Nature's patchwork: How water sources and soil salinity determine the distribution and structure of halophytic plant communities in arid environments of the Eastern Pamir.

Monika Mętrak,Elżbieta Rojan,Paweł Pawlikowski,Małgorzata Suska-Malawska,Dovutsho Navruzshoev,Marcin Sulwiński,Łukasz Chachulski,Dusan Gomory

doi:10.1371/journal.pone.0174496

Monika Mętrak, Elżbieta Rojan + Show 6 more

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https://doi.org/10.1371/journal.pone.0174496

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Abstract

The eastern part of the Pamir Mountains, located in Central Asia, is characterized by great climatic continentality and aridity. Wetlands developed in this hostile region are restricted to spring areas, terraces of shallow lakes or floodplains along rivers, and provide diversified ecosystem services e.g. as water reservoirs, refugia for rare species and pastures for domestic cattle. These ecosystems are particularly susceptible to climate changes, that in the Pamir Mountains result in increased temperatures, intense permafrost/glacial melt and alterations of precipitation patterns. Climatic changes affect pasture management in the mountains, causing overutilization of sites located at lower elevations. Thus, both climate and man-induced disturbances may violate the existing ecological equilibrium in high-mountain wetlands of the Eastern Pamir, posing a serious risk to their biodiversity and to food security of the local population. In this context, we sought to assess how environmental drivers (with special focus on soil features and potential water sources) shape the distribution and diversity of halophytic plant communities developed in valleys in the Eastern Pamir. This task was completed by means of a vegetation survey and comprehensive analyses of habitat conditions. The lake terraces and floodplains studied were covered by a repetitive mosaic of plant communities determined by differences in soil moisture and salinity. On lower, wetter sites, this patchwork was formed by Blysmus rufus dominated salt marshes, saline small sedge meadows and saline meadows with Kobresia royleana and Primula pamirica; and on drier, elevated sites, by endemic grasslands with Hordeum brevisubulatum and Puccinellia species and patches of xerohalophytic vegetation. Continuous instability of water sources and summer droughts occurring in the Pamir Mountains may lead to significant structural and functional transformations of described wetland ecosystems. Species more tolerant to decreased soil moisture and/or increased soil salinity will expand, leading to alterations of ecosystem services provided by the Pamirs’ wetlands. The described research will help to assess the current state of the wetlands and to predict directions of their future changes.

Highlights

The hydrology of a given area, including its water supplies, ground water level and water chemistry, is a widely known factor playing a vital role in structuring and maintaining terrestrial vegetation, most notably in water-limited habitats [1,2]
The later vegetation type was characterized by relatively low numbers of highly specialized halophyte species and, due to the dominance of halophyte species from the Puccinellia genus that have ranges limited to the Pamir Mountains (e.g. Puccinellia pamirica, Puccinellia hackeliana), can be considered endemic
The distribution of plant communities in the valleys of the Eastern Pamir is determined by the water supplies of a given area, comprised of peripheral and underwater springs supplying lakes, meltwater from permafrost remaining relatively close to soil surface, ephemeral run-off from mountain slopes and sparse precipitation

Summary

Introduction

The hydrology of a given area, including its water supplies, ground water level and water chemistry, is a widely known factor playing a vital role in structuring and maintaining terrestrial vegetation, most notably in water-limited habitats [1,2]. According to Gilbert and Freser [3], in the case of high-mountain water bodies and wetlands, salinity may have a comparable impact on the functioning of these ecosystems. Both hydrology and salinity of high-mountain wetlands are under a strong influence of climatic factors and their current changes, which are especially important in arid regions of the world [2, 4]. Together with the Tibetan Plateau, the Himalayas, the Tian Shan, Karakoram, Kunlun, Hindu Kush and Hindu Raj ranges, the Pamir Mountains belong to the largest area of permafrost in mountainous regions, with the permafrost thickness estimated at less than 100 m [5]. According to the studies performed by Gorbunov at lake Karakul, the Pamirs’ permafrost is of Upper Pleistocene and Holocene origin [5]

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