Degeneration of Alpine Steppe Vegetation around Sary-Tash Village, Kyrgyz Republic

Abstract

We investigated whether overgrazing has caused the degeneration of steppe vegetation around SaryTash Village (southern Kyrgyz Republic) at an elevation of 3,100 to 3,400 m. Six vegetation lines, combining slope direction (N, north; S, south) with elevation zone (1, high; 2, middle; 3, low) and containing 8 plots (2 m × 2 m) per line, were established. The line of S2 lies on the slope of degenerated vegetation. In each plot, species composition, coverage, plant height, and plant growth form were surveyed in July 2012. V-values were calculated as an estimate of above-ground biomass. As a result, 6 species, including Carex sp., Artemisia sp., and Deschampsia caespitosum, were distributed along all lines with relatively high consistency and coverage classes, and several species including those in the Poaceae, Asteraceae, and Brassicaceae were characterized along each line. The similarity of species composition was significantly smaller among the south-oriented lines (with CC ranging from 0.309 to 0.339) than among the north-oriented lines (CC from 0.418 to 0.509). Analysis of variance proved that south-facing slopes were covered with a tall, sparse community and north-facing slopes were covered with a short, dense community. Differences in V-values and total number of species were not significant among the lines. The half-change interval (HC), calculated from the similarity in species composition between plots, was significantly smaller in S2 and S3 (the HC values were 2.1 and 1.9 plots, respectively) than the other lines (HC ranged from 5.3 to 11.3). This suggests that the replacement of species was intense (i.e., beta diversity was high) in south-facing slopes, except for S1. The growth form spectrum in S2, comprising a smaller percentage of ‘t’ (tussoks) and larger percentages of ‘r-e’ (erect-form forbs with rosettes) and ‘b’ (branched forms) than the other lines, was inconsistent with the changes generally reported as being caused by grazing. Consequently, we cannot attribute the degeneration of vegetation in S2 to grazing alone. Other environmental factors deserve attention in order to explain the cause of degeneration.