Flower-visiting insects benefit from forest in the surrounding landscape

University essay from Linköpings universitet/Institutionen för fysik, kemi och biologi

Abstract: Habitat loss and fragmentation due to agricultural practices are causing worrying declines in insect diversity and biomass. Agricultural intensification, among other things, have led to a decline in semi-natural grasslands. Forest in the surrounding landscape can have a positive effect on species abundance in grasslands. Clear-cut forest have been identified as a supporting habitat for grassland species as they contain important resources. Clear-cuts can also support a wide variety of insects, both grassland species and forest species. In this study, I examined how different land covers in the surrounding landscape affected species abundance on clear-cuts in southeastern Sweden. Using data of insects collected in three previous studies, I tested the hypothesis that insects on clear-cuts benefit from other clear-cuts in the surrounding landscape. I also tested at which spatial scales the surrounding landscape mainly exerted its influence. The results were not in line with the hypothesis and showed that forest in the surrounding landscape had a positive effect on species abundance on clear-cuts, whereas clear-cuts had a negative effect. There were no clear patterns over different scales, although the smallest scale of a 250 m radius produced the highest number of significant results. A lot of insects recorded on the clear-cuts were generalists associated with both forest and agricultural landscape. The reason for the negative effect of clear-cuts needs further investigation.

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