Articles | Volume 11, issue 23
Biogeosciences, 11, 6633–6656, 2014
Biogeosciences, 11, 6633–6656, 2014

Research article 02 Dec 2014

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 W. Babel et al.
  • 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.

Final-revised paper