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Issue link: http://read.dmtmag.com/i/143980
(Quercus coccinea), and 7 Ginkgos (Ginkgo biloba). To prepare planting areas, pavement was removed and curbs were installed to border the street. Soil was brought in to fill the void left by the pavement and elevate the ground in the planting space to the top of the new curbs. Half of these plots were treated with SPR, and the other half left as is. All plots had trees planted according to the ANSI A300 Part 6 planting standard. The two treatments will be evaluated for differences in tree growth and soil properties. Looking at Outcomes My work with Dr. Day on the Arlington project will focus on evaluating the potential benefits of SPR for stormwater management as well as its effects on soil carbon in an urban setting. The latter will build on research with SPR conducted by PhD candidate Yujuan Chen and M.S. student Rachel Layman at Virginia Tech's Soil Rehabilitation Experiment Site (SRES) that focused on tree growth and soil carbon dynamics. This included measuring greenhouse gas exchange and how much organic carbon from compost and roots was stored in soil aggregates and other carbon pools. Yujuan's study found that urban soil rehabilitation increased total organic carbon and microbial biomass carbon in subsoil four years after rehabilitation; further info about her study can be found at the VT Urban Forestry Gateway: urbanforestry.frec.vt.edu. Arlington urban forester Vincent Verweij and Dr. Susan Day discuss the new SPR project. Photo by David Mitchell www.urban-forestry.com The plan is to collect data for five years. The qualities that we will analyze concerning stormwater and carbon storage include: soil bulk density and saturated hydraulic conductivity, total organic carbon and carbon made up by microbial biomass, size distribution and stability of soil aggregates, soil texture, and temperature fluctuation patterns in the soil. You may wonder why soil temperature is worth measuring when thinking about stormwater. Stream temperature is important for some species of wildlife because oxygen is not held in warm water as easily as in cooler water. Recent research at Virginia Tech also suggests that warm water may be more likely to cause soil erosion than cool water. Finally, temperature plays an important role in how carbon is cycled in the soil, influencing long-term sustainability. We hope that the SPR technique will improve soil characteristics such as infiltration and gas exchange and therefore allow tree roots to colonize higher volumes of soil. This would allow for larger trees to grow in urban areas. More large trees would have stormwater benefits but also a suite of benefits associated with shade and beauty. Virginia Tech is looking for more real-world opportunities to evaluate the Soil Profile Rebuilding technique. Please contact Susan Day (sdd@vt.edu) or me (dmitche5@vt. edu) if your city would like to be involved. Dr. Day points out ongoing compaction in one research plot with a bus stop. Photo by David Mitchell 9