Can soundscape indices be used to reflect biodiversity in an Ecuadorian Andean tropical montane habitat?

Lamond, Ailsa (2016) Can soundscape indices be used to reflect biodiversity in an Ecuadorian Andean tropical montane habitat? Masters thesis (MPhil), University of Sussex.

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The measurement of biodiversity presents a challenging task for conservationists. Traditional ecological descriptors such as species richness, Shannon and Simpson diversities have long been relied on by ecologists to provide an indication of biodiversity, however, the generation of these indices requires manual assessments of local fauna through methods which can often be expensive, time consuming and invasive. Analysis of the Soundscape, the collection of sounds generated by organisms (biophony), humans (anthrophony) and non-biological sounds such as wind and water (geophony), presents new potential for biodiversity sampling. To date, a range of indices have been developed that aim to provide a value relating to acoustic characteristics of an environment, based on the spectral and temporal properties within sound recordings. Several studies have yielded promising results when using the acoustic indices for biodiversity assessments in temperate, and to some extent, tropical habitats. We here aimed to further the current understanding of soundscape indices by investigating how they behave in a tropical habitat of high avifaunal diversity. Point count data for bird species was collected from the Santa Lucia Cloud Forest Reserve, NW Ecuador (0°17'30"N, 78°40'30"W), during Summer 2014, while acoustic recordings were taken simultaneously using a handheld audio recorder. We first analysed the change in bird species composition and diversity along two environmental gradients of habitat disturbance and altitude, and investigated how the acoustic indices behaved along these same gradients. We then explored whether the acoustic indices can be used to estimate biodiversity based on their correlation with traditional ecological indices. From the point count data we found a high turnover in species composition across sample sites. Mean species richness was found to negatively correlate with increasing altitude (p=1.485e-05) and was found to be significantly lower in sites of primary forest than in both secondary forest and silvopasture (p=0.0165). Although each of the acoustic indices showed varying levels of change across the environmental gradients, we found that only four of the eight acoustic indices, the Normalized Difference Soundscape Index (NDSI, p=0.048), spectral entropy Hs, p=0.033), temporal entropy (Ht, p=0.031), and total entropy (H, p=0.031), were found to significantly correlate with species composition. We found that spectral entropy (Hs) and total entropy (H) were the only acoustic indices to significantly correlate with ecological indices, however since the total entropy (H) is developed as a product of the spectral entropy (Hs) we suggest that only the H index should be utilised for biodiversity measurements. We found that while the acoustic indices have the potential to characterise certain features of a habitat or to assist in analysing bird species composition, their use for biodiversity assessment is limited. We would suggest that more work to develop and understand the indices is needed before we can reliably make use of them for measuring biodiversity.

Item Type: Thesis (Masters)
Schools and Departments: School of Life Sciences > Biology and Environmental Science
Subjects: Q Science > QH Natural history > QH0301 Biology > QH0324 Methods of research. Technique. Experimental biology
Depositing User: Library Cataloguing
Date Deposited: 08 Nov 2016 15:51
Last Modified: 08 Nov 2016 15:51

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