Auerswald, Karl

Bai, Y. F.

Maennel, T.

Schnyder, Hans

Wittmer, M.

English

University of Kentucky

University of Kentucky UKnowledge International Grassland Congress Proceedings 21st International Grassland Congress / 8th International Rangeland Congress Large‐Scale Changes in Ratio of C3 and C4 Plants in Central Asian Grassland during the Last Century as Recovered from Wool Archives Karl Auerswald Technische Universität München, Germany T. Maennel Technische Universität München, Germany Y. F. Bai Chinese Academy of Sciences, China M. Wittmer Technische Universität München, Germany Hans Schnyder Technische Universität München, Germany Follow this and additional works at: https://uknowledge.uky.edu/igc  Part of the Plant Sciences Commons, and the Soil Science Commons This document is available at https://uknowledge.uky.edu/igc/21/1-2/16 The 21st International Grassland Congress / 8th International Rangeland Congress took place in Hohhot, China from June 29 through July 5, 2008. Proceedings edited by Organizing Committee of 2008 IGC/IRC Conference Published by Guangdong People's Publishing House This Event is brought to you for free and open access by the Plant and Soil Sciences at UKnowledge. It has been accepted for inclusion in International Grassland Congress Proceedings by an authorized administrator of UKnowledge. For more information, please contact UKnowledge@lsv.uky.edu. 　 Multifunctional Grasslands in a Changing World 　 Volume Ⅰ 　 瞯 ]65　 瞯Grasslands/Rangelands Resources and Ecology ——— Ecology of Grasslands/RangelandsLarge‐scale changes in ratio of C3 and C4 plants in central Asian grassland during the last centuryas recovered from wool archivesK . A uersw ald1 , T . Maennel1 , Y .F . Bai2 , M . W ittmer 1 , H . Schnyder11 Technische Universit惫t München , Lehrstuhl f ür Grünlandlehre , Am Hochanger 1 , D‐85350 Freising‐Weihenstephan . E‐mail : auersw ald ＠ wzw . tum . de , 2 Research Center o f Plant Ecology , Chinese A cademy o f Sciences 20 Nanx incun ,X iangshan 10009 , Bei j ing , ChinaKey words :Carbon Isotope Discrimination , C３ plants , C４ plants , Central Asian GrasslandIntroduction The Central Asian grassland is one of the largest biomes on earth with significant influence on globalbiogeochemical cycles . It is characterized by the co‐existence of plant species with either C４ or C３ photosynthetic pathways ,which differ in carbon isotope composition . The C３ /C４ ratio is controlled by climate and land use which have changed during thepast century ( global warming and atmospheric CO２ increase ; increased stocking rates ) . However , it is unknown if thesechanges have actually elicited changes in the C３ /C４ ratio .We used old and modern woollen materials and carbon isotope analysisto reconstruct vegetation changes , which are recorded in the hair of the grazing animals .Material and methods ４１４ wool samples from ９９ sites in Inner Mongolia ( Figure １ ) dating form １９２８ to ２００５ were collected andanalyzed for carbon isotope composition . The C３ /C４ ratio was then computed from the carbon isotope composition by takinginto account the change in the carbon isotope composition of atmospheric CO２ and the influence of aridity on the carbon isotopecomposition of the C３ component .Results Average C４ abundance in Inner Mongolia increased in two steps from １％ (１９２８ － １９６２ ) to ９％ (１９６３ － １９９８) and ２５％(１９９９ － ２００５ ) w ith simultaneously increasing scatter due to the evolution of a spatial pattern . No significant trends in C４abundance and scatter occurred within any period . These findings contradict predicted decreases in C４ abundance due to risingCO２ concentrations . The increase in C４ abundance seems to be caused by a combination of rising regional temperature , increasedhuman impact ( increased stocking rate and decreased herd mobility ) and short‐term weather events , all favouring the spread ofC４ plants . The C４ abundance especially increased around large towns in the desert steppe .Figure 1 Location o f the samp ling sites in InnerMongolia . The shades o f grey disp lay the meanannual p recip itation o f the last normal period .Figure 2 Proportion o f C4 p lants in f eed o fsmall grazers (mean ± standard dev iation) .Conclusions The C４ abundance in the Inner Mongolian steppe increased probably due to overgrazing and regional warming .These factors were strong enough to override the effect of the rising atmospheric CO２ , which should have favour C３ expansion .46° 45° 42° 112° 41° c::::=-0 krn 100km _i;ik_ [1r Longitude 114° 116° 118° • 100-200 mm • 200-300 mm ■ 300-400 mm ■ >400 mm 1" Town o Samples Q) ~ E "O Q) u5 Q) .9 "O 50 40 30 20 ~ 10 <.3 0 -1 o L__._ _ _j_~ _ _j_~ _ _L_~----=2-='o=--=oo=--' 1940 1960 1980 Year 

Large‐Scale Changes in Ratio of C\u3csub\u3e3\u3c/sub\u3e and C\u3csub\u3e4\u3c/sub\u3e  Plants in Central Asian Grassland during the Last Century as Recovered from Wool Archives

https://uknowledge.uky.edu/cgi/viewcontent.cgi?article=2166&amp;context=igc

Large‐Scale Changes in Ratio of C\u3csub\u3e3\u3c/sub\u3e and C\u3csub\u3e4\u3c/sub\u3e Plants in Central Asian Grassland during the Last Century as Recovered from Wool Archives

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