Shifting sources of soil labile organic carbon after termination of plant carbon inputs in a subtropical moist forest of southwest China |
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Authors: | Feng Wenting Schaefer Douglas A Zou Xiaoming Zhang Min |
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Institution: | (1) Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, 88 Xuefu Road, Kunming, 650223, Yunnan, People’s Republic of China;(2) Institute for Tropical Ecosystem Studies, University of Puerto Rico, PO Box 70377, San Juan, Puerto Rico 00936-8377, USA;(3) Department of Tea Science, Zhejiang University, 268 Kaixuan Road, Hangzhou, 310029, Zhejiang, People’s Republic of China;(4) Earth and Environmental Science, University of Pennsylvania, 240 South 33rd street, Philadelphia, PA 19104-6316, USA |
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Abstract: | Labile organic carbon (LOC) is a critical component of soil organic carbon (C) because of its intimate association with soil
heterotrophic respiration and role in the decomposition of resistant soil organic matter. In a subtropical moist evergreen
broad-leaved forest of southwest China, we examined changes of LOC and its potential turnover time, microbial biomass C (MBC),
and soil microbial activity of the organic and the 0–10 cm mineral soil layers with aboveground plant litter and belowground
root treatments. In February of 2004, removal of organic layer, root-trenching, and tree-girdling treatments were applied
alone and in combination to manipulate plant-C inputs. In 2006, root-trenching and tree-girdling treatments did not significantly
change LOC in the organic layer. In the 0–10 cm mineral soil layer, LOC increased substantially due to tree-girdling treatment,
especially in the plots of tree-girdling and the combinations of three treatments, but this increase was absent in 2007. Soil
MBC in these two layers generally did not change markedly after plant-C inputs manipulations except significant increase under
tree-girdling treatment in 2006. The potential turnover times of LOC increased in all plots with the plant-C inputs manipulations.
The lack of influence of plant-C inputs manipulations on LOC pools is likely due to high total soil organic C here, while
insignificant changes of MBC suggest the soil microbes are not C limited in this forest. The changes of the potential turnover
time of LOC imply that the sources of LOC have been shifted from fresh plant litter or root exudates to old soil organic C.
Our results suggest that LOC recently derived from plants is preferred by microbes when available, but microbes can also use
LOC from soil organic matter when fresh plant C is not available. |
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