Ewa Jabłońska

Low investment in sexual reproduction threatens plants adapted to phosphorus limitation

Plant species diversity in Eurasian wetlands and grasslands depends not only on productivity but also on the relative availability of nutrients, particularly of nitrogen and phosphorus. Here we show that the impacts of nitrogen:phosphorus stoichiometry on plant species richness can be explained by selected plant life-history traits, notably by plant investments in growth versus reproduction. In 599 Eurasian sites with herbaceous vegetation we examined the relationship between the local nutrient conditions and community-mean life-history traits. We found that compared with plants in nitrogen-limited communities, plants in phosphorus-limited communities invest little in sexual reproduction (for example, less investment in seed, shorter flowering period, longer lifespan) and have conservative leaf economy traits (that is, a low specific leaf area and a high leaf dry-matter content). Endangered species were more frequent in phosphorus-limited ecosystems and they too invested little in sexual reproduction. The results provide new insight into how plant adaptations to nutrient conditions can drive the distribution of plant species in natural ecosystems and can account for the vulnerability of endangered species.

Importance of water level dynamics for vegetation patterns in a natural percolation mire (Rospuda fen, NE Poland)

Although conservation of percolation mires is very important for the European biodiversity, our understanding of their functioning is still insufficient, as most of the studied sites are to some extent degraded. We present a study on the relationship between vegetation patterns, hydrochemical gradients and water level fluctuations carried out in the Rospuda valley (NE Poland), which was recently discovered for science as a uniquely preserved fully functioning percolation mire. Vegetation composition, mire water chemistry and water level dynamics were studied along five transects perpendicular to the valley. Eight major vegetation types were identified: brown moss-small and slender sedge fens, Sphagnum-small sedge fens, brown moss-tall sedge fens, tall sedge-reed fens, pine-birch fen woodlands and shrublands, spruce fen woodlands, inundated alder woodlands, alder spring fen woodlands. The seasonal dynamics of water table was revealed as the major factor explaining vegetation patterns. The studied chemical parameters were relatively homogeneous in the whole mire—there is a rather uniform type of mineral-rich nutrient-poor subsurface water all across the fen.

Chloroplast DNA variation of Betula humilis Schrk. in Poland and Belarus

Betula humilis is an endangered plant species in Central Europe. In order to protect this species, it is necessary to document its genetic diversity in this region and to identify areas for conservation prioritisation. As molecular investigations conducted throughout the ranges of many plant species have shown that the highest genetic diversities are found within former glacial refugia and/or within the contact zones of different phylogenetic lineages, we investigated the reasons underlying the considerable genetic variation of B. humilis in northeastern Poland revealed previously using nuclear microsatellites. We analysed 365 individuals of B. humilis from 19 populations and 67 specimens of Betula pendula and Betula pubescens sampled in four geographical regions in Poland and Belarus for polymorphism in chloroplast PCR-restriction fragment length polymorphism markers. Genetic data strongly suggested that B. humilis could have survived the Last Glacial Maximum at higher latitudes, but the hypothesis of a refugium in southeastern Poland was rejected. Chloroplast DNA analysis confirmed high genetic diversity in some populations in northeastern Poland. This phenomenon can likely be explained in terms of a suture zone, as the high haplotypic richness was followed by hT ≤ vT. Similar patterns of haplotype distributions in the birches under study and high introgression ratio (IG = 0.71) among B. humilis and congeneric trees suggested that postglacial recolonisation of the shrub birch was complicated by haplotype sharing with other birches.

Could Betula humilis have survived the last glaciation at a current margin of its distribution? Testing the hypothesis of a glacial refugium using nuclear microsatellites

The probability of population extinction seems to differ within the species range. Populations occupying former glacial refugia could harbor substantial genetic resources, hence they should be less prone to extirpation. It was hypothesized that the shrub birch Betula humilis could have survived the Last Glacial Maximum (LGM) at the current southwestern margin of its range. Using ten nuclear microsatellites, we studied genetic variation within and between 18 localities of B. humilis situated in marginal and subcentral areas. Six marginal populations were located in areas covered by an ice sheet during the LGM, and the remaining samples came from unglaciated areas. Analysis of private allele frequencies as well as hierarchical AMOVAs conducted for geographical regions, marginal versus central populations, and glaciated versus unglaciated areas did not confirm the hypothesis of glacial isolate of the shrub birch in southeastern Poland. On the other hand, very high genetic variation in some localities in northeastern Poland was found. Survival in periglacial areas followed by broad-fronted colonization or the existence of an admixture zone of phylogeographic lineages was proposed to explain this phenomenon.

Understanding the Long Term Ecosystem Stability of a Fen Mire by Analyzing Subsurface Geology, Eco-Hydrology and Nutrient Stoichiometry – Case Study of the Rospuda Valley (NE Poland)

We explored the background of differences in long–term stability between two parts in an undisturbed mire system (Rospuda fen, NE Poland). We re-constructed the Holocene history of the mire and compared it with current vegetation, water level dynamics, water chemistry and nutrient availability in two basins: A, where the mire terrestrialised a deep gyttja–filled lake, and B, where peatland developed directly on fluvial sands. The current vegetation of sedge–moss fens was described in 10 relevés from each basin, groundwater was sampled from piezometers and analysed for major ions, while its relative water level was recorded during three years. N and P content was measured in above ground vascular plant samples collected within the relevés. Fens in basin A were stable in the past, whereas fens in basin B switched between open and wooded or reed–dominated phases. In basin B, where trees are more abundant, we found higher water fluctuations, occurrence of river floods and a higher N:P ratio than in basin A. Our interpretation follows that the subsurface geology of fen basin may govern mire stability by determining its hydrological–buffering capacity, which may affect N:P ratios. Our results suggest that P–limited fens are more vulnerable for changes in water level.

Erratum to: Development of bog-like vegetation during terrestrialization of polyhumic lakes in north-eastern Poland is not accompanied by ecosystem ombrotrophication

The aim of the present study was to use the analysis of surface water chemistry to understand vegetation succession pathways in terrestrializing polyhumic lakes. We hypothesized that Sphagnum mire development was accompanied by a decrease in the mineral content in water. A total of 111 vegetation plots along 23 transects were analysed in 11 lakes and adjacent peat lands in the Wigry National Park (NE Poland). The vegetation of the lake-mire systems forms distinct zones: (1) nymphaeid-, bladderwort- and bryophyte-dominated aquatic vegetation; (2) sedge-dominated edge of the Sphagnumcarpet; (3) quaking, extremely poor fen with various Cyperaceae; (4) non-quaking, Eriophorum vaginatum-dominated bog-like vegetation and (5) pine woodland. Surface water corrected conductivity (ECcorr.), pH, COD-KMnO4 and Ca2+, Mg2+, Fetot. and SiO2 were measured along the transects. The environmental gradients best explaining the observed pattern were pH (with the highest values in the lake and the lowest in the bog-like vegetation) and COD-KMnO4 (showing an inverse direction). At least in some Sphagnum-mires conditions were more minerotrophic than in the lakes. The process of humic lake overgrowing by Sphagnum-mires in NE Poland results in pine woodlands on mineralised peat. The climate conditions in NE Poland, combined with evapotranspiration accelerated by encroaching trees, do not seem to support the development of ombrotrophic bogs.