Effects Of Different Vegetation Restoration On Soil Phosphorus Composition And Availability In Karst Area

Phosphorus is one of the essential elements for plant growth and development.Soil phosphorus is easily fixed by the plasma of calcium,iron and aluminum in the soil,resulting in low available phosphorus content in the soil,and phosphorus has become a limiting factor for plant growth in the karst area.In this study,cultivated land,grassland,shrub,woodland and garden land were taken as research objects to study the distribution of phosphorus form,phosphorus accumulation and phosphorus availability characteristics under different vegetation types,analyze the relationship between phosphorus form and phosphorus availability characteristics and environmental factors,and understand the changes of soil phosphorus components,availability characteristics and influencing factors under different vegetation types in karst areas.It provides theoretical basis for optimizing land resource management,making full use of phosphorus resource and reducing non-point source pollution.The results show that:（1）Soil inorganic phosphorus components of different vegetation types had significant differences,and gradually decreased with the increase of soil depth,mainly accumulating in the surface layer.The content of inorganic phosphorus in forest,garden and cultivated soil(Ca₂-P,Al-P,Fe-P,Ca₈-P,Ca₁₀-P,O-P)was high,while the content of inorganic phosphorus in grassland and shrub soil was low.The O-P of soil was lower in the surface layer and higher in the bottom layer.Ca₂-P,Al-P,Fe-P,Ca₈-P,Ca₁₀-P showed that the proportion of surface layer was high,and the proportion of bottom layer was low.The correlation and path analysis of each component and available phosphorus showed that Ca-P and Al-P were available phosphorus sources in inorganic phosphorus components.（2）The content of each organophosphorus component decreased gradually with the increase of soil depth,and the difference of each component was significant in the surface soil of different vegetation types.The content of organophosphorus components in forest soil was higher,the content of LOP and MLOP in cultivated soil was higher,and the content of organophosphorus components in grassland and shrub soil was lower.The HROP surface layer is low and the bottom layer is high.MLOP and MROP are characterized by high proportion of surface layer and low proportion of bottom layer.The correlation and path analysis of available phosphorus indicate that LOP and MLOP are available phosphorus sources in organophosphorus components.（3）ALP,MBP and PHY in soils of different vegetation types are sensitive indicators to indicate the availability of soil phosphorus,and are significantly correlated with organophosphorus components,inorganic phosphorus components and available phosphorus,etc.,which is extremely important for the effective process of soil phosphorus.（4）The main environmental factors affecting soil phosphorus components are organic matter,available potassium,alkali-hydrolyzed nitrogen and mechanical composition.In conclusion,the differences in soil phosphorus components and availability under different vegetation types are the result of the combined effects of biological and abiotic factors,among which soil microorganisms,nitrogen,available potassium and organic matter play a key role in the soil phosphorus cycle under different vegetation types in karst areas.