Mechanisms for carbon and nutrient release and retention in beech forest gaps

Abstract

Field levels of soil microbial biomass C and N, determined by the chloroform fumigation-extraction method, showed no marked seasonal pattern in limed and unlimed gaps and the surrounding beech stand; average contents were 530, 532 and 674 kg microbial C ha −1 ; and 65, 68 and 87 kg microbial N ha −1 respectively. Liming increased microbial biomass in the stand but had no influence on the size of the microbial pool in the gap. The decrease in microbial biomass in gaps was attributed to a decline of ectomycorrhizal hyphae. Due to the absence of available carbon soil microbial biomass was not a significant nutrient sink following forest disturbance. In situ N mineralization at these sites could not be explained by fluctuations in microbial N. Laboratory measurements of CO 2 evolution from soil samples, which were in good agreement with field CO 2 measurements, indicated a decline in easily decomposable soil organic matter during the growing season. High metabolic quotients (μg CO 2 -C mg C mic −1 d −1 ) of the microflora in gaps indicated inefficient energy use