Vegetation vulnerability to drought on southeastern Europe

Abstract. In this work, the impacts of drought events on vegetation activity in the period 1998–2014 were analysed, on an area located in southeastern Europe, using the Standardized Precipitation Evaporation Index (SPEI) at several time scales, and the Normalized Difference Vegetation Index (NDVI), as obtained by SPOT/VEGETATION. A correlation analysis between monthly NDVI and SPEI was performed, as well as the assessment of the simultaneous occurrence of drought events and low vegetation activity. The analysis was performed from April to October, corresponding to the months showing the highest vegetation activity. The impacts of drought were assessed in the entire period, but also on the drought event in 2000/2001, which was the driest in this area since 1961. The results show the area with positive correlation between the two indices reaches 77 % in July on agricultural land, and its impacts are seen from May to October, pointing to a high vulnerability to drought. Forests seems to be less sensitive to drought, although being more influenced by drought mostly on July and August. However, negative correlations were also observed in June at high altitudes pointing to a positive effect of dryness on the vegetation activity. This feature changed in July, possibly as a result of the increasing temperature coupled to the decrease in precipitation that leads to a water stress situation. The drought event in 2000 provoked a generalized decrease in vegetation activity, and 71 % of the area showed a decrease on at least four months between April and October. Almost 60 % (20 %) of the studied area presents a concordance of anomalous low vegetation activity and dry conditions of at least 50 % (80 %) on the month of August, whereas the Carpathian Mountains generally present a lower value of concordance than the remaining area.