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Bacterial diversity and community structure; barcoded-pyrosequencing; copiotroph/oligotroph model; natural forest soils; soil bacterial co-occurrence patterns
Abstract:
Background and aims The types of natural forests have
long been suggested to shape below-ground microbial
communities in forest ecosystem. However, detailed
information on the impressionable bacterial groups and
the potential mechanisms of these influences are still
missing. The present study aims to deepen the current
understanding on the soil microbial communities under
four typical forest types in Northeast Asia, and to reveal
the environmental factors driving the abundance, diversity
and composition of soil bacterial communities.
Methods Four forest types from Changbai Nature Reserve,
representing mixed conifer-broadleaf forest and
its natural secondary forest, evergreen coniferous forest,
and deciduous coniferous forest were selected for this
study. Namely, Broadleaf-Korean pine mixed forest
(BLKP), secondary Poplar-Birch forest (PB), Spruce-
Fir forest (SF), and Larch forest (LA), respectively. Soil
bacterial community was analyzed using bar-coded pyrosequencing.
Nonmetric multidimensional scaling
(NMDS) was used to illustrate the clustering of different
samples based on both Bray-Curtis distances and
UniFrac distances. The relationship between environmental
variables and the overall community structure
was analyzed using the Mantel test.
Results The two mixed conifer-broadleaf forests (BLKP
and PB) displayed higher total soil nutrients (organic
carbon, nitrogen, and phosphorus) and soil pH, but a
lower C/N ratio as compared to the two coniferous
forests (SF and LA). The mixed conifer-broadleaf forests
had higher alpha-diversity and had distinct bacterial
communities from the coniferous forests. Soil texture
and pH were found as the principle factors for shaping
soil bacterial diversity and community composition.
The two mixed conifer-broadleaf forests were associated
with higher proportion of Acidobacteria,
Verrucomicrobia, Bacteroidetes, and Chloroflexi. While
the SF and LA forests were dominated by Proteobacteria
and Gemmatimonadetes.
Conclusions Different natural forest type each selects
for distinct microbial communities beneath them, with
mixed conifer-broadleaf forests being associated with the
low-activity bacterial groups, and the coniferous forests
being dominated by the so-called high-activity members.
The differentiation of soil bacterial communities in natural
forests are presumably mediated by the differentiation
in terms of soil properties, and could be partially explained
by the copiotroph/oligotroph ecological classification
model and non-random co-occurrence patterns.
