Richness is not all: how changes in avian functional diversity reflect major landscape modification caused by pine plantations

Abstract

Aim: To quantify changes over a 15-year period in bird functional diversity within woodland patches where woodland patches remained unchanged, but the surrounding landscape context has been altered by exotic plantation establishment. Location: South-eastern Australia. Methods: Using statistical modelling and principal coordinate analysis, we explored how a suite of functional diversity measures, bird species richness and the composition of the bird assemblage changed over time and in response to key covariates, including time since plantation establishment, woodland patch size, number of woodland patch boundaries surrounded by plantation and woodland vegetation type. Results: There was no significant change in species richness over time (with woodland patch size being the only significant effect on this measure). In contrast, we identified marked changes in the composition of bird assemblages, as well as significant temporal changes in functional diversity. The most substantial declines in functional diversity occurred in woodland patches completely surrounded by long-established stands of radiata pine. Plantation age also affected the functional diversity of bird assemblages through attracting new (typically closed forest-associated) species to the region. We also found reduced overlap in the amount of functional trait space defined by sets of species surveyed in successive years. This was linked to a shift away from solitary or pair-forming species found in open-woodland environments and which consume seeds and various other food resources, towards insectivorous, nectarivorous and closed forest-associated taxa that occur in flocks or groups. Main Conclusions: Examination of temporal changes in functional diversity added new insights into the biotic changes associated with landscape transformation and the functional role of species being replaced. Show more