Geographical patterns in the flora of Cambridgeshire (v.c.29)

Cambridgeshire data collected for the BSBI’s Atlas 2020 project include 347,496 records at monad (1 km) or finer resolution. We used these data to cluster taxa by spherical k-means to produce 21 clusters of taxa with similar patterns of distribution. Some of the clusters correspond to well-defined habitats such as chalk grassland, ancient woodland, traditional fenland, and saline riversides and roadsides. Other clusters were less expected, corresponding to arable clayland, washland (the Ouse and Nene washes), waste ground and garden escapes. There was a cluster of ubiquitous species and another of common arable weeds. The distributions of the clusters are displayed as coincidence maps. Some species are intermediate between two clusters. These can be recognised by their relatively poor goodness of fit to any one cluster. The clusters differ markedly in ecological attributes and whether they include rare or threatened species. We interpret these differences using Ellenberg values and the vascular plant Red List for England.

Rediscovery of Cyperus flavescens (Cyperaceae) on the northeast periphery of its range in Europe

In recent years, three large populations of Cyperus flavescens were found in Poland, the richest occurrence of this species in over 30 years. The goal of this research is to determine the habitat factors lead to the mass occurrence of C. flavescens and the present situation of that species and its habitat in Central Europe. Soil conditions of the three populations were studied. To determine the correlation between the occurrence and abundance of species and the chemical parameters of the soil, the DCA and CCA methods were used. The DCA of environmental Ellenberg values was made for all relevés known from Poland. The occurrence of C. flavescens in plant communities in Central Europe was studied. The maximum entropy method was used for potential distribution analysis of C. flavescens. All analyzed traits are important for this species and none has an advantage over another, so the environmental factor affecting the occurrence of C. flavescens is different from the tested. Analysis on Ellenberg values indicate that the longest gradients are temperature, moisture and nutrients. The analysis of vegetation data involving Cyperus flavescens available from Central Europe indicates that this species occurs mainly in the company of Juncus bufonius and Plantago intermedia, whereas other species of the Isoëto-Nanojuncetea class appear rarely. In MaxEnt analysis based on bioclimatic variables, the most important variable is BIO1 (Annual Mean Temperature). The results of our observation indicate that anthropogenic factors such as grazing livestock have a positive effect on the occurrence of the species. It is also very likely that the species is promoted by very warm summers with only short periods of heavy rains. A map of the potential distribution of C. flavescens in Central Europe created according historical and future data show an extension of the range of potential habitats to the north and east.