The value of scattered trees for wildlife: Contrasting effects of landscape context and tree size

Abstract

Aim: The biodiversity value of scattered trees in modified landscapes is often overlooked in planning and conservation decisions. We conducted a multitaxa study to determine how wildlife abundance, species richness and community composition at individual trees are affected by (1) the landscape context in which trees are located; and (2) the size of trees. Location: Canberra, south-eastern Australia. Methods: Trunk arthropod, bat and bird surveys were undertaken over 3 years (2012–2014) at 72 trees of three sizes (small (20–50 cm DBH), medium (51–80 cm), large (≥80 cm)) located in four landscape contexts (reserves, pasture, urban parklands, urban built-up areas). Results: Landscape context affected all taxa surveyed. Trunk arthropod communities differed between trees in urban built-up areas and reserves. Bat activity and richness were significantly reduced at trees in urban built-up areas suggesting that echolocating bats may be disturbed by high levels of urbanization. Bird abundance and richness were highest at trees located in modified landscapes, highlighting the value of scattered trees for birds. Bird communities also differed between non-urban and urban trees. Tree size had a significant effect on birds but did not affect trunk arthropods and bats. Large trees supported higher bird abundance, richness and more unique species compared to medium and small trees. Main conclusions: Scattered trees support a diversity of wildlife. However, landscape context and tree size affected wildlife in contrasting ways. Land management strategies are needed to collectively account for responses exhibited by multiple taxa at varying spatial scales. We recommend that the retention and perpetuation of scattered trees in modified landscapes should be prioritized, hereby providing crucial habitat benefits to a multitude of taxa.