| Phosphorus(P)is one of the essential elements for plant growth and plays a vital role in plant growth and development.Soil phosphorus is easily fixed by organic matter,iron and aluminum in soil,resulting in low content of available phosphorus in soil,and phosphorus has become a limiting factor for plant growth in subtropical area.The availability of soil phosphorus is closely related to the form of phosphorus and different forms of phosphorus have different availability.Different forms of phosphorus can be transformed into each other,thus affecting the phosphorus availability.Phosphatase is one of the key factors for the transformation of soil phosphorus forms and it can mineralize organic phosphorus in soil into inorganic phosphorus,which can be used by microorganisms and plants.Alkaline phosphatase,one of the important phosphatases in soil,is mainly derived from soil microorganisms,encoded by the phoD gene,and plays an important role in the mineralization and decomposition of organic phosphorus.In order to reveal the characteristics of soil phosphorus forms and phoD bacteria in different forest types,and to explore the key factors affecting soil phosphorus forms and phoD bacteria.In this study,we investigated the characteristics of soil phosphorus forms,phosphatase activity,soil properties and phoD bacterial community in five forest types(secondary forest,Camellia oleifera,Amygdalus persica,Myrica rubra and Cunninghamia lanceolata)in Lutou National Station for Scientific Observation and Research of Forest Ecosystems,Pingjiang country,Hunan province,and the relationships between soil phosphorus forms,phosphatase activity,soil properties and soil phoD bacteria were explored to provide a deeper understanding of the transformation pattern of soil phosphorus forms,the key factors affecting soil phoD microorganisms in different forest types and the management of forests.The main results of the study are as follows.(1)After the conversion of secondary forest conversion into plantation,soil organic carbon(SOC),total nitrogen(TN)and ammonium nitrogen(NH4+-N)contents in four plantations decreased significantly compared with secondary forest(p<0.05).Soil total potassium(TK)content in Amygdalus and nitrate nitrogen(NO3--N)content in Myrica rubra increased significantly(p<0.05).(2)The content of soil resin-extractable phosphorus(Resin-Pi),NaHCO3-extractable organic phosphorus(NaHCO3-Po)and NaOH-extracted inorganic phosphorus(NaOH-Pi)in plantation soils increased,and the content of NaOH-extracted organic phosphorus(NaOH-Po)and residual phosphorus(Residual-P)decreased significantly after forest conversion(p<0.05).The proportion of easily-available P in total phosphorus in four plantation soils increased and and the proportion of non-available P in total phosphorus decreased in four plantations compared to secondary forests.Acid phosphatase and alkaline phosphatase activities in secondary forest soils were significantly higher than those in the four plantations(p<0.05).Redundancy analysis(RDA)indicated that soil properties had significant effects on organic phosphorus and residual phosphorus content and phosphatase activity(p<0.05).(3)Soil phoD bacterial alpha diversity showed that the community richness and diversity of phoD bacteria in the five stands were the highest in Amygdalus persica and the dominance was the highest in Camellia oleifera.Soil phoD bacterial beta diversity showed the differences between soil phoD bacterial communities in secondary forests and other four plantation.The dominant phylum of soil phoD bacteria was Proteobacteria.The relative abundance of bacterial decreased significantly after forest conversion.The dominant genera of soil phoD bacteria were Bradyrhizobium,Methylobacterium and Ralstonia.The redundancy analysis of soil phoD bacterial community with soil properties,phosphatase and phosphorus forms showed that soil phoD bacterial community was mainly influenced by SOC?NH4+-N?TN?NaOH-Po?NaHCO3-Po and phosphatase activity. |
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