DYNAMICS OF C4 SPECIES CYNODON DACTYLON L. ON PERMANENT GRASLAND FROM BANAT REGION (WESTERN ROMANIA) UNDER THE INFLUENCE OF CLIMATE

A factor that affects the Romanian pastureland patrimony are the climatic changes that are influencing the grassland plant communities, the most common considered in this way are the temperature and rainfalls, in many situations favouring the C4 species. It is well known that in the temperate grasslands are dominant the C3 species, but due to the climatic changes the C4 species have great opportunities to spread and to replace the C3 species. The coverage in sward and the production performances of the C3 and C4 species are dependent by the site conditions (temperature and rainfalls), the grassland type and its management. The paper has the purpose to evaluate the dynamics of a C4 species, respectively Cynodon dactylon L. in relationship with different grassland vegetation parameters influenced by temperature and rainfalls. The monitoring was performed during four years (2012 2015) on five lowland grassland plots from Timis County (Becicherecul Mic, Biled, Sandra, Lovrin and Cenad) with a high contribution of Cynodon dactylon L.. The analysis of the floristic composition was realised using the linear point quadrate method that have helped to the calculation of different vegetation indexes, respectively specific frequency (FS%), specific contribution (CS%), Shannon index (H) and pastoral value. The statistical method used was correlation. The independent variables considered were the climatic factors and the dependent variables were the vegetation features mentioned above. The results obtained highlight the existence of different correlations among the analysed variables, this being reflected on the contribution of the C4 species Cynodon dactylon.