Impact of anthropogenic disturbances on alpine floristic diversity along the altitudinal gradient of Northwestern Himalayas

Vegetation patterns in the high-altitude Himalaya are influenced by a complex set of biotic and abiotic factors. Anthropogenic disturbances are one of the primary factors influencing the community patterns and diversity, which is largely determined by the level of accessibility in the Himalaya. However, with advancing urbanization and accessibility, limited efforts have been made to quantify the impact of road constructions on alpine flora of Himalaya. To overcome this data gap, this study is aimed to quantify the impact of anthropogenic disturbance on the alpine vegetation community pattern along the altitudinal gradient i.e., 3264- 4340m in Kullu district and 3148- 4634m in Lahaul and Spiti district of Himachal Pradesh, Northwestern Himalayas. The impact of anthropogenic disturbance was assessed by comparing species diversity and richness between selected disturbed and undisturbed sites. The diversity profiles of disturbed sites (2.45), near to roads and highways (within 25-50m), were indicative of higher level of anthropogenic disturbances than undisturbed sites (2.56), which were located at a farther distance (more than 25- 50m) from roads and highways. Non-metric dimensional scaling of species composition along the altitudinal gradient showed more heterogenous community composition at lower altitudes for both disturbed sites and undisturbed sites. The variation in diversity profiles of disturbed and undisturbed sites was further favored by significantly lower values of soil moisture, potassium, phosphorous, and nitrogen content in disturbed sites. Also, the disturbed sites have lower numbers of threatened and endemic species (12 and 15 respectively) than undisturbed sites (30 and 28 respectively). Canonical correlation analysis indicated that soil moisture and pH were two major controlling factors for community composition for both disturbed and undisturbed sites. The present study indicated a significant impact of anthropogenic disturbances on the alpine floristic diversity and soil properties which needs urgent mitigation actions to conserve the unique and threatened alpine floristic diversity of Himalaya.