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Nitrogen pools and cycles in Tibetan Kobresia pastures depending on grazing.
- Source :
-
Biology & Fertility of Soils . Jul2018, Vol. 54 Issue 5, p569-581. 13p. - Publication Year :
- 2018
-
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. [ABSTRACT FROM AUTHOR]
- Subjects :
- *PASTURES
*GRAZING
*NITROGEN
*ANIMAL feeding
*AGRICULTURE
Subjects
Details
- Language :
- English
- ISSN :
- 01782762
- Volume :
- 54
- Issue :
- 5
- Database :
- Academic Search Index
- Journal :
- Biology & Fertility of Soils
- Publication Type :
- Academic Journal
- Accession number :
- 130103620
- Full Text :
- https://doi.org/10.1007/s00374-018-1280-y