2.5 Spatial scaling pattern analyses
Two typical spatial scaling patterns were analyzed, including TAR and
DDR. The community richness (alpha-diversity) and Bray-Curtis community
similarity (beta-diversity) were respectively used as diversity metrics
for TAR and DDR analyses. The slope coefficients between log-transformed
diversity indices and log-transformed geographic area/distance were
calculated for TAR and DDR. Both the diversity indices of TAR and DDR
were extended to different diversity orders using Hill numbers, which
are a parametric family of diversity indices differentiated by the
parameter q (Chao, Chiu, & Jost,
2014). The extended TAR and DDR were respectively termed as
DARq and DDRq. The R package
“hillR”(Chiu & Chao, 2014)
(https://github.com/dajiang/hillR)
was used for both alpha- and beta-diversity indices calculation under
different diversity order q .
In addition, we also correlated the diversity metrics with environmental
heterogeneity to investigate how microbial spatial scaling patterns were
affected by environmental conditions. Here, the Euclidean distance based
on normalized environmental variables was calculated to represent the
environmental heterogeneity between different samples. All 19
environmental variables were included for environmental heterogeneity
calculation. The analysis, as well as TAR and DDR, were carried out for
the whole community, the abundant and the rare subcommunities.