Search

This paper studies the relationship between net primary productivity (NPP) and annual average air temperature (GT) at 0cm above ground in permafrost regions by using revised Chikugo NPP model, cubic spline interpolating functions, and nonlinear regression methods. The source regions of the Yangtze and Yellow Rivers were selected as the research areas. Results illustrate that: (1) There is significant non-linear relationship between NPP and GT in various typical years; (2) The maximum value of NPP is 6.17, 5.87, 7.73, and 5.41 DM·t·hm·a respectively, and the corresponding GT is 7.1, 10.0, 21.2, and 8.9°C respectively in 1980, 1990, 2000 and 2007; (3) In 1980, the sensitivity of NPP to GT is higher than in 1990, 2000 and 2007. This tendency shows that the NPP presents change from fluctuation to an adaptation process over time; (4) During 1980∼2007, the accumulated NPP was reduced to 8.05, and the corresponding carrying capacity of theoretical livestock reduced by 11%; (5) The shape of the demonstration region of ecological compensation system, livelihood support system, and science appraisal system in the source regions of Yangtze and Yellow Rivers are an important research for increasing the adaptation capacity and balancing protection and development. [ABSTRACT FROM AUTHOR]

In the source regions of the Yangtze and Yellow Rivers of China, glaciers, frozen ground, the hydrological system, and alpine vegetation have changed over the past decades years. Climatic causes of these variations have been analyzed using mean monthly air temperature and monthly precipitation between 1956 and 2000, and monthly evaporation from φ20 evaporation pans between 1961 and 1996. In the source region of the Yangtze River, lower temperature and plentiful precipitation during the 1960s and continuing into the early 1980s triggered a glacier advance that culminated in the early 1990s, while a robust temperature increase and precipitation decrease since 1986 has forced glaciers to retreat rapidly since 1995. Permafrost degradation is another consequence of the climatic warming. The variations in the hydrological system and alpine vegetation are controlled mainly by the climate during the warm season. Warmer and drier summer climate is the major cause of a degradation of the vegetation, desiccation of the high-cold marshland, a decrease in the areas and numbers of lakes and rivers in the middle and north source regions of the Yangtze and Yellow Rivers, and a reduction in surface runoff in the source region of the Yangtze River for the last 20 years. The causes of eco-environmental change in Dari area, near the outlet from the source area of the Yellow River, are different from those elsewhere in the study area. A noticeable reduction in runoff in the source region of the Yellow River and degradation of alpine vegetation in Dari area are closely related to the permafrost degradation resulting from climate warming. [ABSTRACT FROM AUTHOR]