Effects Of Different Poplar Plantation Types On Soil Phosphorus Leaching Characteristics

Taihu Lake is a typical shallow eutrophication lake in China.It is of great significance to understand the interception effect of artificial forest around Taihu Lake on soil phosphorus leaching.Therefore,in this study,poplar pure plantation(PE),poplar-Ligustrum mixed plantation(PL),and poplar-Photinia mixed plantation(PP)were selected as the objects.The Hedley phosphorus fraction method modified by Sui was used to study the changes of soil phosphorus content,microbial biomass phosphorus,acid phosphatase activity and soil leaching solution phosphorus concentration in different poplar plantation types.Clarifying the influence of different types of poplar plantation on soil phosphorus leaching.The main results are as follows:(1)The contents of total phosphorus,NaOH-Pi,HCl-Pi and Residual-P showed as PE>PL>PP.The content of NaHCO₃-Po was PE>PP>PL.The contents of H₂O-Pi,NaHCO₃-Pi and NaOH-Po were PP>PL>PE.The seasonal variation of total phosphorus H₂O-Pi,NaHCO₃-Pi,NaOH-Pi and HCl-Pi in three types of poplar artificial forest were winter>spring>autumn>summer.The seasonal variation of NaHCO₃-Po was winter>summer>spring>autumn.The seasonal variation of NaOH-Po was winter>summer>autumn>spring.Compared with PE,two mixed forests significantly reduced the NaHCO₃-PO and HCl-Pi in summer and autumn,the NaOH-Pi,HCl-Pi and Residual-P in winter in the 0-20 cm soil layer;the NaHCO₃-Po in spring,summer and autumn,and the Residual-P in winter in the soil layer of 20-40cm;and increased the H₂O-Pi in spring,summer and winter,the NaOH-Po in summer and autumn,and NaHCO₃-Pi in winter in 0-20 cm soil layer;the H₂O-Pi and NaHCO₃-Pi in summer and NaOH-Po in autumn in the 20-40 cm soil layer;the NaHCO₃-Po in spring and H₂O-Pi in summer in the40-60 cm soil layer(P<0.05).Results of redundancy analysis showed that acid phosphatase activity,microbial biomass phosphorus,organic carbon,water content and pH were the main factors affecting soil phosphorus content.(2)Soil microbial biomass phosphorus and acid phosphatase activity were characterized by PP>PL>PE.The seasonal changes of soil microbial biomass phosphorus and acid phosphatase activity in three poplar plantations were winter>spring>autumn>summer.Compared with the pure poplar forest,two mixed forests significantly increased the microbial biomass phosphorus in four seasons in 0-20 cm soil layer and in spring and winter in 40-60 cm soil layer;and the acid phosphatase activity in winter in the 0-20 cm soil layer,in four seasons in the20-40 cm soil layer,and in spring,summer and winter in the 40-60 cm soil layer(P<0.05).(3)The volume and concentration of soil phosphorus leaching solution in different poplar plantations were closely related to throughfall,and increased with the increase of throughfall.The volume of PE,PL and PP in the soil was the highest in August and the lowest in September.The concentration of total phosphorus and dissoluble phosphorus in soil leaching solution was the highest in December and while lowest in September,while the leaching loss of soil phosphorus was mainly dissoluble phosphorus.Compared with the PE,two mixed forests significantly reduced the total phosphorus and dissoluble phosphorus in July,August and December,and the particulate phosphorus in September in the 0-60 cm soil layer,the particulate phosphorus in July and the total phosphorus in January2020 in the 0-20 cm soil layer;the total phosphorus and dissoluble phosphorus in January 2020 in the 20-40 cm soil layer;the particulate phosphorus in July,total phosphorus and dissoluble phosphorus in September in the 40-60 cm soil layer(P<0.05).Redundancy analysis results showed that throughfall,NaOH-Pi and Residual-P were the main factors affecting soil P leaching loss.(4)Compared with the PE,the two mixed forests effectively reduced the risk of phosphorus loss,and the PP had a better effect.Therefore,the mixed forest with arbor and shrub layer should be built in the area around Taihu Lake.