We evaluated the response of vegetation’s photosynthetic activity to drought conditions from 1998 to 2014 over Romania and the Republic of Moldova. The connection between vegetation stress and drought events was assessed by means of a correlation analysis between the monthly Standardized Precipitation Evaporation Index (SPEI), at several time scales, and the Normalized Difference Vegetation Index (NDVI), as well as an assessment of the simultaneous occurrence of extremes in both indices. The analysis of the relationship between drought and vegetation was made for the growing season (from April to October of the entire period), and special attention was devoted to the severe drought event of 2000/2001, considered as the driest since 1961 for the study area. More than three quarters (77%) of the agricultural land exhibits a positive correlation between the two indices. The sensitivity of crop areas to drought is strong, as the impacts were detected from May to October, with a peak in July. On the other hand, forests were found to be less sensitive to drought, as the impacts were limited mostly to July and August. Moreover, vegetation of all land cover classes showed a dependence between the sign of the correlation and the elevation gradient. Roughly 60% (20%) of the study domain shows a concordance of anomalously low vegetation activity with dry conditions of at least 50% (80%) in August. By contrast, a lower value of concordance was observed over the Carpathian Mountains. During the severe drought event of 2000/2001, a decrease in vegetation activity was detected for most of the study area, showing a decrease lasting at least 4 months, between April and October, for more than two thirds (71%) of the study domain.

中文翻译：

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干旱对东南欧植被的影响

我们评估了罗马尼亚和摩尔多瓦共和国从1998年至2014年植被的光合作用活动对干旱条件的响应。通过在几个时间尺度上的每月标准降水蒸发指数（SPEI）与归一化植被指数（NDVI）之间的相关分析，以及同时进行的评估，来评估植被压力与干旱事件之间的联系。在两个指数中都出现极端。分析了整个生长季节（整个时期的4月至10月）的干旱与植被之间的关系，并特别注意2000/2001年的严重干旱事件，该事件被认为是自1961年以来最干旱的一次研究。区。四分之三以上（77％）的农业用地在两个指数之间表现出正相关。作物区域对干旱的敏感性很强，因为从5月到10月发现了影响，而7月达到了顶峰。另一方面，人们发现森林对干旱的敏感性较低，因为其影响主要限于七月和八月。此外，所有土地覆盖类别的植被都显示出相关符号和海拔梯度之间的相关性。大约60％（20％）的研究领域显示出异常的植被活动异常与8月至少50％（80％）的干旱条件一致。相比之下，喀尔巴阡山脉的一致性较低。在2000/2001年的严重干旱事件中，大部分研究区域的植被活动均减少，