Response of long-, medium- and short-term processes of the carbon budget to overgrazing-induced crusts in the Tibetan Plateau
| Autor: | Yakov Kuzyakov, Xingliang Xu, Georg Guggenberger, Jianquan Liu, Sebastian Unteregelsbacher, Georg Miehe, Silke Hafner |
|---|---|
| Jazyk: | angličtina |
| Rok vydání: | 2012 |
| Předmět: |
010504 meteorology & atmospheric sciences
crust 01 natural sciences CO2 efflux from soil regression analysis Soil respiration Overgrazing Land-use changes Kobresia pasture Root exudates 13C pulse labeling Soil organic carbon Nutrient Chlorophyta ddc:550 Lichen skin and connective tissue diseases soil analysis Water Science and Technology 2. Zero hunger biology integumentary system food and beverages 04 agricultural and veterinary sciences Kobresia pasture Crustose China Qinghai-Xizang Plateau carbon budget Botany carbon cycle Environmental Chemistry Animalia 0105 earth and related environmental sciences Earth-Surface Processes animal husbandry Soil organic matter Soil carbon 15. Life on land biology.organism_classification Earth Sciences Biogeosciences Ecosystems Life Sciences general Agronomy Soil water 040103 agronomy & agriculture 0401 agriculture forestry and fisheries grassland |
| Zdroj: | Biogeochemistry 111 (2012) |
| Popis: | The Kobresia pastures of the Tibetan Plateau represent the world’s largest alpine grassland ecosystem. These pastures remained stable during the last millennia of nomadic animal husbandry. However, strongly increased herds’ density has promoted overgrazing, with unclear consequences for vegetation and soils, particularly for cycles of carbon (C), nutrients and water. Vegetation-free patches of dead root-mat covered by blue-green algae and crustose lichens (crusts) are common in overgrazed Kobresia pastures, but their effect on C turnover processes is completely unknown. We tested the hypothesis that the crusts strongly affect the C cycle by examining: (i) the long-term C stock measured as soil organic matter content; (ii) medium-term C stock as dead roots; (iii) recent C fluxes analyzed as living roots and CO2 efflux; and (iv) fast decomposition of root exudates. Up to 7.5 times less aboveground and 1.9 times less belowground living biomass were found in crust patches, reflecting a much smaller C input to soil as compared with the non-crust Kobresia patches. A lower C input initially changed the long-term C stock under crusts in the upper root-mat horizon. Linear regression between living roots and CO2 efflux showed that roots contributed 23% to total CO2 under non-crust areas (mean July–August 5.4 g C m−2 day−1) and 18% under crusts (5.1 g C m−2 day−1). To identify differences in the fast turnover processes in soil, we added 13C labeled glucose, glycine and acetic acid, representing the three main groups of root exudates. The decomposition rates of glucose (0.7 day−1), glycine (1.5 day−1) and acetic acid (1.2 day−1) did not differ under crusts and non-crusts. More 13C, however, remained in soil under crusts, reflecting less complete decomposition of exudates and less root uptake. This shows that the crust patches decrease the rates of medium-term C turnover in response to the much lower C input. Very high 13C amounts recovered in plants from non-crust areas as well as the two times lower uptake by roots under crusts indicate that very dense roots are efficient competitors with microorganisms for soluble organics. In conclusion, the altered C cycle in the overgrazing-induced crustose lichens and blue-green algae crusts is connected with strongly decreased C input and reduced medium-term C turnover. peerReviewed |
| Databáze: | OpenAIRE |
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