| With the influence of human activities and climate factors,grassland degradation and socio-ecological sustainable development have received widespread attention.The process of grassland degradation is relatively long,and the accompanying changes in ecosystem structure and land use may interfere with the diagnosis of remote sensing indicators and affect the assessment of grassland bearing pressure.Grassland degradation is manifested as quantitative degradation that can be directly detected by remote sensing indicators;on the other hand,it is also reflected in structural changes in the ecosystem.For structurally degraded grasslands,verify whether remote sensing indicators can account for ecosystem degradation based on high-resolution remote sensing images and Unmanned Aerial Vehicle Remote Sensing.In order to cope with grassland degradation,rest grazing and grass-animal balance have become the most important protection measures.At present,spring grazing time is basically the same in all regions.The support of clearly expressed data makes no accurate basis for grazing time.This study uses multi-source remote sensing data and animal husbandry statistical data to conduct grassland degradation and grassland carrying pressure assessment studies in Xilinguole League:First,based on the balance between the supply and consumption of grassland ecosystems in Xilinguole League,the supply of grassland resources was estimated by Capacity and animal husbandry consumption of grassland resources,analysis of grassland carrying capacity and its changing mechanism in each area of Xilinguole League;Secondly,the spatial-temporal pattern of quantitative grassland degradation is compared with the bearing pressure,and the experimental area is studied for the degradation of structural grassland degradation area.Combined with object-oriented classification,visible light vegetation index and other methods,in different types of grassland shrub areas Comparative analysis of vegetation index.Finally,the grazing resumption period is one of the most important measures to prevent grassland degradation.A scientific analysis of the grassland regrazing period provides an accurate space and time basis for the formulation of the grazing reversion policy.Research indicates:(1)The grassland bearing pressure in Xilinguole League is a dividing point between 2005 and 2011,showing a fluctuation trend of decreasing first and then increasing steadily.The grassland bearing pressure decreased from the overload state to the surplus state,and then increased to the critical overload state.Due to the impact of ecological protection policies since 2000,the degree of overload has eased.The fluctuation trend after 2011 is also closely related to policy development,animal husbandry and local economic development.Overloaded areas are stably distributed in low-coverage grasslands with low grassland supply and small grassland areas.From the perspective of ecological consumption,the consumption of grassland resources in Xilinguole League first decreased and then increased,and the overall fluctuation trend showed a downward trend.The intensity of grassland resource consumption during this period has always exceeded the supply of grassland resources,and the intensity of the use of local grassland ecosystems has been greater.The areas with the most abundant grassland resources in Dongwu Banner and Xiwu Banner consume 1/3 of the grassland resources of Xilinguole League.The grassland consumption per unit area of Xilinguole League is 23.96gC/m~2.Grassland supply per unit area in Eastern and Southern Banner counties is higher than the league average.From the perspective of ecological supply,the average NPP of the grassland in Xilinguole League is 101.00gC/m~2,which is relatively low in the country.The supply of grassland resources fluctuated within the range of 1.36-3.42 TgC.The lowest supply was about 42%lower than the average state,and the abundant supply was 43%higher than the average state during the high season.From the perspective of spatial location,the NPP spatial distribution of grassland in Xilinguole League is uneven.The NPP value in the eastern,southern and northern regions is higher than that in the central and western regions,which has a great relationship with the local climate and precipitation.(2)The quantitative grassland degradation area in Xilinguole League is relatively wide.Moderate and severely degraded areas are mainly distributed in the grasslands in the north of Abaga Banner,in the west of Dongwu Banner,in the west of Xianghuang Banner,in the southwest of Xilinhot and in the southeast of Xiwu Banner.In the future development of this region,attention should be paid to the protection of grassland resources,reducing the scale of livestock breeding,preventing further degradation of grassland,and excessive consumption of grassland resources.The quantitative grassland degradation results are compared with the spatiotemporal distribution of the bearing state of the Xilinguole League.The grassland degradation distribution is basically consistent with the distribution state of the Xilinguole League bearing state.There are some inconsistent areas,which may be caused by structural degradation in grassland degradation.Therefore,the experimental area verification was performed on the structural grassland degraded area combined with UAS data.Comparing the UAS image with the Sentinel-2A remote sensing image,it can be found that the UAS image and the remote sensing image are basically the same in terms of ground features.However,due to the limited spatial resolution(10m)of satellite remote sensing images,it is difficult to distinguish scattered scrubs.Because the scrubs incorporate mixed pixels in the remote sensing images,the observation of grassland brings certain disadvantages.The distribution characteristics of the shrubs in the two experimental areas are different.The distribution of the shrubs in the desert steppe experimental area is more scattered than that in the typical steppe experimental area.Comparing the vegetation index of the shrub area and the non-shrub area,the mean and standard deviation of the non-shrub area are smaller than the shrub area,and the difference in the distribution of the vegetation index is greater than that of the shrub area.The vegetation index of the clump area is greater than that of the non-shrub area,which causes the error that the vegetation growth in the shrub area is better than that of the non-shrub area,which interferes with the judgment of grassland degradation.(3)The average green-up date of Xilinguole League from 2000 to 2018 was 132days(May 13),and it showed a trend of gradually postponing from the east to the west.This distribution is consistent with grassland coverage and NPP distribution.Green-up dates of grasses with higher NPP distribution are earlier.The high-coverage grasslands in the southeast of Xilinguole League and the northern part of Abaga Banner are more stable,and the green-up dates of the grasslands in the west are more variable and are more susceptible to factors such as temperature and precipitation.From 2000 to 2018,the green-up date of the grassland in Xilinguole League showed an overall trend ahead.Before 2008,the green-up date basically maintained a steady fluctuation trend.After 2008,it showed a"advance-delay-advance"trend.The change trend after 2008 may be related to factors such as temperature and precipitation.Comparing the green-up date of the Xilinguole League grassland extracted from remote sensing in 2018 with the actual grazing time as stipulated by the policy,the remote sensing data and the actual grazing time are different.Extracting the green-up date of grassland by remote sensing and accurately grasping the spatio-temporal changes of pasture growth can provide accurate data support for grazing rest time,guide the implementation of grazing rest policy,strengthen the scientific management of grassland,and protect the vulnerable grassland ecology. |
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