Spatio-temporal trend analysis of vegetation productivity in Europe using MODIS data sets

Some previous studies showed that ecosystem biogeochemical processes were significantly affected by variation of the temperature regime. For example, experimental warming led to photosynthesis intensification and increasing of the vegetation productivity and biomass accumulation (Elmendorf et al. 2012; Lin et al. 2010; Lu et al. 2013; Wu et al. 2011). However, such association is not so clear under natural conditions (Mohamed et al. 2004). This study provides the results of a pixel-wise trend analysis which has been performed to identify regional trends in the vegetation productivity for the European territory over the last 14 years. The moderate-resolution imaging spectroradiometer (MODIS) time series data have been used to analyse net primary productivity (NPP) trends. The changes in terrestrial carbon stock caused by the dynamics of vegetation productivity have been estimated. The negative trend of the vegetation productivity was found for Eastern Europe. It was found that the increased summer temperatures negatively influenced the vegetation productivity in Western, Eastern and Southern Europe. The findings suggest that the mean summer temperatures have reached a threshold in Southern Europe and its subsequent growth would lead to reducing the vegetation productivity. At the same time in the northern regions, the threshold has not been reached; therefore, summer temperatures increasing will stimulate the growth of vegetation. Analysing the changes for different types of vegetation it can be noted that the carbon stocks of agricultural land have been decreased by 2.67 Mt C, while forests and savannah areas have positive dynamic (the carbon stocks have been increased by 1.64 and 3.7 Mt C respectively). Summary results for the whole European region indicate a positive trend (2.67 Mt) of C stock in the terrestrial vegetation.