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不同光照和营养条件下两种不同寿命热带先锋种的对比研究

A Comparative Study of Two Tropical Pioneer Species with Different Lifespan under Different Light and Nutrient Conditions

  • 摘要: 探讨了热带次生演替早期阶段短命先锋种山黄麻(Trema tomentosa)和长命先锋种中平树(Macaranga denticulata)在两种光照(4%和20%的全光照)和营养梯度(低肥和高肥)下,叶片和细根营养物质含量、非结构性碳水化合物含量、生物量分配模式以及形态结构特征的差异。结果表明:(1)两种先锋种叶片和细根氮、磷含量随着光照和营养的增强显著上升,并且山黄麻叶片和细根氮、磷含量要显著高于中平树。(2)山黄麻各器官淀粉和总非结构性碳水化合物(TNC)浓度在高光下低于中平树,但在低光下高于中平树。(3)山黄麻和中平树的叶片都是可溶性糖的主要存储器官,而淀粉和TNC则主要储存在根中,并且淀粉都是二者TNC库最主要的组成形态和成分。(4)山黄麻拥有更高的根生物量比、细根生物量比、根冠比、比叶面积、叶面积比、比细根长、比细根表面积及更小的细根直径等更强大的资源捕获能力的结构和生物量分配特征。总之,与长命先锋种中平树相比,短命先锋种山黄麻有着更适合快速生长的结构和生物量分配特征、更高的组织营养物质含量、更低的非结构性碳水化合物浓度,因而具有更高的生长速率,能够在次生演替的早期阶段占领统治地位,为以后的次生演替创造条件。

     

    Abstract: We compared the contents of nitrogen,phosphorus and carbohydrates in seedlings of a short-lived pioneer species,Trema tomentosa,and a long-lived pioneer species,Macaranga denticulata,by an experiment of two light levels(4% and 20% of full sunlight) and two nutrient levels(low and high).Some morphological traits and biomass allocation patterns of the two species were also examined.The results showed that:(1) The nutrient concentrations of the two species increased with the increasing of light and nutrient availabilities,T.tomentosa exhibited higher concentrations of nitrogen and phosphorus in leaves and fine roots than M.denticulata.(2) The concentrations of starch and total non-structure carbohydrate(TNC) in seedlings of T.tomentosa were lower than in those of M.denticulata when grown in high light while the opposite was true when in low light treatments.(3) For two species,most soluble sugar stored in leaves while most starch and TNC stored in roots and starch is the most major component of non-structure carbohydrates.(4) The seedlings of T.tomentosa had higher root mass ratio,root crown mass ratio,fine root mass ratio,leaf area ratio,specific leaf area,specific fine root length,specific fine root surface area and thinner fine root diameter than M.denticulata.In conclusion,compared with the long-loved pioneer M.denticulata,the short-lived pioneer,T.tomentosa,had higher tissue nutrient contents,lower tissue non-structure carbohydrate concentrations,favorable allocation patterns and morphological traits,which facilitate the resource capture and consequently contribute to the dominance in the early stage of secondary succession.

     

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