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SCIENCE & conservation

Urban forests and ecosystem services - Current projects

Bryant Scharenbroch Carbon Study Soil, Tree Core Samples 079

For each project, a brief description is given with the names of lead staff members and collaborators. Names with no institutional affiliation indicate Arboretum staff; names of external collaborators have their affiliations in parentheses.

Chicago Urban Forest Study
Urban ecosystem
Urban soil



Chicago Urban Forest Study. Led by scientists at The Morton Arboretum, this is a comprehensive multiyear study that examines carbon storage by urban forests, the resilience of urban trees to climate fluctuations, and standardizing the diagnosis of urban site conditions for the planting of tree species most likely to succeed. This study is composed of three parts. B. Scharenbroch, R. Fahey

Potential of urban forests to store carbon. Carbon dioxide emissions from burning fossil fuels are one of the leading causes of climate change. Plants naturally absorb carbon dioxide through photosynthesis. Soils also can absorb carbon dioxide from the atmosphere and store it, in a process that involves photosynthesis, plant respiration, decomposition, and the activity of soil fauna and microbes. However, the amount of carbon stored in urban soils is largely unknown. Researchers are measuring carbon storage and turnover in soil, litter, and vegetation across Chicago’s urban ecosystem to build models that predict carbon storage in urban ecosystems. B. Scharenbroch, R. Fahey

Effect of climate change on tree growth and health of the urban forest. A management goal for urban forests is to increase resiliency, so a forest is better able to withstand the effects of climate change and cope with the diverse and often challenging site conditions trees and shrubs face in urbanized areas. This study investigates the response of trees in different urban land-use contexts to climatic changes, especially their response to extreme droughts, which are predicted to increase in frequency with climate change. Responses will be assessed using dendrochronological data collected from points sampled in 2010 for a regional tree census, Urban Trees and Forests of the Chicago Region (Nowak et al.2013). Data on urban vegetation and soils are also being collected across the region in order to develop management techniques to maintain healthy urban and community forests in a changing climate. E. Bialecki, R. Fahey, B. Scharenbroch

Getting the right tree in the right place: developing an urban site index. Though tree species naturally can live for decades or even hundreds of years, most trees in downtown areas live only seven years. Most urban tree problems are a result of soil and site constraints. A standardized method of evaluating urban site conditions would guide the planting of the types of trees most likely to succeed in each site’s conditions. With collaborators, The Morton Arboretum Soil Science lab is developing a system to evaluate site and soil conditions and predict tree condition and growth in 400 plots across 10 cities. This urban site index will save communities money by helping them plant the right tree in the right place for a healthier, more sustainable urban forest. B. Scharenbroch, R. Fahey; A. Siewert and S. Miller (Ohio DNR); N. Bassuk (Cornell University); S. Raciti, L. Hutyra (Boston University); R. Harper (University Massachusetts-Amherst); R. Pouyat, I. Yesilonis (USDA Forest Service Northern Region); S. Day (Virginia Tech); K. Fite (Bartlett Tree); L. Purcel (Purdue University); L. Werner, R. Hauer (Univeristy of Wisconsin–Stevens Point); G. Johnson (University of Minnesota)


Modeling urban forests to support landscape conservation, green infrastructure planning, and climate change resilience. In 2010, The Morton Arboretum commissioned a tree census of Chicago’s regional forest, in cooperation with the USDA Forest Service. Data were collected from over 2,000 plots across the seven-county region to assess forest structure and composition. In 2007, a similar census had been performed on plots in the city of Chicago. These censuses produced a wealth of data that is valuable to regional planning but has not yet been analyzed. For example, data analysis for the general report indicated that two-thirds of the trees in the region are invasive, subject to major disease and insect damage, or considered undesirable for urban landscapes. Forest composition, structure, and ecosystem services provided by trees will be analyzed and potential future condition will be forecasted. These data will provide a more detailed description of our current urban forest and enhance our ability to project forest scenarios into the future. They will also be used to guide the Chicago Regional Trees Initiative (see p.51), a multi-institutional collaborative effort to develop a regional planning strategy that will shift the balance toward a more desirable and resilient species composition for a healthier urban forest. R. Fahey, G. Watson, J. Dwyer, N. Cavender, L. Darling, L. Scott; M. Johnston (The Field Museum); L. Brand, C. Swanston (USDA Forest Service Northern Institute of Applied Climate Science); D. Nowak (USDA Forest Service Northern Research Station); S. Maco, S. Hirabayashi (Davey Tree Expert Company); B. Toomey (The Nature Conservancy)

