Precipitation is a key climatic factor controlling primary productivity for most of the world’s grassland ecosystems. Clarifying the spatiotemporal variations in precipitation-use efficiency (PUE), the ratio of vegetation above-ground productivity to annual precipitation, will advance people's understanding of how ecosystems’ carbon and water cycles respond to climate change.

The classic model for predicting vegetation productivity at continental and global scales is the Miami model, which describes the relationship between mean annual precipitation and vegetation productivity with an exponential function. Lately Dr.HU Zhongmin, assistant professor of Institute of Geographic Sciences and Natural Resources Research (IGSNRR), and his colleagues proposed a new conceptual model, which might be the update of the Miami model.

The new paper, "Precipitation-use Efficiency along a 4500-km Grassland Transect," has been published on Global Ecology and Biogeography((2010) 19, 842–851). HU and his colleagues collected data on 580 sites along a 4500-km climate-related grassland transect  in China to investigate the variations in PUE at both regional and site scales.

Based on the finding “PUE decreased with decreasing mean annual precipitation (MAP)”, the authors proposed the use of a conceptual model for predicting vegetation productivity at continental and global scales with a sigmoid function, which illustrates an increasing PUE with MAP in arid regions.

The researchers also found the maximum PUE showed large site-to-site variations along the transect, which contradicts the prevailing view as presented in previous reports that a convergent maximum PUE exists among diverse ecosystems.

In addition, their work highlights the importance of further studies to clarify the distinct mechanisms at work in controlling PUE at local and regional scales.

The co-authors of this paper are Dr.YU guirui, Dr.FAN Jiangwen, Dr. ZHONG Huaping, Dr. WANG Shaoqiang, and Dr.LI Shenggong (the corresponding author).