The role of vegetation, especially forest ecosystems, is outstanding as a climatic indicator. In our sample area in Hungary the proportion of the trees is high and the afforestation is intense. For the geographic evaluation of the climate changes, MOD13Q1 NDVI / EVI data in 2000–2017 summer period were investigated. In the whole index series the biomass does not show a trend change in either the deciduous, the coniferous or the mixed forest categories. Reduction process is typical for consecutive drier years, but a subsequent wet season is sufficient for the forests to avoid decrease over the longer term. In the main droughty periods of July-August, the effect of dry year following the rainy years immediately reduces the green biomass. The changes in the vegetation period are also wellassessed; such as a change in spring intensity or an increase in summer biomass product, for example the mixed forest show growth not only in the spring but also at the highest summer values. The deciduous characteristic is the decrease in the maximum biomass production. Changes over the nearly two decade period are currently compensated, but forests are vulnerable within a short period of time. According to the standardized deviations in the consecutive years with significant differences, biomass production in the north and southwest of the sample area was reduced. The determination coefficients between VI data and drought index data show strong relationship (R2 ~0,85). This validation is verified by the LANDSAT VI data as well.
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