Sheep Wool δ13C Reveals No Effect of Grazing on the C3/C4 Ratio of Vegetation in the Inner Mongolia–Mongolia Border Region Grasslands |
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| Authors: | Karl Auerswald Max HOM Wittmer Radnaakhand Tungalag Yongfei Bai Hans Schnyder |
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| Institution: | 1. Lehrstuhl für Grünlandlehre, Technische Universität München, Alte Akademie 12, Freising-Weihenstephan, Germany.; 2. National University of Mongolia, Ikh surguulin gudalmj –1, Baga toiruu, Sukhbataar District, Ulaanbaatar, Mongolia.; 3. State Key Laboratory of Vegetation and Environmental Change, Institute of Botany, Chinese Academy of Sciences, Beijing, China.; The Pennsylvania State University, United States of America, |
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| Abstract: | We tested whether the abundance of C4 vegetation in grasslands of the Mongolian plateau is influenced by grazing conditions. The analysis exploited the politically originated contrast that exists between Mongolia (low stocking rate, transhumant system) and the district of Inner Mongolia, China (high stocking rate, sedentary system). We estimated the proportion of C4 carbon (PC4) in grazed vegetation from the relative carbon isotope ratio (δ13C) of sheep wool sampled from 298 annual shearings originating from 1996 to 2007. Annual stocking rates varying over time and between the districts of both countries were taken from regional statistics. The PC4 pattern within the 0.7 million km2 sampling area was geostatistically analyzed and related to stocking rates and temperature gradients. For similar climatic conditions, PC4 was the same in both countries. Further, a unique relationship was found between PC4 and July temperature on both sides of the border, which explained 71% of the pattern. Stocking rate and grazing system had no significant influences on present-day C3/C4 abundance ratio. This finding suggests that recent changes in the C3/C4 ratio of these grasslands are mainly a consequence of regional warming, not overgrazing. |
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