Health Care (PHC) remediation applications were tracked.

To understand tree health holistically and implement remediation methods, it is essential to include measurable tree and soil parameters. This study developed a detailed set of baseline soil and photosynthetic analytics that can be used and applied in practical terms by current Urban Forest management and provide future managers with benchmark data of methodology supported by measurables to better understand Urban Forest productivity. Four years of data from 2015 up to October 2018 identified the progress of soil remediation works at Veale Gardens/Walyu Yarta (Park 21). The soil analysed by independent laboratories consists of two major categories: soil chemistry (Environmental Analysis Laboratories (EAL) and soil microbiology (Agpath). Soil physical components such as compaction and moisture were measured in the field with specialised equipment. To determine the tree health response a hand-held photosynthesis meter and meta data collection tool called MultispeQ was used http://www.photosynq.org/instruments.

1.2: Impacts of Historic Climate Change and Management at the Research Site

Urban Forest canopy cover takes decades to establish a functional level of essential service. The impacts of extreme weather events on soil health in Urban Forestry are relatively unknown but must not be underestimated. The effect of extreme weather events such as drought on soil health that compounds into tree decline is an ongoing issue to address in Urban Forestry. The effects of extreme weather events on the Veale Gardens/Walyu Yarta study site can be seen in Figure 4. Soil health is more than just moisture content. The complexities of soil must be managed more effectively in Urban Forestry because this fundamental component of growing trees determines how long the natural assets will be viable and productive.

1.3: A Whole System – Plant and Soil Function

Plant and soil health must be defined and managed in Urban Forestry. It is not currently defined adequately throughout many industries including the Urban Forest industry. This project aims to assist in providing a practical framework to achieve a better understanding of soil health and define it in functional terms in relation to our urban environment, and then how that relates to providing a measurable essential service from individual trees. To understand this complexity the whole system including photosynthesis, plants and soil needs to be investigated.

1.4: Defining Soil Health

Soil Health can be defined “as the continued capacity of soil to function as a vital living ecosystem that sustains plants, animals and humans” – (www.nrcs.usda. gov/wps/portal/nrcs/main/soils/health/).

Chemical – understand total, available and exchangeable nutrient pools in soil in relation to the requirements of supporting plant material.

Physical – measure and understand physical soil structure and water holding capacity.

Biological – understand and measure the soil microbiome, a balanced set of functioning bacteria, fungi, protozoa, nematodes and mycorrhizae that develop symbiotic relationships with plants.

1.5: Relationship Between Soil Health and Climate Change in Urban Forestry

Localised extreme weather events caused by climate change, are occurring, being observed on the ground, experienced and documented all over the globe. A common and consistent driving factor associated with these extreme weather events is heat. To mitigate this heat in cities or highly urbanised areas, Urban Forests are being designed, installed and developed around the planet. This is a direct response to urbanised areas getting hotter and described as the Urban Heat Island Effect (UHIE). The concept of mitigating UHIE with vegetative growth to reduce the temperature relies on the plant and soil functioning effectively. It is often assumed soil health is a given and water is the only consideration regarding soil health. Water is a key component, essential to soil health and soil health is critical to plant health, although soil health is more than just water availability.

The effects to Soil Health from heat waves and drought, both short and long have a residual sinister potential to cause tree decline years after the extreme event has occurred. The Millennium Drought and SA Government response in transitioning to GAP water to maintain the Adelaide Park Lands is an example of this and investigated in this study. This intensive study of Veale Gardens/Waylu Yarta aims to understand the change in ecosystem function from a plant and soil health perspective. Through a process of:

  • Defining soil health
  • Measuring the components – developing baselines and monitor changes overtime
  • Intervening with PHC focused soil management principles and practices that address chemistry, physical structure and biology
  • Develop an understanding of how the soil health adjustment have occurred, and if successful, how to continue proactive management of the improved conditions.

An Urban Forest is a sum of its parts, all plants in both public and private realms make up the Urban Forest as a whole. Canopy cover in an Urban Forest provides a potential capacity to mitigate heat with microclimate production. This microclimate supported and stimulated by evapotranspiration, comes from soil and plants.

A result of drought is reduced plant and soil health. It would be fair to say that most would assume this poor plant and soil health resulting from drought could be visualised as “brown grass and trees”. If you ask those same people what caused the “browning off” the response is commonly “Lack of water”. The assumption that the reintroduction of water into the system after a drought resolves any risk to environmental decline, is oversimplified and short-sighted.

These types of extreme droughts that trigger a collapse in ecosystem productivity do not exclude the Urban Forest. The Millennium Drought in Australia that developed into the 2000’s and declared over in 2010 is one such drought. In Adelaide, South Australia the Millennium Drought between 2005 and 2010 became the period in which a compounding amount of plant and soil stressors culminated into a tree decline event in Veale Gardens/ Waylu Yarta, although the effects continued years after the drought had finished and soil moisture returned, because soil health had been damaged in the park.

It is important to consider the long term and compounding effects of severe drought to the Urban Forest ecosystem and how that relates to soil health.

Disclaimer

Note: Any soil analysis or observation taken and recorded in this report will only ever capture the status of the soil and vegetation on that day. It must be emphasized that changes of sometimes considerable magnitude can be expected in response to normal seasonal and extreme weather responses and some management actions. This means that outcomes as anticipated with the available evidence collated may be unpredictable, so regular recording of the soil and vegetation using a Soil Health Card or VSA and VTA or TREE HEALTH CALCULATOR 1.0 is essential, with the taking of photos always encouraged to record a history of change. G.U.F warrants that the methods adopted in its programs are largely a practical application of many years of experience in Plant Health Care together with scientifically verified management directives and measures through numerous sensors which are continually improved as new research findings come to hand.

Words & Images | Matthew R. Daniel – Global Urban Forest, Dr Dan Teravest – Oursci – Michigan, Usa, Veale Gardens/Walyu Yarta – (Park 21) – Part 1

For more information visit http://globalurbanforest.com.au

February 22, 2019 / by / in