Krzysztof Świerkosz

Combining Biodiversity Resurveys across Regions to Advance Global Change Research

More and more ecologists have started to resurvey communities sampled in earlier decades to determine long-term shifts in community composition and infer the likely drivers of the ecological changes observed. However, to assess the relative importance of and interactions among multiple drivers, joint analyses of resurvey data from many regions spanning large environmental gradients are needed. In this article, we illustrate how combining resurvey data from multiple regions can increase the likelihood of driver orthogonality within the design and show that repeatedly surveying across multiple regions provides higher representativeness and comprehensiveness, allowing us to answer more completely a broader range of questions. We provide general guidelines to aid the implementation of multiregion resurvey databases. In so doing, we aim to encourage resurvey database development across other community types and biomes to advance global environmental change research.

Compositional changes in thermophilous oak forests in Poland over time: do they correspond to European trends?

Questions Have compositional changes occurred in thermophilous oak forests in Poland during the past two decades? What kinds of drivers might be responsible for these changes? Are the thermophilous oak woods still rich in species or have they rather lost their diversity? Location Sudetes Mts., SW Poland. Methods The vegetation of thermophilous oak forests within four distinct areas was surveyed on 92 semi-permanent plots in the time periods from 1992 to 1994 and from 2010 to 2014. The overall pattern in vegetation changes, trends in species composition and site parameters, as well as the diversity of studied communities were analysed using ordination and permutation techniques. Results The species composition of thermophilous oak forests has changed significantly. We recorded a decrease in the share of oligotrophic light-demanding species, whereas mesotrophic light-demanding and nitrophilous species showed an upward trend. Regarding the fourth group of shade-tolerant species, their share varied depending on the site. The analysis of habitat parameters revealed that the studied oak forest communities generally shifted from communities of moderately oligotrophic and mesic character towards forests growing on nutrient-richer but drier habitats. Interestingly, the observed change in species composition was not accompanied by the loss of biodiversity that has generally been reported in other types of thermophilous forests in Europe. Conclusions Changes observed within thermophilous and previously coppiced oak forests of southwest Poland are going in a direction which has not been recognized so far in analogous communities. The transition of studied communities is probably a result of the cumulative influence of several drivers, the most crucial of which seem to be soil regeneration, after the period of intensive acidity caused by sulphur emission between 1960 and 2000, and decreasing moisture. The observed changes are independent of the type of forest management (or the lack thereof) within the study sites.

Variability of Abies alba-dominated forests in Central Europe

Using vegetation databases from Poland, the Czech Republic, Austria, Slovakia and our own material collected during a field work, we have analysed the variability of species composition of Abies alba-dominated communities in Central Europe. Analysis was performed using a modified TWINSPAN algorithm in the JUICE software. Ecological analysis was performed on the basis of mean Ellenberg indicator values with a MoPeT_v1.0.r script prepared in R software. In general, the findings indicated that there are at least 8 types of Central European silver fir-dominated forests with different patterns in species composition and habitat conditions. These are the oligotrophic subcontinental silver fir forests of the Polish highlands, oligotrophic (sub)montane silver fir forest, hygrophilous silver fir forests, oligo-mesotrophic (sub)montane silver fir forests, mesotrophic (sub)montane silver fir forests, submontane and montane calcicolous silver fir forests of the Alps and the Carpathians, eutrophic silver fir-beech forests and silver fir ravine forests. The main conclusion is that the diversity of species composition of Abies alba-dominated forests in Central Europe is lower than described in current regional synthesis, which was confirmed by ecological analyses.

Landscape memory in abandoned areas—physical and ecological perspectives (Central European mountains case study)

ABSTRACT Using the concept of landscape memory we examined the relationship between persistence of anthropogenic landforms and their botanical composition several decades after depopulation of Karpno village (Sudetes Mts), which represents the socio-economic and ecological processes typical for mountainous areas in post-war Central Europe. The research was based on geomorphic and botanical field surveys. Evidence of anthropogenic landscape memory still persists in local land morphology and ecosystem composition, despite the apparent homogeneity of large-scale landscape features. Former human activities continue to affect local site properties, which results in a mosaic of diverse habitats. Plant species composition of secondary ecosystems remains different from both their anthropogenic precursors and surrounding natural communities. Persistent habitat eutrophication slows down competitive exclusion of shade intolerant species in sites overgrown by forest canopy. Observed evidence cannot be explained without knowledge of local history, which is vital for planning development and conservation of bio-cultural landscapes.

Observer and relocation errors matter in resurveys of historical vegetation plots

Aim: Revisits of non-permanent, relocatable plots first surveyed several decades ago offer a direct way to observe vegetation change and form a unique and increasingly used source of information for global change research. Despite the important insights that can be obtained from resurveying these quasi-permanent vegetation plots, their use is prone to both observer and relocation errors. Studying the combined effects of both error types is important since they will play out together in practice and it is yet unknown to what extent observed vegetation changes are influenced by these errors. Methods: We designed a study that mimicked all steps in a resurvey study and that allowed determination of the magnitude of observer errors only vs the joint observer and relocation errors. Communities of vascular plants growing in the understorey of temperate forests were selected as study system. Ten regions in Europe were covered to explore generality across contexts and 50 observers were involved, which deliberately differed in their experience in making vegetation records. Results: The mean geographic distance between plots in the observer+relocation error data set was 24m. The mean relative difference in species richness in the observer error and the observer+relocation data set was 15% and 21%, respectively. The mean pseudo-turnover between the five records at a quasi-permanent plot location was on average 0.21 and 0.35 for the observer error and observer+relocation error data sets, respectively. More detailed analyses of the compositional variation showed that the nestedness and turnover components were of equal importance in the observer data set, whereas turnover was much more important than nestedness in the observer+relocation data set. Interestingly, the differences between the observer and the observer+relocation data sets largely disappeared when looking at temporal change: both the changes in species richness and species composition over time were very similar in these data sets. Conclusions: Our results demonstrate that observer and relocation errors are non-negligible when resurveying quasi-permanent plots. A careful interpretation of the results of resurvey studies is warranted, especially when changes are assessed based on a low number of plots. We conclude by listing measures that should be taken to maximally increase the precision and the strength of the inferences drawn from vegetation resurveys.