Differences in nitrogen use efficiency between leaves from canopy and subcanopy trees |
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Authors: | Ryunosuke Tateno Hideyuki Kawaguchi |
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Affiliation: | (1) Laboratory of Forest Ecology, Graduate School of Agriculture, Kyoto University, Kyoto 606-8502, Japan;(2) Faculty of Life and Environmental Science, Shimane University, Matsue 690-8504, Japan |
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Abstract: | We examined the effects of increasing light availability along a vertical gradient within a forest community on the efficiency of leaf nitrogen (N) use in individual trees. The N contents of green and senescent leaves in canopy and subcanopy trees of an evergreen coniferous species, Podocarpus nagi, and an evergreen hardwood species, Neolitsea aciculata, were analyzed in a mixed forest community at Mt Mikasa, Nara City, Japan. The inverse of N concentration (NC) in senescent leaves was used as an index of N use efficiency (NUE) at the leaf-level. The leaf-level NUE was higher in canopy trees than in subcanopy trees in both P.nagi and N.aciculata, although soil N mineralization rates around canopy and subcanopy trees did not differ significantly. The NC in green leaves was lower in canopy trees than in subcanopy trees. The ratio of resorbed N in senescent leaves to the N content in green leaves was higher in canopy trees than in subcanopy trees. The higher leaf-level NUE of canopy trees was partly a result of lower NC in living tissues and partly because of greater N resorption during senescence. The present study suggested that the leaf-level NUE could be increased in response to an imbalance between soil N and light availability caused by spatial community structure. |
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Keywords: | forest structure nutrient use resorption resource ratio soil nitrogen |
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