Data from: Community assembly and functional diversity along succession post-management

1. Despite extensive development of successional theory, few empirical studies have evaluated whether existing models are applicable to human-modified landscapes. Seasonally dry tropical forests are experiencing widespread transformation, and represent a critical system to assess in a successional framework to infer the mechanisms that shape assembly of secondary forests post-management. 2. We used a functional trait-based approach to assess changes in community assembly mechanisms along succession in secondary dry forests of varying stages following abandonment of cattle activity, as well as nearby old-growth forests. We evaluated whether re-assembly proceeded consistent with existing theory, in early successional stages via habitat filtering, leading to reduced trait range, and via competitive exclusion in later stages, leading to increased trait evenness. Using three orthogonal traits and two functional diversity indices we tested for evidence of assembly mechanisms along resource axes that may be particularly important to dry forest systems, dynamic changes in habitat filtering and competitive exclusion, and potential legacy effects of management. 3. We found little support of a progression from habitat filtering to competitive exclusion, with the exception of dispersion patterns for specific leaf area and multi-variate functional richness. Water may underlie species sorting in most stages, as evidenced by range reduction in wood density, and might be a resource particularly important to dry forest assembly. Early successional stages displayed an unexpected pattern of low evenness, which may be due to initial stand composition including remnants and resprouts, a regeneration strategy typical to dry forest species. Beyond influencing initial conditions, management legacy was apparent in late secondary forests, which differed in range, even dispersion, and functional richness from old-growth forests, suggesting the operation of different assembly mechanisms. 4. The departures from expectations suggest the need to re-assess successional models to include effects of management legacies on the operation of community assembly mechanisms in human-modified landscapes, as well as characteristics that distinguish wet and dry forest dynamics.

1. 尽管演替理论（successional theory）已得到长足发展，但鲜有实证研究评估现有模型是否适用于人为改造景观。季节性热带旱林（seasonally dry tropical forests）正经历广泛的景观转变，其作为关键研究系统，可借助演替框架开展评估，以解析驱动管理后次生林群落组装的核心机制。
2. 本研究采用基于功能性状（functional trait）的研究方法，评估了弃牧后不同演替阶段的次生旱林以及邻近原始林（old-growth forests）的群落组装机制沿演替梯度的变化。我们验证了群落再组装是否符合现有理论：演替早期通过生境过滤（habitat filtering）导致性状范围（trait range）缩减，演替后期通过竞争排除（competitive exclusion）导致性状均匀度（trait evenness）提升。本研究选取3个正交性状（orthogonal traits）与2个功能多样性指数（functional diversity indices），检验了旱林系统中可能至关重要的资源轴上的群落组装机制证据、生境过滤与竞争排除的动态变化，以及管理遗留效应的潜在影响。
3. 本研究未发现群落组装从生境过滤向竞争排除转变的显著证据，仅比叶面积（specific leaf area）的分布格局与多变量功能丰富度（multi-variate functional richness）符合该趋势。木材密度（wood density）的范围缩减表明，水分可能是多数演替阶段物种分选的核心驱动因子，或是旱林群落组装中尤为关键的资源。演替早期阶段呈现出意料之外的低均匀度格局，这或许源于初始林分组成包含残留木与萌条——这是旱林物种典型的更新策略。除对初始条件造成影响外，管理遗留效应在晚期次生林中同样显著：晚期次生林的性状范围、性状均匀分布与功能丰富度均与原始林存在差异，暗示其群落组装机制存在差异。
4. 本研究结果与经典演替理论的预期存在偏离，表明需重新审视现有演替模型，将管理遗留效应对人为改造景观中群落组装机制运行的影响，以及区分热带湿林与旱林动态的特征纳入模型框架。