香果树实生苗的光合特性及其与环境因子的关系

Photosynthetic characteristics of Emmenopterys henryi seedlings and their relationships with environmental factors

为确定香果树实生苗的适生环境并为其自然更新提出有针对性策略,研究了不同生境(冠下、冠缘、林窗和林缘)中2年生香果树实生苗的净光合速率、水分利用效率、叶绿素含量、苗高、基径、生物量等的变化及其与生态因子之间的关系.结果表明:4种生境中的光合有效辐射最大值为50~1380μmol·m^(-2)·s^(-1),冠下和冠缘中香果树实生苗的净光合速率日变化呈单峰型,而林窗和林缘实生苗的净光合速率日变化呈双峰型;香果树实生苗为耐阴植物,但耐阴能力较弱,其功能叶的光饱和点、补偿点和暗呼吸在4种生境中大小顺序为:林缘>林窗>冠缘>冠下,表观量子效率的变化规律与之相反;林窗和冠缘2种生境中香果树实生苗的适应能力较强,叶片的蒸腾速率、气孔导度、水分利用效率和净光合速率较高;林窗中香果树实生苗叶片的叶绿素含量较低,但实生苗的生长速度最快,生物量最大;香果树实生苗的净光合速率与光合有效辐射和气孔导度呈显著正相关.对于冠下生境,需降低林冠层密度,增加透光率,以利于香果树实生苗的光合作用;对于林缘生境,则需要增加植被盖度,降低光照强度,以利于其快速生长.

To find appropriate environment for Emmenopterys henryi seedlings and develop corre- sponding strategies for their natural regeneration, the net photosynthetic rate, water use efficiency, chlorophyll content, height, basal diameter and biomass of two-year old seedlings and the relation- ships with environmental factors were studied in different habitats, i.e., undercanopy, crown edge, forest gap, and forest edge. In the four habitats, the maximum photosynthetically active radiation （PAR） was 50-1380 μmol · m-2 · s-1, net photosynthetic rate of E. henryi seedlings showed sin- glet diurnal variation in undercanopy and crown edge, and showed a bimodal pattern in forest gap and forest edge. Seedlings were shade-tolerant plants with the low shade-tolerant ability. The ordr of light saturation point, light compensation point, and dark respiration of their functional leaves in different habitats was the same as follows： forest edge 〉 forest gap 〉 crown edge 〉 undercanopy, and the order was inverse when sequenced by apparent quantum efficiency. Seedlings were highly adaptable to forest gap and crown edge, with higher transpiration rate, stomatal conductance, water use efficiency （WUE）, and net photosynthetic rate, Seedlings in forest gap had lower leaf chloro- phyll content, but they grew fast and thererore s howed the maximum hiomass, Net photosynthetic rate of the seedlings showed significant positive correlation with PAR and stomatal conductance. For undercanopy, seedling photosynthesis was facilitated by reducing canopy density and increasing light transmittance. For forest edge, vegetation cover should be increased with reducing light intensity to ensure rapid growth of the seedlings.