碌曲县生长季草地植被覆盖度与生产力动态特征

Dynamic characteristics of vegetation coverage and productivity in grassland growth season in Luqu county

针对碌曲县地形地貌复杂的特点,应用MODIS产品数据与地面调查相结合,以该县2018年6-9月的数据为例,研究了不同类型草地主要生长季节的植被盖度和产量动态。结果表明:NDVI像元二分模型和回归模型能够较好地反映草地的植被盖度和草产量,碌曲县主要草地类型为高寒草甸和山地草甸,面积为37.55万hm2,高寒草甸占比较大,为56.86%。碌曲县草地生长季植被平均盖度呈先上升后下降的趋势,并在7月达到峰值,为81.77%,9月最小,为49.45%;山地草甸和高寒草甸的平均盖度也是7月最大,分别为82.38%和81.33%;6-8月的草地平均盖度以Ⅰ级为主,分别占全县草地面积的65.53%、93.32%和69.84%,9月以Ⅱ级为主,占比为58.74%。根据样地样方实测数据与相应点影像NDVI提取值,建立6-9月产量估测模型,各月全县和各草地类型的可食牧草干草平均产量呈现逐步增大的趋势,9月产量最高。

Vegetation coverage and yield are usually used as important indicators for the investigation and evaluation of the grassland resources.Due to the complex topography in Luqu County,a combination of telemetry with MODIS data and ground surveys were used to study the vegetation coverage and yield of different types of grassland in growing seasons from June to September in 2018.Our results showed that NDVI pixel binary model and regression model could reflect the vegetation coverage and grass yield of grassland.In Luqu county,the grassland were dominated by alpine meadows and mountain meadows,with a total area of 3.755×105 hm2 and 56.86%being alpine meadows.The vegetation coverage of grassland in Luqu county showed a dynamic trend,with an initial increase from June and a peak in July(81.77%),followed by a decrease with the lowest value in September(49.45%).The vegetation coverage of alpine meadows(82.38%)and mountain meadows(81.33%)also peaked in July.The vegetation coverage from June to August was 65.53%、93.32%and 69.84%of the grassland area and categorized as Grade I;and reduced to 58.74%in September and categorized as Grade II.The production estimation model was developed between June and September from the field data and the corresponding point value of NDVI images.The production of edible pasture hay of Luqu county increased with the growth season and reached a peak value in September.