Abstract
Understanding the ecological processes that regulate microbial community assembly in different habitats is critical to predict microbial responses to anthropogenic disturbances and environmental changes. Rubber (Hevea brasiliensis) and Eucalypt (Eucalyptus urophylla) plantations (thereafter RP and EP) are rapidly established at the expense of forests in tropical China, greatly affecting tropical soils and their processes. However, the assembly processes of soil microbial communities after forest conversions remain unclear. We investigated soil microbial communities’ attributes and quantified the portion of deterministic assembly variation in two RP (a 3- and a 5-year-old) and two EP (a 2- and a 4-year-old) in Southern China. Shannon and Faith’s Phylogenetic α-diversity of both bacterial and fungal communities were higher in RP than in EP, regardless of plantation age or soil depth (0–50 cm). Bacterial and fungal community structure was significantly different among the four plantations. The dominant microbial taxa in RP closely tracked the availability of nitrogen, phosphorus and potassium (K) while those in EP were closely related to the high total K content. Microbial co-occurrence networks in RP were more modular than those in EP, as governed by more keystone taxa that were strongly dependent on soil available nutrients. Environmental filtering imposed by soil nutrients heterogeneity contributed a considerable portion (33–47%) of bacterial assembly variation in RP, but much less (8–14%) in EP. The relative contribution of environmental selection on fungal assembly was also greater in RP than in EP. Our findings suggest that in RP clear microbial community patterns exist with respect to soil nutrients, whereas in EP microbial community assembly patterns are more stochastic and variable. The large variation in soil microbial community assembly patterns in EP could lead to fragile and unstable microbial-soil relationships, which may be one factor driving soil degradation in EP.
Highlights
Understanding microbial assembly processes is a central goal in the field of microbial ecology, as it can reveal the fundamental rules for microbial taxonomic and phylogenetic structure across temporal and spatial scales [1,2,3]
Our findings suggest that in Rubber plantations (RP) clear microbial community patterns exist with respect to soil nutrients, whereas in Eucalypt plantations (EP) microbial community assembly patterns are more stochastic and variable
Soil pH value and content of soil organic carbon (SOC), P, available nitrogen (AN), available phosphorus (AP), Ca, Cu and Zn were higher in RP than those in the EP while K and Cl content was lower in RP compared to EP (p < 0.05, Figure S2)
Summary
Understanding microbial assembly processes is a central goal in the field of microbial ecology, as it can reveal the fundamental rules for microbial taxonomic and phylogenetic structure across temporal and spatial scales [1,2,3]. The stochastic processes, such as drift, dispersal limitation and birth and death, have been proposed to interact with deterministic processes during microbial assembly in various. The relative importance of deterministic versus stochastic processes in regulating microbial community structure can be highly variable across habitats. Soil microbiota is jointly shaped by the deterministic and stochastic processes under anthropogenic disturbances, such as fertilization [12], climate warming [11], and land use changes [10], the relative importance of these two processes is still unclear
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