In our results, only microbial respiration under GBH was
positively correlated with total soil C. Contrary to DOC, total
soil C refers to the sum of various organic carbon pools,
including labile C and recalcitrant C. Microbes generally
used the labile C firstly, which explained why the relationship
between microbial respiration and total soil C were not
significant under CK and GB.
3.4. Implications for global carbon cycling
Our study found the responses of microbial respiration
to plantations were different in different soil layers and
topographies, which means that response of microbial
respiration to plantation treatments depended on soil
properties. Decreased soil respiration under plantation is
somewhat counterintuitive, but is good to mitigate global CO2
emission. However, an increase in soil respiration under
plantation does not necessarily mean a decrease of soil
carbon storage (Xu et al. 2013; Wang et al. 2015). After 12
years plantation, both GB and GBH significantly increased
soil carbon concentration in 0–20 and 20–40 cm, which
led to a net soil C storage. This suggested plantation is a
key measure to enhance soil C sequestration and mitigate
global CO2
emission especially for the soil with low initial
soil carbon content or bared soil.