4.4 Discerning drivers of abundant and rare community assembly
Revealing the factors affecting the relative influences of deterministic
and stochastic ecological processes is important for deeper
understanding of community assembly (Tripathi et al., 2018). In this
study, we found that forest area had a greater association with the
abundant subcommunity assembly than other factors, while TN was more
closely correlated with the rare subcommunity assembly (Table 1). The
strong associations of βNTI values of abundant and rare subcommunities
with differences in forest area and TN, respectively, further suggesting
that forest area and TN were the key factors shaping the stochastic and
deterministic assembly for abundant and rare subcommunities,
respectively (Fig. S5). In recent decades, deforestation is one of the
most visible land use changes in the Yarlung Tsangpo River basin (Hao et
al., 2021; Harris, 2010). Deforestation, combined with climate-induced
soil erosion are the main sources of suspended sediment in the river flow
(Shi et al., 2018; Wang et al., 2020a). On the one hand, soil erosion
can transfer substantial amounts of nutrients (e.g., TN and
NH4-N) into the fluvial sediments to support bacterial
growth (Quinton et al., 2010). More importantly, surrounding soil
derived bacteria inputs can directly affect bacterial composition and
diversity in the fluvial sediments (Crump et al., 2012; Ruiz-González et
al., 2015). Thus, our findings reveal the important linkage between land
use types and community assembly processes, which might influence the
microbial diversity and fluvial sediment ecosystem processes. This is an
important issue in need of further research. Future work to explore the
precise role of land use types for sediment bacterial community assembly
processes, providing scientific support for environmental regulation and
ecological security maintenance in the Yarlung Tsangpo River basin is
needed.