Multi-phase recovery of carabid assemblages during 19 years of secondary succession in forest stands disturbed by windstorm without salvage logging in northern Poland.

Windstorms impact the functioning and structure of forests and cause economic losses. For this reason, various potential methods of regenerating windthrown stands are investigated. Some of these studies use invertebrates, such as carabid beetles (Col., Carabidae). Salvage logging is used to recoup some of the economic ecosystem losses but increases the environmental impact of windthrow. I sampled ground beetles annually over 19 years (2003-2021y) in stands without salvage logging to test the effect of three varying levels of disturbance (severely, moderately and least disturbed stands with canopy cover of 10-30 %, 40-60 % and 70-90 %, respectively) on the regeneration of carabid assemblages and to determine its association with changes in the soil environment and in the recovering stands. Increased disturbance severity increased the abundance (up to 0.4 ind/trap/day) and species richness of ground beetles (up to 16.4) and proportion of beetles associated with early successional habitats (up to 53.5 %). Recovery of carabid assemblages and the environment was slowest in the severely disturbed stands, where at high soil pH nitrification initially increased the pool of nitrogen in the soil (up to 0.3), which was exploited by nitrophilous grasses taking over the space (up to 37,5 %), limiting the occurrence of forest species (decrease from 82.2 % to 51.4 %) and delaying the development of natural regeneration. Carabid recovery and ecosystem regeneration were associated with forest mosses surviving (84.1 % coverage) in patches with a high leaf area index (up to 1.9) and with the presence of Vaccinium vitis-idaea (up to 53.3 % coverage) in the moderately and least disturbed stands. The study indicated advanced successional development of carabid assemblages in less disturbed stands which can regenerate naturally. Natural recovery of carabids and regeneration of the most disturbed stands, rapidly taken over by nitrophilous grasses, was impeded; therefore, such stands should be regenerated traditionally.