Responses of Collembola and Protura to tree girdling – some support for ectomycorrhizal feeding

Abstract

Ectomycorrhizal (EM) fungi are very common in forest soils, but their role as a food resource for fungivorous soil animals is poorly known. We used two tree-girdling experiments in Picea abies forests and one experiment in a Pinus sylvestris forest, all in northern Sweden, to indirectly test if Collembola and Protura in boreal forest soils prefer EM fungi over other fungi. We assumed that tree girdling will stop the flux of carbohydrates to roots and associated fungi, and thereby inhibit growth and long-term survival of EM fungi. After about one year, proturans decreased in abundance after girdling, indicating that they prefer feeding on EM fungi, while most collembolan species seemed to be unaffected by girdling and the presumed reduction in EM fungi. However, the collembolans Mesaphorura macrochaeta, Anurida granaria and Parisotoma notabilis increased in abundance after girdling in one of the three experiments, and Micranurida pygmaea decreased. With the exception of the latter species, this is in accordance with the common opinion that most Collembola prefer saprotrophic fungi over EM fungi, while Protura are at least partly dependent on EM fungi.

Keywords

• ectomycorrhiza
• food-choice
• microarthropods
• mycorrhizal fungi
• field experiment