Effects of grassland converted to cropland on soil microbial biomass and
community from agro-pastoral ecotone in northern China
Abstract
Grassland converted to cropland affected soil physical and chemical
properties and soil microbes. However, these parameters were often
studied separately and their combined responses to grassland reclaim
remain unclear. To evaluate the impacts of grassland cultivation on soil
microbial communities (based on phospholipid fatty acids, PLFAs) and the
links between soil microbes and physicochemical properties, we performed
a paired field experiment following the conversion from native grasslands
to 30-60 year-old cropland in the agro-pastoral ecotone of northern
China. The concentrations of soil organic carbon (SOC), soil total
nitrogen (STN) and the soil microbial biomass consistently decreased
with grassland conversion to cropland. Grassland conversion also
significantly decreased the relative abundance of bacterial and fungal
PLFAs and the fungal to bacterial ratio (F:B) at 0-10cm soil layer, but
those parameters remained unchanged below 10cm soil layers. Grassland
conversion affected the microbial biomass mainly through soil C and N
content rather than soil pH, moisture and aggregation. These findings
revealed that cultivation-induced soil nutrient loss may enhance soil
microbe depletion and affect microbial community assembly (shifts in
fungi, AMF, Act, GP, and GN bacteria). This implies that conversion of
grassland to cropland should be avoided because of the risk of
degradation of soil nutrient and microbes.