| Coastal wetlands play an irreplaceable role in carbon sink formation,climate regulation and biodiversity maintenance.In recent years,coastal wetlands are suffering the land use changes such as alien plants invasions and artificial reclamation.Spatina alterniflora invading bare flat,and then converted into shrimp ponds,and the conversion of mangrove forests into shrimp ponds were the two main habitat changes ways in China.As the main mediators of biogeochemical functions in coastal wetland ecosystems,microbial play an important role in the biogeochemical cycles of elements and ecosystem functions regulation.In this paper,the soil samples were collected from the bare flats,S.alterniflora marshes and shrimp ponds in four coastal provinces and one city in the southeastern China,and also collected from the mangrove and shrimp ponds in three provinces.We studied the effects of the habitat changes on sediment microbial community assembly,microbial network complexity or stability,and the maintenance mechanism of microbes on multifunctionality,and also exploried the difference in community assembly and ecological role of rare and abundant taxa.The paper also focused on the effects of sulfate concentration on sediment microbial diversity,community assembly processes and network relationships in shrimp pond.The results are as follows:(1)The conversion of mangrove forests to shrimp ponds altered the sediment microbial community composition,assembly,and networks.This land use change restricted the movement of microbial by creating a closed system,thus increasing community turnover.Moreover,following this conversion,the microbial diversity decreased and the major driving mechanisms shaping microbial community assembly shifted from deterministic processes in mangrove forests to stochastic processes in shrimp ponds.Furthermore,microbial networks in the shrimp pond sediments were destabilized,while those in mangrove forest sediment were stable.The results of the null model analysis suggest that microbial community assembly may shift from stochastic to deterministic after ten years of habitat transition.(2)Habitat conversion from bare flat to S.alterniflora and then into shrimp ponds altered the α-diversity,β-diversity,the intensity of distance decay relationship,microbial community assembly and microbial network relationship.S.alterniflora invasion increased alpha diversity,led to microbial homogenization,increased the effect of stochastic ratio on community assembly,and promoted species coexistence.Artificial reclamation for shrimp ponds reduced microbial richness,led to community heterogeneity,increased the effect of deterministic on community assembly,and reduced the complexity of microbial network.Overall,S.alterniflora invasion and artificial reclamation resulted in a stronger correlation between microbial similarity and spatial distance by limiting microbial migration rates.Furthermore,habitat changes alterd species coexistence by mediating the relative importance of stochastic to community assembly.(3)Abundant and rare taxa in shrimp ponds showed various community assembly process and differences in response to environmental conditions.Deterministic processes dominate the assembly of rare taxa,while community assembly of abundant taxa is driven primarily by stochastic.Abundant taxa have broader environmental adaptability than rare bacterial.Furthermore,we propose a conceptual framework to describe microbial communities in response to changes in sulfate concentrations in coastal shrimp systems.Sulfate content is an important environmental factor affected microbial richness,community assembly,and microbial network.Specifically,increasing sulfate content decreased bacterial diversity,stochastic assembly processes,and network complexity or connectivity.(4)Habitat conversion from bare flat to S.alterniflora and then into shrimp ponds significantly alterd soil multifunctionality,the strength of the relationship between microbial diversity and soil multifunctionality,and the role of core and non-core microbial in the ecological network.S.alterniflora invasion increased soil multifunctionality,further strengthen the biodiversity ecosystem function(BEF)relationships.It is surprising that microbial diversity was negatively correlated with soil multifunctionality in shrimp ponds.And then soil multifunctionality was reduced.Core microbial have always played a major role in the microbial network.However,non-core microbes also showed their role in the ecological network through strengthening interactions between taxa in response to environmental changes.After conversion S.alterniflora into shrimp ponds,the ecological network of microbial was dominated by the interaction of non-core taxa,and the soil multifunctionality was driven by non-core taxa.Our findings reveal the impact of habitat change on microbial community assembly,network relationships,and provide a mechanism by which microbes maintain soil multifunctionality.Meanwhile,a conceptual framework is proposed to describe microbial communities in response to changes in sulfate concentrations in shrimp pond systems.These results provide a subsurface microbial perspective on the impact of habitat change on soil ecological functions.Our study also provides new insights into the impact of dynamic management on ecological function under habitat change. |
