Pavel Dřevojan

Synanthropic vegetation of the Eragrostion cilianensi-minoris alliance in the Czech Republic

A synthesis of the alliance Eragrostion cilianensi-minoris in the Czech Republic is presented on the basis of 82 relevés including new unpublished data. A TWINSPAN classification and detrended correspondence analysis were used to identify the main vegetation types included in the alliance Eragrostion cilianensi-minoris. A syntaxonomic revision of the data set revealed five associations of the alliance: Digitario sanguinalis-Eragrostietum minoris, Portulacetum oleraceae, Eragrostio poaeoidis-Panicetum capillaris, Cynodontetum dactyli, and Hibisco trioni-Eragrostietum poaeoidis. The latter was recently found in several arable fields in Southern Moravia (Czech Republic) and was newly characterized.

The type of nutrient limitation affects the plant species richness–productivity relationship: evidence from dry grasslands across Eurasia

The species richness-productivity relationship is one of the most debated patterns in ecology. Species coexistence theory suggests that it could be tightly linked to the type of nutrient limitation (no limitation, single-nutrient limitation, colimitation by several nutrients). Yet, the effects of nutrient limitation on the species richness-productivity relationship have been rarely studied at the regional and continental scales. Combining the predictions of the humped-back model and the niche dimension hypothesis, we hypothesized that an increase in plant species richness with the number of different limiting nutrients is detectable only at higher productivity levels, at which competition for nutrients is more intense. Therefore, we expected the shape of the diversity-productivity relationship to differ between sites colimited by nitrogen (N) and phosphorus (P), sites limited by a single nutrient (either N or P), and sites not limited by any of these nutrients. To test this hypothesis, we used species richness data collected in 10 m x 10 m plots at 694 temperate dry grassland sites across eight regions in northern Eurasia. Productivity ranged from 10 to similar to 500 g/m(2) of above-ground standing biomass. The type of nutrient limitation was identified by critical nutrient ratios alone and their combination with critical nutrient concentrations measured in the plant tissue. Relationships were analysed using generalized linear and mixed-effect models. In line with our expectations, species richness of Eurasian temperate dry grasslands increased more steeply and peaked higher under higher productivity levels at N&P-colimited sites. When nutrient limitation was assessed by both ratios and concentrations, species richness at N&P-colimited sites continued to increase monotonically until the maximum productivity sampled in this study. In contrast, at sites with a single-nutrient limitation or no limitation, the peak in species richness was lower and occurred at a lower productivity of about 300-400 g/m(2). Synthesis. We provide the first evidence that the species richness-productivity relationship may depend on the type of nutrient limitation as predicted by the species coexistence theory. To generalize these findings, the role of nutrient limitation needs to be tested in other ecosystems, including more productive plant communities.

Diversity of fungi and bacteria in species-rich grasslands increases with plant diversity in shoots but not in roots and soil

&NA; Microbial communities in roots and shoots of plants and in soil are important for plant growth and health and take part in important ecosystem processes. Therefore, understanding the factors that affect their diversity is important. We have analyzed fungal and bacterial communities associated with plant shoots, roots and soil over a 1 km2 area in a semi‐natural temperate grassland with 1‐43 plant species per 0.1 m2, to describe the relationships between plant and microbial diversity and to identify the drivers of bacterial and fungal community composition. Microbial community composition differed between shoots, roots and soil. While both fungal and bacterial species richness in shoots increased with plant species richness, no correlation was found between plant and microbial diversity in roots and soil. Chemistry was a significant predictor of bacterial and fungal community composition in soil as was also the spatial location of the sampled site. In this species‐rich grassland, the effects of plants on the microbiome composition seemed to be restricted to the shoot‐associated taxa; in contrast, the microbiomes of roots or soil were not affected. The results support our hypothesis that the effect of plants on the microbiome composition decreases from shoots to roots and soil. &NA; Graphical Abstract Figure. Grassland plant diversity influences the diversity of bacterial and fungal communities in plant shoots but not in roots or soil.