Future scenarios for high-mountain wetlands in the Eastern Pamir under the ongoing climate changes

The Pamir Mountains are located in the southeastern part of Central Asia. Their eastern part is characterized by cold desert climate, with an annual sum of precipitation below 100 mm, high insolation, strong winds and the presence of permafrost. High-altitude wetlands located there at approximately 3800 m a.s.l., establish in the vicinity of lakes and in the river valleys, and function as complex systems influenced by a combination of arid or hyperarid climate with glacial, cryogenic, fluvial and shore processes. They play several important roles, including that of water sources and forage grounds for people and their livestock. In the presented study we proposed a scenario of potential transformations of high-altitude wetlands caused by climatic changes currently observed and projected in the nearest future for the Eastern Pamir. To obtain this goal, we collected data on the spatial structure and biodiversity of vegetation mosaic accompanying selected water bodies located in the watersheds of Yashilkul and Rangkul lakes, during field expeditions between 2014 and 2019.  Apart from vegetation survey, we also collected soil samples, which were dried, ground and their salinity and CNP content were analyzed with standard analytical methods. Moreover, we identified present changes in temperature and precipitation in both catchments using data from two meteorological stations located there, and analyzed alterations in area of lakes and small water bodies in the vegetation mosaic using Landsat 1-8 data from 1972 to 2018.

Biodiversity observed in the vegetation patchwork around the lakes and along the rivers comprised 110 vascular plant species, forming 10 distinct associations with different environmental requirements and adaptations. Such diversification was possible due to local differences in soil properties resulting from varied terrain features formed as a consequence of intense cryogenic processes. The dominating species belonged to the groups relatively resistant to temperature changes (i.e. graminoids, small shrubs and forbs) and were characterized by rather broad elevational ranges (reaching even below 1000 m a.s.l.). According to the meteorological data, mean annual air temperatures in the studied locations increased over the last 10 years by ~1^oC as compared to the period of 1950-1997. Simultaneously, areas of the studied lakes and small water bodies around them have showed an increasing trend since 1972. These observations, combined with the presence of shallow ground ice in the studied area, indicate that wetlands may be currently supplied in water by the thawing processes. Thus, in the nearest future vegetation will expand further from the water bodies, yet its spatial structure may change, in favor of species adapted to growth in brackish stagnant water. Some habitats may be also restricted or damaged due to intensified river flow and local disturbances caused by cryogenic processes. When temperatures become high enough to prevent the renewal of ground ice and to significantly lower the level of impermeable permafrost, vegetation will retreat following receding shoreline of the water bodies, and drought and salinity tolerant species will dominate. The described alterations will heavily impact the use of high-mountain wetland as pastures.