Forest Ecology and Forest Management Group, Wageningen University & Research, P.O. Box 47, Wageningen, NL-6700 AA, The Netherlands.
Faculty of Renewable Natural Resources Management, University of Kisangani, B.P.O. 2012, Kisangani, DR Congo.
Ecology. 2020 May;101(5):e03004. doi: 10.1002/ecy.3004. Epub 2020 Mar 17.
Lianas, woody climbing plants, are increasing in many tropical forests, with cascading effects such as decreased forest productivity, carbon sequestration, and resilience. Possible causes are increasing forest fragmentation, CO fertilization, and drought. Determining the primary changing species and their underlying vital rates help explain the liana trends. We monitored over 17,000 liana stems for 13 yr in 20 ha of old-growth forest in the Congo Basin, and here we report changes and vital rates for the community and for the 87 most abundant species. The total liana abundance declined from 15,007 lianas in 1994 to 11,090 in 2001 to 9,978 in 2007. Over half (52%) of the evaluated species have significantly declining populations, showing that the community response is not the result of changes in a few dominant species only. Species density change (i.e., the change in number of individuals per hectare) decreased with mortality rate, tended to increase with recruitment rate, but was independent of growth rate. Species change was independent of functional characteristics important for plant responses to fragmentation, CO , and drought, such as lifetime light requirements, climbing and dispersal mechanism, and leaf size. These results indicate that in Congo lianas do not show the reputed global liana increase, but rather a decline, and that elements of the reputed drivers underlying global liana change do not apply to this DR Congo forest. We suggest warfare in the Congo Basin to have decimated the elephant population, leading to less disturbance, forest closure, and declining liana numbers. Our results imply that, in this tropical forest, local causes (i.e., disturbance) override more global causes of liana change resulting in liana decline, which sharply contrasts with the liana increase observed elsewhere.
藤本植物是木质攀援植物，在许多热带森林中不断增加，具有级联效应，如森林生产力下降、碳固存和恢复力降低。可能的原因包括森林破碎化加剧、CO2 施肥和干旱。确定主要变化物种及其潜在的关键生活率有助于解释藤本植物的趋势。我们在刚果盆地的一个 20 公顷的原始森林中监测了超过 17000 根藤本植物茎 13 年，这里报告了社区和 87 种最丰富物种的变化和关键生活率。总藤本植物丰度从 1994 年的 15007 个下降到 2001 年的 11090 个，再到 2007 年的 9978 个。评估的物种中有一半以上（52%）的种群明显减少，表明社区的反应不是少数几个主要物种变化的结果。物种密度变化（即每公顷个体数量的变化）随死亡率而降低，倾向于随繁殖率而增加，但与生长率无关。物种变化与对破碎化、CO2 和干旱的植物反应很重要的功能特征无关，如寿命光需求、攀援和扩散机制以及叶片大小。这些结果表明，在刚果，藤本植物并没有表现出全球公认的藤本植物增加，而是减少，而且全球公认的驱动藤本植物变化的因素并不适用于这个刚果民主共和国的森林。我们认为，刚果盆地的战争使大象种群锐减，导致干扰减少、森林封闭和藤本植物数量下降。我们的结果表明，在这片热带森林中，地方因素（即干扰）超过了全球因素，导致藤本植物减少，这与其他地方观察到的藤本植物增加形成鲜明对比。
