Mao Peili, Zang Runguo, Shao Hongbo, Yu Junbao
Key Laboratory of Coastal Zone Environmental Processes, Yantai Institute of Coastal Zone Research, Chinese Academy of Sciences (CAS), Yantai, Shandong 264003, China ; Key Laboratory of Forest Ecology and Environment, The State Forestry Administration, Research Institute of Forest Ecology, Environment and Protection, Chinese Academy of Forestry, Beijing 100091, China.
Key Laboratory of Forest Ecology and Environment, The State Forestry Administration, Research Institute of Forest Ecology, Environment and Protection, Chinese Academy of Forestry, Beijing 100091, China.
ScientificWorldJournal. 2014;2014:649031. doi: 10.1155/2014/649031. Epub 2014 Jun 11.
Differences among tropical tree species in survival and growth to light play a key role in plant competition and community composition. Two canopy species with contrasting functional traits dominating early and late successional stages, respectively, in a tropical montane rain forest of Hainan Island, China, were selected in a pot experiment under 4 levels of light intensity (full, 50%, 30%, and 10%) in order to explore the adaptive strategies of tropical trees to light conditions. Under each light intensity level, the pioneer species, Endospermum chinense (Euphorbiaceae), had higher relative growth rate (RGR), stem mass ratio (SMR), specific leaf area (SLA), and morphological plasticity while the shade tolerant climax species, Parakmeria lotungensis (Magnoliaceae), had higher root mass ratio (RMR) and leaf mass ratio (LMR). RGR of both species was positively related to SMR and SLA under each light level but was negatively correlated with RMR under lower light (30% and 10% full light). The climax species increased its survival by a conservative resource use strategy through increasing leaf defense and root biomass investment at the expense of growth rate in low light. In contrast, the pioneer increased its growth by an exploitative resource use strategy through increasing leaf photosynthetic capacity and stem biomass investment at the expense of survival under low light. There was a trade-off between growth and survival for species under different light conditions. Our study suggests that tree species in the tropical rainforest adopt different strategies in stands of different successional stages. Species in the earlier successional stages have functional traits more advantageous to grow faster in the high light conditions, whereas species in the late successional stages have traits more favorable to survive in the low light conditions.
热带树种在对光照的存活和生长方面的差异在植物竞争和群落组成中起着关键作用。在中国海南岛的一个热带山地雨林中，分别选取了两种具有不同功能性状、主导早期和晚期演替阶段的冠层树种，在4种光照强度水平（全光照、50%、30%和10%）下进行盆栽试验，以探究热带树木对光照条件的适应策略。在每个光照强度水平下，先锋树种海南梭子果（大戟科）具有较高的相对生长速率（RGR）、茎质量比（SMR）、比叶面积（SLA）和形态可塑性，而耐荫的顶极树种乐东拟单性木兰（木兰科）具有较高的根质量比（RMR）和叶质量比（LMR）。在每个光照水平下，两种树种的RGR均与SMR和SLA呈正相关，但在较低光照（30%和10%全光照）下与RMR呈负相关。顶极树种通过在低光照下增加叶片防御和根系生物量投资，以牺牲生长速率为代价，采用保守的资源利用策略来提高其存活率。相比之下，先锋树种通过在低光照下增加叶片光合能力和茎生物量投资，以牺牲存活率为代价，采用开拓性的资源利用策略来增加其生长。在不同光照条件下，树种的生长和存活之间存在权衡。我们的研究表明，热带雨林中的树种在不同演替阶段的林分中采用不同的策略。早期演替阶段的树种具有在高光条件下更有利于快速生长的功能性状，而晚期演替阶段的树种具有在低光条件下更有利于存活的性状。
