Pastoralism in the highest peaks: Role of the traditional grazing systems in maintaining biodiversity and ecosystem function in the alpine Himalaya

Trans-Himalaya by 61%. They attributed this increase to preferential investment in above- ground fraction. The results are consistent with herbivore-mediated positive feedback effect on ANPP and nutrient availability between soil nutrients [72,73]. In my study ANPP increased by 32.07%, 35.64%, 33.28% and 26.53% in all elevations combined, lower, middle, and higher zones respectively under grazing treatment. The results of this study demonstrate the importance of the traditional grazing system in maintaining high plant diversity and productivity. Significantly higher diversity indices and productivity in grazed areas suggest plant community composition, structure and function benefit or depend indirectly on grazing for their persistence in the high-elevation alpine pas- tures of the Himalaya. Grazing may be a driver for higher species diversity in three ways. First, in free grazing systems like in the study site, higher diversity could be facilitated by the important role livestock play as seed dispersers. Seed dispersal by grazing animals is impor- tant in grasslands throughout the world, being vital for conservation of not only species but genetic diversity [74–76]. Grazing animals are dispersal vectors through epizoochory (trans- porting outside the body e.g. on fur) or endozoochory (transporting after ingestion). Studies have found higher survival of small seeds in the digestive tract of mammals increasing effec- tiveness of endozoochory [77–79]. This could explain higher PD of small seeded species such

Fig 4. Spatial distribution of 72 quadrates based on four diversity indices (rarity- Leroy’s rarity index, Menhinick -heterogeneity, Dstar-taxonomic distinctness and McIntosh index-evenness). The size of the circles increases with richness, and a color-code (gradient) is used to indicate the rarity index. Circles are labelled G for grazed quadrates and U for ungrazed quadrates. Numbers in circles represent quadrate numbers (1–12 lower zone, 13–24 middle zone, 25–36 higher zone). https://doi.org/10.1371/journal.pone.0245221.g004 PLOS ONE Role of the traditional grazing systems in maintaining biodiversity and ecosystem function in alpine Himalaya PLOS ONE | https://doi.org/10.1371/journal.pone.0245221 January 7, 2021 10 / 19