Rapid assessment of habitat quality in riparian rainforest vegetation

Abstract

GIS and aerial photographic techniques were applied to assessing riparian vegetation quality in an agricultural landscape formerly covered in lowland rainforest. Canopy cover and width of woody riparian vegetation, both easily determined from remotely sensed data, were investigated as indicators of riparian quality. High correlations between field measurements of canopy cover and width of woody riparian vegetation with several other vegetation attributes indicative of vegetation quality (weed abundance, debris, human disturbance, native species richness) demonstrated that these two habitat attributes were suitable field vegetation quality surrogates. Desktop quality analysis combined GIS measurement of riparian width with aerial photographic analysis of canopy cover. Desktop quality equalled field quality in 78% of cases, with a further 13% showing errors due to clearing or thickening of vegetation after aerial photographs were taken. Bird communities in higher vegetation quality areas comprised mainly rainforest-dependent species, whereas poor quality areas mostly supported birds of open habitats. Bird community diversity and rainforest-dependent bird diversity increased significantly both with increasing levels of canopy cover and greater riparian width, but a combination of these factors explained more variance than each factor separately. Desktop riparian vegetation quality therefore proved a satisfactory indicator of habitat quality for birds in rainforest riparian zones. This quick and efficient desktop method of riparian habitat quality assessment can determine conservation values of rainforest riparian areas with minimal field validation, thereby allowing more effective targeting of appropriate management practices, identification of areas of conservation concern and prioritisation of revegetation and rehabilitation efforts.