Mulching time of forest meadows influences insect diversity

1. The diversity in meadows is affected by numerous aspects, such as the amount and type of fertilisation and the timing and frequency of cutting. The effects of mowing on the diversity of plants and insects have been studied in detail. However, the effect of mulching (vegetation is cut, shredded, and left in place, instead of being removed) on insects in small forest meadows has received limited scrutiny to date.2. In this study, we examined how different mulching times influenced insect diversity of forest meadows. We sampled insect larvae and observed flower-visiting insects at 24 sites in the Northern Black Forest in south-west Germany. We applied four treatments with six replicates each: (i) mulching in June, (ii) mulching in September, (iii) mulching in June and September, and (iv) no mulching as a control.3. The overall larval community was dominated by Symphyta (45%, Hymenoptera) and Lepidoptera (44%). The flower-visiting insect community was dominated by Syrphidae (80%, Diptera).4. The insect larvae were negatively influenced by all mulching treatments. The abundance and species richness of flower visitors was reduced by mulching in June only and by mulching in both June and September.5. Summary: Given that meadow management is required for conserving grassland diversity our results indicate that for insect larvae other mulching methods, than those we tested, such as mulching with an arthropod-friendly mulching machine, strip-mulching, or delayed mulching may help this crucial stage of insect development. For insect flower visitors mulching in September is beneficial.