Connecting soundscape to landscape: Which acoustic index best describes landscape configuration?

Abstract

a b s t r a c tSoundscape assessment has been proposed as a remote ecological monitoring tool for measuring biodiversity, but few studies have examined how soundscape patterns vary with landscape configuration and condition. The goal of our study was to examine a suite of published acoustic indices to determine whether they provide comparable results relative to varying levels of landscape fragmentation and ecological condition in nineteen forest sites in eastern Australia. Our comparison of six acoustic indices according to time of day revealed that two indices, the acoustic complexity and the bioacoustic index, presented a similar pattern that was linked to avian song intensity, but was not related to landscape and biodiversity attributes. The diversity indices, acoustic entropy and acoustic diversity, and the normalized difference soundscape index revealed high nighttime sound, as well as a dawn and dusk chorus. These indices appear to be sensitive to nocturnal biodiversity which is abundant at night in warm, subtropical environments. We argue that there is need to better understand temporal partitioning of the soundscape by specific taxonomic groups, and this should involve integrated research on amphibians, insects and birds during a 24 h cycle. The three indices that best connected the soundscape with landscape characteristics, ecological condition and bird species richness were acoustic entropy, acoustic evenness and the normalized difference soundscape index. This study has demonstrated that remote soundscape assessment can be implemented as an ecological monitoring tool in fragmented Australian forest landscapes. However, further investigation should be dedicated to refining and/or combining existing acoustic indices and also to determine if these indices are appropriate in other landscapes and for other survey purposes.Crown

Comparisons Between Autonomous Acoustic Recordings and Avian Point Counts in Open Woodland Savanna

“…In addition, to link the composition and dynamics of biophony with biological and ecological processes, ornithologists would bring valuable knowledge concerning species behavior, phylogenetic history, and ecology. Soundscape ecology would bring complementary knowledge about landscape contexts (Tucker et al 2014, Fuller et al 2015. Extensive, currently accessible soundscape libraries from which such data could be derived include those of the Center for Global Soundscapes (http://centerforglobalsoundscapes.org) and the REAL (Kasten et al 2012 Kasten et al (2012), may also have to be applied or developed in order for ornithologists to consider representative samples from any given dataset.…”

Listening to ecosystems: data‐rich acoustic monitoring through landscape‐scale sensor networks

“…The Normalized difference soundscape index (NDSI) has been shown to accurately reflect anthropogenic noise when values are low (Gage and Axel 2014), and avian species richness when values are high (Fuller et al 2015). We found that, on average, our urban site in Sueyoshi park had higher values than our suburban sites in Nago and Nakagusuku.…”

“…Previous studies have found that ACI increases drastically in the presence of cicadas and other orthopterans that produce a broadband signal (Farina et al 2011;Fuller et al 2015). BioA was also highest at night in Nago and Nakagusuku, likely due to the persistent broadband signaling of several orthopteran species, especially Hexacentrus unicolor.…”

“…Further, passive recordings produce a dataset of species behavior and interactions in a complex sensory environment. However, practical limitations to soundscape ecology have also been identified (Digby et al 2013), and caution is advised when interpreting several of the common soundscape indices currently in use (Fuller et al 2015). One consistent challenge in soundscape ecology is the presence of wind and insect sounds, which may obscure and even deter other animal signals in a manner similar to inclement weather, particularly in late summer (Seki 2012;Hart et al 2015).…”

Full Issue

“…In addition, to link the composition and dynamics of biophony with biological and ecological processes, ornithologists would bring valuable knowledge concerning species behavior, phylogenetic history, and ecology. Soundscape ecology would bring complementary knowledge about landscape contexts (Tucker et al 2014, Fuller et al 2015. Extensive, currently accessible soundscape libraries from which such data could be derived include those of the Center for Global Soundscapes (http://centerforglobalsoundscapes.org) and the REAL (Kasten et al 2012).…”