Leaf‐level nitrogen‐use efficiency of canopy and understorey species in a beech forest
Leaf‐level nitrogen‐use efficiency of canopy and understorey species in a beech forest
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DOI：
10.1046/j.1365-2435.2002.00691.x
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发表时间：
2002-12
影响因子：
5.2
通讯作者：
Y. Yasumura;K. Hikosaka;K. Matsui;T. Hirose
中科院分区：
文献类型：
--
作者：
Y. Yasumura;K. Hikosaka;K. Matsui;T. Hirose
摘要1在林分中，树冠和林下物种在完全不同的光照下生长，因此具有不同的碳和氮可利用性比率。我们研究了在成熟的山毛榉森林中，生长光照度的差异如何影响植物的氮素利用。2WE定义叶片水平氮素利用效率(NUEL)为叶片吸收每单位氮素所产生的叶干重。冠层树种(Fagus Crenata)和林下树种(Lindera umellata和Magnolia salicifolia)的NUEL相似。3NUEL进一步分析为叶水平N生产力(NPL)和叶N平均停留时间(MRTL)两个分量的乘积。冠层树种的NPL显著大于林下树种，而MRTL显著小于林下树种。4由于物种间的光合作用能力相似，物种间的NPL差异很大程度上归因于其叶片所处的光照条件的差异。5MRTL的差异不是由于叶片衰老时测定的潜在氮素吸收效率(REFF)，而是实际的REFF，这取决于完全衰老前绿叶的损失量。由于冠层内的强风作用，冠层物种的实际REFF值明显较小。6虽然冠层树种由于光照大而实现了较高的净光合速率，但由于风对前期衰老叶片的伤害，其最大净光合力较短。另一方面，在阴天条件下，冠层树种的NPL较短，而MRTL较长，风害较小。当地环境因素如光和风的相互作用强烈影响了山毛榉森林植物对氮素的利用。
Summary 1In a forest stand, canopy and understorey species grow at completely different irradiances and consequently with different carbon and nitrogen availability ratios. We studied how the difference in growth irradiance influenced plant N use in a mature beech forest. 2We defined leaf-level nitrogen-use efficiency (NUEL) as the amount of the leaf dry mass produced per unit N taken up by leaves. NUEL was similar between the canopy species (Fagus crenata) and the understorey species (Lindera umbellata and Magnolia salicifolia). 3NUEL was analysed further as the product of two components: leaf-level N productivity (NPL) and mean residence time of leaf N (MRTL). The canopy species had significantly larger NPL and significantly shorter MRTL than the understorey species. 4As the photosynthetic capacity was similar among the species, different NPL between the species was attributable largely to the difference in light conditions to which their leaves were exposed. 5The difference in MRTL was not attributable to potential efficiency of N resorption (REFF) determined at leaf senescence, but to actual REFF, which depended on the amount of green leaf lost before full senescence. The canopy species had significantly smaller actual REFF because of strong wind actions in the canopy. 6Although the canopy species realized higher NPL by virtue of high irradiance, it had shorter MRTL due to wind damage to pre-senescent leaves. On the other hand, the canopy species had shorter NPL under shady conditions, but had longer MRTL with little wind damage. Interplay of local environmental factors such as light and wind strongly influenced N use by plants in the beech forest.