Seasonal shift in carabid phenology over a period of 18 years

Abstract

The present study is based on a 20-year study of fields that were previously farmed conventionally and then changed to being farmed organically and a 10-year study of a conventionally farmed field in south-eastern and central Schleswig-Holstein, North Germany, respectively. The carabid beetles were sampled throughout each year using pitfall traps. The analysis aimed to study the changes in the phenology in terms of activity-density associated with changing climate. Climate data revealed an increase in temperature during the period of this study, which was not significant during the single study periods, but significant if a longer period of 70 years is considered. In particular, spring temperatures (March/April) increased. Approximately 36% of the species became active earlier. For 25% of the species their earlier start was not significant but nevertheless associated with temperature increase in spring or the number of cold days (< 0°C) and warm days (> 5°C) in March/April. In total, the earlier start of 69% of the species can in some way be associated with a change in climate in spring. Species with a flexible response to temperature were mostly indifferent to the temperature increase. Comparisons of the data over the 30-year period indicate that the process lasted for at least one to three decades. It is likely that the changes in biological processes caused by global climate change will affect the composition of species and competition between them in the future.