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

At the species level Kobresia nepalensis (Cyperaceae) was the most dominant species in grazed and ungrazed plots. The five most dominant species in all quadrats combined repre- sented 55.95% of PD. In grazed and ungrazed quadrats the five most dominant species repre- sented 48.09% and 61.18% of dominance, respectively. These included graminoid species in all quadrats combined and ungrazed plots. Rumex nepalensis and Primula dendiculata were the only forbs representing the five most dominant species in grazed plots. The other three species were represented by graminoid species namely Kobresia nepalensis, Festuca coelestis (Poaceae) and Juncus sp (Juncaceae). ANPP The mean ANPP in all quadrats combined was 756.46 g/m2 (Table 1). Productivity showed a decreasing trend with elevation with the maximum (829.77 g/m2) in lower zones and mini- mum (674.93 g/m2) in the higher zone quadrats (Fig 2E, Table 1). The analysis showed that elevation had a significant (p<0.001) role on ANPP. The mean ANPP was highest in July for all grazed quadrats in lower zone, middle zone and all zones combined but it was highest in August in higher zone (Fig 2K). Productivity was significantly higher in grazed areas than in ungrazed areas (Table 1). Overall, the average ANPP in grazed areas was 32.07% higher than in ungrazed areas. Maxi- mum ANPP (955.27 g/m2) was found in quadrats laid in the grazed areas in the lower zone and minimum (595.9 g/m2) in ungrazed areas in the higher zone (Table 1). Grazing signifi- cantly increased ANPP by 35.64%, 33.28% and 26.52% in the lower, middle and higher zones,

respectively. The analysis showed that grazing had a statistically significant effect (p<0.001) on productivity within each elevation zone and all elevation zones combined (Table 1). The linear regression revealed a statistically significant (p<0.001, R2 = 0.457) relationship between species richness and ANPP (Fig 2L). Table 1. Diversity indices and above ground net primary productivity (average per quadrate ±standard deviation) for plots in grazed and ungrazed areas in the three elevation zones and all elevations combined. Elevation Zone Quadrates S H D J ANPP (g/m2) All elevations combined All 11.39 ±5.01 2.08 ±0.5 0.83 ±0.09 0.89 ±0.06 756.46 ± 143.33 Grazed (G) 14.92 ±4.3 2.47 ±0.28 0.9 ±0.03 0.93 ±0.02 861 ±105.63 Ungrazed (U) 7.86 ±2.61 1.70 ±0.35 0.77 ±0.09 0.84 ±0.05 651.92 ±89.65 Difference (G-U) 7.06��� 0.77��� 0.13��� 0.08��� 209.08��� Lower elevations All 13.38 ±5.71 2.23 ±0.49 0.85 ±0.07 0.89 ±0.05 829.77 ±144.73 Grazed (G) 17.83 ±4.3 2.63 ±0.26 0.91 ±0.02 0.92 ±0.02 955.27 ±52.24 Ungrazed (U) 8.92 ±2.5 1.84 ±0.3 0.80 ±0.58 0.86 ±0.04 704.26 ± 81.87 Difference (G-U) 8.91��� 0.79��� 0.11��� 0.06��� 251.01��� Middle elevations All 11.42 ±5.01 2.13 ±0.48 0.85 ±0.07 0.90 ±0.04 764.68 ±135.45 Grazed (G) 15.33 ±3.8 2.53 ±0.24 0.90 ±0.02 0.94 ±0.03 873.76 ±79.28 Ungrazed (U) 7.50 ±2.11 1.73 ±0.28 0.79 ±0.06 0.88 ±0.04 655.60 ±78.18 Difference (G-U) 7.83��� 0.8��� 0.11��� 0.06��� 218.16��� Higher elevations All 9.38 ±3.41 1.90 ±0.49 0.80 ±0.12 0.87 ±0.08 674.93 ±107.29

Grazed (G) 11.58 ±2.15 2.26 ±0.23 0.88 ±0.04 0.93 ±0.03 753.96 ±64.13 Ungrazed (U) 7.17 ±3.01 1.54 ±0.41 0.72 ±0.13 0.82 ±0.07 595.90 ±79.56 Difference (G-U) 4.41��� 0.72��� 0.16��� 0.11��� 158.06��� P-values (represented by asterixis) indicate difference between grazed and ungrazed areas based on the Kruskal-Wallis. S = Species richness; H = Shannon index; D = Simpsons diversity index; J = Pielou’s evenness; ANPP = Above ground net primary productivity. P values- <0.001 “���” <0.01 ‘��’ <0.05 ‘�’. https://doi.org/10.1371/journal.pone.0245221.t001 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 8 / 19