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A Quarter-Century of Carbon Sequestration in Global Grasslands
Reference
Xia, J., Liu,S., Liang, S., Chen, Y., Xu, W. and Yuan, W. 2014. Spatio-temporal patterns and climate variables controlling of biomass carbon stock of global grassland ecosystems from 1982 to 2006. Remote Sensing 6: 1783-1802.

Background
The authors write that "grasslands, occupying about 20% of the world's land surface, play an important role in the global carbon cycle," citing the work of Hall and Scurlock (1991), Scurlock and Hall (1998), and Ma et al. (2010). And they say that grasslands "likely contribute an annual carbon sink of up to ~0.5 Pg carbon," which they state is "equivalent to about 18% of the total current global terrestrial carbon sink," citing Canadell et al. (2007), although they add that "the global spatio-temporal patterns and environmental controls of grassland biomass are not well quantified and understood."

What was done
Hoping to advance the state-of-the-art in this regard, Xia et al. estimated the spatial and temporal patterns of global grassland biomass and analyzed the driving forces behind them by means of a Normalized Difference Vegetation Index (NDVI) time series obtained from satellite data, along with climate reanalysis data and a satellite-based statistical model. In addition, they studied 81 sites worldwide, obtaining a total of 158 site-years of field observations of aboveground live biomass that they used for model development.

What was learned
The six scientists found that global grassland carbon storage increased over the study period at a rate of 2.43 Tg carbon per year; and they indicate that "the change of biomass was significantly and positively correlated with temperature and precipitation."

What it means
In spite of all of the doom and gloom associated with anthropogenic CO2 emissions - the greening of planet earth continues!

References
Canadell, J.G., LeQuere, C., Raupach, M.R., Field, C.B., Buitenhuis, E.T., Ciais, P., Conway, T.J., Gillett, N.P., Houghton, R.A. and Marland, G. 2007. Contributions to accelerating atmospheric CO2 growth from economic activity, carbon intensity, and efficiency of natural sinks. Proceedings of the National Academy of Sciences USA 104: 18,866-18,870.

Hall, D.O. and Scurlock, J.M.O. 1991. Climate change and productivity of natural grasslands. Annals of Botany 67: 49-55.

Ma, W., Fang, J., Yang, Y. and Mohammat, A. 2010. Biomass carbon stocks and their changes in northern China's grasslands during 1982-2006. China Life Science 53: 841-850.

Scurlock, J.M.O. and Hall, D.O. 1998. The global carbon sink: A grassland perspective. Global Change Biology 4: 229-233.

Reviewed 3 September 2014