City Trees is a premier publication focused on urban + community forestry. In each issue, you’ll learn how to best manage the trees in your community and more!
Issue link: https://read.dmtmag.com/i/723399
32 City Trees Where Can SPR Be Used? SPR reduces soil compaction and thus associated chal- lenges such as poor drainage. It was originally designed to treat that familiar archetype of degraded urban soil that is left behind after land development. This is soil that is stripped of surface horizons (O and A horizons) and graded to facilitate building, traffic movement, or surface drainage. These soils are typically extremely compacted and compaction can run deep. SPR is ideal for alleviating this compaction and creating conditions that can lead to long-term soil recovery. It is intended to apply to a large area, not just immediately around individual trees. For To the left of the sidewalk is a tree pit that is an excellent candidate for SPR. In spite of its reasonably generous size, the prognosis for trees planted in this area is poor unless soil quality is improved. The backhoe subsoiling technique allows for soil manipulation even in such confined spaces. Photo by Susan D. Day example, let's say an access road is being built for a com- mercial building and grading for the road has compacted the soil. Performance of roadside tree plantings could be enhanced by applying SPR the entire length of the road for the full width of the compacted area. For projects seeking SITES certification, SPR can be a useful restoration tool. The SITES voluntary certification program for land devel- opment requires that healthy soils be protected first and be restored if damage during construction is unavoidable. Implementing SPR What's involved and what can you expect? The proce- What sites are good candidates for SPR? What soil conditions does SPR NOT treat? Sites with compacted soils High or low soil pH Sites that will be reasonably protected from further compaction by vehicles or heavy pedestrian traffic Contamination by heavy metals or other pollutants Soils where topsoil has been stripped Poor drainage caused by impermeable layers below 24 inches Sites not currently occupied by large trees Undesirable soil texture