Response of selected soil biological properties to stump presence and age in a managed subtropical forest ecosystem

Stumps are an important component of coarse woody debris in intensively managed forest ecosystems. However, the effect of stumps on soil biological properties is poorly understood. Therefore, the present work investigated soil microbial biomass C, soil respiration, potentially mineralizable N, and enzyme activities related to nutrient cycling (invertase, urease and acid phosphatase) in both bulk and stump soils with four different stump ages (stumps 5, 11, 20 and 27 years after tree cutting) in Chinese fir (Cunninghamia lanceolate Hook.) plantation ecosystems. The presence of stumps significantly enhanced invertase and acid phosphatase activities, but reduced soil microbial biomass C and urease activity. However, the effect of stump presence on soil respiration and potentially mineralizable N had an inverse pattern. Additionally, the effect of stump presence on soil biological properties depended upon stump age. Soil respiration and invertase activity were highly and positively related to stump presence, but negatively related to stump age and soil pH. On the other hand, soil microbial biomass C and urease activity showed inverse results. Acid phosphatase activity was highly and positively related to soil total P and organic C, but negatively related to Olsen-P. Potentially mineralizable N was negatively related to NO3-N content and stump age. Using variation partitioning, stumps and soil chemical variables together explained 88.3% of the total variance in soil biological properties. When either stumps or soil chemical variables was adjusted, soil chemical properties and stumps explained 30.8% and 13.7% of the total variance, respectively. These results suggest that soil chemical properties should be considered when assessing the effect of stumps on soil biological properties. (C) 2012 Elsevier B.V. All rights reserved.