Mountain pastures and grasslands in the SW Tien Shan, Kyrgyzstan — Floristic patterns, environmental gradients, phytogeography, and grazing impact

Vast grasslands are found in the walnut-fruit forest region of southern Kyrgyzstan, Middle Asia. Located above the worldwide unique walnut-fruit forests and used for grazing, they play a pivotal role in the mixed mountain agriculture of local farmers. Accordingly, these pastures are subject to an increasing utilization pressure reflecting the changing political and social conditions in the transformation process from a Soviet republic to an independent state. A first detailed analysis of mountain pasture vegetation in the Ferghana Range answers the following questions: What are the main plant community types among Kyrgyzstan’s mountain pastures? What are the main environmental gradients that shape their species composition? Which phytogeographical distribution types are predominant? How does grazing affect community composition and species richness in these grasslands? Species composition was classified by cluster analysis; underlying environmental gradients were explored using DCA. A dataset of 395 relevés was used for classification, and a subset of 79 relevés was used in a DCA to analyze the correlation between vegetation, environment, and grazing impact. The investigated pastures were classified into four distinctive plant communities. The site factors altitude, heat load, inclination and grazing impact were found to be the major determinants of the vegetation pattern. A significant overlap between floristic composition and structural and spatial properties was shown. The majority of the species pool consisted of Middle Asian endemics and Eurosiberian species. However, disturbance-tolerant species played a significant role with respect to species composition and coverage of the herbaceous layer in vast areas of southern Kyrgyzstan’s mountain pastures. In general, an intense grazing impact is clearly reflected by both species composition and structural variables of plant communities. The highly diverse and unique ecosystem is modified by an increasing utilization pressure. In order to maintain vital processes and functioning of this valuable ecosystem — in both economical and ecological terms -, it is indispensable to adopt appropriate pasture management strategies.