Consequences of climate change and land use intensification on the nitrogen (N) cycle of organic-matter rich grassland soils in the alpine region remain poorly understood. We aimed to identify fates of fertilizer N and to determine the overall N balance of an organic-matter rich grassland in the European alpine region as influenced by intensified management and warming. We combined 15N cattle slurry labelling with a space for time climate change experiment, which was based on translocation of intact plant-soil mesocosms down an elevational gradient to induce warming of +1 °C and + 3 °C. Mesocosms were subject to either extensive or intensive management. The fate of slurry-N was traced in the plant-soil system. Grassland productivity was very high (8.2 t - 19.4 t dm ha−1 yr−1), recovery of slurry 15N in mowed plant biomass was, however, low (9.6–14.7%), illustrating low fertilizer N use efficiency and high supply of plant available N via mineralization of soil organic matter (SOM). Higher 15N recovery rates (20.2–31.8%) were found in the soil N pool, dominated by recovery in unextractable N. Total 15N recovery was approximately half of the applied tracer, indicating substantial loss to the environment. Overall, high N export by harvest (107–360 kg N ha−1 yr−1) markedly exceeded N inputs, leading to a negative grassland N balance. Here provided results suggests a risk of soil N mining in montane grasslands, which increases both under climate change and land use intensification.

中文翻译：

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集约化泥浆管理和气候变化促进从富含有机质的山地草原土壤中开采氮

气候变化和土地利用集约化对高山地区富含有机质的草地土壤的氮 (N) 循环的影响仍然知之甚少。我们旨在确定肥料 N 的命运，并确定受强化管理和变暖影响的欧洲高山地区富含有机物的草地的整体 N 平衡。我们将 15N 牛泥浆标记与时间空间气候变化实验相结合，该实验基于完整的植物 - 土壤中层空间沿海拔梯度易位以诱导 +1°C 和 +3°C 升温。Mesocosms 受到广泛或密集的管理。在植物-土壤系统中追踪了浆液氮的归宿。草地生产力非常高（8.2 t - 19.4 t dm ha−1 yr−1），然而，割草植物生物量中浆液 15N 的回收率很低（9.6-14. 7%)，说明化肥氮利用效率低，通过土壤有机质 (SOM) 的矿化提供植物有效氮的高供应。在土壤 N 池中发现了更高的 15N 回收率（20.2-31.8%），主要是在不可提取的 N 中的回收。 15N 的总回收率约为所用示踪剂的一半，表明对环境的大量损失。总体而言，收获时的高氮输出（107-360 kg N ha−1 yr−1）明显超过 N 输入，导致草地 N 负平衡。此处提供的结果表明山地草原存在土壤氮开采的风险，这在气候变化和土地利用集约化的情况下都会增加。以不可提取的 N 中的回收率为主。 15N 的总回收率约为所用示踪剂的一半，表明对环境造成了重大损失。总体而言，收获时的高氮输出（107-360 kg N ha−1 yr−1）明显超过 N 输入，导致草地 N 负平衡。此处提供的结果表明山地草原存在土壤氮开采的风险，这在气候变化和土地利用集约化的情况下都会增加。以不可提取的 N 中的回收率为主。 15N 的总回收率约为所用示踪剂的一半，表明对环境造成了重大损失。总体而言，收获时的高氮输出（107-360 kg N ha−1 yr−1）明显超过 N 输入，导致草地 N 负平衡。此处提供的结果表明山地草原存在土壤氮开采的风险，这在气候变化和土地利用集约化的情况下都会增加。