Department of Ecosystem Trace Gas Exchange, Global Change Research Institute of the Czech Academy of Sciences, Belidla 4a, CZ-60300 Brno, Czech Republic.
Department of Ecosystem Trace Gas Exchange, Global Change Research Institute of the Czech Academy of Sciences, Belidla 4a, CZ-60300 Brno, Czech Republic; Department of Geography, Institute of Ecology & Earth Sciences, University of Tartu, 46 Vanemuise, EST-51014 Tartu, Estonia.
Sci Total Environ. 2024 Jul 15;934:173122. doi: 10.1016/j.scitotenv.2024.173122. Epub 2024 May 9.
Similar to soils, tree stems emit and consume nitrous oxide (NO) from the atmosphere. Although tree leaves dominate tree surface area, they have been completely excluded from field NO flux measurements and therefore their role in forest NO exchange remains unknown. We explored the contribution of leaf fluxes to forest NO exchange. We determined the NO exchange of mature European beech (Fagus sylvatica) stems and shoots (i.e., terminal branches) and of adjacent forest floor, in a typical temperate upland forest in Germany. The beech stems, and particularly the shoots, acted as net NO sinks (-0.254 ± 0.827 μg NO m stem area h and -4.54 ± 1.53 μg NO m leaf area h, respectively), while the forest floor was a net source (2.41 ± 1.08 μg NO m soil area h). The unstudied tree shoots were identified as a significant contributor to the net ecosystem NO exchange. Moreover, we revealed for the first time that tree leaves act as substantial NO sinks. Although this is the first study of its kind, it is of global importance for the proper design of future flux studies in forest ecosystems worldwide. Our results demonstrate that excluding tree leaves from forest NO flux measurements can lead to misinterpretation of tree and forest NO exchange, and thus global forest greenhouse gas flux inventories.
与土壤类似，树干也会向大气中排放和消耗氧化亚氮（NO）。尽管树叶占据了树木表面积的主导地位，但它们完全被排除在野外 NO 通量测量之外，因此它们在森林 NO 交换中的作用仍不清楚。我们探讨了叶片通量对森林 NO 交换的贡献。我们确定了德国典型温带高地森林中成熟山毛榉（Fagus sylvatica）树干和嫩枝（即末梢枝）以及相邻林床的 NO 交换。山毛榉树干，尤其是嫩枝，充当净 NO 汇（-0.254 ± 0.827 μg NO m 树干面积 h 和-4.54 ± 1.53 μg NO m 叶片面积 h），而林床则是净源（2.41 ± 1.08 μg NO m 土壤面积 h）。未被研究的树木嫩枝被确定为净生态系统 NO 交换的重要贡献者。此外，我们首次揭示了树叶是大量的 NO 汇。尽管这是此类研究中的首次，但对于正确设计全球范围内未来森林生态系统通量研究具有全球重要意义。我们的研究结果表明，将树木叶片排除在森林 NO 通量测量之外可能导致对树木和森林 NO 交换的错误解释，从而影响全球森林温室气体通量清单。
