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Sammanfattning

Pure forest stands are commonly believed to be more susceptible to insect herbivore attacks than mixed stands. However, the existing experimental evidence of tree species diversity effects on herbivores in forest ecosystems is scarce and contradictory. In the present study, we compared insect herbivore abundance and Leaf damage on silver birch (Betula pendula) in monocuttures and paired mixtures with Scots pine (Pinus sylvestris) and Norway spruce (Picea abies) in three experiments in the boreal forest zone (SW Sweden, SW and central Finland). In the Finnish experiment, total densities of insect defoliators were highest in birch monocultures and decreased with increase in the proportion of Scots pine in a stand. Densities of Leaf rollers, gall mites and aphids also tended to be higher in birch monocultures than in mixed stands. At the beginning of the season the proportion of birch Leaves damaged by chewing insects in the Finnish experiment was significantly Lower in mixed stands containing 25% of birch and 75% of pine as compared to birch monocuttures and mixtures with 50% of birch and 50% of pine. However, by the end of the season there were no significant differences in herbivore damage between the treatments. In the Swedish experiment, where herbivory monitoring was conducted at the end or at the middle of summer, neither herbivore abundance nor damage differed between birch monocuttures and paired mixtures with Scots pine and Norway spruce. Our results provide only a partial support for the hypothesis that pure forest stands are more susceptible to insect herbivores and demonstrate that the benefits of mixed forests in terms of reduced herbivory are not as straightforward as commonly thought. (C) 2005 Gesellschaft fur Okologie. Published by Elsevier Gmbh. All rights reserved.

Nyckelord

associational resistance; associational susceptibility; forest diversification; herbivore community; pest management; species mixtures

Publicerad i

Basic and Applied Ecology
2006, volym: 7, nummer: 1, sidor: 45668
Utgivare: ELSEVIER GMBH, URBAN & FISCHER VERLAG

SLU författare

UKÄ forskningsämne

Skogsvetenskap

Publikationens identifierare

  • DOI: https://doi.org/10.1016/j.baae.2005.05.003

Permanent länk till denna sida (URI)

https://res.slu.se/id/publ/8635