Abstract:

The heating effect (or mass elevation effect, MEE) of the Tibetan Plateau (TP) is intense due to its massive body. Some studies have been undertaken on its role as the heat source in summer and its implications for Asian climate, but little has been known of the implications of its MEE for the distribution of mountain altitudinal belts (MABs). Using air temperature data observed and remotely sensed data, MAB/treeline data, and ASTER GDEM data, this paper compares the height of MABs and alpine treelines in the main TP and the surrounding mountains/lowland and explains the difference from the point of view of MEE. The results demonstrate: 1) at same elevation, air temperature and the length of growing season gradually increase from the eastern edge to the interior TP, e.g., at 4500 m (corresponding to the mean altitude of the TP), the monthly mean temperature is 3.58°C higher (April) to 6.63°C higher (June) in the interior plateau than in the Sichuan Basin; the 10°C isotherm for the warmest month goes upward from the edge to the interior of the plateau, at 4000 m in the Qilian Mts. and the eastern edges of the plateau, and up to 4600-5000 m in Lhasa and Zuogong; the warmth index at an altitude of 4500 m can be up to 15°C·month in the interior TP, but much lower at the eastern edges. 2) MABs and treeline follow a similar trend of rising inwards: dark-coniferous forest is 1000-1500 m higher and alpine steppe is about 700-900 m higher in the interior TP than at the eastern edges.

Key words: Tibetan Plateau, mass elevation effect, mountain altitudinal belt, treeline, the warmth index, the 10℃ isotherm in the warmest month