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

Question Reed 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 ostlige Vejler," Northern Jutland, Denmark. Methods We 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). Results The 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. Conclusions To 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.Peer reviewe

A multi-nuclide approach to constrain landscape evolution and past erosion rates in previously glaciated terrains

Cosmogenic nuclides are typically used to either constrain an exposure age, a burial age, or an erosion rate. Constraining the landscape history and past erosion rates in previously glaciated terrains is, however, notoriously difficult because it involves a large number of unknowns. The potential use of cosmogenic nuclides in landscapes with a complex history of exposure and erosion is therefore often quite limited. Here, we present a novel multi-nuclide approach to study the landscape evolution and past erosion rates in terrains with a complex exposure history, particularly focusing on regions that were repeatedly covered by glaciers or ice sheets during the Quaternary. The approach, based on the Markov Chain Monte Carlo (MCMC) technique, focuses on mapping the range of landscape histories that are consistent with a given set of measured cosmogenic nuclide concentrations. A fundamental assumption of the model approach is that the exposure history at the site/location can be divided into two distinct regimes: i) interglacial periods characterized by zero shielding due to overlying ice and a uniform interglacial erosion rate, and ii) glacial periods characterized by 100% shielding and a uniform glacial erosion rate. We incorporate the exposure history in the model framework by applying a threshold value to the global marine benthic δ18O record and include the threshold value as a free model parameter, hereby taking into account global changes in climate. However, any available information on the glacial-interglacial history at the sampling location, in particular the timing of the last deglaciation event, is readily incorporated in the model to constrain the inverse problem. Based on the MCMC technique, the model delineates the most likely exposure history, including the glacial and interglacial erosion rates, which, in turn, makes it possible to reconstruct an exhumation history at the site. We apply the model to two landscape scenarios based on synthetic data and two landscape scenarios based on paired 10Be/26Al data from West Greenland, which makes it possible to quantify the denudation rate at these locations. The model framework, which currently incorporates any combination of the following nuclides 10Be, 26Al, 14C, and 21Ne, is highly flexible and can be adapted to many different landscape settings. The model framework may also be used in combination with physics-based landscape evolution models to predict nuclide concentrations at different locations in the landscape. This may help validate the landscape models via comparison to measured nuclide concentrations or to devise new effective sampling strategies

Neutron guide-split: A high performance guide bundle concept for elliptical guides

We present a new guide-split concept for transporting cold and thermal neutrons to multiple instruments from a single beam port at a neutron facility without compromising the useful neutron brilliance notably for any of the instruments.Elliptical guides are capable of transporting an almost completely filled phase space within a large divergence (±2° for cold neutrons). It is therefore possible to place several secondary guides side by side pointing in slightly different directions using the end of a primary guide as a virtual source. The instruments placed at the secondary guides hence exploit different parts of the phase space transported by the primary guide. In addition, the resulting kink between the primary and secondary guide eliminates line of sight.Using ray-tracing simulations of three different set-ups (with two, four, and eight secondary guides) we show that it is possible to illuminate at least eight sample positions from one beam port with a brilliance transfer above 90% on each sample on a 150 m long instrument. This has been done for a phase space volume comprised of an area of 1×1 cm2 and a maximum divergence of±0.5° within a wavelength band of 4.25–5.75 Å. We show, by a full virtual experiment, an example of applying the guide-split concept to an instrument proposed for the European Spallation Source, namely a magnetism diffractometer

Can reed harvest be used as a management strategy for improving invertebrate biomass and diversity?

The succession-driven reed bed habitat hosts a unique flora and fauna including several endangered invertebrate species. Reed beds can be managed through commercial winter harvest, with implications for reed bed conservation. However, the effects of winter harvest on the invertebrate community are not well understood and vary across studies and taxonomic levels. The aim of this study was to investigate the effects of reed harvest on invertebrate communities. Ground-dwelling and aerial invertebrates were continuously sampled for 10 weeks in the largest coherent reed bed of Scandinavia in order to assess how time since last reed harvest (0, 3, and 25years) influences invertebrate biomass, biodiversity and community structure across taxonomic levels. Biomass was measured and all specimens were sorted to order level, and Coleoptera was even sorted to species level. The invertebrate community showed distinct compositional differences across the three reed bed ages. Furthermore, biomass of both aerial and ground-dwelling invertebrates was highest in the age-0 reed bed and lowest in the age-25 reed bed. Generally, biodiversity showed an opposite trend with the highest richness and diversity in the age-25 reed bed. We conclude that it is possible to ensure high insect biomass and diversity by creating a mosaic of reed bed of different ages through small-scale harvest in the largest coherent reed bed in Scandinavia. The youngest red beds support a high invertebrate biomass whereas the oldest reed beds support a high biodiversity. Collectively, this elevate our understanding of reed harvest and the effects it has on the invertebrate communities, and might aid in future reed bed management and restoration.Peer reviewe