Effects of woodland islets introduced in a Mediterranean agricultural landscape on local bird communities

I Razola,J M Rey Benayas

doi:10.5194/we-9-44-2009

Abstract

Abstract. This study assesses whether the afforestation approach consisting in the introduction of woodland islets in “agricultural seas” can reconcile the restoration of woody vegetation and the persistence of open-habitat bird populations, providing further opportunities for other forest species to enrich bird diversity at the landscape level. We compared the species richness and abundance of bird communities in a field with 16 introduced woodland islets and in a nearby abandoned field located in central Spain during spring and winter time. The woodland islets presented higher accumulated species richness as well as a higher probability of finding new species if sampling effort were increased only in winter time. These trends were the opposite during spring time. Mean species richness and mean bird abundance were lower at the woodland islets than at the abandoned field in both seasons. We found a higher abundance of open-habitat specialist species in the abandoned field. Woodland islets favoured the wintering of chiffchaff Phylloscopus collybita. We did not find any effects on the only forest specialist species (blue tit Parus caeruleus) in spring. Bird richness and abundance were higher in edge islets than in inner islets. The introduction of larger and mixed plantations connected by hedgerows and a management that favoured the development of big trees, a lower tree density and a diverse shrub layer could promote bird diversity, allowing forest specialists and open-habitat species to coexist at the landscape scale.

Highlights

This study assesses whether the afforestation approach consisting in the introduction of woodland islets in ‘agricultural seas’ can reconcile the restoration of woody vegetation and the persistence of open-habitat bird populations, providing further opportunities for other forest species to enrich bird diversity at the landscape level
We focused on two main objectives: 1) to analyse the influence of woodland islets on local bird communities as compared with non-afforested abandoned cropland, and 2) to study the structural characteristics and landscape design that condition the utilization of the islets by birds
The results indicate that the introduced woodland islets excluded open-habitat species at the local scale and that breeding of forest species was not favoured, but they tend to promote some forest species’ wintering

Summary

Introduction

This study assesses whether the afforestation approach consisting in the introduction of woodland islets in ‘agricultural seas’ can reconcile the restoration of woody vegetation and the persistence of open-habitat bird populations, providing further opportunities for other forest species to enrich bird diversity at the landscape level. Suárez-Seoane et al (2002) found in the bird community of agricultural land in northern Spain that the trend in avian diversity with successional stage differed little between Mediterranean and Eurosiberian species in winter time. One of the alternatives proposed for abandoned farmland is the recovery of forest ecosystems by planting woody species, especially where the lack of propagules, their dispersers or environmental constraints reduce the potential for natural regeneration This is the case of large expanses of croplands, olive groves and vineyards in central Spain, where plantations subsidized by the Common Agricultural Policy are increasingly frequent since 1993. With regards to bird conservation, the aim of these programs could be to promote forest species diversity in areas where open-habitat species have declined. It is necessary to find a proper design and management of plantations that optimises their value for forest species, while making them compatible with the maintenance of open-habitat bird populations

Methods

Results

Conclusion