Data from: Can terrestrial laser scanners (TLSs) and hemispherical photographs predict tropical dry forest succession with liana abundance?

Tropical dry forests (TDFs) are ecosystems with long drought periods, a mean temperature of 25 °C, a mean annual precipitation that ranges from 900 to 2000 mm, and that possess a high abundance of deciduous species (trees and lianas). What remains of the original extent of TDFs in the Americas remains highly fragmented and at different levels of ecological succession. It is estimated that one of the main fingerprints left by global environmental and climate change in tropical environments is an increase in liana coverage. Lianas are non-structural elements of the forest canopy that eventually kill their host trees. In this paper we evaluate the use of a terrestrial laser scanner (TLS) in combination with hemispherical photographs (HPs) to characterize changes in forest structure as a function of ecological succession and liana abundance. We deployed a TLS and HP system in 28 plots throughout secondary forests of different ages and with different levels of liana abundance. Using a canonical correlation analysis (CCA), we addressed how the VEGNET, a terrestrial laser scanner, and HPs could predict TDF structure. Likewise, using univariate analyses of correlations, we show how the liana abundance could affect the prediction of the forest structure. Our results suggest that TLSs and HPs can predict the differences in the forest structure at different successional stages but that these differences disappear as liana abundance increases. Therefore, in well known ecosystems such as the tropical dry forest of Costa Rica, these biases of prediction could be considered as structural effects of liana presence. This research contributes to the understanding of the potential effects of lianas in secondary dry forests and highlights the role of TLSs combined with HPs in monitoring structural changes in secondary TDFs.

热带干旱森林（Tropical dry forests, TDFs）是一类伴随长期干旱期的生态系统，其年均气温为25℃，年平均降水量介于900毫米至2000毫米之间，且富含落叶物种（乔木与木质藤本（liana））。美洲地区原生热带干旱森林的现存区域已高度碎片化，且处于不同的生态演替阶段。据估算，全球环境与气候变化在热带环境中留下的主要印记之一，便是木质藤本覆盖范围的扩张。木质藤本是林冠中的非结构组分，最终会导致其宿主树木死亡。本研究评估了地面激光扫描仪（Terrestrial Laser Scanner, TLS）结合半球摄影（Hemispherical Photographs, HPs）的应用方案，用于表征森林结构随生态演替与木质藤本丰度的变化规律。我们在覆盖不同林龄、木质藤本丰度各异的次生林的28个样地中部署了TLS与HP系统。通过典型相关分析（Canonical Correlation Analysis, CCA），我们探究了VEGNET型地面激光扫描仪与半球摄影对热带干旱森林结构的预测能力。同样，通过单变量相关分析，我们阐释了木质藤本丰度对森林结构预测结果的影响机制。研究结果表明，地面激光扫描仪与半球摄影能够区分不同演替阶段的森林结构差异，但随着木质藤本丰度的提升，此类差异会逐渐消失。因此，在哥斯达黎加热带干旱森林这类已被充分研究的生态系统中，此类预测偏差可被视为木质藤本存在所引发的结构性效应。本研究有助于深化对次生干旱森林中木质藤本潜在影响的认知，并凸显了地面激光扫描仪结合半球摄影在次生热带干旱森林结构变化监测中的应用价值。