Although tropical dry forests are among the most degraded and fragmented biomes in the world, we still have a poor understanding of their basic ecological features and conservation status, particularly in the Neotropics. Here, we assess the diversity, composition, structure and conservation value of tropical dry forests in a highly fragmented landscape in Nicaragua. We established 31 plots and transects in and along river corridors, secondary forests, living fences and pasture-woodlands. We recorded all trees with diameters at breast height ≥ 2.5 cm using Hill numbers (qD, where q = 0, 1 or 2) and estimated the richness and diversity of trees in each forest type. We calculated the Importance Value Index (IVI) to species and family levels and, finally, performed a Non-Metric Multidimensional Scaling (NMDS) ordination and an Analysis of Similarities (ANOSIM) using the Bray–Curtis index of similarity. Diversity (1D, 2D) but not species richness (0D) differed between forest types (P = 0.01 and 0.66, respectively). IVI was highest for the legume family Fabaceae, followed by the Moraceae and Malvaceae (27.8, 11.1 and 10.5, respectively). Vachellia pennatula, Guazuma ulmifolia and Bursera simaruba had IVIs >30%, the former two being the most abundant trees in all forest types. An analysis of community similarity revealed that each forest type had a distinct composition (P < 0.01, R2 = 0.30), thereby underlining the importance of conserving all these different types of land cover.
摘要：
破碎化景观格局中热带干旱森林的结构、多样性与保护价值
尽管热带干旱森林是世界上退化和破碎化程度最严重的生物群落之一，但我们对它们的基本生态特征和保护状况仍然知之甚少，尤其是在新热带地区。在本研究中，我们对尼加拉瓜破碎化景观格局中的热带干旱森林的多样性、组成、结构和保护价值进行了评估。我们在河流廊道、次生林、绿篱和林间牧地之中和沿线地区建立了31处样地和样带。我们使用希尔数(Hill number)对胸高处直径
≥2.5 cm的所有树木进行了记录，并对每种森林类型中树木的丰富性和多样性进行了估算，接着计算了种级分类和科级分类上的重要值指数(Importance Value Index, IVI)，最后则使用Bray-Curtis相似性指数进行了非度量多维标度(Non-Metric Multidimensional Scaling, NMDS)排序和相似性分析(Analysis of Similarities, ANOSIM)。不同森林类型之间在多样性上存在差异，但物种丰富度却不存在差异。豆科植物
的IVI值最高，其次是桑科植物和锦葵科植物。Vachellia pennatula、Guazuma ulmifolia和Bursera simaruba的IVI值都>30%，其中前两种是所有森林类型中最为丰富的树木。对群落的相似性进行分析后可知每种森林类型都有着不同的组成，从而凸显了对所有这些不同类型的土地覆盖开展保护
的重要性。
关键词:
豆科植物,
破碎化,
希尔数(Hill number),
重要值指数,
河流廊道,
热带干旱森林