Using remotely sensed data to estimate the value of urban forest. Remotely sensed data analyzing forest structure can be quickly collected for large areas using satellites or special aircraft, while ground-based data collection is more time-consuming and often more expensive. Using publicly available data from airborne LiDAR, a type of active remote sensing, the canopy structure of the Chicago region urban forest is being assessed and estimates are being made of biomass and carbon storage. These will be compared to data collected on the ground, including data from the 2010 Chicago-region urban tree census, to help improve methods used in estimating the value of the urban forest by determining if remotely sensed data can be used to link structural complexity of urban forests to functional value. R. Fahey; M. Johnston (The Field Museum); J. Jung (Purdue University)


Biology and ecology of highly modified urban soils. In urban areas, natural soil has often been stripped away, layers mixed, and substrates added during building and development. Soil biology is a key component of urban forest health, but we know little about the biology and ecology of highly modified urban soils. Morton Arboretum scientists are working to describe this ecology. This information can help maximize soil health, leading to healthier trees and shrubs for communities to enjoy. B. Scharenbroch

Pavement alternatives allow soil to do its job. Rainwater and snowmelt filter through healthy soils filled with organic matter before reaching streams and lakes. Impurities stay behind in the soil, keeping streams and lakes clean for drinking water, fishing, and swimming. However, urban areas have a large proportion of impermeable surfaces, such as pavement, that rainwater cannot penetrate. This means rainwater washes high amounts of fertilizers and other pollutants into storm sewers or directly into streams and lakes. This project collects data on the effects of trees, permeable pavement, and bioswales on water quality by monitoring stormwater runoff on a permeable-pavement parking lot at The Morton Arboretum and an impermeable parking lot nearby. The parking lot at the Arboretum is one of the largest projects in the Midwest to use permeable pavers, bioswales, and other best management practices. Evaluating its effectiveness to mitigate stream and lake pollution will help understand how these practices can be improved upon and more widely implemented. B. Scharenbroch, K. Dreisilker

Determining a role for trees in removing toxic lead from contaminated sites. Lead is a main contaminant of hazardous waste sites in the US. Plants can be used to degrade, extract, or immobilize contaminants in soil and water, a process known as phytoremediation. However, very little is known about trees’ effectiveness in this process. The Morton Arboretum’s soil science lab is studying the ability of urban tree species (London planetree, Platanus × acerifolia, and white willow, Salix alba) to accumulate lead in their tissues. An herbaceous species and known hyper-accumulator of lead, mustard greens (Brassica juncea), is being evaluated for comparison. Students from Downers Grove North High School who are participating in the Exemplary Student Research Program at Argonne National Laboratory are helping to collect and analyze data for this project. B. Scharenbroch

Using biochar to improve urban soils. Biochar, a waste product from the burning of biomass, has tremendous potential as a soil amendment for urban tree care. Because biochar has a high affinity for nutrients and long persistence, it may be a superior organic amendment for urban soil restoration. Urban trees generate a great amount of woody waste that could potentially be turned into biochar for soil improvement. This research aims to take a comprehensive look at biochar for urban tree care. Multiple projects are underway comparing biochars to other amendments in greenhouse, tree nursery, and urban landscape settings. Biochar application technologies include top-dressing, drilling, and air-cultivation techniques. Various biochars, application rates, and mixes are being assessed. Soil sampling and tree health and growth assessments are performed annually on these projects. B. Scharenbroch, K. Fite (Bartlett Tree Research Laboratories)

Using biosolids for urban soil improvement. Biosolids are the nutrient-rich organic materials from the treatment of sewage sludge. Land application of biosolids reduces pressure on landfills and also may improve soil fertility and stimulate plant growth. Biosolids may have potential for managing fertility of degraded urban soils with trees. However, a limited body of knowledge exists for this area of study. We are performing research to determine the effects of biosolids on urban soil properties and tree growth and health. We are also considering the socioeconomic advantages and disadvantages of using biosolids for managing urban trees. B. Scharenbroch, L. Hundal (Metropolitan Water Reclamation District of Greater Chicago)

Improving urban soil with aerated compost tea. Aerated compost tea is made by putting compost in water with addition of oxygen. Its use for restoring degraded urban soils is increasing. Compost tea is advocated for nutrient retention and mineralization; building soil structure and decreasing compaction; increasing aeration and water-holding capacity; increasing tree rooting depth and decreasing water use; detoxifying soil and water; and suppressing disease. However, data from controlled, replicated experiments documenting its effects on trees, soil, and the environment are scarce; all evidence for its effectiveness comes from practice. Arboretum scientists are evaluating compost tea’s effectiveness in increasing soil quality and promoting tree growth and health. Different compost tea recipes and application rates are being assessed and numerous soil and tree response variables are being measured. B. Scharenbroch