Assessing Tolerance to the Hydrodynamic Exposure of Posidonia oceanica Seedlings Anchored to Rocky Substrates

Among a suite of abiotic and biotic factors, the hydrodynamic regime strongly influences the success of seagrass recruitment through sexual propagules. Uprooting of propagules by drag forces exerted by currents and waves is one of the main causes for the failed establishment and the consequent recruitment. Substrate type and stability play a key role in determining the success of colonization through sexual propagules, as seedling establishment probabilities proved to be significantly higher on rocky bottoms than on unstable unconsolidated substrates. In this research, the current and wave flow intensity that Posidonia oceanica seedlings anchored to rocky substrates can withstand before uprooting were evaluated and the influence of substrate complexity on seedling anchorage success and anchorage strength was investigated. P. oceanica seedlings withstood the current velocity of 70 cm s–1 and increased orbital flow velocities up to 25 cm s–1. Seedling adhesion strength ranged from 3.92 to 29.42 N. Results of the present study corroborate the hypothesis that substrate complexity at scales relevant to the size of propagules is a crucial feature for P. oceanica seedling establishment. The intensity of unidirectional and oscillatory flow that seedlings can withstand without being dislodged assessed in this study support the hypothesis that P. oceanica sexual propagules, once adhered to a consolidated substrate, are able to tolerate high hydrodynamic stress. The results of the present study contribute to re-evaluation of the habitat requirements of P. oceanica, assessing the range of hydrodynamic conditions that this species can tolerate during the early stages of its life history.

Dziedzictwo dawnej Rzeczypospolitej w języku pierwszego polskiego przekładu poematu „Metai” Kristijonasa Donelaitisa

The author analysed the language of the first Polish translation of the eighteenth-century poem “Metai” [The Seasons] by Kristijonas Donelaitis, a Lithuanian Lutheran pastor. The translation was made in 1933 by a socialist activist and close associate of Józef Piłsudski, Kazimierz Pietkiewicz. The analysis showed that the language of the translation is peculiar. On the one hand, this peculiarity consists in refraining from archaizing the translation and the use of elements that are close to the translator’s style of social-political journalism (e.g., dorobkiewicz [vulgarian], feministka [feminist]), on the other hand, the presence at all levels of language of peculiarities characteristic for Kresy Polish language in both its territorial variations. These are generally old features of common Polish, the retention of which in the eastern areas of the Polish Rzeczpospolita was supported by the influence of substrate languages, later also Russian, or by borrowing. This layer was natural in the language of the translator, born in Ukraine, who spent part of his life in Vilnius, some in exile in Russia. This is the colourful linguistic heritage of the former Republic of Poland.

Development of Mechanical Soil Stability In An Initial Homogeneous Loam And Sand Under In-Situ Field Conditions

PurposeSoil structure evolving from physical and biological processes is closely related to soil mechanical characteristics and texture. A soil plot experiment in Bad Lauchstädt, Germany, allowed us to study the influence of substrate and genotype on the initial development of mechanical traits, differences between depths, and changes over the course of two years. MethodsPlots were homogeneously filled with a loam and a sand and planted with two maize (Zea mays L.) genotypes (wild type (WT) and rth3 mutant) with contrasting root hair attributes. Undisturbed soil cores were taken in 2019 and 2020 at 14 and 34 cm depth. Confined uniaxial compression tests were performed to determine pre-compression stress (σpc), compressibility (Cc, Cs) and elasticity index (EI). Mechanical energy was calculated based on penetration resistance tests with a penetrometer needle resembling root geometries. Resultsσpc, Cc and Cs were significantly higher in loam as compared to sand, whereas the factor genotype proved to be negligible. Over time, σpc increased and Cc decreased in loam from 2019 to 2020 and Cs declined in both substrates. Higher mechanical energies were observed in loam and partially in WT. Required energy was higher at 14 cm than at 34 cm depth and decreased from 2019 to 2020 in sand. Airdry sand samples required four times as much energy than those at -50 kPa.ConclusionFor the development of the mechanical traits examined texture proved to be the dominating factor and changes in soil stability could be observed within a short period of time.