Terrestrial Ecology Group (TEG-UAM). Department of Ecology, Universidad Autónoma de Madrid, Madrid, Spain.
Centro de Investigación en Biodiversidad y Cambio Global, Universidad Autónoma de Madrid, Madrid, Spain.
Ecol Appl. 2022 Dec;32(8):e2707. doi: 10.1002/eap.2707. Epub 2022 Sep 29.
Arthropod biomass is a key element in ecosystem functionality and a basic food item for many species. It must be estimated through traditional costly field sampling, normally at just a few sampling points. Arthropod biomass and plant productivity should be narrowly related because a large majority of arthropods are herbivorous, and others depend on these. Quantifying plant productivity with satellite or aerial vehicle imagery is an easy and fast procedure already tested and implemented in agriculture and field ecology. However, the capability of satellite or aerial vehicle imagery for quantifying arthropod biomass and its relationship with plant productivity has been scarcely addressed. Here, we used unmanned aerial vehicle (UAV) and satellite Sentinel-2 (S2) imagery to establish a relationship between plant productivity and arthropod biomass estimated through ground-truth field sampling in shrub steppes. We UAV-sampled seven plots of 47.6-72.3 ha at a 4-cm pixel resolution, subsequently downscaling spatial resolution to 50 cm resolution. In parallel, we used S2 imagery from the same and other dates and locations at 10-m spatial resolution. We related several vegetation indices (VIs) with arthropod biomass (epigeous, coprophagous, and four functional consumer groups: predatory, detritivore, phytophagous, and diverse) estimated at 41-48 sampling stations for UAV flying plots and in 67-79 sampling stations for S2. VIs derived from UAV were consistently and positively related to all arthropod biomass groups. Three out of seven and six out of seven S2-derived VIs were positively related to epigeous and coprophagous arthropod biomass, respectively. The blue normalized difference VI (BNDVI) and enhanced normalized difference VI (ENDVI) showed consistent and positive relationships with arthropod biomass, regardless of the arthropod group or spatial resolution. Our results showed that UAV and S2-VI imagery data may be viable and cost-efficient alternatives for quantifying arthropod biomass at large scales in shrub steppes. The relationship between VI and arthropod biomass is probably habitat-dependent, so future research should address this relationship and include several habitats to validate VIs as proxies of arthropod biomass.
节肢动物生物量是生态系统功能的关键要素，也是许多物种的基本食物来源。它必须通过传统的昂贵野外采样来估计，通常只在几个采样点进行。节肢动物生物量和植物生产力应该密切相关，因为绝大多数节肢动物是草食性的，而其他节肢动物则依赖于这些草食性动物。利用卫星或航空飞行器图像来量化植物生产力是一种简单快速的方法，已经在农业和实地生态学中进行了测试和实施。然而，卫星或航空飞行器图像量化节肢动物生物量及其与植物生产力关系的能力却很少被提及。在这里，我们使用无人机 (UAV) 和卫星 Sentinel-2 (S2) 图像来建立在灌木草原中通过地面真实野外采样估计的植物生产力和节肢动物生物量之间的关系。我们以 4 厘米像素分辨率对 7 个 47.6-72.3 公顷的地块进行了 UAV 采样，随后将空间分辨率下采样到 50 厘米分辨率。同时，我们使用来自同一日期和地点以及其他日期和地点的 10 米空间分辨率的 S2 图像。我们将几个植被指数 (VI) 与在 UAV 飞行地块的 41-48 个采样站和 S2 的 67-79 个采样站估计的节肢动物生物量（表生的、粪食性的和四个功能消费者群体：捕食性的、碎屑食性的、植食性的和多样的）联系起来。来自 UAV 的 VI 与所有节肢动物生物量群体始终呈正相关。S2 衍生的 7 个 VI 中有 3 个和 7 个 VI 中的 6 个分别与表生的和粪食性的节肢动物生物量呈正相关。蓝色归一化差异植被指数 (BNDVI) 和增强归一化差异植被指数 (ENDVI) 与节肢动物生物量始终呈正相关，无论节肢动物群体或空间分辨率如何。我们的结果表明，无人机和 S2-VI 图像数据可能是在灌木草原中大规模量化节肢动物生物量的可行且具有成本效益的替代方法。VI 与节肢动物生物量之间的关系可能依赖于栖息地，因此未来的研究应该解决这种关系，并包括几个栖息地来验证 VI 作为节肢动物生物量的替代物。
