评估1982年至2015年气候对东非植被动态的影响。,Scientific Reports

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评估1982年至2015年气候对东非植被动态的影响。
Scientific Reports ( IF 3.8 ) Pub Date : 2019-11-14 , DOI: 10.1038/s41598-019-53150-0
Wilson Kalisa ₁ , Tertsea Igbawua _{1,

2} , Malak Henchiri ₁ , Shahzad Ali ₁ , Sha Zhang _{1,

2} , Yun Bai _{1,

2} , Jiahua Zhang ₂

Affiliation

东非地区位于赤道对面，是以前知道严重植被退化的非洲地区之一。一些已知的原因与气候变化事件和不专业的农业实践有关。为此，使用了降水量和温度的超高分辨率高分辨率辐射计（AVHRR）版本3 NDVI（NDVI3g）和气候研究单位（CRU）数据集来评估1982年至2015年气候因素对东非植被动态的影响还探讨了NDVI与气候因子的皮尔逊相关性，以调查短（十月至十二月）雨季。还提取了该地区的物候指标，以了解植被的季节性周期。结果表明，1998年之前的年均NDVI呈14.50×10-4的正线性趋势，其中1998年之后发现负线性趋势为-9.64×10-4。断裂点（BP）于1998年获得，表明NDVI对气候和非气候驱动因素的非线性响应。厄尔尼诺年代的ENSO植被显示ENSO与农田植被生长变化之间的弱遥相关性。此外，分析的NDVI数据相关性导致NDVI与降水之间的相关性高于温度相关性。Hurst指数结果显示，约有18.63％的像素表现出典型的随机游走行为（H = 0.5），这表明NDVI的增长变化最终可能最终持续，翻转或随驱动因素而随机波动。具有可持续（不可持续）趋势的植被趋势为36.8％（44.6％）。惊人地从退化到改善，约占植被总面积的20％呈现不可持续的趋势。此外，结果显示，东非上空的农田（非作物地）的植被变化很小，为6.9×10-5 /年（5.16×10-4 /年），这表明非作物地正在迅速减少。 NDVI对气候的每月和季节性变化的响应被认为是复杂而动态的。在季节性上，短雨季显示出NDVI的变异性高于长雨季。另外，DJF，MAM和SON季节受ENSO和NDVI系列降水变化的影响很大。这表明非耕地正在迅速减少。但是，NDVI对气候的月度和季节变化的响应被认为是复杂而动态的。在季节性上，短雨季显示出NDVI的变异性高于长雨季。另外，DJF，MAM和SON季节受ENSO和NDVI系列降水变化的影响很大。这表明非耕地正在迅速减少。但是，NDVI对气候的月度和季节变化的响应被认为是复杂而动态的。在季节性上，短雨季显示出NDVI的变异性高于长雨季。另外，DJF，MAM和SON季节受ENSO和NDVI系列降水变化的影响很大。

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Assessment of climate impact on vegetation dynamics over East Africa from 1982 to 2015.

Located across the equator, the East Africa region is among regions of Africa which have previously known the severe vegetation degradation. Some known reasons are associated with the climate change events and unprofessional agricultural practices. For this purpose, the Advanced Very High Resolution Radiometer (AVHRR) version 3 NDVI (NDVI3g) and Climate Research Unit (CRU) datasets for precipitation and temperature were used to assess the impact of climate factors on vegetation dynamics over East Africa from 1982 to 2015. Pearson correlation of NDVI and climate factors were also explored to investigate the short (October - December) rainy seasons. The phenological metrics of the region was also extracted to understand the seasonal cycle of vegetation. The results show that a positive linear trend of 14.50 × 10-4 for mean annual NDVI before 1998, where as a negative linear trend of -9.64 × 10-4 was found after 1998. The Break Point (BP) was obtained in 1998, which suggests to nonlinear responses of NDVI to climate and non-climate drivers. ENSO-vegetation in El-nino years showed a weak teleconnection between ENSO and vegetation growth changes of croplands. Also, the analyzed correlations on NDVI data resulted to the higher correlation between NDVI and precipitation than that with temperature. The Hurst exponent result showed that about, 18.63% pixels exhibited a behavior, typical of random walk (H = 0.5) suggesting that NDVI growth changes may eventually persist, overturn or fluctuate randomly in the future depending on the drivers. Vegetation trends with sustainable (unsustainable) trends were 36.8% (44.6%). Strikingly, about 20% of the total vegetated area showed unsustainable trend from degradation to amelioration. More so, results reveal that the vegetation of the croplands (non-croplands) over East Africa changed insignificantly by 6.9 × 10-5/yr (5.16 × 10-4/yr), suggesting that non-croplands are fast getting reduced Nonetheless, the NDVI growth responses to monthly and seasonal changes in climate were adjudged to be complex and dynamic. Seasonally, the short rainy season showed the higher variability in NDVI than the long rainy season. Also, the DJF, MAM and SON seasons are strongly driven by precipitation variation effect of ENSO versus NDVI series.

更新日期：2019-11-14

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