Atmospheric nitrogen (N) deposition alters plant biodiversity and ecosystem function in grasslands worldwide. This study examines the impact of 6 years of nutrient addition and grazing management on a sand dune grassland. Results indicate that co-limitation of N and phosphorus (P) moderates the impact of realistic rates of N addition (7.5, 15 kg N ha−1 year−1). Combined NP addition (15 kg N + 10 kg P ha−1 year−1) was the only nutrient treatment to differ significantly from the control, with greater above-ground biomass (mainly moss), and enhanced N and P mineralisation rates. Grazing management altered plant functional group composition, reduced above-ground biomass and meso-faunal feeding rates, and decoupled N and P mineralisation. There were no synergistic effects of grazing and N treatment. Although NP co-limitation apparently prevents adverse impacts of N deposition above the critical load, excess N is likely to be stored in moss biomass and soil, with unknown future consequences.
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机译:大气氮(N)的沉积改变了世界范围内草原的植物生物多样性和生态系统功能。本研究考察了6年养分添加和放牧管理对沙丘草地的影响。结果表明,氮和磷(P)的共同限制减轻了实际添加氮的速率(7.5、15千克N ha-1年-1)的影响。 NP的联合添加(15 kg N + 10 kg P ha-1 year-1)是唯一与对照显着不同的养分处理方法,具有更大的地上生物量(主要是苔藓),并提高了N和P矿化率。放牧管理改变了植物官能团的组成,降低了地上生物量和中观动物的摄食速率,并使氮和磷矿化解耦。放牧和氮肥处理没有协同作用。尽管NP共限制显然可以防止临界负载以上的N沉积的不利影响,但过量的N可能会存储在苔藓生物量和土壤中,未来的后果未知。
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