Understory vegetation removal significantly affected soil biogeochemical properties in forest ecosystems

Understory vegetation plays a crucial role in mediating the natural development of forest ecosystems. The removal of understory vegetation, as a common forest management practice, may have a significant impact on soil properties. However, a global perspective on how understory removal might affect soil biogeochemical properties is still lacking. To fill this knowledge gap, we performed a meta-analysis with 2059 observations collected from 71 peer reviewed publications to evaluate the effects of understory vegetation removal on soil carbon (C), nitrogen (N), phosphorus (P), potassium (K), and microbial biomass. We found that (1) removal of the understory significantly increased soil nitrates (NO3−) concentration by 6.5 %, but decreased the stocks of C and N, the concentrations of N, available K (AK) and microbial biomass C (MBC), and fine root biomass by 19.4, 15.1, 7.9, 19.9, 13.5 and 32.2%, respectively; (2) mycorrhizal association significantly mediated understory removal effects on soil organic C (SOC) and dissolved organic C (DOC) concentrations, and soil pH, while canopy type had a significant impact on the effects of understory removal on soil K, AK, NO3−, MBC concentrations, C:N ratio, and soil pH; (3) soil depth had a negative impact on the effects of understory removal on SOC, AK, ammonium nitrogen (NH4+) concentrations, and soil moisture; and (4) mycorrhizal association, soil depth, slope, forest stand age, elevation, and MAT were the most important moderator variables. Our results suggest that the removal of understory vegetation generally have negative effects on soil biogeochemical properties, and that managing understory vegetation is important for promoting the healthy development of forest ecosystems.