Carbon storage in phosphorus limited grasslands may decline in response to elevated nitrogen deposition: a long-term field manipulation and modelling study
Carbon storage in phosphorus limited grasslands may decline in response to elevated nitrogen deposition: a long-term field manipulation and modelling study
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DOI：
10.5194/bg-2020-392
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发表时间：
2020-11
期刊：
影响因子：
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通讯作者：
Christopher R. Taylor;Victoria Janes‐Bassett;G. Phoenix;B. Keane;I. Hartley;J. Davies
中科院分区：
文献类型：
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作者：
Christopher R. Taylor;Victoria Janes‐Bassett;G. Phoenix;B. Keane;I. Hartley;J. Davies
抽象的。在许多温带生态系统中，氮 (N) 限制了生产力，这意味着人为氮沉降可以刺激植物生长，进而刺激碳 (C) 固存。磷（P）和氮磷共限草原广泛存在，但对其对氮沉降的响应了解有限，这可能会使更多的生态系统向磷有限或氮磷共限状态转变。在这里，我们研究了增加氮添加对不同养分限制状态下草地 C-N-P 库的影响。我们探索了在两个氮磷共限草原上进行的长期养分控制实验的响应；通过将数据与综合 C-N-P 循环模型 (N14CP) 相结合，划分出 N 限制较强的酸性草原和 P 限制较强的钙质草原。为了探索磷获取机制在确定生态系统状态中的作用，我们允许磷获取发生变化，并将输出与植物-土壤 C-N-P 数据进行比较。最接近代表数据的有机磷获取和无机磷有效性的组合被用来模拟草原并量化其对养分操纵的时间响应。该模型表明，氮的添加增加了酸性草地的碳储量，但减少了钙质草地的碳储量，其中氮的供应加剧了磷限制并减少了土壤的生物量输入。此外，植物对有机磷的获取可能在减少磷限制方面发挥重要作用，因为两种模拟草地都增加了有机磷的吸收以满足磷的需求。我们得出的结论是，不同限制养分的草地可能以不同的方式对氮沉降做出反应，并强调，当氮沉降使生态系统转向磷限制时，全球重要的碳汇面临退化的风险。
Abstract. In many temperate ecosystems, nitrogen (N) limits productivity, meaning anthropogenic N deposition can stimulate plant growth and subsequently carbon (C) sequestration. Phosphorus (P) and N-P co-limited grasslands are widespread, yet there is limited understanding of their responses to N deposition, which may transition more ecosystems toward P-limited or N-P co-limited states. Here, we investigate the consequences of enhanced N addition on the C-N-P pools of grasslands in different states of nutrient limitation. We explored the response of a long-term nutrient-manipulation experiment on two N-P co-limited grasslands; an acidic grassland of stronger N-limitation and a calcareous grassland of stronger P-limitation, by combining data with an integrated C-N-P cycling model (N14CP). To explore the role of P-access mechanisms in determining ecosystem state, we allowed P-access to vary, and compared the outputs to plant-soil C-N-P data. Combinations of organic P access and inorganic P availability most closely representing data were used to simulate the grasslands and quantify their temporal response to nutrient manipulation. The model suggested N additions have increased C stocks in the acidic grassland, but decreased them in the calcareous, where N provision exacerbated P-limitation and reduced biomass input to the soil. Furthermore, plant acquisition of organic P may play an important role in reducing P-limitation, as both simulated grasslands increased organic P uptake to meet P demand. We conclude that grasslands of differing limiting nutrients may respond to N deposition in contrasting ways, and stress that as N deposition shifts ecosystems toward P-limitation, a globally important carbon sink risks degradation.