Systematic randomised sampling along three landscape transects in the Netherlands reveals the geographically structured variation in Rubus scrubs

Rubus scrubs belong to the least known and understood vegetation types in Europe. At least in part this is due to the complicated taxonomy and species richness of the main genus in these scrubs. In this study, we explored the regional diversity of Rubus scrubs in the Netherlands. In order to get a clear picture on their species composition free from personal preferences, we used a systematic-randomised sampling scheme to collect data in the three main Rubus regions in the Netherlands along three 100 km long transects. In 185 releves we recorded 67 known (and three unknown) Rubus species. The releves could be assigned to seven units described in the Dutch national vegetation classification: the Rubetum grati, Rubetum silvatici, Lonicero-Rubion silvatici, Dicrano-Juniperetum, Pruno-Rubetum vestiti, Pruno-Rubion radulae, and the Basal Community Rubus armeniacus. From our study we conclude that the regional variation in Rubus scrubs is substantial, and that only a part of this variation was described in the Dutch national vegetation overview. Especially within the Rubetum silvatici and the Pruno-Rubion radulae regionally distributed types can be distinguished, which seem to be confined to old landscapes, whereas younger landscapes only harbour common types, or are even devoid of bramble scrubs. The density of releves made in this study emphasize the importance of bramble scrubs in the landscape of north-western Europe, and we advocate more awareness of the value represented by bramble dominated communities. The vast number of Rubus species, many of which having a (very) restricted distribution area, complicate the classification of these scrubs, and can easily lead to the description of countless vegetation types with only a regional distribution. On the other hand, such regionally distributed communities can be of importance for nature conservation because they can harbour rare species, and they add to the regional identity and ?-diversity, and therefore should be recognised at some level.