Abstract

Vegetation net primary productivity (NPP) reveals the plants capability to transform solar energy to photosynthesis. It can be used as an indicator of status of environmental processes affected by climate changes and human activities, especially in degraded areas such as Gadarif State, Sudan, where vegetation degradation has progressively taken place. In this study, three types of net primary productivity from 2000 to 2017 were used to assess the relative roles of climate variables and human activities on vegetation variability in the eastern part of Sudan (Gadarif State) by ordinary least-square regression technique. The three types of NPP are the actual NPP derived from MODIS data, potential NPP estimated using Thornthwaite memorial model and human-related NPP, the difference between the Potential NPP and actual NPP. The correlations between NPP and climate variables are calculated using Pearson’s correlation coefficient. The results revealed that 91.7% of the study area has experienced vegetation degradation caused by human activities with a variation of 97.95% in NPP. In contrast, 8.3% of the study area has a recovery by 2.05% of increase in NPP favored by climate change. The main driving forces of vegetation degradation are human activities, and the dominant factor for vegetation reversion is climate. No clear interaction between the two factors (climate change and human activities) was observed in the study area throughout the period of study. Thus, we concluded that NPP is a good indicator for assessing the relative roles of climate changes and human activities in vegetation cover dynamics that has obviously occurred in almost all districts of Gadarif, Sudan.

中文翻译：

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利用GIS和遥感技术评估气候和人类活动对植被退化的影响

摘要

植被净初级生产力（NPP）揭示了植物将太阳能转化为光合作用的能力。它可以用作指示受气候变化和人类活动影响的环境过程状态的指标，尤其是在苏丹加达里夫州等退化地区，那里的植被已经逐步退化。在这项研究中，使用2000年至2017年的三种类型的净初级生产力，通过普通最小二乘回归技术评估了苏丹东部（加达里夫州）的气候变量和人类活动对植被变异的相对作用。三种类型的NPP是从MODIS数据得出的实际NPP，使用Thornthwaite纪念模型和与人相关的NPP估算的潜在NPP，潜在NPP与实际NPP之差。NPP和气候变量之间的相关性是使用Pearson相关系数计算的。结果表明，研究区域的91.7％经历了人类活动引起的植被退化，NPP的变化为97.95％。相反，受气候变化影响，研究区域的8.3％的NPP增长恢复了2.05％。植被退化的主要驱动力是人类活动，而植被恢复的主要因素是气候。在整个研究期间，研究区域内未观察到两个因素（气候变化和人类活动）之间的明显相互作用。因此，我们得出结论，NPP是评估气候变化和人类活动在植被覆盖动态中相对作用的一个很好的指标，这种变化显然已经在加达里夫的几乎所有地区发生，