title: Carbon pools and fluxes in a Tibetan alpine Kobresia pygmaea pasture partitioned by coupled eddy-covariance measurements and ¹³CO₂ pulse labeling.
abstract: The Tibetan highlands host the largest alpine grassland ecosystems worldwide, bearing soils that store substantial stocks of carbon (C) that are very sensitive to land use changes. This study focuses on the cycling of photoassimilated C within a Kobresia pygmaea pasture, the dominating ecosystems on the Tibetan highlands. We investigated short-term effects of grazing cessation and the role of the characteristic Kobresia root turf on C fluxes and belowground C turnover. By combining eddy-covariance measurements with (13)CO₂ pulse labeling we applied a powerful new approach to measure absolute fluxes of assimilates within and between various pools of the plant-soil-atmosphere system. The roots and soil each store roughly 50% of the overall C in the system (76 Mg C ha(-1)), with only a minor contribution from shoots, which is also expressed in the root:shoot ratio of 90. During June and July the pasture acted as a weak C sink with a strong uptake of approximately 2 g C m(-2) d(-1) in the first half of July. The root turf was the main compartment for the turnover of photoassimilates, with a subset of highly dynamic roots (mean residence time 20 days), and plays a key role for the C cycling and C storage in this ecosystem. The short-term grazing cessation only affected aboveground biomass but not ecosystem scale C exchange or assimilate allocation into roots and soil.
authors.affiliation: Department of Agroecosystem Research, University of Bayreuth, Bayreuth, Germany. Electronic address: johannes.ingrisch@uibk.ac.at.
authors.forename: Johannes
authors.initials: J
authors.lastname: Ingrisch
authors.affiliation: Dept. of Micrometeorology, University of Bayreuth, Bayreuth, Germany.
authors.forename: Tobias
authors.initials: T
authors.lastname: Biermann
authors.affiliation: Senckenberg Museum of Natural History, Görlitz, Germany.
authors.forename: Elke
authors.initials: E
authors.lastname: Seeber
authors.affiliation: Dept. of Micrometeorology, University of Bayreuth, Bayreuth, Germany.
authors.forename: Thomas
authors.initials: T
authors.lastname: Leipold
authors.affiliation: Cold and Arid Regions Environment and Engineering Research Institute, Chinese Academy of Sciences, Lanzhou, China.
authors.forename: Maoshan
authors.initials: M
authors.lastname: Li
authors.affiliation: Key Laboratory of Tibetan Environment Changes and Land Surface Processes, Institute of Tibetan Plateau Research, Chinese Academy of Sciences, Beijing, China.
authors.forename: Yaoming
authors.initials: Y
authors.lastname: Ma
authors.affiliation: Institute of Geographical Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing, China.
authors.forename: Xingliang
authors.initials: X
authors.lastname: Xu
authors.affiliation: Faculty of Geography, Philipps University Marburg, Marburg, Germany.
authors.forename: Georg
authors.initials: G
authors.lastname: Miehe
authors.affiliation: Institute of Soil Science, Leibniz University Hannover, Hannover, Germany.
authors.forename: Georg
authors.initials: G
authors.lastname: Guggenberger
authors.affiliation: Dept. of Micrometeorology, University of Bayreuth, Bayreuth, Germany; Member of Bayreuth Center of Ecology and Ecosystem Research (BayCEER), Germany.
authors.forename: Thomas
authors.initials: T
authors.lastname: Foken
authors.affiliation: Dept. of Soil Science of Temperate Ecosystems, Georg-August University Göttingen, Göttingen, Germany; Dept. of Agricultural Soil Science, Georg-August University of Göttingen, Göttingen, Germany; Institute of Environmental Sciences, Kazan Federal University, Kazan, Russia.
authors.forename: Yakov
authors.initials: Y
authors.lastname: Kuzyakov
mesh_terms: D000531:Altitude; D002244:Carbon / Q000032:analysis*; D057486:Carbon Cycle; D002250:Carbon Radioisotopes / Q000032:analysis; D029785:Cyperaceae / Q000502:physiology; D017753:Ecosystem; D004777:Environment; D065948:Grassland; D006109:Poaceae / Q000502:physiology; D012987:Soil; D018609:Tibet
chemical_list: D002250:Carbon Radioisotopes; D012987:Soil; D002244:Carbon
keywords: Alpine grassland; Carbon cycle; Grazing; Land use changes; Tibetan-Plateau