Changes in species richness and species composition of vascular plants and bryophytes along a moisture gradient

Změny druhové bohatosti a druhového složení cévnatých rostlin a mechorostů podél vlhkostního gradientu Eva H e t t e n b e r g e r o v á 1 , Michal H á j e k 1,2 , David Z e l e n ý 1 , Jana J i CZ-61137 Brno, Czech Republic, e-mail: [email protected], [email protected], [email protected], [email protected], [email protected] We focused on the gradient in moisture along transects of from 8 to 30 m in length from spring fen to semi-dry grassland vegetation. We selected an area in the calcium-rich part of the Western Carpathian flysch zone (Czech and Slovak Republics) where small spring-fed fens occur in close contact with semi-dry grasslands. Altogether 126 vegetation plots of 75 × 75 cm were sampled along 15 transects (one per locality) that each extended from the wettest part of a spring-fed fen into the surrounding semi-dry grassland. In addition, samples of standing plant biomass and soils were analysed for nutrients (N, P, K, C, Ca) and the upper-soil moisture measured. Using this study system and these sampling methods, we can test directly the effects of moisture and so avoid the confounding effects of different background environmental conditions that occur when data from many distinct sites is used. Data were processed using linear mixed-effect models and other statistical techniques. The trend in the number of species of vascular plants was unimodal with the optimum skewed towards lower moisture values. This response was not caused by an edge effect alone as replacing the moisture gradient with the positions of plots on transects resulted in a much weaker unimodal relationship and there was a group of species that occurred mainly in the species-richest moderately moist plots but did not occur in fens or the driest grasslands. The correlations between species richness and productivity (positive) and soil calcium (negative) differed from most of those reported in the literature, which suggests that the observed relationship between species richness and moisture was probably not greatly confounded by these factors. Species richness correlated negatively and the percentage of endangered species positively with the N:P biomass ratio, which is in accordance with other published results, but their correlations with moisture were stronger. For bryophytes, species richness linearly decreased towards the dry plots and did not correlate with any of the nutrients measured. Most of the species of vascular plants and bryophytes in the wettest patches were fen specialists, while more generalists made up the species richness in grasslands, including the species-richest patches. For bryophytes, the percentage of specialists was very high in fen plots. Although Mantel tests showed that bryophyte and vascular plant species turnovers were similar, we recorded substantial differences in their species richness patterns. Comparison with the results of a previous study on molluscs revealed a greater similarity between bryophytes and molluscs than between molluscs and vascular plants in terms of correlations between species richness and environmental variables. We argue that soil moisture should be taken into account when explaining current patterns in diversity in extremely rich temperate grasslands. K e y w o r d s

GrassPlot - a database of multi-scale plant diversity in Palaearctic grasslands

GrassPlot is a collaborative vegetation-plot database organised by the Eurasian Dry Grassland Group (EDGG) and listed in the Global Index of Vegetation-Plot Databases (GIVD ID EU-00-003). GrassPlot collects plot records (releves) from grasslands and other open habitats of the Palaearctic biogeographic realm. It focuses on precisely delimited plots of eight standard grain sizes (0.0001; 0.001;... 1,000 m(2)) and on nested-plot series with at least four different grain sizes. The usage of GrassPlot is regulated through Bylaws that intend to balance the interests of data contributors and data users. The current version (v. 1.00) contains data for approximately 170,000 plots of different sizes and 2,800 nested-plot series. The key components are richness data and metadata. However, most included datasets also encompass compositional data. About 14,000 plots have near-complete records of terricolous bryophytes and lichens in addition to vascular plants. At present, GrassPlot contains data from 36 countries throughout the Palaearctic, spread across elevational gradients and major grassland types. GrassPlot with its multi-scale and multi-taxon focus complements the larger international vegetationplot databases, such as the European Vegetation Archive (EVA) and the global database " sPlot". Its main aim is to facilitate studies on the scale-and taxon-dependency of biodiversity patterns and drivers along macroecological gradients. GrassPlot is a dynamic database and will expand through new data collection coordinated by the elected Governing Board. We invite researchers with suitable data to join GrassPlot. Researchers with project ideas addressable with GrassPlot data are welcome to submit proposals to the Governing Board

Is species richness of small spring fens influenced by the spatial mass effect?

Ecological theory predicts that the species composition of island habitats is, among others, shaped by the mass effect of nearby ill-adapted populations, but this has rarely been tested. We investigated small calcareous spring fens scattered within species-rich grasslands in a region in which particular locations differ in climatic and edaphic conditions. Fens in colder, moister and less calcareous north-eastern (NE) locations harboured more plant species from surrounding grasslands and displayed higher similarity with the surroundings than the fens in warmer, drier and more calcareous south-western (SW) locations. Fen species richness correlated significantly with surrounding species richness in the NE locations, whereas no correlation was found for the SW locations. Fens in SW locations are characterized by both intense tufa formation, which creates extreme ecological conditions, and the contrasting environmental conditions compared to surrounding grasslands. We demonstrated that the mass effect does not always significantly shape the species composition of island habitats and that the landscape species pool may not influence extreme habitats. This finding accords with the Intermediate difference hypothesis, which predicts a unimodal relationship between the strength of the spatial mass effect and the ecological similarity between neighbouring plots, and could be utilized in the selection of model habitats for exploring large-scale ecological phenomena without the possibly confounding spatial mass effects