Response of livestock carrying capacity of alpine meadows in the source area of the Yangtze River to simulated warming during the growth season
In recent decades,global warming has become an undeniable fact.The alpine meadows on the Qing-hai-Tibet Plateau are one of the main animal husbandry bases in China,as well as climate change sensitive areas and ecologically fragile zones.To investigate the impact of climate warming on the livestock carrying capacity of alpine meadows in the source area of the Yangtze River during the growing season,a simulated warming experi-ment was conducted on a typical alpine meadow in the Beilu River Basin of the source area of the Yangtze River.We measured the aboveground biomass and forage quality of alpine meadows during warming and non-warming scenarios,respectively,and determined their quantity and nutrient carrying capacity of alpine meadows,as to provide scientific basis for formulating reasonable alpine meadows carrying capacity.The result showed:(1)The increase of temperature(150 W·m-2)increased the annual average soil temperature at depths of 5 and 30 cm in alpine meadows,and decreased the annual average soil moisture at depths of 0-10 cm,but increased the annual average soil moisture at depths of 20-40 cm.(2)Warming significantly increased the community aboveg-round biomass by 78.55 g·m2 and 79.74 g·m-2 in the early growth season(June 2017 and 2018),but had no sig-nificant effect on the later growth season(September 2017 and 2018);warming increased the proportion of aboveground biomass of forbs and grasses in the community,but decreased the proportion of sedge plants.(3)Warming reduces the crude protein and fat content in communities and forbs,resulting in a decrease in for-age quality.(4)Under warming treatment,the quantity carrying capacity,digestible protein carrying capacity,and metabolic energy carrying capacity increased by 2.37±0.22,6.72±0.41,and 3.89±0.32 sheep units per hect-are in June 2017,and 2.41±0.30,6.29±0.25,and 3.95±0.17 sheep units per hectare in June 2018,respectively;However,there was no significant change in the later growth season.According to the actual situation in the re-search area,under the background of warming,it is advisable to arrange grazing based on the quantity carrying capacity in the early growth season of the alpine meadow in the source area of the Yangtze River,and to arrange grazing based on the metabolic energy carrying capacity in the later growth season.
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