Mapping forest patches and scattered trees from SPOT images and testing their ecological importance for woodland birds in a fragmented agricultural landscape

Abstract

Scattered trees represent an important element within the agricultural matrix for birds. The aims of this study were to develop methods for mapping isolated trees from satellite imagery and to assess the importance of isolated trees for bird species richness. Field sampling of birds and plants was conducted at 120 sites in south-east Australia. We mapped tree cover from Landsat and SPOT images using a combination of spectral and segmentation based methods. Mapping of isolated trees as point objects was highly accurate (80–90%). Tree cover at spatial extents of 3–28 ha around sites explained 60% of the variability in woodland–dependent bird species richness. However, isolated trees in agricultural areas made just a small contribution to explaining the spatial variability in overall avian richness. This approach can be used for more extensive assessment of avian habitat quality from high spatial resolution images across a range of human modified landscapes.

Acknowledgements

This study was funded by the Australian Research Council (ARC) Discovery Project: ‘Beyond discrete landscape metrics: spatial analysis tools and surface textural measures for quantifying gradients in landscape structure’, project ID DP0667029.

The New South Wales Department of Natural Resources, Parramatta and the North‐East Catchment Management Authority, Wodonga are gratefully acknowledged for the supply of the SPOT 5 imagery. We thank the referees for their very helpful comments.