This study aimed to determine the influence of soil traits, vegetation structure and climate on litterfall dynamics along a successional gradient in a tropical dry forest (TDF) in southeastern Brazil. We used a chronosequence design consisting of three successional stages (early, intermediate, and old-growth) defined based on forest age and vertical and horizontal structures. Litterfall was recorded monthly for three years in 12 plots of 50 × 20 m (four plots per stage) where vegetation parameters (species richness, basal area, density and height for trees with diameter at breast height ≥ 5 cm) and soil chemical and physical traits were previously obtained. We placed eight 0.5-m2 litter traps in each plot, totalling 96 traps. Samples were sorted into leaves, twigs, reproductive parts, and debris. Litterfall mass was composed mainly of leaves and varied slightly among years (4 to 4.5 Mg∙ha− 1), within the range observed for other TDFs. Annual litterfall mass was higher at the old-growth forest than at the early and intermediate forest stages and this successional pattern was driven by vegetation characteristics (forest structural parameters and plant functional groups) and soil traits related to water-holding capacity. Litter amount in the intermediate stage was lower than expected for its forest structure (and similar to the early stage), possibly because its higher soil clay content increased the water holding capacity and leaf retention during the dry season. Seasonal variations in monthly litterfall were strongly driven by forest deciduousness and affected by climatic factors related to water availability. This pattern was consistent across the successional gradient, although differences for each litterfall component were observed. Our results suggest that litter production in the studied TDF is influenced by multiple factors along succession, such as above-ground biomass and the degree of leaf retention mediated by soil water-holding capacity. Further studies on community phenological patterns can allow a better understanding of successional changes on litterfall and how fast this fundamental function recovers in secondary forests.

中文翻译：

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巴西热带干燥森林中凋落物沿演替梯度的动态

这项研究旨在确定巴西东南部热带干旱森林（TDF）中土壤特征，植被结构和气候对凋落物动态的影响，该凋落物动态特征是沿演替梯度的。我们使用了一个时序序列设计，该时序序列设计基于森林年龄以及垂直和水平结构定义了三个连续的阶段（早期，中期和老龄阶段）。连续三年每月记录凋落物，记录在12个50×20 m的样地中（每个阶段四个样地），其中植被参数（物种丰富度，基础面积，胸径≥5 cm的树木的密度和高度）以及土壤的化学和物理特性特质是先前获得的。我们在每个样地中放置了八个0.5平方米的垃圾收集器，总计96个收集器。将样品分类为叶子，树枝，生殖部分和碎片。凋落物质量主要由叶子组成，并且在几年内略有变化（4至4.5 Mg∙ha-1），在其他TDF的观测范围内。老龄森林的年凋落物质量要比森林早期和中期的要高，而这种演替模式是由植被特征（森林结构参数和植物功能群）以及与持水能力有关的土壤性状驱动的。中期的凋落物数量低于其森林结构的预期值（与早期相似），这可能是因为其较高的土壤黏土含量增加了旱季的持水量和叶片保持力。每月落叶量的季节性变化主要受到森林落叶的影响，并受到与水供应相关的气候因素的影响。尽管观察到每个凋落物成分的差异，但在整个演替梯度中该模式是一致的。我们的研究结果表明，研究的TDF中的凋落物生产受到多个因素的影响，这些因素包括地上生物量以及土壤持水量介导的叶片滞留程度。对群落物候形态的进一步研究可以更好地理解凋落物的连续变化以及这种基本功能在次生森林中恢复的速度。