Invasive species in the grasslands of the central caucasus.
Biological invasions and grassland transformation are significant problems in pasture ecosystems of the Central Caucasus. The aim was to study the main patterns of invasive processes in grasslands and included identification the main vegetation parameters and abiotic factors affecting the invasion and distribution of alien species (Erigeron annuus, Ambrosia artemisiifolia, and Xanthium albinum) in plant communities. We assessed vegetation parameters of steppe grasslands with the presence of alien species within 122 model plots on plains, in foothills and low mountains (250-1000 m above sea level). We also modeled the current habitats of the species in grasslands of the Central Caucasus by using the Maxent method. The most suitable for invasion and distribution of Erigeron annuus are productive grasslands (NDVI is 0.25 and more) of the foothills and low mountains with a moderately warm humid climate (average annual temperature is 5-10°C; precipitation of the most humid quarter is 240-300 mm). The most suitable for Ambrosia artemisiifolia are medium-productive grasslands (NDVI is 0.25-0.38) of the foothills and low mountains with low vegetation coverage (65-85%) and moderately humid climate (precipitation of the most humid quarter is 225-275 mm). The most suitable for Xanthium albinum at present are dry unproductive disturbed grasslands of plains.