Soil toxicity and species dominance rather than nutrient availability drive plant species richness in swamp forests of Central Europe
Data files
Dec 12, 2023 version files 36.85 KB
Abstract
Aim: A resource-based conceptual model of plant diversity (RBCM) assumes direct relationships between resource supply and the diversity of a local plant assembly. However, the RBCM largely ignores variation imposed by soil toxicity due to climatic effects. Both soil-limiting resources and soil toxicity vary along climatic gradients but their net and interactive effects on plant species diversity remain unknown. We asked how climatic gradients shape resource availability, soil toxicity and dominance of herb-layer graminoids, and how these predictors control local species diversity of herbs and bryophytes.
Location: Swamp forests, Central Europe
Taxon: Vascular plants, bryophytes
Methods: Alpha taxonomic diversity of vascular plants and bryophytes was counted for 101 vegetation plots sampled in temperate swamp forests distributed along an 800-km geographical gradient across the Continental, Alpine and Pannonian biogeographical regions. Path analysis (structural equation modelling) was used to quantify the direct and indirect effects of climatic variables (potential evapotranspiration; PET), limiting resources (soil N/P, Ca, C/N, proxies for light and water availability), and soil toxicity (Mn) on graminoid dominance and community diversity.
Results: PET negatively influenced species richness of both groups analysed either directly or indirectly through its positive effect on the cover of graminoid species. Alpha diversity of herbs was additionally reduced by soil toxicity (Mn). Limiting resources correlated either with species dominance (canopy shading, soil Ca) or with PET (soil N/P ratio), but they did not control species richness pattern.
Main Conclusions: Climate, soil toxicity and species dominance determined alpha diversity instead of the expected importance of soil limiting resources. These results are key to advancing the theoretical framework of the RBCM. Increased soil toxicity (Mn) in well-watered regions favours the dominance of plant competitors at the expense of less tolerant species. This implies a potential threat to wetland diversity under ongoing climate change.
README: Soil toxicity and species dominance rather than nutrient availability drive plant species richness in swamp forests of Central Europe
https://doi.org/10.5061/dryad.djh9w0w6g
Vegetation and ecological data were retrieved from original field research of authors conducted in three biogeographical regions (Continental, Alpine and Pannonian) of Central Europe. We sampled 101 vegetation plots in stands of the Alnus swamp forests during the period of 2010–2019 using the traditional European phytosociological approach. A list of all vascular plants and ground-dwelling bryophytes was created in each plot. The dataset includes species richness for herb-layer plants (referred to as herbs) and bryophytes. Alpha diversity values are accompanied by a set of explanatory variables associated with the resource based conceptual model of plant diversity. We measured and/or calculated climatic (large-scale) variables and several site productivity variables (i.e. soil fertility measures, light and water conditions), environmental harshness (soil toxicity) and plant graminoid dominance. Summary statistics for all predictors (explanatory variables) and plant taxonomic diversity (dependent variable) in swamp forests are shown in Appendix S1 of the study.
Description of the data and file structure
The first column shows vegetation plots (numbered consecutively) recorded in swamp (alder-dominated) forests, and the row shows the names of the variables. Alpha taxonomic diversity (species richness) was counted for herb-layer species (herbs) and for ground-dwelling bryophytes. The species richness values are followed by the predictors used. These include climate (temperature [°C], precipitation [mm], aridity index, potential evapotranspiration [mm] and their seasonal values, latitude and elevation [m a.s.l.]), soil (pH, concentration of Ca [mg/kg], Mg [mg/kg], K [mg/kg], P [mg/kg], Mn [mg/kg], Fe [mg/kg], total C [%], total N [%], C/N, N/P, N/K ratios), proxies for light (canopy shading [%]) and water (waterlogging) conditions [binary variable], and plant graminoid dominance [%]. The column entitled "Biogeographical regions" shows the affiliation of each vegetation plot to the biogeographical region (Continental, Alpine, Pannonian). The last two columns give the geographical coordinates (latitude and longitude) of each plot.
Sharing/Access information
The geographical coordinates of each plot were used to derive climatic data. Temperature and precipitation (including their seasonal values) were retrieved from the CHELSA database. Aridity index and potential evapotranspiration (PET) were obtained from the Global Aridity and Potential Evapotranspiration Database ver. 3. Soil sampling and recording of water and light conditions (waterlogging/canopy shading) were performed in each plot.
Code/Software
All statistical analyses were conducted in R (R Core Team, 2021). Piecewise SEM models were calculated using the ‘piecewiseSEM’ package (ver. 2.1.2).