Graduate School of Agriculture, Hokkaido University, Sapporo 060-8689, Japan.
Research Faculty of Agriculture, Hokkaido University, Sapporo, 060-8689, Japan.
Sci Total Environ. 2019 May 1;663:587-595. doi: 10.1016/j.scitotenv.2019.01.292. Epub 2019 Jan 24.
Larch (Larix sp.) tree is a critical species for the future afforestation in Northeast Asia. The impacts of elevated concentrations of ground-level ozone (O) and nitrogen (N) deposition are raising concerns. However, knowledge of the combined effects of elevated O and N loading are still limited. We investigated whether nitrogen loading mitigates the negative impacts of ozone on two larch species: the Japanese larch (L. kaempferi) and its hybrid larch F (L. gmelinii var. japonica × L. kaempferi) or not. We used open-top cambers and compared responses of the larch seedlings. Results showed the N loading mitigated the negative effects of O on Japanese larch. However, in hybrid larch F, N loading did not mitigate O-induced inhibition of growth and photosynthetic capacity. Mitigation effect of N loading on negative O impacts may vary between the two Larix spp., Hybrid larch F could be more affected by the combined effects of O and N loading due to its higher growth response to N loading. Elevated O also reduced leaf nitrogen/phosphorus (N/P) ratio by elevated O, with significant effects in hybrid larch F, particularly under N loading. In the present study, leaf N/P ratio was utilized to validate the hypothesis that a positive effect of N loading may be observed if O does not induce P limitation in Larix spp. We demonstrated a potential leaf N/P ratio function, which could reflect responses to O and N loading in hybrid larch F.
落叶松（Larix sp.）是东北亚未来造林的关键物种。地面臭氧（O）和氮（N）沉降浓度升高的影响引起了人们的关注。然而，关于升高的 O 和 N 负荷的综合影响的知识仍然有限。我们研究了氮负荷是否减轻了臭氧对两种落叶松物种的负面影响：日本落叶松（L. kaempferi）及其杂种落叶松 F（L. gmelinii var. japonica × L. kaempferi）。我们使用开顶室并比较了落叶松幼苗的反应。结果表明，氮负荷减轻了臭氧对日本落叶松的负面影响。然而，在杂种落叶松 F 中，氮负荷并没有减轻 O 诱导的生长和光合作用能力抑制。氮负荷对 O 负面影响的缓解作用可能因两种落叶松物种的不同而不同，杂种落叶松 F 可能由于其对氮负荷的更高生长响应而更容易受到 O 和 N 负荷的综合影响。升高的 O 还通过升高的 O 降低了叶片氮/磷（N/P）比，在杂种落叶松 F 中尤其明显，尤其是在氮负荷下。在本研究中，叶片 N/P 比被用来验证这样一个假设，即如果 O 不会在落叶松物种中引起 P 限制，那么氮负荷可能会产生积极的影响。我们展示了一个潜在的叶片 N/P 比函数，它可以反映杂种落叶松 F 对 O 和 N 负荷的响应。
