Standing herbage nutrition characters and herbivore carrying capacities of typical alpine grasslands in Sanjiangyuan National Park during cold season

Sanjiangyuan National Park is the first and biggest of 10 pilot national parks in China. Systematically investigating the herbage nutrition features and herbivore carrying capacity in typical alpine grasslands during cold season is of great significance to promote the balanced management of grasslands-herbivores in the National Park. However, there was few reports that focus on the ground research, due to harsh alpine conditions in highland plateau. In late December 2019, we collected the standing heibage samples of Stipa purpurea steppe, Kobresia tibetica meadow. and Carex moorcroftii steppe located in the Yangtze River Source Park of the Sanjiangyuan National Park. analyzed the herbage biomass and nutritional quality, and calculated the herbivore quantity carrying capacity and nutrition carrying capacity (digestible crude protein carrying capacity and metabolic energy carrying capacity) based on the agricultural industry standard of China (calculation of rangeland carrying capacity, NY/T635-2015). The results showed that: (1) Standing heibage biomasses of typical alpine grasslands were revealed as Kobresia tibetica meadow (103.03 g DM/m(2)) > Stipa purpurea steppe (72.24 g DM/m(2)) > Carex moorcroftii steppe (21.08 g DM/m(2)) (P<0.01). (2) Herbage in Kobresia tibetica meadow shared higher crude protein content (5.16%) than that of Stipa purpurea steppe (3.95%) and Carex moorcrqftii steppe (4.32%) (P<0.01). (3) Total nutrient output (kg nutrient yield per hectare grassland) of crude protein, ether extract and metabolic energy were revealed as Kobresia tibetica meadow > Stipa purpurea steppe> Carex moorcrgitii steppe (P<0.01). (4) Compared with quantity carrying capacity and metabolic energy carrying capacity, the digestible crude protein (DCP) carrying capacity is more consistent with the ecological protection goal in the National Park. The suitable cold season DCP carrying capacities for Stipa purpurea steppe, Kobresia tibetica meadow. and Carex moorcroftii steppe were 0.84 +/- 0.04, 1.57 +/- 0.07 and 0.27 +/- 0.02 SHU/ha (standard sheep unit per hectare grassland), respectively. Regional suitable cold season DCP carrying capacities for corresponding herbivores were 0.17 +/- 0.01 Yak/ha (Stipa purpurea steppe), 0.39 +/- 0.02 Kiang/ha (Kobresia tibetica meadow) and 0.22 +/- 0.02 Tibetan antelope/ha (Carex moorcrofiii steppe), respectively. (5) We found that the standing herbage biomass and herbivore carrying capacity of typical alpine grasslands in Sanjiangyuan National Park were quite low during cold season. We suggested that pastoralists in the livestock production area of the National Park should transform livestock husbandry management to increase the livestock production efficiency, turnover rate and economic returns, then effectively reduce the grazing livestock population in Sanjiangyuan National Park, and finally release more grassland resource and ecological space for the wildlife in Sanjiangyuan National Park.