Securing Biodiversity in Breckland - European Commission

River Valley AssemblagesRiver valley habitats include wet alluvial woodlands, valley fen and valley-head fen and river channelswith diverse within-river habitats and micro-habitats.The biodiversity value of riverine habitatsThe Natural England Natural Area Profile recognised the value of riverine habitats to species such asbats, water vole and otter, but the resources were not available at that time to conduct a fullysystematic audit across all landscape elements in Breckland.Compared to wetlands, littoral margins and standing water, many fewer species were found to beassociated with running water habitats. Species did however; include 39 RDB species that requireeither standing or running water, 16 only occurring in running water in open conditions and 2requiring running water in shaded conditions. It is notable that the mapped distribution of Brecklandconservation priority species picks out the River Nar as a linear hotspot (Figure 32).There were no Breckland specialities associated with running water. However, it is important torealise the importance of littoral, wet meadow, reedbed, carr and isolated trees along river marginsin providing conditions suitable for species in the wetland and littoral guilds.Wet woodlandAromia moschata - Notable: BColeoptera – Cerambycidae (Longhorn Beetle)This beetle is one of a number of invertebrates withinthe wet woodland guild which can be regarded as carrand woodland close to water, e.g. riverine, species. Itrequires mature poplars (Populus) and willows (Salix).Oviposition occurs on the trunk or the base of healthybranches, larvae then bore into the sapwood and whenat the heartwood tunnel vertically for 30-40cm. Adultsare recorded from May to September and occur on avariety of flowers particularly Umbelliferae (e.g.angelica, cow parsley and chervil). Formerly it was© Christoph Benisch www.kerbtier.demuch more widespread and it is threatened by theclear-felling of wet woodland and riverside trees. Furthermore the cessation of pollarding maythreaten this species, but it is important that pollarding should be carried out on rotation as largepopulations of the beetles can occur in lines of pollards.180