Understanding the relationship between soundscape and landscape features in a Tropical Andean environment, Colombia

The acoustic component of the landscape (soundscape) has been suggested as an indicator of landscape conditions as it has been related to physical, biological and anthropogenic features of the local environment. Despite of acoustic indices have been used as measurements of soundscape complexity, their relationship with landscape features has shown to be highly variable and not direct. This relationship has not been examined on the tropical Andes then it is not clear if soundscape can be a reliable indicator of landscape conditions. In this study, we assess the relationship between 14 acoustic indices and landscape conditions in an area on the northern Andes of Colombia. This region is highly fragmented and characterized for a highly diverse community of animals and plants thus representing an excellent opportunity to test such relationship. Soundscape recordings were obtained from 31 randomly selected sites surveyed among May and July 2017. A Song Meter SM4 device was deployed at each site for five consecutive days, and programmed to collect 1-min recordings every 15 minutes for a total of 95 samples per day. Recordings were obtained as monaural 16 bits and at a sampling rate of 22.05 kHz. Out of 14 indices, we calculated 9 non-correlated acoustic indices for each 1-min recording and selected the maximum value per hour to estimate the hourly average over the five days at each site. Thirteen landscape features were derived from satellite images and metrics describing vegetation, fragmentation, water availability, terrain, and soil attributes at 100 m radius around each site. Indices did not present a similar pattern of variation with respect to landscape conditions. Acoustic evenness (AE) and temporal entropy (TE) indices were related to changes in terrain conditions, while acoustic diversity index (ADI) was associated to fragmentation. The bioacoustic index (BI), acoustic complexity index (ACI), and the number of peaks (NP) were positively related with water availability. Our results suggest that in Andean environments specific acoustic indices could be connected to particular aspects of landscape.