BackgroundUnderstanding spatiotemporal climate and vegetation changes and their nexus is key for designing climate change adaptation strategies at a local scale. However, such a study is lacking in many basins of Ethiopia. The objectives of this study were (i) to analyze temperature, rainfall and vegetation greenness trends and (ii) determine the spatial relationship of climate variables and vegetation greenness, characterized using Normalized Difference in Vegetation Index (NDVI), for the Dhidhessa River Basin (DRB). Quality checked high spatial resolution satellite datasets were used for the study. Mann–Kendall test and Sen’s slope method were used for the trend analysis. The spatial relationship between climate change and NDVI was analyzed using geographically weighted regression (GWR) technique.ResultsAccording to the study, past and future climate trend analysis generally showed wetting and warming for the DRB where the degree of trends varies for the different time and spatial scales. A seasonal shift in rainfall was also observed for the basin. These findings informed that there will be a negative impact on rain-fed agriculture and water availability in the basin. Besides, NDVI trends analysis generally showed greening for most climatic zones for the annual and main rainy season timescales. However, no NDVI trends were observed in all timescales for cool sub-humid, tepid humid and warm humid climatic zones. The increasing NDVI trends could be attributed to agroforestry practices but do not necessarily indicate improved forest coverage for the basin. The change in NDVI was positively correlated to rainfall (r2 = 0.62) and negatively correlated to the minimum (r2 = 0.58) and maximum (r2 = 0.45) temperature. The study revealed a strong interaction between the climate variables and vegetation greenness for the basin that further influences the biophysical processes of the land surface like the hydrologic responses of a basin.ConclusionThe study concluded that the trend in climate and vegetation greenness varies spatiotemporally for the DRB. Besides, the climate change and its strong relationship with vegetation greenness observed in this study will further affect the biophysical and environmental processes in the study area; mostly negatively on agricultural and water resource sectors. Thus, this study provides helpful information to device climate change adaptation strategies at a local scale.

中文翻译：

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埃塞俄比亚 Dhidhessa 河流域的时空气候和植被绿度变化及其关系

背景了解时空气候和植被变化及其关系是在局部范围内设计气候变化适应策略的关键。然而，埃塞俄比亚的许多盆地都缺乏这样的研究。本研究的目的是 (i) 分析温度、降雨量和植被绿度趋势，以及 (ii) 确定气候变量和植被绿度的空间关系，使用植被指数归一化差异 (NDVI) 进行表征，对于 Dhidhessa 河流域 ( DRB）。质量检查的高空间分辨率卫星数据集用于研究。Mann-Kendall 检验和 Sen 斜率方法用于趋势分析。使用地理加权回归（GWR）技术分析气候变化与 NDVI 之间的空间关系。 结果根据研究，过去和未来的气候趋势分析普遍显示 DRB 的湿润和变暖，其中趋势程度随时间和空间尺度的不同而变化。该盆地还观察到降雨量的季节性变化。这些调查结果表明，该流域的雨养农业和水资源供应将受到负面影响。此外，NDVI 趋势分析普遍显示大多数气候带在年度和主要雨季时间尺度上都呈现绿化。然而，在凉爽的半湿润、温和湿润和温暖湿润气候区的所有时间尺度上都没有观察到 NDVI 趋势。NDVI 趋势的增加可归因于农林业实践，但并不一定表明该流域的森林覆盖率有所提高。NDVI 的变化与降雨量呈正相关（r2 = 0. 62) 并且与最低 (r2 = 0.58) 和最高 (r2 = 0.45) 温度呈负相关。该研究揭示了流域气候变量与植被绿度之间的强烈相互作用，进一步影响了地表的生物物理过程，如流域的水文响应。结论该研究得出结论，DRB 的气候和植被绿度趋势在时空上发生变化. 此外，本研究观测到的气候变化及其与植被绿度的密切关系将进一步影响研究区的生物物理和环境过程；主要对农业和水资源部门不利。因此，这项研究为当地规模的设备气候变化适应策略提供了有用的信息。该研究揭示了流域气候变量与植被绿度之间的强烈相互作用，进一步影响了地表的生物物理过程，如流域的水文响应。结论该研究得出结论，DRB 的气候和植被绿度趋势在时空上发生变化. 此外，本研究观测到的气候变化及其与植被绿度的密切关系将进一步影响研究区的生物物理和环境过程；主要对农业和水资源部门不利。因此，这项研究为当地规模的设备气候变化适应策略提供了有用的信息。该研究揭示了流域气候变量和植被绿度之间的强烈相互作用，进一步影响了地表的生物物理过程，如流域的水文响应。结论该研究得出结论，DRB 的气候和植被绿度趋势在时空上发生变化. 此外，本研究观测到的气候变化及其与植被绿度的密切关系将进一步影响研究区的生物物理和环境过程；主要对农业和水资源部门不利。因此，这项研究为当地规模的设备气候变化适应策略提供了有用的信息。