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作 者 ：胡启鹏,郭志华*,李春燕,马履一

期 刊 ：生态学报 2008年 28卷 7期 页码：3262~3270

关键词：光环境；比叶重；光合能力；光合氮利用效率；叶绿素荧光；叶氮分配；

Keywords:light regimes, leaf mass per area, photosynthetic capability, photosynthetic nitrogen use efficiency, Chlorophyll fluorescence, partition for leaf nitrogen,

摘 要 ：由于地球环境的演变，亚热带常绿阔叶林中常有落叶阔叶成分的存在，但从生态角度，其存在的机理尚不清楚。通过比较研究常绿阔叶优势树种大头茶与落叶阔叶树种枫香幼苗的叶形态和光合生理特征对不同光环境（旷地、林窗、林下）的响应，尝试解释落叶成分遗留的基础。结果表明：①枫香具有较小的比叶重(LMA)和较高的光合氮利用效率(PNUE)，在高光环境中，并未受到光抑制，具有较高的光合可塑性，尤其在林窗，表现出较大头茶高3倍的光合能力(Pnmax)，保证了其在较短的生长季节积累更多的光合产物，增强与常绿树种的竞争力；②常绿阔叶树种大头茶具有较大的LMA，在旷地受到严重的光抑制，将更多的氮用于化学防御中。在林窗和林下具有相对高的Pnmax，生长幅度较广，但在林下将更多的氮投入到比生长更为重要的生存消耗中。而枫香在林下响应表现为Rubisco活性降低，光合受阻；③两树种在林窗均表现出较高的光合适应性，具有最大的光合能力(Pnmax)及合理的氮在光合机构中的分配系数，说明林窗是它们更新的最佳环境。但枫香的光合作用更依赖于光照，而大头茶则更依赖于CO2浓度；④总之，落叶阔叶树种以其较高的形态可塑性和对高光的光合生理可塑性能够在常绿阔叶林种生存、生长，并成为常绿阔叶林中固有成分的主要原因之一。

Abstract:As the result of earth environmental evolution, some deciduous broadleaf species are able to remain naturally in evergreen broad-leaved forests, but the reason for their survival is unclear. This study examined the responses of leaf morphology and photo-physiology of seedlings of a deciduous broadleaf species Liquidambar formosana and an evergreen broadleaf species Gordonia acuminate to three natural light regimes (open, gap and understory), in the purpose of elucidating eco-physiological mechanism of the survival of the deciduous species in the evergreen broadleaf forest. The main results are as follows: ①Compared to the evergreen species, the deciduous L. formosana had lower leaf mass per unit area (LMA), and higher Photosynthetic nitrogen use efficiency (PNUE). And in high light regimes it did not suffered from photoinhibition and showed a high photosynthetic plasticity, especially in gap, performed three times higher Pnmax in the evergreen species. Therefore, the deciduous species should be able to accumulate more carbohydrate in its shorter growth season, thus enhancing its competition ability; ②In the open site, the evergreen species displayed greater LMA, and suffered from photoinhibition, and allocated more nitrogen into chemical defense. Moreover, it showed a relative higher Pnmax in the gap and understory than in the open site, suggesting its preference to the gap and understory environments. Also, growing in the understory it allocated more nitrogen for survival which turns out to be much more important than growth. In contrast, in the understory the deciduous species displayed a low activity of Rubisco and thus a low photosynthesis. ③In the gap, the seedlings of both species exhibited a greater photosynthetic acclimation, a photosynthetic capacity (Pnmax) and the reasonable leaf nitrogen allocation coefficient in relation to photosynthetic activity suggesting that the gap is the optimal environment for their regeneration. However, the photosynthesis of the deciduous is more dependent on light and that of the evergreen is more on CO2 concentration. ④It is concluded that the deciduous broadleaf species with higher morphological and photosynthetic flexibility should be able to compete with the evergreen broadleaf species and hence survive in evergreen broadleaf forests.

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