| Under the combined effect of global climate change and human overactivity,the alpine grassland ecosystem in the Three Rivers Source Region of the Qinghai-Tibetan Plateau has undergone severe degradation,seriously reducing the ecosystem service functions of the Three Rivers Source Region.In order to reverse the situation of grassland degradation,China has implemented“Three Rivers Ecological Protection and Construction Phase I and Phase II Projects”and Sanjiangyuan National Park Construction and other projects,of which the ecological restoration of degraded grasslands is an important task.In recent years,large-scale grassland degradation in the Sanjiangyuan region has occurred on mountain slopes,which has caused difficulties in implementing ecological restoration techniques.So how to effectively and sustainably implement degraded grassland restoration technology on the hillside is an important problem in the current ecological construction of the Three Rivers Source Region.Therefore,the evaluation of the effect of different slopes and topography,different degrees of degradation,and different restoration techniques is an important scientific basis for the subsequent large-scale ecological restoration projects.The thesis takes Dawu Town,Maqin County,Qinghai Province as the research area,which has the characteristics of typical degraded grassland in Qinghai Province,and selects mild,moderate and severe degraded grassland.Under the theoretical support of the classification and classification of degraded grassland on the slope,natural restoration,The ecological restoration technology experiment of semi-artificial grassland supplementary sowing and artificial grassland reconstruction.Through field monitoring and laboratory analysis for two consecutive years（2018,2019）,the impact of degraded grassland restoration on hillsides on vegetation and soil was explored,and a benefit evaluation was established.In the index system,the application effects of different restoration techniques on the degraded grassland ecology in the hillside of the Sanjiang source area were studied.At the same time,the soil erosion model（RUSLE）was used to study the current soil erosion intensity and classification of the study area,and the regional adaptability of the ecological restoration model of degraded grassland on the slope was analyzed.The main findings are as follows:In the first part,the impact of the restoration of degraded grassland on the slope on vegetation and soil.（1）After the natural restoration technology was implemented on the lightly degraded grassland（0-7°flat beach;7-25°gentle slope;>25°steep slope）,the aboveground vegetation biomass,average species height,species richness,soil total nitrogen（except 0-10 cm soil layer）all increased significantly（P<0.05）,and the soil bulk density decreased significantly P<0.05).Except for total potassium in the soil,slope has a very significant effect on other vegetation and soil indicators（P<0.01）.As slope increases,soil bulk density,available phosphorus,and pH increase;aboveground vegetation biomass,vegetation coverage,average species height,species richness,soil organic carbon,total nitrogen,and total phosphorus decrease（P<0.05）.At the same time,the recovery time and slope have a very significant interaction on the average height of species,soil bulk density,total potassium,total nitrogen,available nitrogen,and available phosphorus（P<0.01）.（2）After implementing semi-artificial grassland supplementary sowing on moderately degraded grassland（0-7°flat beach;7-25°gentle slope;>25°steep slope）,aboveground vegetation biomass,average species height,species richness,and soil organic carbon all increased significantly（P<0.05）,and soil bulk density and pH decreased significantly（P<0.05）.In addition to species richness and total soil potassium,slope has a very significant effect on other communities and soil indicators（P<0.01）.The slope increased,soil bulk density and pH increased;aboveground vegetation biomass,coverage,average species height,total soil phosphorus,available nitrogen,available phosphorus decreased and the difference was significant（P<0.05）.（3）After the implementation of artificial grassland reconstruction technology on severely degraded grassland（0-7°flat beach;7-25°gentle slope;>25°steep slope）,the aboveground vegetation biomass,average species height,species richness,and soil water content all increased significantly（P<0.05）,and soil pH decreased.In addition to the average species height,species richness and soil total potassium,slope has a very significant effect on other vegetation and soil indicators（P<0.01）.The slope increased,the soil bulk density increased,and the aboveground vegetation biomass,vegetation coverage,and soil indicators all decreased significantly（P<0.05）.The second part is the analysis of application effects of different ecological restoration technologies.（1）After implementing three restoration techniques of natural restoration,semi-artificial grassland supplementary sowing and artificial grassland reconstruction on 0-7°beach and 7-25°gentle slope,the aboveground vegetation biomass and vegetation coverage（Compared with one year）,the change of soil comprehensive quality index（compared with not restored）from high to low are artificial grassland reconstruction technology,semi-artificial grassland supplementary seeding technology and natural restoration technology;input to output ratio from high to low The order is natural restoration technology,artificial grassland reconstruction technology and semi-artificial grassland supplementary seeding technology（flat beach:1.53,1.11,0.97;gentle slope:1.05,0.97,0.75）.（2）After the restoration techniques of natural restoration,semi-artificial grassland supplementary planting and artificial grassland reconstruction on steep slopes>25°,aboveground vegetation biomass,vegetation coverage（compared to the first year of restoration）,soil comprehensive quality index Compared with the restoration,the change amount from high to low is semi-artificial grassland supplementary seeding technology,artificial grassland rebuilding technology and natural restoration technology;Grassland supplementary sowing technology（0.88,0.64,0.56）.（3）The implementation of the entire ecological project generated 182,500 yuan（RMB）for the surrounding herdsmen.In the survey of the ecological restoration project support,82%of the surrounding herdsmen recognized the project.The third part,the assessment of regional adaptability of ecological restoration technology.（1）Through the comprehensive calculation of RUSLE,the minimum value of soil erosion modulus in Dawu Town is 0,the maximum value is 591.2 t?hm-2?a-1,and the average value is 106.3 t?hm-2?a-1,of which The amount of soil erosion in the area is small,and the amount of soil erosion in the north,south and southwest is large.（2）The distribution of soil erosion intensity in Dawu Town is basically consistent with the change in slope distribution.The soil erosion intensity of the beach area with a slope of 0-7°and an altitude of 3700-3900m is dominated by slight and light erosion,and the area accounts for about 30%.The soil erosion intensity in the gentle slope area with a slope of 7-25°and an altitude of 3900-4300m is dominated by very strong and severe erosion,and the area accounts for about 50%.The amount of soil erosion in this area is the highest in the entire Dawu Town area.The intensity of soil erosion on steep slopes with slopes above 25°and altitudes above 4300m is dominated by violent erosion,accounting for approximately 9%of the area.（3）Soil erosion in the gentle slope area and steep slope area of Dawu Town is extremely serious,and the soil erosion in the beach area is relatively slight.According to the distribution map of slope and soil erosion intensity,it is effective to determine the location and soil erosion intensity of beach land,gentle slope land and steep slope land,and implement the natural restoration,semi-artificial grassland supplementary sowing and artificial grassland reconstruction restoration technology on gentle and steep slope land according to different degradation degrees Guide the next step of the restoration of degraded grasslands on Dawu Town.Summary:Slope is one of the most important factors that affect the ecological restoration of degraded grasslands on hillsides.Under different grades,the restoration effect of beach land is the best,and the restoration effect of steep slope land is not ideal.Among the ecological restoration technologies implemented on degraded grasslands with gentle slopes,the artificial grassland reconstruction technology has the best restoration effect.Among the ecological restoration technologies implemented on degraded grassland with steep slopes,the semi-artificial grassland supplementary seeding technology has the best restoration effect.Determining the locations of beaches,gentle slopes and steep slopes,and the intensity of soil erosion in their respective regions from the slope and soil erosion intensity distribution maps can more effectively guide the restoration of degraded grasslands on Dawu Town. |
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