Towards a better understanding of linear species distribution in river valleys: The abundance of river corridor plants is linked to soil exchangeable potassium and pH.

The phenomenon that some vascular plant species grow mainly or exclusively in the large river valleys of Central Europe constitutes a long-standing distribution puzzle. In our study, we focused on determining which physicochemical properties of soil affect the distribution of river corridor plant (RCP) species. Research that included RCP coverage, the physicochemical properties of soil as well as several topographic and spatial variables were conducted in 10 transects perpendicular to the San River (SE Poland). The sampled plots were located both in close proximity to the river, where the greatest number of RCP populations are concentrated, and along anthropogenic linear landscape elements which have proven to be important for RCP occurrence in areas located away from the riverbed. Spearman rank correlation matrices were constructed to observe the general relationships between particular variables and Boosted Regression Tree models were used for explaining RCP coverage. Our study indicated that in the case of plots located in proximity to the river, the expected coverage of RCP species was highest in plots characterized by a higher soil exchangeable potassium (K) content, as well as in those located closer to the San River and at lower altitudes. In plots situated along anthropogenic linear landscape elements, the expected coverage of RCPs was highest in plots with a high soil exchangeable K content and in those with a high soil pH. The analyses clearly showed that the physicochemical properties of soils indeed affect RCP species occurrence and they require soils with a high exchangeable K content and a high pH. Since these two soil parameters are closely related to soil fertility, and additionally K enhances root development, we suppose that both factors strengthen the competitiveness of RCPs in floodplain ecosystems.

Context matters: the landscape matrix determines the population genetic structure of temperate forest herbs across Europe.

Context: Plant populations in agricultural landscapes are mostly fragmented and their functional connectivity often depends on seed and pollen dispersal by animals. However, little is known about how the interactions of seed and pollen dispersers with the agricultural matrix translate into gene flow among plant populations. Objectives: We aimed to identify effects of the landscape structure on the genetic diversity within, and the genetic differentiation among, spatially isolated populations of three temperate forest herbs. We asked, whether different arable crops have different effects, and whether the orientation of linear landscape elements relative to the gene dispersal direction matters. Methods: We analysed the species' population genetic structures in seven agricultural landscapes across temperate Europe using microsatellite markers. These were modelled as a function of landscape composition and configuration, which we quantified in buffer zones around, and in rectangular landscape strips between, plant populations. Results: Landscape effects were diverse and often contrasting between species, reflecting their association with different pollen- or seed dispersal vectors. Differentiating crop types rather than lumping them together yielded higher proportions of explained variation. Some linear landscape elements had both a channelling and hampering effect on gene flow, depending on their orientation. Conclusions: Landscape structure is a more important determinant of the species' population genetic structure than habitat loss and fragmentation per se. Landscape planning with the aim to enhance the functional connectivity among spatially isolated plant populations should consider that even species of the same ecological guild might show distinct responses to the landscape structure. Supplementary Information: The online version contains supplementary material available at 10.1007/s10980-021-01376-7.

Roadsides provide refuge for orchids: characteristic of the surrounding landscape.

Seminatural habitats are declining throughout the world; thus, the role of small anthropogenic habitats in the preservation of plants is becoming increasingly appreciated. Here, we surveyed the orchid flora of roadside verges in five Central European countries (Austria, Hungary, Romania, Slovakia, and Slovenia) and tested how the surrounding landscape matrix affects the overall number of species and individuals, and also different functional groups of orchids. We found more than 2,000 individuals of 27 orchid species during our surveys. According to our results, the increasing coverage of agricultural and urban areas negatively affects both the number of orchid species and individuals on roadsides. Our study further suggests that differences in the surrounding habitats affect which species are found on roadsides, since the increasing coverage of grasslands or forested areas around orchid occurrences had a significant positive effect on the number of grassland or forest-dwelling species and individuals, respectively. Most variance in orchid numerosity and diversity was explained by the cover of the suitable habitat types of the respective taxa in the surrounding landscape of the sampling points. This highlights the importance of roadsides acting as refugia for numerous species and valuable plant communities as well as in supporting biodiversity in general.