Data from: LiDAR-derived canopy structure supports the more-individuals hypothesis for arthropod diversity in temperate forests

Despite considerable progress in the ability to measure the complex 3-D structure of forests with the improvement of remote-sensing techniques, our mechanistic understanding of how biodiversity is linked to canopy structure is still limited. Here we tested whether the increase in arthropod abundance and richness in beech forest canopies with increasing canopy complexity supports the more-individuals hypothesis or the habitat-heterogeneity hypothesis. We used fogging to collect arthropod samples from 80 standardized plots from canopies of single- to multi-layered mature montane European beech stands. Tree height and an independent measure of vertical heterogeneity — the vertical distribution ratio — on each arthropod sampling plot were derived from high-resolution full-waveform airborne laser scanning data. Mixed-model path analysis based on almost 20,000 specimens of 762 species from 11 orders provided support for the more-individuals hypothesis, with higher arthropod abundance but not higher species richness in stands with a more equal vertical distribution of plant biomass. By contrast, we found no support for the habitat-heterogeneity hypothesis. The increase in the number of individuals with increasing vertical distribution of biomass might be caused either by increasing leaf area, as indicated by higher space filling and productivity in multi-layered stands, or by higher persistence of arthropod populations owing to better shelter, reduced competition and more refuges under harsh conditions, or by both. High-resolution airborne laser scanning, with its ability to penetrate dense canopies under leaf-on conditions, has proved suitable for measuring vertical structures as a predictor for canopy diversity. Expanding combinations of remote-sensing and canopy-biodiversity data opens many avenues for improving our understanding of the link between diversity and forest structures.

尽管随着遥感技术的迭代升级，森林复杂三维结构的测量能力已取得长足进展，但学界对生物多样性与林冠结构之间关联的机制性理解仍存在显著局限。本研究旨在验证：欧洲山毛榉林冠中节肢动物的丰度与物种丰富度随林冠复杂度提升的变化趋势，究竟支持个体数假说（more-individuals hypothesis）还是生境异质性假说（habitat-heterogeneity hypothesis）。我们采用雾采法，从单层至多层的成熟山地欧洲山毛榉林分的林冠中，于80个标准化样地内采集节肢动物样本。每个节肢动物采样样地的树高数据，以及表征垂直异质性的独立指标——垂直分布比，均源自高分辨率全波形机载激光扫描（full-waveform airborne laser scanning）数据。基于涵盖11个目、762个物种的近20000号标本开展的混合模型路径分析结果，支持个体数假说：在植物生物量垂直分布更均匀的林分中，节肢动物丰度显著更高，但物种丰富度未出现明显提升。与之相反，本研究未发现支持生境异质性假说的有效证据。生物量垂直分布随林冠复杂度提升而带来的个体数增加，可能源于两方面因素：一是多层林分中更高的空间填充度与生产力所指示的叶面积扩张；二是严苛环境下更优良的遮蔽条件、更低的种间竞争与更多庇护所所带来的节肢动物种群存续性提升，或二者共同作用。高分辨率机载激光扫描能够在叶片覆盖状态下穿透茂密林冠，已被证实可作为林冠多样性的有效预测因子，用于精准表征林冠垂直结构。遥感技术与林冠生物多样性数据的融合拓展，为深化学界对生物多样性与森林结构之间关联的认知开辟了诸多研究方向。