Abstract
Changing quantity and quality of plant C input to soils under global change influences soil C cycling in terrestrial ecosystems. However, how soil CO2 emission responds to changes in C input remains poorly understood. A detritus input and removal experiment was conducted in a subtropical forest (Cunninghamia lanceolata) to investigate how aboveground and belowground litters affect soil respiration (RSoil). In this experiment, four treatments with three replicates were included, as follows: control (CK), litter removal (NL), root trenching (NR), and no C-input (i.e. litter removal combined with root trenching, NI). RSoil was measured for 4 years from 2011 to 2014. The mean annual CO2 effluxes in the NL, NR, and NI plots were lower (23.4%, 24.9%, and 38.8%, respectively) than those in the CK plots, suggesting that decreasing C input significantly decreased RSoil. Soil heterotrophic respiration (soil organic matter decomposed by microorganisms) accounted for 52.1% of RSoil, and aboveground recent litter decomposition and belowground autotrophic respiration (live roots and associated microorganism) contributed to 23.7% and 24.2% of RSoil, respectively. RSoil was significantly and positively correlated with soil temperature, but negatively correlated with volumetric soil moisture. The variation in RSoil was more explained by soil temperature than soil moisture, and the responses of RSoil to soil temperature and moisture were altered by C input manipulation. Annual RSoil rate was strongly and negatively related to the Gram-positive bacteria concentration and the ratio of Gram-positive to -negative bacteria. This study highlighted that aboveground recent leaf litter and belowground live roots and associated microbes had similar contributions to RSoil, and soil temperature and Gram-positive bacteria were the dominant factors controlling RSoil in a subtropical forest.
Published Version
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