Increases in atmospheric carbon dioxide (CO 2 ) and global air temperature affect all terrestrial ecosystems and often lead to enhanced ecosystem productivity, which in turn dampens the rise in atmospheric CO 2 by removing CO 2 from the atmosphere. As most terrestrial ecosystems are limited in their productivity by the availability of nitrogen (N), there is concern about the persistence of this terrestrial carbon sink, as these ecosystems might develop a progressive N limitation (PNL). An increase in the gross soil N turnover may alleviate PNL, as more mineral N is made available for plant uptake. So far, climate change experiments have mainly manipulated one climatic factor only, but there is evidence that single-factor experiments usually overestimate the effects of climate change on terrestrial ecosystems. In this study, we investigated how simultaneous, decadal-long increases in CO 2 and temperature affect the soil gross N dynamics in a native Tasmanian grassland under C3 and C4 vegetation. Our laboratory 15 N labeling experiment showed that average gross N mineralization ranged from 4.9 to 11.3 µg N g −1 day −1 across the treatment combinations, while gross nitrification was about ten-times lower. Considering all treatment combinations, no significant effect of climatic treatments or vegetation type (C3 versus C4 grasses) on soil N cycling was observed.

中文翻译：

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塔斯马尼亚草原土壤氮循环对十年长期气候变化无反应

大气中二氧化碳 (CO 2 ) 和全球气温的增加会影响所有陆地生态系统，并常常导致生态系统生产力的提高，从而通过从大气中去除 CO 2 来抑制大气 CO 2 的上升。由于大多数陆地生态系统的生产力受到氮 (N) 可用性的限制，因此人们担心这种陆地碳汇的持久性，因为这些生态系统可能会发展出渐进式氮限制 (PNL)。土壤总氮周转量的增加可能会减轻 PNL，因为更多的矿物质氮可用于植物吸收。迄今为止，气候变化实验主要只操纵了一个气候因素，但有证据表明，单因素实验通常高估了气候变化对陆地生态系统的影响。在这项研究中，我们调查了在 C3 和 C4 植被下，CO 2 和温度在十年内同时增加对土壤总氮动态的影响。我们的实验室 15 N 标记实验表明，在处理组合中，平均总氮矿化范围为 4.9 至 11.3 µg N g -1 天 -1，而总硝化作用低约 10 倍。考虑到所有处理组合，未观察到气候处理或植被类型（C3 与 C4 草）对土壤氮循环的显着影响。而总硝化作用大约低十倍。考虑到所有处理组合，未观察到气候处理或植被类型（C3 与 C4 草）对土壤氮循环的显着影响。而总硝化作用大约低十倍。考虑到所有处理组合，未观察到气候处理或植被类型（C3 与 C4 草）对土壤氮循环的显着影响。