Acoustic dissimilarities between an oil palm plantation and surrounding forests: Analysis of index time series for beta-diversity in South Sumatra, Indonesia

Land use and land use change are central issues to consider during the establishment of sustainable oil palm production systems in tropical and neotropical areas. Owing to the limited availability of biodiversity data in these areas, ecoacoustics and soundscape ecology are expected to play an important role in assessing the impacts of oil palm production on biodiversity. However, the application of acoustic indices for alpha-diversity to land use impact assessment is not straightforward because of inconsistent results. Therefore, this study focuses on whether acoustic indices for pairwise beta-diversity can be used to distinguish between oil palm plantations and surrounding forests; the existence of a difference implies that it is possible to construct acoustic indices for alpha-diversity. To that end, we collected sound data from the Dawas Plantation and its surrounding forests (South Sumatra, Indonesia) and made comparisons using acoustic dissimilarity indices. The results indicate that there are significant differences in location and time factors between the oil palm plantation and the surrounding forests; that is, we found significant differences among pairs of locations and a daily periodicity (natural rhythm) in acoustic dissimilarities. In contrast, although another natural rhythm between stable and unstable times was found, it was independent of land use. Moreover, a systematic relationship between acoustic dissimilarity indices and physical distances was not established. We expect that these findings will be useful in improving the homogenized soundscape in oil palm plantations through the introduction of sustainable management practices. Furthermore, biodiversity appraisal using acoustics will play an important role in the establishment of sustainable oil palm production systems.