Human beings affect the life on Earth for millenia, but using of natural resources during the last centuries and particularly decades is so intense, that has triggered global environmental changes having very negative consequences for life on our planet and humanity itself. This work presents and summarizes scientific outcomes of the author, which focus particularly on impacts of climate change, deposition of air-borne pollutants and changes in land use on species composition and diversity of temperate forest vegetation. The work is divided into three topic sections. The first one deals with climate change and its effects on i) plant species distribution along altitudinal gradient and ii) forest microclimate specificity and ability to buffer impact of global warming on forest understorey vegetation. The second section consists of impact of i) nitrogen deposition and ii) land and forest use change on understorey vegetation. These are two seemingly distinct phenomena, but their influence on vegetation is very interactive and thus written within single section. The last section introduces several methodological aspects of using data from permanent plots. Separately the topic of i) bias resulting from species overlooking during field sampling and uncertain spatial relocation of permanent plots, then ii) the using of community weighted means to identify environmental changes and iii) combining of different data to advance global change effects on forest ecosystems. The results of author`s work show and emphasize particularly the important role of forest structure in the mitigation of global warming. Moreover, structure of forests and its changes due to the abandonment of historical forest use were identified in several author`s studies also as a key feature that drives understory responses to nitrogen deposition. Therefore, the way how forests are managed and consequently how is the structure of forest stands is crucial for impacts of global environmental changes on forest biodiversity. Majority of author`s work is based on data from (semi-) permanent plots. Utilizing their potential however uncovered also their weaknesses and limits which originate particularly in observer bias and spatial variability of vegetation and environmental changes. The last part of the work therefore elucidates these methodological constrains and suggests future research directions that should be based on data combination from different sites and regions, resurvey studies and experiments, covering larger scales and environmental gradients. This approach increases the representativeness of results and improves their applicability in forest management guidelines to halt the loss and support the recovery of forest biodiversity during ongoing environmental changes.