Effects Of Vegetation Restoration On Soil Aggregates And Stoichiometric Characteristics In Photovoltaic Power Station

Large-scale development and construction of photovoltaic power stations have a significant impact on local soil properties,which worsen soil stability and reduced soil fertility.Therefore,vegetation restoration is needed to improve soil fertility.The 30MWp Photovoltaic Agriculture,Forestry and Animal Husbandry Demonstration Base of Dayou Light Energy in Tumote Left Banner,Hohhot city,Inner Mongolia was selected as the research area.The restoration modes of Pinus sylvestris L.,Astragalus membranaceus and Medicago sativa L.were selected in the artificially constructed vegetation as three treatments.Soil aggregate composition and stability and contents of soil aggregate carbon nitrogen and phosphorus and their Stoichiometric characteristics and stock were analyzed of 0～20 cm and 20～40 cm soil layer in every treatment.The purpose was to explore the mechanism of soil aggregate stability and nutrients of carbon and nitrogen and phosphorus and sink of carbon and nitrogen.It provided a theoretical basis for vegetation restoration of photovoltaic power stations.The main results were as follows:（1）In 0～40 cm soil layer,soil organic carbon（SOC）,total nitrogen（TN）and total phosphorus（TP）were decreased significantly with increase of soil depth.This varieties were weak variation.The increase of soil SOC and TN in Astragalus membranaceus and Medicago sativa L.treatments were significantly higher than that in Pinus sylvestris L..（2）The C:P and N:P of Astragalus membranaceus treatment and the C:N and C:P and N:P of Medicago sativa L.treatment were significantly decreased with increasing of soil depth.The C:N in Astragalus membranaceus treatment was the lowest,but C:P and N:P were significantly higher than those in other treatments.Soil C:N,C:P and N:P of different treatments ranged from 6.89 to 9.18,5.63 to 10.51 and 0.66 to 1.28respectively,which were lower than the average in China.So nitrogen was the main limiting factor in this study area.（3）The content of 0.25～0.053 mm aggregate was the main content in the 0～20 cm soil layer,while the content of>2 mm aggregate was the highest in the 20～40 cm soil layer.The soil mechanical stability of Medicago sativa L.treatment in 0～20 cm layer was the highest,and that of Astragalus membranaceus treatment in 20～40 cm layer was the highest.Astragalus membranaceus and Pinus sylvestris L.treatments had the strongest soil water stability.（4）The contents of SOC,TN and TP in<0.053 mm aggregates were significantly higher than other grains.The contribution of>2 mm and 2～0.25 mm aggregates to soil SOC,TN and TP was the most.（5）Soil aggregate C:N in Astragalus membranaceus treatment was the lowest,but its C:P and N:P were higher than those in Pinus sylvestris L.and Medicago sativa L.treatments.The C:N difference between<0.053 mm aggregate and large aggregate（>2mm,2～0.25 mm）was intensified in the Pinus sylvestris L.treatment,while the C:N difference between 2～0.25 mm aggregate and>2 mm aggregate and 0.25～0.053 mm aggregate was intensified in the Astragalus membranaceus and Medicago sativa L.treatments.The maximum values of C:P and N:P in the three treatments were distributed in 2～0.25 mm aggregates,which indicating that the content of phosphorus in soil aggregates was high.Soil aggregates C:N,C:P and N:P varied from 6.35 to 11.51,3.81 to 15.31 and 0.43 to 2.19,respectively,which were close to the average C:N in China,but far lower than the average C:P and N:P in China.（6）The SOC,TN and TP stocks of different treatment ranged from 8.32 to 18.12t·hm^-2,1.02 to 2.15 t·hm^-2and 1.15 to 2.14 t·hm^-2,respectively.The SOC and TN stocks were decreased significantly with increasing of soil depth.Compared with Pinus sylvestris L.and Medicago sativa L.treatments,SOC stock in Astragalus membranaceus treatment increased by 3.38 t·hm^-2and 1.29 t·hm^-2,TN stock increased by 0.58 t·hm^-2and 0.34 t·hm^-2,while TP stock was the lowest,only 1.71 t·hm^-2.The aggregate carbon and nitrogen stocks of the Astragalus membranaceus treatment were higher than those of the other treatments.The SOC,TN and TP stocks of<0.053 mm aggregates were the highest,which were significantly higher than those of other aggregates.Carbon,nitrogen and phosphorus stocks of soil and aggregates were closely related to their own content and water content.In general,Astragalus membranaceus had a better effect on enhancing soil carbon and nitrogen sinks,which is of great significance for improving soil fertility in photovoltaic power station area.