Data from: Forest composition modifies litter dynamics and decomposition in regenerating tropical dry forest

We investigated how forest composition, litter quality, and rainfall interact to affect leaf litter decomposition across three successional tropical dry forests in Costa Rica. We monitored litter stocks and bulk litter turnover in 18 plots that exhibit substantial variation in soil characteristics, tree community structure, fungal communities (including forests dominated by ecto- or arbuscular mycorrhizal host trees), and forest age. Simultaneously, we decomposed three standard litter substrates over a 6-month period spanning an unusually intense drought. Decay rates of standard substrates depended on the interaction between litter identity and forest type. Decomposition rates were correlated with tree and soil fungal community composition as well as soil fertility, but these relationships differed among litter types. In low fertility soils dominated by ectomycorrhizal oak trees, bulk litter turnover rates were low, regardless of soil moisture. By contrast, in higher fertility soils that supported mostly arbuscular mycorrhizal trees, bulk litter decay rates were strongly dependent on seasonal water availability. Both measures of decomposition increased with forest age, as did the frequency of termite-mediated wood decay. Taken together, our results demonstrate that soils and forest age exert strong control over decomposition dynamics in these tropical dry forests, either directly through effects on microclimate and nutrients, or indirectly by affecting tree and microbial community composition and traits, such as litter quality.

本研究针对哥斯达黎加三处不同演替阶段的热带旱生林，探究森林组成、枯落物质量与降雨的交互作用如何影响叶片枯落物分解过程。我们在18个样地中监测了枯落物储量与整体枯落物周转速率，这些样地在土壤特性、树木群落结构、真菌群落（包括以外生菌根（ectomycorrhizal）或丛枝菌根（arbuscular mycorrhizal）宿主树木占优的林分）以及林分年龄上均存在显著差异。与此同时，我们在为期6个月、覆盖异常严重干旱的时段内，对3种标准枯落物基质开展了分解实验。标准底物的分解速率取决于枯落物特性与林分类型的交互作用。分解速率与树木及土壤真菌群落组成、土壤肥力均存在相关性，但这类相关性因枯落物类型而异。在外生菌根栎树占优的低肥力土壤中，整体枯落物周转速率较低，且不受土壤含水量影响。与之相反，在以丛枝菌根树木为主的高肥力土壤中，整体枯落物分解速率则强烈依赖于季节性水分可获得性。两种枯落物分解指标均随林分年龄增长而升高，白蚁介导的木材腐朽频率亦呈现相同趋势。综合来看，本研究结果表明，土壤与林分年龄对这些热带旱生林的分解动态存在强烈调控作用：既可通过直接影响微气候与养分状况实现，也可通过改变树木与微生物群落组成及枯落物质量等性状间接发挥调控作用。