Three-River Source Region Research Articles

Influences of climate variation on thawing?freezing processes in the northeast of Three-River Source Region China

Abstract In cold region, precipitation, air temperature and snow cover significantly influenced soil water and heat transfer, and thus freezing–thawing processes of active soil layer. On the basic of physical processes of water and heat balances and their transfers in the snow covered soil, a water-heat coupling model for snow cover and its underlying soil layers was established in this paper. Numerical solution of the model was conducted by a full-implicit finite volume method. Observation data of snow cover depth, soil water content and active soil depth at two typical sites in the northeast of Three-River Source Region of China were selected for model calibration and validation. The results indicate that the model can capture soil freezing–thawing processes at the two sites. Simulated results reveal that variations of soil water content, soil temperature and soil freezing depth depend on climate conditions of air temperature, precipitation and snow cover as well. In comparison of the simulated results at two sites, we know that thick snow cover hinders temperature transfer from air to soil, resulting in prolonging the time lag between air and soil temperatures, decreasing variations of soil temperature and soil water content and reducing soil freezing depths of active soil.

Changes in plant community diversity and aboveground biomass along with altitude within an alpine meadow on the Three-River source region

The grassland is an important component of terrestrial ecosystems and plays a significant role in biodiversity and ecosystem functions. In the present study, the changes of plant species diversity and aboveground biomass productivity were examined along with the altitude in natural alpine grassland in the source region of three rivers on the Qinghai-Tibetan Plateau. Eleven experimental locations were selected with altitudes ranging from 3862 to 4450 m above sea level (a.s.l.). The results indicated that Kobresia pygmaea meadow, Kobresia humilis meadow and Salix cupularis shrub meadow had higher indices of diversity and aboveground biomass. The distribution of species diversity, richness and aboveground biomass showed similarly unimodal patterns across the altitude gradient with the highest indices appeared at mid-altitudes locations. The changing trend of species diversity, richness and evenness also showed significant unimodal patterns with total aboveground biomass, and the highest species diversity occurred at intermediate level of productivities. This research would provide a valuable reference for the protection of grassland biodiversity and maintaining of the grazing ecosystem function in the source region of the Three Rivers.

Temporal and spatial variation of the main water balance components in the three rivers source region, China from 1960 to 2000

The three rivers source region (TRSR) is the most sensitive region of global climate change in China. The temporal and spatial variations of main water balance components (precipitation, snowmelt, actual evaporation, runoff, etc.) during the period from 1960 to 2000 in the TRSR were analyzed by hydrologic simulation and statistical detection. The results showed that: when compared with the components in 1960s, (1) the variation of precipitation from 1970s to 1990s was not significant in the whole TRSR though it increased slightly in the Yellow River Source Region (YeSR) and Yangtze River Source Region (YaSR), but decreased slightly in the Lancang River Source Region (LcSR); (2) the snowmelt increased in most regions of TRSR except the downstream of YeSR and YaSR, but the trend was statistically significant only in the YeSR; (3) the actual evaporation increased continually in the whole TRSR, but the trends were significant in the middle stream of the YeSR and YaSR, and the YeSR was the greatest; (4) Although the runoff depth decreased gradually in the TRSR, the trends were significant only in the middle stream of the YeSR and YaSR and the YeSR was the greatest. Inevitably, the discharge decreased in the TRSR but the trend was not statistically significant. Climate change (i.e., the slightly decreasing of precipitation and the increasing of air temperature) was the most important factor to affect the variations of water balance components. The most sensitive region to climate change was YeSR, followed by YaSR, and the least one was LcSR. This study was expected to provide the foundation and a reference to analyze the water resources evolution and test the climate change impacts in TRSR as well as the whole China.

