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The Effects of Climate Change on Terrestrial Ecosystems in Northwestern Yunnan, China

PI: Barry Baker
Institution: The Nature Conservancy
Additional Investigators: Shi Xuezheng, Sun Jihua, Achim Brauning
Abstract:
1) Changes in the Hengduan Mountains: Advancing treeline and retreating glaciers

Historic climate data and repeat photographs taken over a ninety-year period (1913-2003) were used to assess and document changes in alpine treeline and glacial recession in the Hengduan Mountains of northwestern Yunnan, China. Our results show that mean annual temperature in the last two decades of the 20th century has been increasing at a rate of 0.6 deg C/10 yr. This rate of warming is nearly twice the mean rate of warming (0.3 deg.C/10 yr) that calculated for China. Analysis of seasonal trends also indicate that since the early 1970s summer and winter mean temperatures have increased as well as a general decreasing trend in summer precipitation. The banning of fire in the alpine, instituted to prevent the accidental burning subalpine forests, and changes in grazing patterns have contributed to the advance of sapling trees and shrubs into alpine meadows. Clearly, two spatially and temporally distant anthropogenic disturbances, a rapidly warming climate and changes in land use, appear to be affecting alpine glaciers and upper treeline vegetation dynamics, thus threatening both biodiversity and Tibetan livelihoods in the Hengduan Mountains of northwestern Yunnan China. This work indicates the need for developing land management strategies that will address all critical scales.

Baker, B.B. and Moseley, R.K. 2005. Changes in the Hengduan Mountains: Advancing treeline and retreating glaciers. Arctic, Antarctic, and Alpine Research (accepted).


2) Effects of climate change and land management practices in the Hengduan Mountains of northwestern Yunnan, PR China: options for alpine conservation.

We have documented that herbaceous alpine meadows are decreasing and being replaced by woody vegetation as forest treelines advance and alpine shrub biomass increases. Alteration of land management practices and shifts in climate are thought to be the primary drivers of these changes. Furthermore, the growth of woody vegetation may be enhanced by changes in climate. Analyses of historical climate station data show that mean annual temperature in the last two decades has increased. at a rate of 0.6 deg C/10 yr. We are using simulation results from the MC1 dynamic vegetation model (2 km cell size) and output from various state-of-the-art climate models to show how future climate may further alter these alpine ecosystems. Results from these simulations will be used to identify fire and grazing strategies to offset these threats to biodiversity and livelihoods of local inhabitants.


3) Influence of past climatic variability on upper treeline and alpine vegetation in northwestern Yunnan.

A rapidly warming climate and changes in land use, appear to be affecting upper treeline and alpine vegetation dynamics, thus threatening both biodiversity and Tibetan livelihoods in the Hengduan Mountains of northwestern Yunnan China. Conservation strategies designed to maintain or increase the viability of a particular species or community may be perfectly formulated for a predicted range of climatic conditions. However, future climate regimes may be outside the range of the natural variability for the target thereby reducing the viability of the conservation target under consideration. We maintain that in order to understand how future climate regimes may influence alpine ecosystems and what conservation strategies will be effective in conserving alpine biological diversity, we must first characterize the nature of past variability. However, climate stations in this region were not installed prior to 1950. In addition the closet station is approximately 1000 m below and 20 km distant from our research sites Therefore, we are establishing a climate history from high-resolution proxy data like tree rings in order to reconstruct historical long-term climate trends.
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