Data to: Acoustic indices as proxies for biodiversity in certified and non-certified cocoa plantations in Indonesia

Acoustic indices allow time efficient analysis of large acoustic datasets obtained from passive acoustic monitoring, but results regarding their effectiveness in assessing biodiversity are inconsistent. We evaluated the efficacy of six acoustic indices (ACI, ADI, AEI, H, BI, NDSI) for studying bird and structural diversity in 51 cocoa plantations, 24 of which were certified by Rainforest Alliance, in Luwu Timur, Sulawesi, Indonesia. We used linear models to assess the correlation of index values with bird species richness, and linear mixed models to test the influence of canopy closure, shade tree basal area, distance to primary forest and tree cover in a 200 m buffer on index values. Bird species richness was positively correlated with BI (p = 0.02) and negatively with H (p = 0.03), yet predictive power was low (R² = 0.10 and 0.09, respectively). Acoustic indices did not differ significantly for certified cocoa plantations. Tree cover within the 200 m buffer moderately well predicted ACI values (marginal R² = 0.37) while for the other indices effect sizes were low or correlations were not significant. Comparing our results to other studies, acoustic indices may reflect biodiversity across land uses, but were of limited value for tracking subtle differences in cocoa plantations in Sulawesi. Future studies may include more land uses (i.e., rice paddies, secondary forest, oil palm) as well as more taxa (i.e., insects). More research is needed on the comparability of acoustic indices, as we found them to be influenced by recording equipment and calculation settings.

声学指数使得对从被动声学监测中获取的大量声学数据集进行时间高效的分析成为可能，然而，关于其在评估生物多样性方面的有效性的研究结果并不一致。本研究评估了六个声学指数（ACI、ADI、AEI、H、BI、NDSI）在研究51个可可种植园中的鸟类和结构多样性方面的有效性，其中24个种植园经雨林联盟认证，位于印度尼西亚苏拉威西省鲁武东。我们采用线性模型来评估指数值与鸟类物种丰富度之间的相关性，并使用线性混合模型来检验林冠密闭度、遮荫树基底面积、距离原生林以及200米缓冲区内的树冠覆盖对指数值的影响。鸟类物种丰富度与BI指数呈正相关（p = 0.02），与H指数呈负相关（p = 0.03），但其预测能力较低（R²分别为0.10和0.09）。声学指数在认证的可可种植园中并无显著差异。200米缓冲区内的树冠覆盖对ACI值的预测能力尚可（边缘R² = 0.37），而对于其他指数，效应量较低或相关性不显著。将我们的研究结果与其他研究进行比较，声学指数可能反映了不同土地利用下的生物多样性，但对于跟踪苏拉威西省可可种植园中细微差异的价值有限。未来的研究可能包括更多土地利用类型（例如，稻田、次生林、油棕）以及更多分类群（例如，昆虫）。关于声学指数的可比性，需要更多的研究，因为我们发现它们受录音设备和计算设置的干扰。