Study On The Regulation And Control Benefits Of Different Treatment Modes For Soil And Water Loss Under Pinus Massoniana In Granite Red Soil Area

In order to reveal the improvement of soil physical and chemical properties by different treatments in typical red soil erosion areas,the research analyzed the characteristics of slope runoff and sediment yield to rainfall in different treatments and evaluated the comprehensive quality of soil and benefits of reducing flow and sediment.The research provided scientific basis and technical support for mechanism and management of soil erosion under the Masson pine forest in the red soil region of southern China.This study relied on Chang ting County,a typical red soil erosion area,to set up 12 standard runoff plots with a slope of 15° and an area of 20×5 m.Five treatments were set: contour grass filling belt(M1)and small hole sowing grass(M2),replanting broadleaf tree + strip ditch sowing grass(M3),arbor-shrub-grass mixture(M4),fish scale pit(M5),Masson pine pure forest(CK),respectively,setting two repetitions.Positioning observations were carried out on the runoff plots.Collecting Soil samples in June 2017,December 2017 and June 2018,the physical and chemical properties were analyzed.The analysis was carried out to evaluate the runoff and sediment yield,benefit of reducing flow and sediment and comprehensive quality of soil in different treatments.The main results as follows:(1)Compared with CK plots,M1,M2,M3,M4 and M5 treatments can significantly increase soil water content in 0-20 cm soil layer.The soil bulk density of M3,M4 and M5 plots was significantly lower than that of CK plots,and the soil porosity of M3,M4 and M5 plots was significantly higher than that of CK.The proportion of aggregates > 2 mm in M1,M2,M3,M4 and M5 plots was higher than that in CK,and decreased with the increase of soil depth.Compared with CK plots,M1,M2,M3,M4 and M5 treatments could significantly reduce soil disintegration coefficient and Erodibility K value.(2)The chemical characteristics of soils under different treatments were significantly improved.The contents of organic matter,total nitrogen,total phosphorus,available phosphorus and available potassium in M1,M2,M3,M4 and M5 were significantly higher than in CK,and showed obvious surface aggregation effects.Thetotal potassium content of each plot did not change obviously,and there was no obvious law with the change of soil depth.The pH of each sample plot did not change obviously with the change of soil depth,and had no obvious improvement compared with CK.(3)The total rainfall in 2017 was 1368.84 mm and mostly concentrated in March-June;the monthly runoff and rainfall were extremely positive in each plot.The monthly sediment yield of M3,M4,M5 and CK was significantly positively correlated with monthly rainfall.Under the condition of sub-rainfall,the runoff of each measure was significantly positively correlated with the rainfall.Sediment yield in M3,M4,M5 and CK was significantly positively correlated with rainfall,while M1 and M2 not.In addition to M2,the runoff of each measure was positively correlated with the sediment yield,and the impact of rainfall on runoff is greater than the impact on sediment yield.(4)The comprehensive quality of soil in different treatments was better than that of in control plot.The comprehensive quality grade of soil showed that M3 and M5 were the best,M4 was better,M1 and M2 were the second and CK was the worst.The comprehensive quality of soil in different treatments showed a downward trend with the soil depth increased.(5)The annual runoff depth of different treatment modes is between 233.86~276.37 mm,and the CK plot ground runoff depth is 376.33 mm.The different flow control modes of CK plots were M3>M4>M5>M1>M2 and sand reduction benefit of different treatment modes was M3>M2>M5>M4>M1.The sediment reduction rate of different treatment modes is greater than 75%.Comprehensive evaluation showed that M3 plot had the best benefit in reducing flow and sediment.According to the comprehensive evaluation,the M3 treatments had the best benefit,among which the trench grass planting engineering measures can prevent runoff,promote litter accumulation and change soil porosity;replanting broad-leaved trees can effectively reduce rainfall kinetic energy and soil nutrient loss,increase infiltration,and thus achieve the function of water and soil conservation and improve soil quality.