| 摘 要： |
Background and aims Grazing drives carbon (C) and nitrogen (N) dynamics of grasslands through livestock trampling, defoliation, and excretion. Still, the responses of N uptake by plant species and simultaneous C allocation into the soil to grazing intensity remain unclear. Methods In-situ (NH4+)-N- 15 / (NO3-)-N-15 and C-13-CO2 labeling experiment was conducted in Inner Mongolia grasslands under 5 years of grazing with no, light (4 sheep 1.33 ha(-1)) and heavy (12 sheep 1.33 ha(-1)) intensity to reveal the contribution of plant-derived C into the soil and the fate of N on day one and three after C-13-labeling. Experiment had a completely randomized design (n = 3), and every plot included Leymus chinensis, Carex korshinskyi, Cleistogenes squarrosa, and Stipa grandis. Results Grazing increased plants' total N uptake compared to control (no grazing); higher NO3- uptake was found compared to NH4+ (aboveground: 0.40-20.78 vs. 0.32-6.58 mu g N m(-2); belowground: 0.04-9.92 vs. 0.01-0.49 mu g N m(-2)), irrespective of grazing intensity. C. korshinskyi showed the highest N uptake (3-21 mu g N m(-2)) under the three grazing intensities. C-13-CO2 assimilation was the lowest under heavy grazing (aboveground: 1.06-10.67 mg C m(-2); belowground: 0.25-1.53 mg C m(-2)) regardless of plant species. C-13-CO2 assimilation by L. chinensis and C. squarrosa decreased 3-5 times with grazing intensity. Grazing increased C-13-SOC irrespective to soil depth compared to no grazing. Conclusions Grazing patterns affected the plants' total assimilation C capacity and N uptake and the response varies among plant species, as well as the allocation of plant-C transfer into the soil. |
在线留言
联系我们
所长信箱