| The current climate system is undergoing unprecedented changes.The increasing impact of warming and altered precipitation patterns on the biocapacity and biogeochemical cycles of terrestrial ecosystems has attracted much attention.The total phosphorus content of subtropical soil is at a moderate level,but the availability of phosphorus is limited.According to published data,subtropical soil has high potential for phosphorus sequestration,and we assume that the underlying mechanism may associate with high adsorption and low desorption of water-soluble phosphorus in the soil.Soil aggregates are the basic structure of soil and the fundation of soil ecosystem functions,by providing physical protection for soil organic matter creating microhabitats for soil organisms,and regulating soil nutrient availability.The exploration of soil phosphorus adsorption-desorption characteristics mostly relies on soil physical and chemical properties,yet less attention was paid on the participation of microorganisms during soil phosphorus activation and migration processes.This study was based on a long-term precipitation reduction field experiment,investigated the spatiotemporal distribution of phosphorus composition,examined the relative abundances of phosphorus cycling genes pho C and pho D as well as the phosphatase activities,and assessed the impact of soil microorganisms on phosphorus adsorption-desorption characteristics of soil aggregates.Results of this study provide theoretical and data support for better prediction of the response of forest soil phosphorus biogeochemical cycling to extreme drought.Specifically,this research revealed that:(1)Long-term drought resulted in significant spatial and temporal differences in aggregate distribution characteristics and phosphorus composition characteristics.The increasedof the proportion of small-sized aggregates under drought was more pronounced in the growing season;drought may stabilize the phosphorus pool,which is significant in large aggregates.Drought increased the soil phosphorus pool in microaggregates,especially for the moderately active organic phosphorus fraction.(2)The temporal differences in the relative abundances of phosphorus cycling genes pho C and pho D are stronger than the spatial differences and show moderate resistance(RS value)to drought.Long-term drought affected the relative abundances of pho C and pho D by affecting soil phosphorus composition,further affecting the downstream phosphatase activities.Moderately active organic phosphorus was an important indicator for predicting the relative abundances of phosphorus cycling genes and micro-aggregates may be the most active niche of phosphatase.The correlation between the relative abundances of pho C and pho D and phosphatase activity of microbial phosphorus cycling function genes was stronger in the non-growing season than in the growing season.(3)Drought changed the phosphorus adsorption-desorption behavior in the soil,possibly through its effect on soil phosphorus composition and physico-chemical characteristics as well as the relative abundances of phosphorus cycling microbes and enzymatic activities.When different forms of exogenous phosphorus were added,long-term drought reduced the adsorption potential and sequestration potential of soil available phosphorus,and limited the phosphorus mineralization potential of microorganisms.In summary,long-term drought led to an increase in soil microaggregate fraction,and it may increase the inertness of the phosphorus pool,and the phosphorus cycling tends to turn over stable phosphorus components;prolonged drought reduced the relative abundances of phosphorus cycling microorganisms and their mineralization potential for organophosphorus,which may further aggravate phosphorus limitation.Results of this study may deepen understanding the processed of soil phosphorus cycle in the subtropical evergreen broad-leaved forest ecosystem forest ecosystems and its response to long-term drought. |
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