Study On The Change Of Vegetation Coverage And The Response Mechanism To Hydrology

Vegetation is an important factor affecting the hydrological process in the basin.Since the new century,the vegetation changes in the loess hilly and gully region have changed significantly,which has greatly changed the relationship between rainfall and runoff and sediment in the region.The single vegetation coverage index can not characterize the important influence of vegetation hierarchy on soil and water conservation efficiency.It is of great scientific significance to study the mechanism of vegetation structure change in the hilly and gully region on the hydrological process of the basin.In this paper,the vegetation change region of the typical watershed in the loess hilly and gully region is taken as the research object.The combination of field fixed-point monitoring experiment,remote sensing inversion and watershed hydrological monitoring is used to explore a new method of structural vegetation cover measurement and establish a structural vegetation index remote sensing model.And quantitative research on the mechanism of the influence of vegetation structure changes on hydrological processes.The main work and achievements are as follows:(1)The measured model of structural vegetation coverage of different vegetation communities.According to the concept of structural vegetation coverage and the role of different structural levels in vegetation communities in soil and water conservation,Luoyugou is used as the research area,for different vegetation communities,sampling in the field,and using ENVI remote sensing platform for vegetation coverage calculation.Construct a measured model of structural vegetation coverage of different vegetation communities.(2)Construction and verification of remote sensing model of structural vegetation index.Luoyugou was selected as a typical watershed,based on ground measured green vegetation coverage,litter cover,structural vegetation coverage,and Landsat remote sensing data from 1990 to 2017,using the selected greenness index and yellowness index to construct the structure.Remote sensing estimation model of sexual vegetation coverage,and using the verification data to evaluate the model adaptability.The remote sensing model of structural vegetation index can more accurately reflect the structural vegetation coverage of vegetation communities.(3)Analysis of temporal and spatial variation characteristics and influencing factors of structural vegetation coverage in Luoyugou watershed.Using MK trend test and complex regression analysis to analyze the spatial and temporal variation characteristics and influencing factors of the structural vegetation index in Luoyugou watershed from 1990 to 2017,the structural vegetation index in most areas of Luoyugou watershed showed an increasing trend,and the climatic factors were The increase of structural vegetation index in the study area has played a major role in promoting,and human activities have also had a certain impact on the structural vegetation index of the Luoyugou watershed.(4)Establish the influence function of vegetation structure change on runoff and sediment yield in the basin.Based on the hydrological data of the basin,using the indicators of runoff coefficient,sediment yield index and P50/P10,the effects of vegetation structure changes on the hydrological processes such as sediment runoff in the basin are simulated.Under the same precipitation conditions,the greater the coverage of structural vegetation,the smaller the runoff coefficient or the water production rate in the basin.Under the same structural vegetation coverage level,the annual precipitation in the basin is more,and the runoff yield is on the structural vegetation cover.The sensitivity of the degree is stronger;the greater the rainfall intensity in the basin,the weaker the response of structural vegetation cover to the amount of sediment production.