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The Carbon Dynamics of the Tibetan Plateau
Reference
Zhuang, Q., He, J., Lu, Y., Ji, L., Xiao, J. and Luo, T. 2010. Carbon dynamics of terrestrial ecosystems on the Tibetan Plateau during the 20th century: an analysis with a process-based biogeochemical model. Global Ecology and Biogeography 19: 649-662.

What was done
The authors used a process-based biogeochemistry model -- the Terrestrial Ecosystem Model or TEM, which also employed a soil thermal model -- to examine permafrost dynamics and their effects on the carbon dynamics of the Tibetan Plateau over the past century. This was done by "parameterizing and verifying" the TEM using existing real-world data for soil temperature, permafrost distribution and carbon and nitrogen distributions throughout the region, and then extrapolating the model and its parameters to the whole of the plateau.

What was learned
The six scientists report that "during the 20th century, the Tibetan Plateau changed from a small carbon source or neutral in the early part of the century to a sink later," noting that "net primary production and soil respiration increased by 0.52 and 0.22 Tg C/year, respectively, resulting in a regional carbon sink increase of 0.3 Tg C/year," so that "by the end of the century, the regional carbon sink reached 36Tg C/year and carbon storage in vegetation and soils is 32 and 16 Pg C, respectively."

What it means
Zhuang et al. say the "increasing soil temperature and deepening active layer depth enhanced soil respiration, increasing the net nitrogen mineralization rate," and that "together with the [positive] effects of warming air temperature and rising CO2 concentrations on photosynthesis, the stronger plant nitrogen uptake due to the enhanced available nitrogen stimulate[d] plant carbon uptake, thereby strengthening the regional carbon sink as the rate of increase in net primary production was faster than that of soil respiration." Thus, they say their study implies that "future warming will increase thawing of the permafrost, increase soil temperature and dry up soil moisture," and that "these physical dynamics may enhance [the] future strength of the regional carbon sink, since the rate of increase of net primary production is higher than that of soil respiration on the Tibetan Plateau" ... as the greening of the earth continues.

Reviewed 22 December 2010