Evaluation of species inter-relations and soil conditions in Arnica montana L. habitats: a step towards active protection of endangered and high-valued medicinal plant species in NE Poland

Arnica montana L. is a critically endangered and highly valued medicinal plant species in Europe. We show the inter-relationships between arnica and accompanying plant species, as well as soil factors, that promote the persistence of the studied forest arnica populations in terms of active protection of this species in the northeast region of Europe. The population characteristics and plant species composition were assessed during a field study. Additionally, soil samples were taken and analyzed to assess variation in soil conditions in the habitats of arnica populations. Correlations between population characteristics and soil properties were highlighted. The forest habitats of arnica presented in this study differ from those described in other European mountain and submountain areas. The sandy and very poor soils are characterized by a very low content of macro- and microelements, and a strong acid reaction. The positive correlation between population characteristics and Ca and K indicates an important role of these macroelements in flower head production. Acidity, K, Ca, the sum of exchangeable bases, and base saturation play crucial roles in the persistence of arnica populations in pine forests. The level of acidity and its consequences result from soil-forming processes and climatic conditions rather than air pollution. When planning active protection scenarios, special attention should be paid to the frequency and cover of Vaccinium myrtillus, which can act as a competitor in forest habitats. Assessment of soil conditions that favor the persistence of the studied arnica populations and species relationships is important for improving knowledge of the ecology of the species and for the active protection of endangered plant species

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

Differentiation and Propagation Potential of <i>Arnica montana</i> L. Achenes as a Consequence of the Morphological Diversity of Flowers and the Position of Flower Heads on the Plant

Arnica montana L. is a very important medicinal plant and simultaneously a European endemic endangered plant species. The morphological features and details of seed development and achene variability are poorly recognized. The aim of this study was to determine the impact of the achene position in the infructescence and the location of the inflorescence on the plant on the (i) morphological characteristics and germination ability of achenes, and (ii) recruitment of seedlings and their biometric features. Infructescences containing fully ripe achenes were randomly collected from A. montana individuals for the measurements and the germination experiment. Scanning electron microscopy, fluorescence microscopy, and light microscopy were used for characterization of flowers and achenes. The morphological traits of achenes and reproductive characteristics of A. montana were determined by the position of the achenes in the infructescence and the location of the inflorescence on the plant. The surface of arnica achenes is equipped with non-glandular and glandular trichomes, which is very rarely presented in species of the family Asteraceae. It is possible that the fluid-containing glandular trichomes are a source of essential oils. The peripherally located achenes were longer, thinner, and lighter. They were characterized by lower embryo weight, lower embryo/achene weight ratio, and lower germination capacity in comparison to the centrally located ones. The results presented in this article fill the gap in the knowledge of the morphology of achenes and the biology of the species, and provide information that can help in breeding programs, active protection, and field cultivation