基于Landsat数据的乌鲁木齐市草地地上生物量时空演变及趋势分析

Temporal and Spatial Evolution and Trend Analysis on the Grassland Above Ground Biomass in Urumqi Based on Landsat Data

为探究乌鲁木齐市草地地上生物量(Above ground biomass,AGB)的时空演变规律及未来变化趋势,本研究采用1990—2021年Landsat数据及实测数据构建乌鲁木齐市草地AGB反演模型,分析研究区草地生长期(4—10月)各月AGB时空演变特征及稳定性,运用趋势分析法和Hurst指数等方法,揭示草地AGB的历史演变和未来变化趋势。结果表明,建立的AGB模型中,二次多项式反演模型精度最高,为86.07%;时空演变上,草地生长期整体及5—10月的AGB随年际变化呈波动增加趋势,4月则呈波动减少趋势,随经纬度的增加均表现为减少趋势,呈现出草甸区高,荒漠区低的水平分布格局,随海拔升高总体表现为山区>平原,且草地波动较为稳定;历史变化趋势上,生长期整体及5—10月AGB累计变化率均呈增加趋势,4月呈减少趋势,演变分级均以退化和稳定为主;未来变化趋势上,生长期整体及5—10月趋势变化均以稳定和改善为主,4月以退化和改善为主。研究结果可为乌鲁木齐市草地的科学评价及合理利用提供理论依据。

In order to explore the spatio-temporal changes and the trend of grassland above ground biomass(AGB)in Urumqi,this study used Landsat data and site measured data from 1990 to 2021 to establish an AGB inversion model for the grasslands in Urumqi.The spatio-temporal change characteristics and stability of AGB in each month of the grassland growth period(from April to October)in the study area were analyzed using trend analysis and Hurst index methods,the historical evolution and future trend of grassland AGB also revealed.The results show that for the establishment of the AGB models,the quadratic polynomial inversion model has the highest accuracy in simulation,reaching 86.07%.In terms of spatio-temporal evolution,the AGB during the growth period as a whole and from May to October showed a fluctuating increasing trend,while in April,it showed a fluctuating decreasing trend.With the increase of longitude and latitude,it showed a horizontal distribution pattern of high meadow areas and low desert areas.With the increase of altitude,the AGB overall showed a trend of mountainous areas>plains,and the fluctuation of grassland was relatively stable;In terms of historical change trend,both the overall growth period and the cumulative change rate of AGB from May to October showed an increasing trend,while in April,it showed a decreasing trend.The evolution grading was mainly characterized by degradation and stability;In terms of future trends,both the overall growth period and the trend changes from May to October are mainly stable and improved,while in April,they are mainly degraded and improved.The research results can provide theoretical basis for scientific evaluation and rational utilization of grassland in Urumqi.