Abstract:

Grassland ecosystem is a complex social-ecological system. Permafrost, as an important factor to maintain the structure and function of alpine grassland ecosystem, is an important aspect to describe the ecological carrying capacity of alpine grassland objectively. The impact of permafrost on the ecological carrying capacity of alpine grassland is poorly understood. In this study, using the structural dynamics method, we established a numerical model to estimate the ecological carrying capacity of alpine grassland. Variation of the grassland ecological carrying capacity of the permafrost regions of the Qinghai-Tibetan Plateau (QTP) was analyzed, while the contribution of the permafrost active layer to the ecological carrying capacity of alpine grassland was also quantified. Results show that the ecological carrying capacity of alpine grassland in permafrost regions displayed an increasing trend, especially after 1998, due to increases of precipitation, air temperature, net primary productivity during growing season of grassland, and the establishment of ecological protection projects. The thickness variation of permafrost active layer is negatively correlated with ecological carrying capacity of alpine grassland. The mean contribution of permafrost active thickness to the ecological carrying capacity of alpine grassland was 10% in the QTP during 1980?2013. That is, for every 1 unit increase in the thickness of the permafrost active layer, the ecological carrying capacity of the alpine grassland will be reduced by 0.1 units. Owing to the significant spatial differences over the QTP and the uncertainty of climate change, this result is only a rough estimate of role of permafrost in the ecological carrying capacity.

Key words: Ecological carrying capacity, Permafrost, Thickness of permafrost active layer, Structural dynamics, Qinghai-Tibetan Plateau (QTP)