Stages of grassland degradation in subalpine ecosystems of the Central Caucasus, Russia

Overgrazing and grassland degradation are significant environmental problems in the mountain ecosystems of the Central Caucasus. The aim was to define the criteria for the stages of grassland degradation to provide land managers with useful guidelines on evaluating grassland status. We identified four stages of grassland degradation based on a statistical analysis of 23 vegetation and soil parameters at 126 model plots in the subalpine meadows. Main indicators of grassland degradation were grass height, coverage of forage species, coverage of grazing-resistant species, and fresh herbage yield. Grass height decreased significantly (P < 0.05) with each stage of grassland degradation from 31.4 ± 3.6 cm in untransformed grasslands to 3.3 ± 1.7 cm in severely degraded pastures. Fresh herbage yield in untransformed grasslands (120.8 ± 12.5×102 kg ha-1) was 81% higher than in highly degraded pastures. Coverage of forage species decreased in the row of grassland degradation from 72% to 34%, while coverage of grazing-resistant species increased with grazing intensity from 23% to 77%. Critical values of the integral degradation index based on these four parameters are useful for a reliable assessment of grassland status in the field.