Data from: Lianas reduce community-level canopy tree reproduction in a Panamanian forest

Lianas are a key component of tropical forests, where they compete intensely with trees, reducing tree recruitment, growth and survival. One of the most important potential outcomes of liana competition is the reduction of tree reproduction; however, no previous study has experimentally determined the effects of lianas on tree reproduction beyond a single tree species.
We used a large-scale liana removal experiment to quantify the effect of lianas on community-level canopy and understorey tree and palm reproduction. In 2011, we removed lianas from eight 6,400-m2 plots (eight plots served as controls) and surveyed understorey tree reproduction in 2012, canopy tree and palm reproduction in 2013, and a second census of all plants in 2016.
We found that lianas significantly reduced canopy tree community flowering and fruiting after liana removal. Two years after liana removal, the number of canopy trees with fruits was 173% higher, fruiting individuals had 50% more of their canopy covered by fruits and the number of tree species with fruits was 169% higher than in control plots where lianas were present. Five years after liana removal, the number of canopy trees with fruits was 150% higher, fruiting individuals had 31% more of their canopy covered by fruits and the number of tree species with fruits was 109% higher than in unmanipulated control plots.
Liana removal had only a slight positive effect on palms and on understorey tree flower and fruit production, even though understorey light levels had increased 20% following liana cutting.
Synthesis. Our findings provide the first experimental demonstration that competition from lianas significantly reduces community-level canopy tree reproduction. Reduced reproduction increases canopy tree seed and dispersal limitations, and may interfere with deterministic mechanisms thought to maintain tropical canopy tree species diversity, as well as reduce food availability to many animal species. Because lianas are increasing in abundance in many neotropical forests, the effects of lianas on tree reproduction will likely increase, and if the effects of lianas on tree reproduction vary with tree species identity, lianas ultimately could have a destabilizing effect on both tree and animal population dynamics.

藤本植物（lianas）是热带森林的关键组成部分，它们与树木展开激烈竞争，抑制树木的更新、生长与存活。藤本植物竞争最具重要性的潜在后果之一，是降低树木的繁殖能力；然而此前尚无研究通过实验手段，探明藤本植物对单一树种之外的树木繁殖的影响。

本研究依托大规模藤本移除实验，量化了藤本植物对群落水平冠层树木、林下树木以及棕榈类植物繁殖的影响。2011年，我们在8块面积为6400平方米的样地中移除藤本植物（另设8块样地作为对照），并分别于2012年调查林下树木的繁殖情况、2013年调查冠层树木与棕榈类植物的繁殖情况，2016年开展第二次所有样株的普查。

研究结果显示，移除藤本植物后，冠层树木群落的开花与结实情况显著改善。藤本移除两年后，结实冠层树木的数量较保留藤本的对照样地提升173%，结实个体的冠层被果实覆盖的比例增加50%，结实树木物种的数量提升169%。藤本移除五年后，结实冠层树木的数量较未处理对照样地提升150%，结实个体的冠层果实覆盖率增加31%，结实树木物种的数量提升109%。

尽管藤本砍伐后林下光照水平提升了20%，但藤本移除仅对棕榈类植物以及林下树木的开花、结实产生轻微的正向影响。

综合分析表明，本研究首次通过实验证实，藤本植物的竞争会显著降低群落水平的冠层树木繁殖能力。繁殖能力下降会加剧冠层树木的种子与扩散限制，或干扰被认为维持热带冠层树木物种多样性的确定性机制，同时还会降低众多动物类群的食物可获得性。鉴于许多新热带界森林中的藤本植物丰度正持续上升，藤本植物对树木繁殖的影响可能会进一步增强；若藤本植物对树木繁殖的影响因树木物种而异，则藤本植物最终可能会对树木与动物种群动态产生不稳定影响。