The impact of landslides on chemical and microbial properties of soil in a temperate secondary forest ecosystem

In forest ecosystems, landslides are one of the most common natural disturbances, altering the physical, chemical and microbial characteristics of soil and thus further altering ecosystem properties and processes. Although secondary forests comprise more than 50% of global forests, the influence of landslides on the soil properties in these forests is underappreciated. Therefore, this study investigates the influence of landslides on the chemical and microbial nature of the soil. Study of these modifications is critical, as it provides baseline evidence for subsequent forest revegetation. We selected four independent landslides and adjacent secondary forest stands as references in a temperate secondary forest in northeastern China. Soils were obtained from each stand at 0–10 cm and 10–20 cm depths to determine chemical and microbial properties. Soil total carbon (TC), total nitrogen (TN), nitrate (NO3−-N), available phosphorus (P), microbial biomass carbon (MBC), microbial biomass nitrogen (MBN), microbial biomass phosphorus (MBP) and phenol oxidase, exoglucanase, β-glucosidase, N-acetyl-β-glucosaminidase, L-asparaginase and acid phosphatase activities were 29.3–70.1% lower at the 0–10 cm soil depth in the landslide sites than at the secondary forest sites, whereas total phosphorus (TP) and ammonium (NH4+-N) were unaffected by the landslides. N-related enzymes, N-acetyl-β-glucosaminidase and L-asparaginase were reduced by more than 65% in the landslide sites, consistent with the decrease in nitrate concentration at the same 0–10 cm depth. At a depth of 10–20 cm, the variations in the soil properties were consistent with those at the 0–10 cm depth. The results demonstrated that soil chemical and microbial properties were significantly disrupted after the landslides, even though the landslides had occurred 6 years earlier. A long time is thus needed to restore the original C and nutrient levels. In temperate secondary forests, soil TC and TN contents were found to be more suitable for estimating the state of soil restoration than soil TP content.