Abstract: In recent years, grassland has been severely degraded in parts of the Qinghai-Tibet Plateau(QTP) under the combined influence of climate change and human activities. In this study, the thermal infrared heaters were used to simulate climate warming in moderately degraded and non-degraded alpine meadows in the permafrost regions of the Beiluhe basin of the QTP to study the effects of grassland degradation and climate change on the grassland quantity and quality(digestible crude protein and metabolic energy) bearing capacity in the growing season. The result showed:(1) Degradation reduced the importance value of sedges species in the community, while that of grasses and forbs species gradually increased;(2) Degradation had no significant effect on above-ground biomass of vegetation, but degradation with climate warming reduced above-ground biomass by(87.17±6.93) g·m^-2 and(38.89±2.23) g·m^-2 in June and September;(3) Degradation reduced the content of crude protein by 29.15% and 33.74%, but increased the content of acid detergent fiber by 11.68% and 15.34% in June and September;(4) With climate warming, degradation reduced the quantity bearing capacity and metabolic energy bearing capacity by 2.63±0.21 and 6.94±0.55 sheep unit/hectare in June, and 1.17±0.07 and 3.1±0.17 sheep unit/hectare in September. The bearing capacity in the study area was in the sequence of metabolic energy bearing capacity>digestible crude protein bearing capacity>quantity bearing capacity. The nutrients supply of forage in the growing season in the study area is sufficient to livestock, and the suitable bearing capacity is the quantity bearing capacity.

Key words: degradation, simulated warming, alpine meadow, forage quality, bearing capacity