Carabid community succession during the forestry cycle in conifer plantations

Pitfalls and soil heat extraction were used to sample Carabidae in recently felled (1-4 yr from felling), young (5-27 yr after planting), and old plantations (42-63 yr after planting of Picea sitchensis in northern England, Pitfall catches were useful in recording swift-running species, present at low densities, and a DCA ordination based on the pitfall catches indicated major distribution changes during the plantation cycle. Soil extractions allowed estimation of minimum densities of the abundant species and indicated that both diversity and density were highest in young plantations and lowest in the old plantations. The flightless Trechus obtusus (3.8 mm) was the most abundant species in the soil samples and its population density did not differ significantly between the three stages in the forestry cycle, The winged, highly surface-active species that were early colonisers of clear felled sites and formed a high proportion of the pitfall catch were present at low densities only. The peak in carabid density and diversity coincided with the stage at which the ground flora was most diverse (in both species and structure) and the densities of other soil surface macro-invertebrates were highest, The high carabid density in the young plantations coincided with a the presence of a relatively high proportion of larger carabids (> 5.9 mm) and it is suggested that the increased carabid biomass m(-2) could reflect increased prey availability, The density of winged individuals was higher in the soil samples of carabids from the young plantations than from the clear felled areas and this is attributed to a build up over time of colonising species, adapted to exploiting the short-lived open habitat stage. Species that overwinter in the adult stage were more abundant in the young than in the old plantations and it is suggested that these species are favoured by the relatively high summer daytime temperatures of the open habitat. The interpretation of the successional sequence in the Carabidae was enhanced by the use of heat extraction sampling in conjunction with pitfall catches.