Percorrer por autor "Czortek, Patryk"
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- Environmental drivers and spatial scaling of species abundance distributions in Palaearctic grassland vegetationPublication . Ulrich, Werner; Matthews, Thomas J.; Biurrun, Idoia; Campos, Juan Antonio; Czortek, Patryk; Dembicz, Iwona; Essl, Franz; Filibeck, Goffredo; del Galdo, Gian‐Pietro Giusso; Güler, Behlül; Naqinezhad, Alireza; Török, Péter; Dengler, JürgenSpecies abundance distributions (SADs) link species richness with species abundances and are an important tool in the quantitative analysis of ecological communities. Niche-based and sample-based SAD models predict different spatial scaling properties of SAD parameters. However, empirical research on SAD scaling properties is largely missing. Here we extracted percentage cover values of all occurring vascular plants as proxies of their abundance in 1725 10-m2 plots from the GrassPlot database, covering 47 regional data sets of 19 different grasslands and other open vegetation types of the Palaearctic biogeographic realm. For each plot, we fitted the Weibull distribution, a model that is able to effectively mimic other distributions like the log-series and lognormal, to the species–log abundance rank order distribution. We calculated the skewness and kurtosis of the empirical distributions and linked these moments, along with the shape and scale parameters of the Weibull distribution, to plot climatic and soil characteristics. The Weibull distribution provided excellent fits to grassland plant communities and identified four basic types of communities characterized by different degrees of dominance. Shape and scale parameter values of local communities on poorer soils were largely in accordance with log-series distributions. Proportions of subdominant species tended to be lower than predicted by the standard lognormal SAD. Successive accumulation of plots of the same vegetation type yielded nonlinear spatial scaling of SAD moments and Weibull parameters. This scaling was largely independent of environmental correlates and geographic plot position. Our findings caution against simple generalizations about the mechanisms that generate SADs. We argue that in grasslands, lognormal-type SADs tend to prevail within a wider range of environmental conditions, including more extreme habitats such as arid environments. In contrast, log-series distributions are mainly restricted to comparatively species-rich communities on humid and fertile soils.
- The proper middle class: assessing the importance of subordinate species on plant community assembly and functional diversityPublication . Ulrich, Werner; Matthews, Thomas; Biurrun, Idoia; Aleksanyan, Alla; Borovyk, Dariia; Burrascano, Sabina; Campos, Juan Antonio; Chusova, Olha; Czarniecka-Wiera, Marta; Czortek, Patryk; Dembicz, Iwona; Essl, Franz; Janišová, Monika; Labadessa, Rocco; Napoleone, Francesca; Pielech, Remigiusz; Vynokurov, Denys; Puchałka, Radosław; Peres-Neto, PedroABSTRACT: The local species abundance distribution (SAD) and the associated distributions of species functional traits (TADs) both result from the process of plant community assembly. Community assembly has been extensively studied for dominant and rare plants, while subordinates, the species of intermediate abundance in a community, have received less research attention although this group is comparatively species rich and important for community functioning. Here, we study the functional role of subordinate species (those covering the intermediate 50% of abundance ranks) using a large data set of Palearctic dry and semi-dry grassland plant communities and data on specific leaf area, seed mass and plant height. Our findings indicate that species rank orders of SADs and TADs tend to be negatively correlated, causing the TAD to have higher evenness than the associated SAD. Subordinate species represented on average less than 15% of total plant abundance and trait space. Functional diversity of subordinates was lower than expected by a null model that assumed an equiprobable random distribution of trait values among plant species. Climate seasonality and elevation appeared to be the most important drivers of subordinate abundance and functional diversity. We conclude that subordinates differ from dominants in trait composition, leading to their partial functional independence from dominants.