Vegetation dynamics in Dzhily-su stow (Central Caucasus) against the background of anthropogenic impact variations on meadow ecosystems over the last 35 years

Abstract

High-mountain meadow phytocenoses in the upper Malka-river of the Kabardino-Balkarian Republic (Central Caucasus) have been long used by the local population in cattle-breeding, and the unique thermal spring of mineral water “Dzhily-Su” has been put to medicinal use. The pasture/recreation ratio of anthropogenic impact on meadow ecosystems of this region has varied with time. Vegetation has varied correspondingly. The comparative geobotanical vegetation analysis of meadow phytocenoses in Dzhily-Su stow using the data on five model plots in the subalpine belt over the years of 1983, 2010 and 2017 was performed. The long-term absence (10–20 years) or insignificant pasture load on high-mountain meadows of Dzhily-Su stow facilitates restoration of the initial state in the pasture ecosystem. The following moderate grazing in the same areas doesn’t cause pasture degradation and improves feeding properties of arable lands. High parameters of grass projective cover and average grass height are preserved, species abundance of phytocenoses increases, species of higher feeding value (Kobresia capilliformis, Bromopsis variegata) displace Festuca woronowii, and Veratrum lobelianum abundance declines. Conversely, intensive recreational load on mountain-meadow pasture ecosystems of the initial state decreases total grass projective cover with active ruderal species invasion of free plots including synanthropic species. The long-term (over 30 years) overgrazing causes phytocenosis degradation: decrease of grass projective cover, grass height, reserves of living superterranean phytomass, and distribution of ruderal species, poisonous species and inedible species in phytocenoses. Weed phytocenosis of low-feeding value-, inedible-, and partly nitrophilious species is formed instead of the degraded pasture under attendant soil nitrate pollution.