Research On Dynamic Monitoring Of Vegetation Productivity In Desert Steppe At Village Scale

The desert steppe area in the farming-pastoral zone in northern China is not only an important part of the grassland,it plays an important role in my country's ecological barrier,and it is also an important animal husbandry production base.The fragile environment and lack of resources are the key to restricting the coordinated development of ecology and production in this region.Timely and accurately grasping the vegetation growth status and changing trends in the desert grassland area is conducive to promoting the sustainable use of resources in the agricultural and pastoral system and grassland security.The application of the domestic high-resolution series of remote sensing satellites provides a reliable technical route for this.Based on the remote sensing satellites of BJ-2 and GF-6,with Wanjigou Village in Yanchi County of Ningxia as the object,this study carried out the construction and verification of the vegetation parameter estimation model with high time resolution at the village scale,and tried to use it in the pasture.Dynamic and precise management of the productivity of the scale farming and pastoral system.The main research results and conclusions are as follows:(1)Construction and verification of remote sensing estimation model for vegetation parameters at village scale with high temporal resolution.Through the collection of the BJ-2 with high spatial resolution in 2019 and 15 high time resolution GF-6 satellite remote sensing image data in 2020,combined with ground measurement of land vegetation canopies of different types of use Layer spectrum and vegetation growth parameter data,analyze the canopy spectrum characteristics of vegetation in different growth stages in the growing season.After screening,seven different types of vegetation indices were selected,and models were constructed with the aid of three methods.According to the results of comparative analysis,the Leaf area index(LAI)and biological indicators for grassland,Caragana korshinskii shrub and farmland crops in desert grasslands were established respectively.Estimation model of parameters such as volume and coverage.At the same time,the study found that when constructing a desert grassland vegetation parameter estimation model,multiple input parameters are used at the same time,and the model accuracy and application ability obtained are higher.The participation of the vegetation index in the red band is beneficial to increase the accuracy of the multi-parameter estimation model.Due to its own advantages,the neural network algorithm has higher accuracy than the model established by using a single vegetation index and multiple vegetation indexes with the help of multiple linear regression to establish the LAI,biomass and coverage of desert grassland vegetation.The model constructed based on the vegetation index for the vegetation LAI and biomass in the study area has good estimation ability,but the estimation ability of the model for vegetation coverage is weak.(2)Using the pre-processed GF-6 remote sensing image data,the vegetation growth status and change trend of different land use types in the desert grassland can be monitored in a timely,rapid and accurate manner.Studies have confirmed that the use of GF-6 remote sensing images with high temporal resolution and medium spatial resolution can quickly and accurately obtain vegetation growth status and change information in desert grasslands over a large area.The monitoring results show that vegetation parameters such as grassland LAI,coverage,and biomass on desert grasslands will change rapidly in a short period of time,while the vegetation parameters of artificial Caragana korshinskii forest change relatively smoothly after the main growth period ends.During the whole growing season,the surface LAI and biomass in the northeast region of the study area were relatively low.During the same period,the vegetation parameters of the same land use type had relatively small differences,and the vegetation parameters of different land use types were significantly different.The highlight is that between July and November when vegetation is growing vigorously,LAI and biomass are displayed as farmland>caragana korshinskii forest>grassland at the same time throughout the year.(3)Combining the number of sheep raised by different farmers,the quality of the pasture and the yield of crops,the problems of the fencing-scale pasture carrying capacity and the farming and pastoral productivity fine management at the farmer-scale are analyzed.The actual grazing capacity of the grassland in the study area is relatively small.The feed obtained through natural grassland can only meet 30.17%of the number of sheep in 2020,and the natural forage obtained through natural conditions cannot meet the normal grazing production activities of farmers.The suitable grazing intensity of most fences is between 0.71 and 1.48 sheep/hm2,and most of them are in a state of overload and overgrazing.Grazing has a greater impact on grassland vegetation and stability.On the premise of maintaining the ecological functions of the desert grassland and grazing production,the sheep feed gap in Wanjigou Administrative Village is relatively large,with a gap of 6517.39t.In order to meet the purpose of animal husbandry production,the harvest time of farmland crops in the study area can be appropriately advanced according to the monitoring results.For example,the harvest time in 2020 is more appropriate between September 6 and September 23.Under grazing conditions,the maximum value of vegetation above-ground organisms in the pasture will be lower than that in enclosed areas,and high-intensity grazing will delay the appearance of the maximum value of vegetation above-ground organisms.