Long-term changes in the invertebrates associated with the litter of Phragmites australis in a managed reedbed

Faunal changes within a managed bed of the common reed (Phragmites australis (Cav.) Trin.) were monitored by bi-monthly sampling over 6 years. The reedbed was subject to an annual cycle of summer draw-down and winter reflooding. Water level fluctuations annually result in two distinct communities becoming established, a wet (submersion) community composed of aquatic invertebrates and a dry (exposure) community composed of terrestrial and semi-aquatic taxa. The most numerous family found in the sampling programme was the Chironomidae. Reedbeds are ecotonal wetlands with the fauna being opportunistic resulting principally from range extension of communities in the neighbouring aquatic and terrestrial areas of permanence. Colonization from aquatic refugia following flooding is relatively slow. The alternation annually between the submergence and exposure conditions is highly disruptive and results in low species diversity and a reduction in invertebrate numbers. The high degree of inter-annual variability recorded demonstrates the importance of long-term sampling programmes.