Nitrification and denitrification in the Community Land Model compared to observations at Hubbard Brook Forest
Nitrification and denitrification in the Community Land Model compared to observations at Hubbard Brook Forest
复制标题
社区土地模型中的硝化和反硝化与哈伯德布鲁克森林的观测结果相比
DOI：
10.1002/eap.2530
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发表时间：
2022
影响因子：
5
通讯作者：
Groffman, Peter M.
中科院分区：
文献类型：
--
作者：
Nevison, Cynthia;Goodale, Christine;Hess, Peter;Wieder, William R.;Vira, Julius;Groffman, Peter M.
陆地系统动力学模型通常包括氮(N)循环，以更好地表示N对陆地碳(C)吸收的限制，但事实证明，模拟N在生态系统中的命运是具有挑战性的。在这里，来自社区土地模型5.0版(CLM5.0)的关键土壤N通量和通量比与来自新罕布夏州哈伯德·布鲁克森林长期生态研究站点的大量观测结果进行了比较。模拟通量包括微生物固定化和植物吸收，它们分别与硝化和反硝化竞争土壤有效态铵(NH_4+)和硝酸盐(NO_3-−)。在其默认构型下，CLM5.0预测植物的吸收和固定都强烈地被NH4+所支配，而硝化作用和反硝化作用的模型比为~1：1。相反，哈伯德·布鲁克的观察表明，NO3-−在植物吸收中起着更重要的作用，硝化作用可能比反硝化作用高一个数量级。Hubbard Brook对CLM5.0标准的修改表明，为了使土壤氮通量比与观测结果更好地吻合，需要同时增加硝化微生物对NH4+的竞争能力，降低反硝化细菌对NO3−的竞争能力。尽管总初级生产力和净初级生产力等C通量对模型修正的敏感性不如土壤N通量，但这种调整，再加上对观测结果的评估，可能有助于提高目前和未来对C循环N限制模拟的置信度。
Models of terrestrial system dynamics often include nitrogen (N) cycles to better represent N limitations on terrestrial carbon (C) uptake, but simulating the fate of N in ecosystems has proven challenging. Here, key soil N fluxes and flux ratios from the Community Land Model version 5.0 (CLM5.0) are compared with an extensive set of observations from the Hubbard Brook Forest Long‐Term Ecological Research site in New Hampshire. Simulated fluxes include microbial immobilization and plant uptake, which compete with nitrification and denitrification, respectively, for available soil ammonium (NH4+) and nitrate (NO3−). In its default configuration, CLM5.0 predicts that both plant uptake and immobilization are strongly dominated by NH4+over NO3−, and that the model ratio of nitrification:denitrification is ~1:1. In contrast, Hubbard Brook observations suggest that NO3−plays a more significant role in plant uptake and that nitrification could exceed denitrification by an order of magnitude. Modifications to the standard CLM5.0 at Hubbard Brook indicate that a simultaneous increase in the competitiveness of nitrifying microbes for NH4+and reduction in the competitiveness of denitrifying bacteria for NO3−are needed to bring soil N flux ratios into better agreement with observations. Such adjustments, combined with evaluation against observations, may help to improve confidence in present and future simulations of N limitation on the C cycle, although C fluxes, such as gross primary productivity and net primary productivity, are less sensitive to the model modifications than soil N fluxes.