Castellanos Maria Clara, Stevenson Pablo R
Centro de Investigaciones Ecológicas La Macarena, Universidad de Los Andes. Cr. 1 no. 18a-12. Bogotá, Colombia.
Rev Biol Trop. 2011 Jun;59(2):921-33.
Life history and recruitment information of tropical trees in natural populations is scarce even for important commercial species. This study focused on a widely exploited Neotropical canopy species, Pachira quinata (Malvaceae), at the southernmost, wettest limit of its natural distribution, in the Colombian Amazonia. We studied phenological patterns, seed production and natural densities; assessed the importance of seed dispersal and density-dependent effects on recruitment, using field experiments. At this seasonal forest P. quinata was overrepresented by large adult trees and had very low recruitment caused by the combination of low fruit production, high seed predation and very high seedling mortality under continuous canopies mostly due to damping off pathogens. There was no evidence of negative distance or density effects on recruitment, but a clear requirement of canopy gaps for seedling survival and growth, where pathogen incidence was drastically reduced. In spite of the strong dependence on light for survival of seedlings, seeds germinated readily in the dark. At the study site, the population of P. quinata appeared to be declining, likely because recruitment depended on the rare combination of large gap formation with the presence of reproductive trees nearby. The recruitment biology of this species makes it very vulnerable to any type of logging in natural populations.
即使对于重要的商业树种，热带树木自然种群的生活史和补充信息也很稀少。本研究聚焦于一种在新热带地区被广泛开发利用的冠层树种——瓜栗（锦葵科），其研究地点位于该树种自然分布最南端、最湿润的边界，即哥伦比亚亚马逊地区。我们研究了物候模式、种子产量和自然密度；通过田间试验评估了种子传播和密度依赖效应在补充过程中的重要性。在这片季节性森林中，瓜栗的大树占比过高，由于果实产量低、种子捕食率高以及在连续树冠下幼苗死亡率极高（主要是由于猝倒病原体），导致其补充率极低。没有证据表明距离或密度对补充有负面影响，但幼苗的存活和生长显然需要树冠间隙，在树冠间隙中病原体发生率会大幅降低。尽管幼苗的存活对光照有很强的依赖性，但种子在黑暗中很容易发芽。在研究地点，瓜栗种群似乎在减少，可能是因为补充依赖于大树冠间隙与附近有繁殖树木这种罕见的组合。该树种的补充生物学使其在自然种群中极易受到任何形式采伐的影响。
