Passive acoustic monitoring (PAM) has become a prevalent tool for assessing ecosystem health and monitoring vocal animal communities (also known as acoustic community). Many studies have explored the variations in acoustic alpha diversity and the factors influencing these changes. However, the potential of acoustic beta diversity as an ecological indicator for assessing biodiversity still necessitates further empirical research for confirmation.
In a study published in Ecological Indicators, researchers from Xishuangbanna Tropical Botanical Garden (XTBG) of the Chinese Academy of Sciences (CAS)and their collaborators evaluated the efficacy of acoustic beta indices as proxies of dissimilarity in vocal bird composition. They also investigated the relative importance of vegetation characteristics dissimilarity, topographic dissimilarity, and geographical distance on acoustic beta diversity.
The researchers deployed 16 acoustic recorders at the Ailao Mountain subtropical evergreen broad-leaved forest, collecting data during the bird breeding season. They identified bird species through recordings and used the Mantel test to analyze the relationship between the composition differences of vocalizing bird species and eight acoustic beta diversity indices.
The researchers utilized drone LiDAR and forest dynamics plot inventory data to procure vegetation characteristics and topographic factors. They then employed distance matrix multiple regression and generalized dissimilarity models to examine the relative significance of vegetation characteristics, topographic factors, and geographical distance in relation to acoustic beta diversity.
The study revealed a highly significant positive correlation among the eight acoustic beta diversity indices. However, the relationship between the acoustic beta diversity index and the variation in bird species composition, as determined by audio identification, was relatively weak.
The combination of vegetation feature differences, topographical variations, and geographical distance only accounted for a minimal amount of variation in acoustic beta diversity. Notably, differences in vegetation features explained more of the variation in acoustic beta diversity than topographical differences.
Acoustic diversity was revealed to be a novel component of biodiversity, distinct from the diversity of vocalizing species. Furthermore, it was demonstrated for the first time that acoustic beta diversity does not reflect the dissimilarity of environmental factors, including vegetation and topographical features.
A bird in the forest. (Image by HE Xuelian)
First Published: 25 February 2025
