基于MODIS植被指数的青海省玛多县草畜关系分析

The analysis of relationship between grassland and livestock based on MODIS vegetation index in Madoi in Qinghai

为了研究青海玛多县草畜关系特征,对2008—2009年9个样地的实测地上生物量与MODIS(Moderate-resolution Imaging Spectroradiomete)归一化植被指数(NDVI)、增强型植被指数(EVI)分别基于线性、幂和指数函数建立回归模型,对理论地上生物量进行反演估算,并依据相关公式计算理论载畜量。结果表明:线性函数模型具有较好的模拟效果;2009年玛多县草地地上生物量显著高于2008年;玛多县基于NDVI的2008,2009年理论载畜量分别为40.93万、57.45万羊单位,基于EVI的理论载畜量分别为41.30万、59.03万羊单位;而玛多县2008,2009年年末的牲畜存栏数分别为33.11万、33.71万羊单位,可见玛多县这2年的理论载畜量尚有盈余。说明玛多县总体上正在由草畜关系极不平衡状态向逐渐草地恢复状态逐渐改变。

To study the relationship characteristics between grassland and livestock in Madoi, the regression model of linear, power and exponen- tial functions were established between measured aboveground biomass from nine sample plots and MODIS （ Moderate - resolution Imaging Spec- troradiometer） vegetation indices NDVI （Normalized Difference Vegetation Index） and EVI （Enhanced Vegetation Index） in 2008 and 2009, based on which to estimate theoretical grassland aboveground biomass, and to calculate theoretical grazing capacity according to the related for- mula. The results showed that linear function model had a preferable effort of simulation ; the estimation results based on NDVI and EVI conclu- ded that the theoretical aboveground grass biomass in 2009 was obviously higher than that of in 2008, which might be related with increased an- nual precipitation in the later year. The theoretical grazing capacity based on NDVI were 409.3 and 574.5 thousands standard sheep units in 2008 and 2009 respectively; while based on EVI they were 413.0 and 590.3 thousands sheep units respectively. Since the livestock inventories at the end of 2008 and 2009 in Madoi were only 331.1 and 337.1 thousands sheep units respectively, indicating that the theoretical grazing capacities of the two years were to some degree surplus. It indicates that the grassland - livestock relationship in Madoi has generally changed from terrible imbalance to gradually recovering state.