Evaluation of Nature-Based and Traditional Solutions for Urban Soil Decompaction

Abstract

Background: Urban forests play a significant role in mitigating the adverse effects of climate change by absorption of greenhouse gases and carbon sequestration. However, soil compaction caused by anthropogenic activities can be a major detriment to urban forest health. Method: Two potential nature-based soil decompaction solutions (addition of earthworms, nitrogen-fixing white clover cropping) were evaluated in combination with existing soil decompaction systems (vertical mulching, woodchip surface layer). Effects on soil quality (bulk density, organic matter, pH, estimated nitrogen release, cotton strip degradation, and earthworm counts) and tree health (diameter at breast height [DBH], canopy density, root dry mass) were then monitored over 3 years. Results: All decompaction treatments independently and in combination significantly reduced soil compaction and improved tree growth with little difference recorded between treatments. Over time, however, earthworm populations migrated from the treated decompacted soil into the surrounding untreated compacted soil, in turn, significantly improving soil quality allowing for enhanced root growth outside the treated area. Conclusion: A long-term, sustainable, nature-based solution exists for professionals involved in urban tree management to improve compacted soil quality and subsequent tree health.