| Dianchi watershed is one of the most serious non-point source pollution basins in Yunnan Province.Transport and control of phosphorus in the basin has become an important part of non-point source pollution prevention and control in this area.In the past,many studies have focused on the control of agricultural non-point source pollution,but at the same time,there are large areas of phosphorus-rich mountain areas in the basin.Soil phosphorus with higher background value is easy to migrate to the lake with runoff to intensify water eutrophication.Therefore,the control of soil phosphorus loss in phosphorus-rich areas is one of the key points in the prevention and control of water eutrophication in Dianchi Lake.In order to understand the characteristics of phosphorus loss in phosphorus-rich degraded mountainous areas in Dianchi watershed,Pinus yunnanensis and Erianthus rockii the dominant plants in phosphorus-rich mountainous areas,were selected as the research objects.Soil phosphorus forms and leaching characteristics were analyzed by collecting the soil under the influence of plants.Combined with indoor simulated infiltration experiments,the characteristics of soil phosphorus leakage were determined.In order to provide data support and basis for ecological restoration and phosphorus pollution control in phosphorus-rich degraded mountainous areas.The main results are as follows:(1)The analysis of soil phosphorus morphology in the field showed that the phosphorus content in the canopy and out-canopy soil under the influence of Pinus yunnanensis and Erianthus rockii did not show a significant change trend in the horizontal direction,while in the vertical direction,the total phosphorus content of Pinus yunnanensis increased with the depth of soil layer,but the total phosphorus content of Erianthus rockii did not change significantly;in the middle of rainy season,the total phosphorus content was high In the early and late rainy season.Multivariate analysis of variance showed that sampling location,soil depth and their interaction had significant effects on total phosphorus and available phosphorus content of soil under the influence of Pinus yunnanensis and Erianthus rockii.Combined with environmental factor analysis,it was indicated that soil organic matter was the main factor affecting the change of soil phosphorus content of Pinus yunnanensis.(2)The analysis of Hedley phosphorus components under the influence of plants showed that NaOH-Po content was the highest and Water-P content was the lowest under the influence of both plants.However,under the influence of Pinus yunnanensis.soil phosphorus content from high to low was NaOH-Po>NaOH-Pi>D.HCl-Pi>Residual-P>C.HCl-Po>NaHCO3-Po>C.HCl-Pi>NaHCO3-Pi>Water-P.Soil phosphorus content under the influence of Erianthus rockii from high to low was NaOH-Po>NaOH-Pi>C.HCl-Po>C.HCl-Pi>D.HCl-Pi>Residual-P>NaHCO3-Po>NaHCO3-Pi>Water-P.According to the proportion of active phosphorus,middle active phosphorus and inactive phosphorus to total phosphorus,the soil phosphorus components under the influence of the two plants showed a similar proportion range.The proportion of active phosphorus was about 4-6%,the proportion of medium active phosphorus was about 60%,and the proportion of inactive phosphorus was about 30%.In general,inorganic phosphorus accounts for 60-80%of total phosphorus,while organic phosphorus accounts for 10-30%of total phosphorus.Inorganic phosphorus accounts for the main part of soil phosphorus.(3)In order to assess the loss risk of soil phosphorus at different locations,by comparing the content of total phosphorus extracted by water in soil.it was found that the total phosphorus extracted by water decreased with the increase of soil depth in vertical direction,while in horizontal direction,the loss of phosphorus at the midpoint of canopy under the influence of Pinus yunnanensis was higher than that around the root and outside the canopy,and there was no obvious regularity under the influence of Erianthus rockii.The content of phosphorus components extracted from soil water shows that TPP and TDP are two forms of phosphorus with a large proportion in soil phosphorus loss.Under the influence of Pinus yunnanensis,the total phosphorus extracted by water accounted for 0.01%-0.15%of the total phosphorus content in the soil,and the total phosphorus extracted by sugarcane grass accounted for 0.04%-0.39%of the total phosphorus content in the soil.(4)In order to understand the characteristics and influencing factors of soil phosphorus under the influence of Pinus yunnanensis,the phosphorus content in soil leachate under different soil treatments(low temperature,normal temperature,normal temperature + carbon and nitrogen source)was analyzed by simulation experiments.The results showed that the phosphorus leachate loss in 0-20 cm soil layer was higher than that in 20-40 cm soil layer,indicating that the phosphorus loss in surface soil layer was easier.Particular phosphorus TPP is the most easily lost form of phosphorus,accounting for more than half of the total phosphorus content.The effects of different treatments on phosphorus infiltration were as follows:low temperature<normal temperature<normal temperature + carbon and nitrogen source,indicating that soil microorganisms played a significant role in the transformation of soil phosphorus forms.Based on the results of the study,it was concluded that the spatial heterogeneity of soil phosphorus content and its components in horizontal and vertical directions was high due to the presence of different species in the phosphorus-rich Degraded Mountain areas,which led to the change of soil phosphorus infiltration characteristics.Combined with the main environmental factors affecting the behavior of phosphorus,the results showed that the content of soil organic matter affected the change of total phosphorus and available phosphorus content,and soil microbial community affected the change of phosphorus form,thus affecting the process of soil phosphorus transport underground. |
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