Early Succession of a Boreal Spider Community After Forest Fire‪.‬

ABSTRACT. Ground-living spiders were studied, using pitfall traps, 3-4 months after a wildfire, and then during three post-fire summers. The study area was a pine (Pinus sylvestris) forest in southwestern Finland. Lycosidae dominated in individual numbers at the burned site and Linyphiidae at the control. In species numbers, Linyphiidae dominated at both sites, and Lycosidae, Gnaphosidae and Theridiidae were more species-rich at the burned than control site. The lycosid Xerolycosa nemoralis was dominant at the burned site, and the linyphiid Agyneta cauta at the control. Abundant species found only at the burned site included Xerolycosa nemoralis, Pardosa riparia, Acantholycosa lignaria and Micaria silesiaca. Tapinocyba pallens and Pardosa lugubris occurred at both sites in large numbers. A slight positive effect of fire on the species richness was found. Species with more or less stable abundance at the burned site during the study period included Pardosa riparia, P. lugubris and Diplostyla concolor. Increasing abundance in successive years occurred for Acantholycosa lignaria, Micaria silesiaca, Xerolycosa nemoralis and for the family Lycosidae. Euryopis flavomaculata, Agyneta rurestris, Tapinocyba pallens and the family Linyphiidae showed a decreasing abundance during the study years. The spider community at the burned site remained clearly different compared to the control during three post-fire summers, primarily caused by the abundance of Gnaphosidae and Lycosidae. Keywords: Araneae, ground-living spiders, post-fire succession, pine forest, Finland