Sun, Y; Schleuss, P-M; Pausch, J; Xu, X; Kuzyakov, Y: Nitrogen pools and cycles in Tibetan Kobresia pastures depending on grazing, Biology and Fertility of Soils, 54, 569-581 (2018), doi:10.1007/s00374-018-1280-y | |
Abstract: Kobresia grasslands on the Tibetan Plateau comprise the world’s largest pastoral alpine ecosystem. Overgrazing-driven degradation strongly proceeded on this vulnerable grassland, but the mechanisms behind are still unclear. Plants must balance the costs of releasing C to soil against the benefits of accelerated microbial nutrient mineralization, which increases their availability for root uptake. To achieve the effect of grazing on this C-N exchange mechanism, a 15NH4+ field labeling experiment was implemented at grazed and ungrazed sites, with additional treatments of clipping and shading to reduce belowground C input by manipulating photosynthesis. Grazing reduced gross N mineralization rates by 18.7%, similar to shading and clipping. This indicates that shoot removal by grazing decreased belowground C input, thereby suppressing microbial N mining and overall soil N availability. Nevertheless, NH4+ uptake rate by plants at the grazed site was 1.4 times higher than at the ungrazed site, because plants increased N acquisition to meet the high N demands of shoot regrowth (compensatory growth: grazed > ungrazed). To enable efficient N uptake and regrowth, Kobresia plants have developed specific traits (i.e., efficient above-belowground interactions). These traits reflect important mechanisms of resilience and ecosystem stability under long-term moderate grazing in an N-limited environment. However, excessive (over)grazing might imbalance such C-N exchange and amplify plant N limitation, hampering productivity and pasture recovery over the long term. In this context, a reduction in grazing pressure provides a sustainable way to maintain soil fertility, C sequestration, efficient nutrient recycling, and overall ecosystem stability. |
Antrittsvorlesung: |
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Mi. 22.05.2024 Funktionelle Pilzökologie: Diversität und Prozesse auf unterschiedlichen Skalen |
BayCEER-Kolloquium: |
Do. 06.06.2024 Tracking plant diversity dynamics on islands over thousands of years |
Mo. 10.06.2024 Arsenic biogeochemistry from paddy soil to rice grain |
Do. 13.06.2024 Seeing the forest beneath the trees: Mycorrhizal fungi as trait integrators of ecosystem processes |
Ökologisch-Botanischer Garten: |
Mi. 29.05.2024 Führung | "Grüne Apotheke: Heilpflanzen" |