Biogeosciences, 11, 6633-6656, 2014
© Author(s) 2014. This work is distributed under
the Creative Commons Attribution 3.0 License.
Research article
02 Dec 2014
Pasture degradation modifies the water and carbon cycles of the Tibetan highlands
W. Babel1,17, T. Biermann1,*, H. Coners2, E. Falge1,**, E. Seeber3, J. Ingrisch4,***, P.-M. Schleuß4, T. Gerken1,5,****, J. Leonbacher1, T. Leipold1, S. Willinghöfer2, K. Schützenmeister6, O. Shibistova7,8, L. Becker7, S. Hafner4, S. Spielvogel4,6, X. Li9, X. Xu4,10, Y. Sun4,10, L. Zhang11, Y. Yang12, Y. Ma11, K. Wesche3,13, H.-F. Graf5, C. Leuschner2, G. Guggenberger7, Y. Kuzyakov4,14,15, G. Miehe16, and T. Foken1,17 1University of Bayreuth, Department of Micrometeorology, Bayreuth, Germany
2University of Göttingen, Department of Plant Ecology and Ecosystem Research, Göttingen, Germany
3Senckenberg Museum Görlitz, Department of Botany, Görlitz, Germany
4University of Göttingen, Department of Soil Sciences of Temperate Ecosystems, Göttingen, Germany
5University of Cambridge, Department of Geography, Centre for Atmospheric Science, Cambridge, UK
6University of Koblenz-Landau, Institute of Integrated Environmental Sciences, Koblenz, Germany
7Leibniz Universität Hannover, Institute for Soil Science, Hanover, Germany
8V.~N. Sukachev Institute of Forest, Krasnoyarsk, Russia
9School of Life Sciences, Lanzhou University, Lanzhou, China
10Chinese Academy of Sciences, Institute of Geographical Sciences and Natural Resources Research, Beijing, China
11Chinese Academy of Sciences, Institute of Tibetan Plateau Research, Key Laboratory of Tibetan Environment Changes and Land Surface, Processes, Beijing, China
12Chinese Academy of Sciences, Institute of Tibetan Plateau Research, Laboratory of Alpine Ecology and Biodiversity Focuses, Processes, Beijing, China
13German Centre for Integrative Biodiversity Research (iDiv) Halle–Jena–Leipzig, Germany
14University of Göttingen, Department of Agricultural Soil Science, Göttingen, Germany
15Institute of Environmental Sciences, Kazan Federal University, Kazan, Russia
16University of Marburg, Faculty of Geography, Marburg, Germany
17Member of Bayreuth Center of Ecology and Ecosystem Research, Bayreuth, Germany
*now at: Lund University, Centre for Environmental and Climate Research, Lund, Sweden
**now at: Thünen Institute of Climate-Smart Agriculture, Braunschweig, Germany
***now at: University of Innsbruck Institute of Ecology Research, Innsbruck, Austria
****now at: The Pennsylvania State University, Department of Meteorology, University Park, PA, USA
Abstract. The Tibetan Plateau has a significant role with regard to atmospheric circulation and the monsoon in particular. Changes between a closed plant cover and open bare soil are one of the striking effects of land use degradation observed with unsustainable range management or climate change, but experiments investigating changes of surface properties and processes together with atmospheric feedbacks are rare and have not been undertaken in the world's two largest alpine ecosystems, the alpine steppe and the Kobresia pygmaea pastures of the Tibetan Plateau. We connected measurements of micro-lysimeter, chamber, 13C labelling, and eddy covariance and combined the observations with land surface and atmospheric models, adapted to the highland conditions. This allowed us to analyse how three degradation stages affect the water and carbon cycle of pastures on the landscape scale within the core region of the Kobresia pygmaea ecosystem. The study revealed that increasing degradation of the Kobresia turf affects carbon allocation and strongly reduces the carbon uptake, compromising the function of Kobresia pastures as a carbon sink. Pasture degradation leads to a shift from transpiration to evaporation while a change in the sum of evapotranspiration over a longer period cannot be confirmed. The results show an earlier onset of convection and cloud generation, likely triggered by a shift in evapotranspiration timing when dominated by evaporation. Consequently, precipitation starts earlier and clouds decrease the incoming solar radiation. In summary, the changes in surface properties by pasture degradation found on the highland have a significant influence on larger scales.

Citation: Babel, W., Biermann, T., Coners, H., Falge, E., Seeber, E., Ingrisch, J., Schleuß, P.-M., Gerken, T., Leonbacher, J., Leipold, T., Willinghöfer, S., Schützenmeister, K., Shibistova, O., Becker, L., Hafner, S., Spielvogel, S., Li, X., Xu, X., Sun, Y., Zhang, L., Yang, Y., Ma, Y., Wesche, K., Graf, H.-F., Leuschner, C., Guggenberger, G., Kuzyakov, Y., Miehe, G., and Foken, T.: Pasture degradation modifies the water and carbon cycles of the Tibetan highlands, Biogeosciences, 11, 6633-6656,, 2014.
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