Data from: Effect of lianas on forest-level tree carbon accumulation does not differ between seasons: results from a liana removal experiment in Panama

1. Lianas are prevalent in Neotropical forests, where liana-tree competition can be intense, resulting in reduced tree growth and survival. The ability of lianas to grow relative to trees during the dry season suggests that liana-tree competition is also strongest in the dry season. If correct, the predicted intensification of the drying trend over large areas of the tropics in the future may therefore intensify liana-tree competition, resulting in a reduced carbon sink function of tropical forests. However, no study has established whether the liana effect on tree carbon accumulation is indeed stronger in the dry than in the wet season. 2. Using six years of data from a large-scale liana removal experiment in Panama, we provide the first experimental test of whether liana effects on tree carbon accumulation differ between seasons. We monitored tree and liana diameter increments at the beginning of the dry and wet season each year to assess seasonal differences in forest-level carbon accumulation between removal and control plots. 3. We found that median liana carbon accumulation was consistently higher in the dry ( 0.52 Mg C ha-1 yr-1) than the wet season (0.36 Mg C ha-1 yr-1), and significantly so in three of the years. Lianas reduced forest-level median tree carbon accumulation more severely in the wet (1.45 Mg C ha-1 yr-1) than the dry (1.05 Mg C ha-1 yr-1) season in all years. However, the relative effect of lianas was similar between the seasons, with lianas reducing forest-level tree carbon accumulation by 46.9% in the dry and 48.5% in the wet season. 4. Synthesis: Our results provide the first experimental demonstration that lianas do not have a stronger competitive effect on tree carbon accumulation during the dry season. Instead, lianas compete significantly with trees during both seasons, indicating a large negative effect of lianas on forest-level tree biomass increment regardless of seasonal water stress. Longer dry seasons are unlikely to impact liana-tree competition directly; however, the greater liana biomass increment during dry seasons may lead to further proliferation of liana biomass in tropical forests, with consequences for their ability to store and sequester carbon.1. 藤本植物（liana）在新热带森林中分布广泛，藤本与树木间的竞争往往十分激烈，会抑制树木的生长与存活。藤本植物在旱季相对于树木的生长优势，暗示藤本-树木竞争在旱季最为强烈。若这一推论成立，未来热带大面积区域干旱趋势加剧的预测，可能会强化藤本与树木间的竞争，进而削弱热带森林的碳汇功能。然而，目前尚无研究证实藤本对树木碳积累的影响确实在旱季强于湿季。 2. 本研究依托巴拿马一项大型藤本移除实验的6年监测数据，首次通过实验验证了藤本对树木碳积累的影响是否存在季节差异。我们于每年旱季和湿季初期监测树木与藤本的直径生长量，以此对比移除样地与对照样地的森林尺度碳积累的季节差异。 3. 研究结果显示，藤本的碳积累中位数在旱季（0.52 兆克碳·公顷⁻¹·年⁻¹）持续高于湿季（0.36 兆克碳·公顷⁻¹·年⁻¹），且在其中3个年份差异显著。所有年份中，藤本对森林尺度树木碳积累的抑制作用在湿季（1.45 兆克碳·公顷⁻¹·年⁻¹）均强于旱季（1.05 兆克碳·公顷⁻¹·年⁻¹）。但藤本的相对影响在两季间并无显著差异：旱季藤本使森林尺度的树木碳积累降低46.9%，湿季则降低48.5%。 4. 综合与结论：本研究结果首次通过实验证实，藤本在旱季对树木碳积累的竞争抑制作用并未更强。实际上，藤本在两季均会对树木产生显著竞争，表明无论季节水分胁迫程度如何，藤本都会对森林尺度的树木生物量增量产生强烈的负面效应。更长的旱季不太会直接影响藤本与树木间的竞争；但旱季藤本生物量增量更高，可能会推动热带森林中藤本生物量进一步扩增，进而影响森林的碳储存与固存能力。