Short-term canopy and understory nitrogen addition differ in their effects on seedlings of dominant woody species in a subtropical evergreen broadleaved forest
Short-term canopy and understory nitrogen addition differ in their effects on seedlings of dominant woody species in a subtropical evergreen broadleaved forest
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短期冠层和林下氮添加对亚热带常绿阔叶林优势木本树种幼苗的影响不同
DOI：
10.1016/j.gecco.2021.e01855
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发表时间：
2021-11
影响因子：
4
通讯作者：
Hongfang Lu
中科院分区：
文献类型：
--
作者：
Hongfang Lu
随着大气氮沉降的持续增加，氮沉降如何影响树种幼苗生长的信息对于预测森林更新至关重要。在这项研究中，我们研究了在25和50 kg ha− 1 year − 1的N（CAN 25和CAN 50），以及在25和50 kg ha− 1 year − 1的N（UAN 25和UAN 50）的林下N添加对两种主要木本物种（木荷和五角紫金牛）的存活，生理和生长的影响，这些物种被移植到亚热带万年青阔叶林中。在移栽后两年，林下氮的添加大大降低了两个物种的苗高和生物量生产，特别是在50 kg ha− 1 year − 1的N。然而，氮添加处理对幼苗存活和生物量分配的影响很小。UAN 50降低了干旱季节叶片光饱和光合速率（Asat），提高了茎N浓度; UAN 25提高了内在水分利用效率（WUEi）; CAN 50提高了S.超级贱种UAN 25和UAN 50均提高了A. quinquegonaseedlings。UAN 50降低了两种植物的全株氮素利用效率，CAN 50降低了S.超级贱种总体而言，S.超基础种表现优于A.五角豆幼苗的高度、生物量、Asat和WUEi。结果表明，氮沉降对木本植物幼苗生长有显著影响，林下施氮对幼苗株高、地径和生物量的影响大于冠层施氮，即：传统的用林下添加氮素模拟大气氮沉降的方法可能高估了氮沉降对幼苗生长的影响。
As atmospheric nitrogen (N) deposition continues to increase, information on how N deposition affects seedling performance of tree species is critical for predicting forest regeneration. In this study, we examined the effects of canopy N addition at 25 and 50 kg ha−1year−1of N (CAN25 and CAN50), and understory N addition at 25 and 50 kg ha−1year−1of N (UAN25 and UAN50) on the survival, physiology, and growth of seedlings of two dominant woody species (Schima superbaandArdisia quinquegona) that were transplanted into a subtropical evergreen broadleaved forest. At two years after transplanting, understory N additon greatly decreased seedling height and biomass production for both species, especially at 50 kg ha−1year−1of N. N-addition treatments, however, had only minor effects on seedling survival and biomass allocation. UAN50 decreased leaf light-saturated photosynthesis (Asat) in the dry season and increased stem N concentration; UAN25 increased intrinsic water-use efficiency (WUEi); and CAN50 increased concentrations of N and P in the roots and stems ofS. superbaseedlings. Both UAN25 and UAN50 generally increased stem and leaf N concentrations and the leaf N/P ratio inA. quinquegonaseedlings. UAN50 decreased whole-plant N-use efficiency of both species, and CAN50 reduced whole-plant N- and P-use efficiencies ofS. superbaseedlings. Overall,S. superbaseedlings performed better thanA. quinquegonaseedlings in terms of height, biomass,Asat, and WUEi. Our results indicate that N deposition can profoundly influence the seedling growth of woody species, and that seedling height, basal diameter and biomass are more sensitive to the understory addition of N than to the canopy addition of N, i.e., the traditional use of understory addition of N to simulate atmospheric N deposition may overestimate the effects of N deposition on seedling performance.
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