Soil Simple Sugars And Amino Acids In An Evergreen Forest Of Ailao Mountains

The objective of our research is to address the following questions: What were the seasonal variations of soil simple sugars and total free amino acids in a montane evergreen broad-leaved forest? What were the effects of above-ground litterfall, below-ground root exudates and root debris, and plant nutrient uptake on soil simple sugars and total free amino acids? To what extent will soil simple sugars and total free amino acids influence soil microbial activity?The experiments were conducted with a split-plot design in a montane evergreen broad-leaved forest of the Ailao Mountains, southwest of China. We employed girdling, litter exclusion and root trenching to separate the effects of above-ground input, below-ground input, and plant nutrient uptake on simple sugars and total free amino acids from October 2004 to August 2005. Four replicated control and tree-girdling plots of 20 x 20 m were established in the research area of Ailao Station for Forest Ecosystem Studies. Four subplots of 2 x 3 m within each plot were randomly assigned as secondary control, litter exclusion, root trenching, and litter exclusion plus root trenching.Our results were:1 There were significant seasonal variations in plant litterfall, soil total free amino acids, soil simple sugars and soil respiration.2 Above-ground litterfall input had significant influence and below-ground root exudates and debris had no influence on the concentration of soil simple sugars. The influence of above-ground litter input on soil simple sugars was much more pronounced than that of below-ground inputs of root exudates and debris.3 Neither above-ground litterfall nor below-ground root exudates and root debris had significant effects on the concentration of soil total free amino acids. The seasonal change of the concentration of total free amino acids in the soil might be explained by variations in soil microbial activity and plant uptake of low weight molecular organic nitrogen. 4 There was no correlation between the concentration of simple sugars in the soil and soil microbial activity, suggesting that microbial growth was not limited by the availability of soil labile organic carbon in the montane evergreen broad-leaved forest.