Nitrogen source utilization in co-existing canopy tree and dwarf bamboo in a northern hardwood forest in Japan
Nitrogen source utilization in co-existing canopy tree and dwarf bamboo in a northern hardwood forest in Japan
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DOI：
10.1007/s00468-020-01980-1
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发表时间：
2020-04
期刊：
影响因子：
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通讯作者：
R. Tateno;Masataka Nakayama;M. Yano;Karibu Fukuzawa;Y. Inagaki;K. Koba;S. Ugawa
中科院分区：
文献类型：
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作者：
R. Tateno;Masataka Nakayama;M. Yano;Karibu Fukuzawa;Y. Inagaki;K. Koba;S. Ugawa
林下矮秆竹通过在深层土壤中觅食和增加对与冠层树木不同的N形态的依赖来减轻与共存的冠层橡树的土壤N竞争。通过调查橡树和矮秆竹的N源，探讨了利用不同菌根类型的共存植物物种之间的N竞争。对细根的垂直分布、土壤氮库、叶片δ 15 N、可能的土壤氮源和硝酸还原酶活性进行了定量分析。冠层乔木的细根比林下矮竹的细根更集中于表层土壤。土壤NH 4+和可提取有机氮（EON）含量（以单位重量计）从有机层（O层）向深层逐渐减少，单位体积NH 4+库的大小随土壤深度的增加而增加，EON基本不变。在任何土壤深度都没有检测到土壤NO3−，或者值不显著，而通过实验室培养在所有土壤深度观察到埋在10 cm土壤深度的离子交换树脂（IER）捕获的NO3−和净硝化作用。NH 4+和EON的δ 15 N随土层深度的增加而增加，除O层NH 4+的δ 15 N外，IER的NO3-的δ 15 N均低于其他形态的N。此外，根NRA往往是较低的冠层树木比林下，这意味着较低的依赖NO3-的冠层树木。的根系分布和菌根真菌协会的林下植被（以及高根NRA）的模式表明，在深层土壤中的N的依赖性更高的林下植物比冠层树木。这些研究结果表明，林下植被减轻土壤氮竞争对共存的树冠树木通过使用替代N源。
Key messageUnderstory dwarf bamboo mitigated soil N competition with co-existing canopy oak trees by foraging in deeper soils and increasing dependence on N forms that differ from those used by canopy trees.AbstractNitrogen (N) competition among co-existing plant species utilizing different mycorrhiza types was explored through the investigation of N sources of oak trees and dwarf bamboo. Vertical distribution of fine roots, soil N pools, δ15N of leaves, and possible soil N sources and nitrate reductase activity (NRA) were all quantified. The fine roots of canopy trees were more concentrated in the surface soils than roots of the understory dwarf bamboo. Soil NH4+and extractable organic N (EON) content (based on unit weight) decreased from the organic horizon (O horizon) to the deep soils, the size of the NH4+pool per unit volume increased with soil depth, and the EON was approximately constant. Soil NO3−was not detected at any soil depth or was not significant in value, while NO3−captured by ion-exchange resin (IER) buried at a 10 cm soil depth and net nitrification were observed via laboratory incubation at all soil depths. The δ15N of the NH4+and EON pools increased with soil depth and the δ15N of NO3−of IER was lower than that of other N forms, except for the δ15N of NH4+in the O horizon. Furthermore, root NRA tended to be lower in canopy trees than in the understory, implying lower dependency on NO3−by canopy trees. The pattern of root distribution and mycorrhizal fungi association of the understory vegetation (as well as the high root NRA) suggested that dependence on N in deeper soils was higher in understory plants than in canopy trees. These findings indicate that understory vegetation mitigates soil N competition against co-existing canopy trees via the use of alternative N sources.