Frozen soil change and adaptation of animal husbandry: a case of the source regions of Yangtze and Yellow Rivers

This paper discusses the spatial and temporal change of different frozen soil types from 1980s to 2000s, and the impacts of frozen soil change on rangeland productivity and sustainable livelihood in the source regions of Yangtze and Yellow Rivers employed numerical model and GIS technology. Authors use the analytical framework of adaptation of animal husbandry according to national, regional, community and household scales, and release three key instruments of cryospheric change adaptation, including adaptive capacity of the policies, adaptive capacity of the people, and adaptive capacity of the grassland ecosystem. Analysis result shows that there is clearly a need, to develop institutional processes that support policy analysis to draw on existing information, that facilitate multidisciplinary research on topics of policy relevance, and that link the accumulation of credible cryosphere scientific evidence with policy making. Finally, Authors suggest that further support to mainstream climatic and cryospheric change concerns in adaptation policies and strategies of animal husbandry must include a focus on: (1) Formulating ecological compensation policy and mechanism for grassland ecosystem maintenance; (2) Strengthening vocational training, long-term essential-qualities-oriented education to improve indigenous people's professional skills and abilities; (3) Strengthening development of livestock replacement industries to broaden employment channels of indigenous people; (4) Strengthening the consciousness of ecosystem maintenance, improvement the social civilization level for indigenous people; (5) Continuous implementation the Ecological Protection and Restoration Program in the Three-River Source Region in national scale. Crown Copyright (C) 2011 Published by Elsevier Ltd. All rights reserved.

High positive correlation between soil temperature and NDVI from 1982 to 2006 in alpine meadow of the Three-River Source Region on the Qinghai-Tibetan Plateau

Using satellite-observed Normalized Difference Vegetation Index (NDVI) data and Rotated Empirical Orthogonal Function (REOF) method, we analyzed the spatio-temporal variation of vegetation during growing seasons from May to September in the Three-River Source Region, alpine meadow in the Qinghai-Tibetan Plateau from 1982 to 2006. We found that NDVI in the centre and east of the region, where the vegetation cover is low, showed a consistent but slight increase before 2003 and remarkable increase in 2004 and 2005. Impact factors analysis indicted that among air temperature, precipitation, humid index, soil surface temperature, and soil temperature at 10cm and 20cm depth, annual variation of NDVI was highly positive correlated with the soil surface temperature of the period from March to July. Further analysis revealed that the correlation between the vegetation and temperature was insignificant before 1995, but statistically significant from 1995. The study indicates that temperature is the major controlling factor of vegetation change in the Three-River Source Region, and the currently increase of temperature may increase vegetation coverage and/or density in the area. In addition, ecological restoration project started from 2005 in Three-River Source Region has a certain role in promoting the recovery of vegetation.

Climate change tendency and grassland vegetation response during the growth season in Three-River Source Region

Climate change, climate suitablity change for grassland vegetation, and grassland response to climate change during the growth season are studied systematically by using meteorological data of temperature, precipitation, and length of sunlight from 1961 to 2007, NOAA/AVHRR NDVI from 1982 to 2006, and observations of grass height, biomass, and coverage in enclosed grassland from 1994 to 2006. Two models are developed to evaluate climate change and the climatic suitability of grassland vegetation growth. Average temperature, accumulative precipitation, and length of sunlight during the growth season increased from 1961 to 2007 at rates of 0.24°C/10 yr, 2.32 mm/10 yr, and 2.81 h/10 yr, respectively. The increase rates of average temperature between April and May, and between June and August are 0.17 and 0.30°C/10 yr; accumulative rainfall between April and May increased at a rate of 2.80 mm/10 yr, and accumulative rainfall between June and August decreased at a rate of 0.38 mm/10 yr; the increase rates of accumulative length of sunlight between April and May, and between June and August are 2.15 and 1.2 h/10 yr. The climatic suitability of grassland vegetation growth showed an increasing trend, and the increase rate between April and May is greater than that between June and August. Both NDVI observations from 1982 to 2006 and measurements of grass height, dry biomass, and coverage from 1994 to 2006 show that the climate change has resulted in an increase in plant productivity of the grassland in Three-River Source Region. If some protection measures are taken as soon as possible, the deteriorated grassland in Three-River Source Region can recover.