PNNL

Abstract

Although there are many studies on assembly mechanisms of microbial communities, we still know little about how press (long-term) disturbance influences phylogenetic turnover of soil microbial communities responding to pulse disturbance. Here, we investigated phylogenetic spatial turnover (based on DNA) of soil prokaryotic communities after long-term nitrogen (N) deposition and temporal turnover (based on RNA) of communities responding to pulse by conducting short-term rewetting experiments. We found that at a high phylogenetic level, moderate N addition increased ecological stochasticity and led to an increase in phylogenetic diversity. In contrast, a large N addition slightly increased homogeneous selection and led to decreased phylogenetic diversity. Examining the system with higher phylogenetic resolution revealed a moderate contribution of variable selection across the whole N gradient. We also found distinct phylogenetic turnover patterns of prokaryotic communities in low and high N soils under simulated moisture pulse. High N soil had a higher rate of phylogenetic turnover across short phylogenetic distances and revealed a significant changes in community composition through time; these results point to a more important role of deterministic processes under high N. Taken together, our results indicate that long-term N input influenced spatial turnover of microbial communities, but the dominant community assembly mechanisms differed across N deposition rates. We further revealed an interaction between press and pulse disturbances whereby deterministic processes were particularly important following pulse disturbance in high N soil.