Regulation Effects Of Water Erosion Under Pinus Massoniana Woodland By Different Governance Modes In The Red Soil Region Of South China

Pinus massoniana is the main tree species for vegetation restoration in the red soil region of southern China.Affected by the superposition of natural conditions,human activities and other factors,there is moderate or even more intensive soil erosion under forests.Popularizing typical Masson pine governance modes can effectively reduce soil erosion,improve soil quality and promote the ecological restoration of degraded Masson pine forest.Taking typical forest soil and water loss governance modes such as mixed arbor and shrub and grass(M1),planting shrub and seeding grass at the line-shaped ditch(M2),seeding grass at the whole slope(M3),transformation of inefficient forests(M4)closed management(M5)and serious erosion of ungoverned land(CK)as research objects.The research methods of field sample survey,sampling and indoor experiment analysis are adopted.This paper discusses vegetation characteristics,ecological and hydrological function characteristics of litter and soil hydrological and physical properties under different governance modes,and analyzes rainfall characteristics and runoff and sediment yield characteristics of runoff plots in the study area in combination with runoff and sediment yield under natural rainfall conditions.To reveal the regulation effect of different governance modes on forest soil and water loss.It provides a scientific basis for effectively controlling undergrowth erosion and promoting ecological environment succession,and contributes to the reasonable selection of vegetation restoration models and scientific evaluation of vegetation and soil ecological effects in the red soil region of south China.The main conclusions were as follows:(1)The implementation of governance modes under forests could significantly increase the coverage of surface vegetation,increased the number of vegetation species in the eroded poor land,and maintained good growth conditions.The governance modes could significantly increase the reserves and the maximum water holding capacity of the surface litter,and the litter reserve and maximum water capacity of M1 are significantly higher than other modes(P<0.05).There was a consistent rule between effective detention amount and effective detention rate of litter in each governance mode.That is,the effective detention rate of M1 and M2 was more than 100%and significantly higher than that of other governance modes(P<0.05).There was a significant positive correlation between water holding capacity and soaking time of litters in the five governance modes(P<0.05),which was consistent with the logarithmic function model.There was a significant negative correlation between water absorption rate and soaking time(P<0.05),which was in line with the power function model.(2)Under different governance modes,the soil bulk density,hardness and anti-scour coefficient of 0-10 cm soil significantly reduced,soil disintegration coefficient and soil shear strength of 0-20 cm soil significantly increased,and root biomass of 0-40 cm soil significantly increased.There was a significant difference between control plot and soil moisture content of 0-10 cm in different modes sites(P<0.05).There were significant differences in total soil porosity between the three soil layers of M1,M2,and M5(P<0.05).Compared with the CK,M1,M2,M3,M5 significantly increased the initial infiltration rate of soil.(3)From 2016 to 2018,the average annual rainfall of runoff plot was 1677.43 mm and the average annual rainfall days were 155 days.Heavy rain and rainstorm accounted for 15.70% of the total rainfall,but the rainfall reached 2875.7 mm,accounting for57.13% of the total rainfall.Preventing heavy rain and rainstorm was very important to reduce soil erosion in the region.There was a linear regression relationship between rainfall and runoff depth in different governance modes,and there was a very significant positive correlation.There was a positive linear regression relationship between runoff depth and sediment yield.The runoff coefficient and sediment concentration were significantly reduced,and the accumulated runoff depth and soil loss were significantly reduced in the CK.Among the five governance modes,M2 had the best effect of reducing flow and sediment.M3 and M5 tooks the second place.M4 had the lowest effect of reducing flow and sediment.The benefit of sediment reduction was higher than that of flow reduction in the treatment area.(4)Regional erosive rainfall could be divided into three types.Among them,Type?was characterized by short duration,heavy rain and small rainfall,with rainfall duration mostly ranging from 150?480 min,rainfall intensity mostly ranging from 1.9?7.2mm/h and rainfall mostly ranging from 8?28 mm.It was the main rainfall type causing soil erosion.Type?was characterized by medium duration,light rain intensity and medium rainfall,with rainfall duration mostly ranging from 990?1570 min,rainfall intensity mostly ranging from 0.7?2.0 mm/h and rainfall mostly ranging from 15?45mm.So it was the secondary rainfall type causing soil erosion.Type?was characterized by long duration,moderate rain intensity and large rainfall,with rainfall duration mostly ranging from 2000?3100 min,rainfall intensity mostly ranging from1.0?2.5 mm/h and rainfall mostly ranging from 30?130 mm,which made little contribution to soil erosion.The critical criteria for erosive rainfall in Changting County,a typical understory erosion area in southern red soil region,are rainfall of 7.88 mm and I₃₀ of 1.00 mm/h.Different governance modes can effectively preventing the occurrence of soil erosion and nutrient loss by restoring vegetation,using litter and soil to regulate the ecological and hydrological processes on the slope.