Submitted to: Geophysical Research Letters
Publication Type: Peer reviewed journal
Publication Acceptance Date: 6/25/2010
Publication Date: 8/6/2010
Citation: Yang, Y., Fang, J., Fay, P.A., Bell, J.E., Ji, C. 2010. Rain use efficiency across a precipitation gradient on the Tibetan Plateau. Geophysical Research Letters. 37:L15702. Interpretive Summary: For most grasslands, productivity is moderately to intensely limited by water availability. Soil properties and temperature regimes play an important role in mediating water limitation in grasslands by affecting the availability of water to plants (soils) and the demand for water (temperature). This study reports on spatial variability in ANPP in high alpine grasslands of Tibet, examining how the productivity of grasslands varies in response to annual precipitation across two types of alpine grassland varying in soil properties. These two kinds of grassland had opposite relationships of productivity with rainfall total, one increasing and one decreasing. The differences were attributed to soil texture and carbon content, and suggest that these two grasslands may exhibit different response to future altered rainfall patterns.
Technical Abstract: Rain use efficiency (RUE), commonly described as the ratio of aboveground net primary production (ANPP) to mean annual precipitation (MAP), is a critical indicator for predicting potential responses of grassland ecosystems to changing precipitation regimes. However, current understanding on patterns and controls of RUE is primarily derived from temperate grasslands, and little is known about alpine grasslands. In this study, we examined RUE in the Tibetan alpine grasslands across a precipitation gradient using biomass measurements from 675 plots and soil physical and chemical properties from 405 soil profiles obtained from a regional biomass and soil survey across the plateau during 2001-2004. Our results showed that RUE in alpine steppe was significantly lower than in alpine meadow. The different RUE in these two grassland types were largely induced by their differences in species richness, soil texture, and soil carbon content. RUE exhibited an initial increase in alpine steppe and a subsequent decrease in alpine meadow along the precipitation gradient, suggesting that alpine steppe and meadow may respond differently to the alteration in precipitation patterns.