Data from: Comparing forest structure and biodiversity on private and public land: secondary tropical dry forests in Costa Rica

Secondary forests constitute a substantial proportion of tropical forestlands. These forests occur on both public and private lands and different underlying environmental variables and management regimes may affect post‐abandonment successional processes and resultant forest structure and biodiversity. We examined whether differences in ownership led to differences in forest structure, tree diversity, and tree species composition across a gradient of soil fertility and forest age. We collected soil samples and surveyed all trees in 82 public and 66 private 0.1‐ha forest plots arrayed across forest age and soil gradients in Guanacaste, Costa Rica. We found that soil fertility appeared to drive the spatial structure of public vs. private ownership; public conservation lands appeared to be non‐randomly located on areas of lower soil fertility. On private lands, areas of crops/pasture appeared to be non‐randomly located on higher soil fertility areas while forests occupied areas of lower soil fertility. We found that forest structure and tree species diversity did not differ significantly between public and private ownership. However, public and private forests differed in tree species composition: 11 percent were more prevalent in public forest and 7 percent were more prevalent in private forest. Swietenia macrophylla, Cedrela odorata, and Astronium graveolens were more prevalent in public forests likely because public forests provide stronger protection for these highly prized timber species. Guazuma ulmifolia was the most abundant tree in private forests likely because this species is widely consumed and dispersed by cattle. Furthermore, some compositional differences appear to result from soil fertility differences due to non‐random placement of public and private land holdings with respect to soil fertility. Land ownership creates a distinctive species composition signature that is likely the result of differences in soil fertility and management between the ownership types. Both biophysical and social variables should be considered to advance understanding of tropical secondary forest structure and biodiversity.次生林在热带林地中占据相当大的比例。这类次生林分布于公有与私有两类林地，不同的潜在环境变量与经营管理模式可能会影响弃耕后的演替过程，进而改变最终形成的森林结构与生物多样性。本研究针对土壤肥力与林龄梯度，探究林地产权差异是否会造成森林结构、树木多样性以及树种组成的差异。我们在哥斯达黎加瓜纳卡斯特地区沿林龄与土壤肥力梯度布设了82块公有林地样地与66块私有林地样地，每块样地面积为0.1公顷，采集土壤样本并对样地内所有树木开展调查。研究发现，土壤肥力似乎塑造了公有与私有林地的空间分布格局：公有保护林地并非随机分布，而是多集中于土壤肥力较低的区域；而私有土地中，农田与牧场用地同样并非随机分布，多集中于土壤肥力较高的区域，私有次生林则占据土壤肥力较低的地块。研究结果显示，公有与私有次生林的森林结构与树木多样性并无显著差异，但二者的树种组成存在显著差异：11%的树种在公有次生林中占比更高，7%的树种则在私有次生林中更为常见。大果桃花心木（Swietenia macrophylla）、洋椿（Cedrela odorata）与Astronium graveolens在公有次生林中分布更为广泛，这可能得益于公有林地对这些极具经济价值的用材树种的更强保护。羽叶苹婆（Guazuma ulmifolia）是私有次生林中分布最广的树种，这可能是因为该物种被牛广泛取食并通过牛传播种子。此外，部分树种组成差异源于土壤肥力的差异——这是因为公有与私有林地在土壤肥力梯度上的布设并非随机。林地产权会形成独特的树种组成特征，这一特征大概率源于不同产权类型间土壤肥力与经营管理模式的差异。若要深化对热带次生林结构与生物多样性的认知，需同时考虑生物物理与社会经济两类变量。