Interactions of ectomycorrhizas and above-ground insect herbivores on silver birch.

Mycorrhizas are mostly beneficial to host plant growth and survival, e.g., due to improved water and nutrient uptake and enhanced pathogen protection, but also a significant amount of host plant carbon is allocated below-ground to support the mycorrhizal growth. These facts and on the other hand the possibility of mycorrhizas to mediate changes in above-ground defensive chemistry may affect performance of above-ground insect herbivores with different feeding guilds. To see the functionality of complex interaction between mycorrhizal status of plants, host plant chemical quality and insect herbivore performance in a wider ecological scale, studies should be conducted in field conditions and factors contributing to global climate change, such as elevated tropospheric ozone (O), should also be considered. We recently demonstrated in laboratory study, that insect herbivore response to ectomycorrhizal status of birches was dependent on the fungal species forming ectomycorrhiza and the degree of specialization and feeding guild of insects. In this addendum we provide results from the field study where silver birch ( Roth.) seedlings were, in addition to mycorrhizal manipulation, exposed to low-level O and the host plant growth and chemical quality was analysed as well as the performance of two insect herbivores with different feeding guilds was tested.