Reed bed vegetation structure and plant species diversity depend on management type and the time period since last management

Abstract

AbstractQuestionReed beds, dominated by common reed (Phragmites australis), have high ecological value. Several studies have examined the differences between managed and unmanaged reed beds without taking into account the time passed since the last management. In this paper, we seek to answer the question: how does the time passed since last management and the management method itself affect the plant community and the habitat structure of reed beds?Location“De Østlige Vejler,” Northern Jutland, Denmark.MethodsWe examined four reed bed treatments — beds either cut or harvested during the year of the study (0‐year‐old reed beds) and reed beds harvested 3 and 25 years ago, respectively. The reed bed plant communities and the reed bed habitat structure were determined in May and August. We tested the data for overall between‐treatment differences (multivariate analysis of variance [MANOVA] and principal components analysis [PCA]) and specific differences in the plant community and habitat structure (Kruskal–Wallis).ResultsThe plant community differed significantly between the four reed beds according to treatment, and each reed bed exhibited unique species. Species richness was significantly higher in the recently harvested reed beds (0 and 3 years since harvest) compared with the 25‐year‐old reed beds. Harvest sparked reed rejuvenation and increased the growth of new reeds. The 3‐year‐old reed bed had a habitat structure that equally resembled that of the newly harvested (e.g., similar green reed shoot density) and the 25‐year‐old reed beds (e.g., similar height). Cutting, as opposed to harvesting, created a plant community adapted to less light availability.ConclusionsTo secure most plant species and most variation in habitat structure, reed beds should contain a mosaic of differently aged and differently managed patches. Previous studies have disagreed on the effect of management on plant species diversity, which could be explained either by different reed bed age or different sampling periods.