基于不同地貌类型区甘南州植被覆盖时空变化及其影响因素研究

    Study on Spatial and Temporal Changes of Vegetation Coverage in Gannan Prefecture Based on Different Geomorphological Zones and Their Influencing Factors

    • 摘要: 甘南藏族自治州(简称甘南州)位于青藏高原东北边缘, 处在第一阶梯与第二阶梯的过渡区, 地貌类型复杂多变, 且在不同地貌区的植被覆盖差异十分明显。基于2000-2018年MODIS EVI数据研究甘南州不同地貌区植被覆盖时空变化趋势及其影响因素。结果表明: (1)从时间变化上来看, 2000-2018年甘南州西北部山原区、东部山地丘陵区和南部岷迭山谷区增强植被指数(EVI)增长趋势分别为0.000 8、0.001 1和0.000 9 a-1。(2)从空间变化上来看, 甘南州植被覆盖度(FCV)呈现由西南部向东北部逐渐递减的空间分布特征, 其中, 西北部山原区以较高覆盖度类型为主, 东部山地丘陵区以中等覆盖度类型为主, 南部岷迭山谷区呈现较低覆盖度与较高覆盖度类型的相间分布。(3)甘南州植被覆盖改善比例(约54%)高于退化比例(37%), 其中, 植被覆盖退化区主要分布在西北部山原区的玛曲、碌曲及南部山谷区的迭部等地; 植被覆盖改善区主要分布在东部山地丘陵区。(4)甘南州不同地貌区EVI的影响因素有所不同, 自然环境因子和人类活动因子是影响西北部山原区EVI的主要影响因素, 而自然环境因子是东部山地丘陵区、南部岷迭山谷区EVI的主要影响因素。

       

      Abstract: Gannan Tibetan Autonomous Prefecture is situated at the northeastern edge of the Tibetan Plateau, in the transition area between the first and second terraces, with complex and variable landform types and very pronounced differences in vegetation coverage. Based on MODIS EVI data from 2000 to 2018, the spatial and temporal trends of the change of vegetation coverage in different geomorphological zones of Gannan Prefecture and their influencing factors were studied and the results show that: (1) Based on temporal changes, the enhanced vegetation index (EVI) growth trends of the northwestern mountain plateau zones, the eastern mountainous hilly zones, and the southern Mindie Valley zones in Gannan Prefecture between 2000 and 2018 were 0.000 8, 0.001 1, and 0.000 9 a-1, respectively. (2) Based on spatial changes, the fractional vegetation coverage (FVC) of Gannan Prefecture demonstrated a decreasing spatial distribution from southwest to northeast. The mountainous area in the northwest was dominated by high coverage, the mountainous and hilly area in the east was dominated by medium coverage, and the Mindie Valley area in the south showed the alternate distribution of low coverage and high coverage. (3) In Gannan, the proportion of EVI improvement (approximately 54%) is greater than the proportion of degradation (about 37%). The majority of degraded EVI areas are located in the northwestern mountain plateau of Maqu and Luqu and the southern valleys of Diebu. The majority of EVI improvement areas are located in the eastern mountainous and hilly terrain. (4) The EVI influencing factors in various geomorphological zones of Gannan Prefecture are different. In this regard, human activity factors and natural environmental factors are the primary determinants of EVI in the northwestern mountain plateau zones, whereas natural environmental factors are the primary determinants of EVI in the eastern mountainous hilly zones and the southern Mindie valley zones.

       

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