Global Change Research Institute of the Czech Academy of Sciences, Belidla 4a, CZ-60300, Brno, Czech Republic.
Environmental Soil Science, Department of Agricultural Sciences, University of Helsinki, P.O.Box 56, FI-00014, Helsinki, Finland.
Nat Commun. 2019 Nov 1;10(1):4989. doi: 10.1038/s41467-019-12976-y.
The role of trees in the nitrous oxide (NO) balance of boreal forests has been neglected despite evidence suggesting their substantial contribution. We measured seasonal changes in NO fluxes from soil and stems of boreal trees in Finland, showing clear seasonality in stem NO flux following tree physiological activity, particularly processes of CO uptake and release. Stem NO emissions peak during the vegetation season, decrease rapidly in October, and remain low but significant to the annual totals during winter dormancy. Trees growing on dry soils even turn to consumption of NO from the atmosphere during dormancy, thereby reducing their overall NO emissions. At an annual scale, pine, spruce and birch are net NO sources, with spruce being the strongest emitter. Boreal trees thus markedly contribute to the seasonal dynamics of ecosystem NO exchange, and their species-specific contribution should be included into forest emission inventories.
尽管有证据表明树木对氧化亚氮（NO）平衡有很大的贡献，但它们在北方森林中的作用一直被忽视。我们测量了芬兰北方树木土壤和茎干中 NO 通量的季节性变化，发现茎干 NO 通量随着树木生理活动的变化而呈现明显的季节性，特别是 CO 吸收和释放的过程。茎干 NO 的排放在植被季节达到峰值，10 月迅速下降，在冬季休眠期间保持较低水平，但对年总量仍有显著影响。生长在干燥土壤上的树木甚至在休眠期间从大气中吸收 NO，从而减少其整体 NO 排放。在年度尺度上，松树、云杉和桦树是净 NO 源，其中云杉的排放量最大。因此，北方树木对生态系统 NO 交换的季节性动态有显著贡献，其物种特异性的贡献应该被纳入森林排放清单中。
