Fig. 3 Compositions of microbial communities along
anthropogenic disturbance gradients in the river ecosystems of Qinling
Mountains. Non-metric multidimensional scaling (NMDS) ordination based
on Bray-Curtis dissimilarity showing microbial community variation in
water (a: autumn, b: spring) and sediment (c: autumn, d: spring) samples
under
different land-use types.
We used Mantel’s test to determine the impacts of environmental factors
and land-use types on microbial community composition in the study area.
NH4+-N, Cond, T, TN, and
NO3--N
showed
significant correlations (P < 0.01, Mantel’s r> 0.1) with microbial community composition in water. N and
P contents increased with an increase in the proportion of agricultural
land; however, both elements tended to decrease with an increase in the
proportion of forest land, which further affected microbial community
composition. In addition, the proportions of agricultural land, forest,
and grassland areas were significantly correlated (Mantel’s r> 0.2, P < 0.01) with sediment microbial
community composition (Fig. 4). Based on results of microbiota community
composition analyses in river water and sediment over the two seasons,
different land-use types had considerable impacts on microbial community
composition in river water and sediment (Fig. S5a-b).