Data from: Combined effects of seed and soil quality drive seedling performance of a late-successional canopy tree in a tropical forest

Habitat loss and fragmentation affect the structure and functioning of forested ecosystems worldwide, yet we lack an understanding of how species respond to environmental changes. Here, we examined reproductive success and seedling performance of Poulsenia armata (Moraceae) in continuous and fragmented forests of Los Tuxtlas, southern Mexico. We further investigated how maternal habitat and soil conditions manifested in the seedling stage. We determined seed quality and seedling performance by combining isotopic analyses in seed quality with field observations of P. armata fruit production and a common--garden experiment. Soil conditions in forest fragments negatively impacted P. armata reproductive success. Trees of P. armata in forest fragments were smaller in size and produced fewer fruits and smaller seeds with lower quality compared with trees from the continuous forest. The combined effects of maternal habitat and soil conditions determined seedling survival and growth of this tropical tree. Notably, seedlings had restricted plasticity for biomass allocation to roots, limiting the capacity of fragmented populations to compensate for the initial low N content in seeds. Trees in forest fragments at Los Tuxtlas produced offspring competitively inferior and potentially less resilient than counterparts in continuous forest, jeopardizing future persistence of this late-successional tree species.

生境丧失与片段化会影响全球森林生态系统的结构与功能，但目前学界仍未充分明确物种对环境变化的响应机制。本研究以墨西哥南部洛斯图斯特拉斯（Los Tuxtlas）地区的连续林与片段化林为研究样地，调查了桑科（Moraceae）植物Poulsenia armata的繁殖成功率与幼苗表现，并进一步探究了母本生境与土壤条件如何作用于幼苗阶段。本研究通过将种子质量的同位素分析、野外P. armata结实量观测与同质园实验（common garden experiment）相结合，测定了种子质量与幼苗表现。结果显示，森林片段中的土壤条件对P. armata的繁殖成功率产生了负面影响；与连续林中的植株相比，片段化林中的P. armata个体体型更小，结实量更少，所结种子更小且质量更低。母本生境与土壤条件的共同作用决定了该热带树种的幼苗存活与生长情况。值得注意的是，幼苗对根系的生物量分配可塑性有限，这限制了片段化种群弥补种子初始氮含量偏低的能力。洛斯图斯特拉斯地区片段化林中的P. armata植株所产生的后代，在竞争力与恢复力上均弱于连续林中的同类个体，这将危及该迟演替树种的未来存续。