Changes in tree phenology along natural regeneration in a seasonally dry tropical forest

The applicability of succession models from temperate and tropical wet forests to threatened seasonally dry tropical forests (SDTFs) is questioned. Plant phenology affects ecosystem functions and changes along forest regeneration gradient. To investigate the recovery of ecological functions after disturbances in a SDTF, we recorded the vegetative and reproductive phenologies for trees (DBH >5 cm) for 17 months in southeast Brazil in three successional stages: early (10–15 years after clearing), intermediate (25–30) and late (>50). The vegetative phenology of the 523 individuals was strongly seasonal, with 3% of individuals presenting green leaves in a deciduous dry season. Besides structural and floristic differences, phenological trends were similar between the later stages. Reproduction occurred with higher intensities in the early stage and in the advanced stages only in the dry season, providing key resources to local fauna. The studied SDTF is resilient to ecological functions, rapidly recovering functional processes. The integration of structural and functional knowledge of succession of STDFs may lead to better management of its secondary remnants. Our study suggests that classical forest succession theory developed for other ecosystems may not fully reflect the pattern of SDTF succession, an ecosystem that originally covered 42% of the earth's tropical and subtropical landmass.

温带与热带湿润林的演替模型应用于受威胁的季节性干燥热带林（seasonally dry tropical forests, SDTFs）的适用性受到质疑。植物物候会影响生态系统功能，并随森林更新梯度发生变化。为探究季节性干燥热带林受干扰后生态功能的恢复机制，本研究于巴西东南部开展了为期17个月的野外观测，针对3个演替阶段（早期：伐后10~15年；中期：25~30年；晚期：>50年）内胸径（DBH）>5厘米的乔木，记录了其营养物候与生殖物候。本研究共观测523株个体，其营养物候呈现显著季节性特征，仅3%的个体在落叶旱季仍保有绿叶。尽管不同演替阶段在林分结构与植物区系组成上存在差异，但晚期演替阶段的物候趋势较为相似。繁殖活动在早期演替阶段强度更高，而晚期演替阶段仅在旱季出现繁殖高峰，为当地动物区系提供了关键的食物资源。本研究涉及的季节性干燥热带林具备生态功能韧性，能够快速恢复其生态功能过程。整合季节性干燥热带林演替的结构与功能认知，或可优化其次生残余林分的管理策略。本研究表明，针对其他生态系统建立的经典森林演替理论，或无法完全反映季节性干燥热带林的演替规律——这类生态系统原本覆盖了全球42%的热带与亚热带陆地总面积。