grassland such as exclusion of grazing has been considered to increase
aboveground plant diversity and soil fertility. However, knowledge on the
effect of long-term exclusion of grazing on soil bacterial community structure
and diversity is not well understood. The two sites were selected in the Inner
Mongolian grassland, i.e., one fenced
off since 1979 (UG79) and the other continually grazed by sheep (FG) all along.
Soil microbial biomass was measured using fumigation method and bacterial
community structure and diversity were assessed using methods of Denaturing
Gradient Gel Electrophoresis (DGGE) and clone library. Results showed that the
UG79 soil had significantly higher microbial biomass carbon and nitrogen compared
with the FG soil. There was a clear separation in soil bacterial community
structure, but not in bacterial diversity between the two sites. Moreover, 55
clones from the UG79 soil and 56 clones from the FG soil were selected and
sequenced. Phylogenetic analysis of all clone sequences indicated that
bacterial communities were dominated by the groups of Actinomycetes, Proteobacteria and Bacteroidetes, but there were no
significant differences in bacterial diversity between the two sites,
consistent with the results obtained from DGGE. The results highlighted that
although long-term exclusion of grazing increased soil microbial biomass, but
it did not harbor higher bacterial diversity compared with freely grazed site.
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