Effects Of Different Carbon Input Of Pinus Yunnanensis On Distribution And Dynamic Of Soil Phosphorus In Phosphorus-enriched Mountain Area Of Dianchi Lake Basin

In the process of vegetation restoration in phosphate degraded mountainous areas,how to fix and reduce soil phosphorus loss is one of the important purposes of vegetation restoration,and plants play the key role in this process.Previous studies on soil phosphorus in phosphorus-rich areas focused on the distribution and loss characteristics of soil phosphorus under different vegetation types and under or outside the canopy of single plant.However,there are few reports on how plants affect the distribution and dynamic change of soil phosphorus through the carbon input by litterfall and root system.Therefore,the dominant species Pinus yunnanensis in phosphorus-rich areas was treated with litter removal and bark cutting for one year in this study.Soil physical properties,chemical properties,microbial community structure and distribution and dynamics of phosphorus pool under different carbon input conditions were measured to discuss the mechanism that how carbon input by plants through litterfall and root affect soil phosphorus comprehensively.This study provides data support and management basis for the mechanism of plant phosphorus control and vegetation management mode in the process of vegetation restoration in phosphorus-rich areas.The main results are as follows:(1)As for soil physical properties,the moisture content of 0-15 cm soil increased significantly after litter removal,while the proportion of large aggregates(>250?m)and MWD of 0-15 cm soil decreased after litter removal*bark cutting,and the stability of soil structure decreased.As for soil chemical properties,the contents of total carbon and total nitrogen in 0-15 cm soil large aggregates decreased significantly after litter removal.(2)As for soil bacteria microorganisms,the relative abundance of Actinomycetes,Acidobacteria and Chloroflexi in 0-15 cm soil after litter removal decreased by 4.85%,2%and 2.72%respectively,compared with untreated soil.The treatment of cutting bark increased soil bacterial diversity,while different carbon input treatments decreased soil acid phosphatase content.(3)As for soil phosphorus,phosphorus adsorption index(PSI)and Na OH-Pi content in 0-15 cm soil increased significantly after litter removal.The measurement results of?¹⁸O_Psignal showed that carbon input treatment changed the exchange flux between Na HCO₃,Na OH,HCl-P and H₂O-P,and the exchange flux between HCl-P and H₂O-P increased in 0-15 cm soil,which led to the risk of release and loss of low-activity HCl-P in soil.(4)The results of structural equation model showed that the soil microbial process in 0-15 cm was the main factor leading to the change of HCl-P content.The results of RDA indicated that physical and chemical properties of soil,such as Fe_ox,TC and AN,and bacteria community,such as Acidobacteriia,AD3 and Planctomycetacia,were the main factors affecting the distribution of different phosphorus fractions in soil.Therefore,the study suggested that in the process of vegetation restoration and management in phosphorus-rich mountainous areas of Dianchi Lake Basin,disturbance of surface litter should be avoided as far as possible,so as to avoid the decline of phosphorus fixation ability of plants and the release and loss of inactive phosphorus in soil.