Dynamics of soil organic carbon (SOC) content in stands of Norway spruce (Picea abies) in central Europe

Norway spruce is the main forest tree species in the Czech Republic. Until now, little attention has been given in the literature to the dynamics of soil organic carbon (SOC) content under Norway spruce stands as a function of stand characteristics. The aim of this study is to estimate soil organic carbon (SOC) content and stock changes in organic and surface mineral soil horizons on forest sites with a dominant representation of Norway spruce. In the study area, a significantly higher content of SOC was found in the surface mineral soil horizon than in the organic soil horizon. In both soil horizons, there was evidence of an increasing trend of SOC with the increasing age of forest stands, a decreasing trend of SOC with increasing density of stocking and an increasing trend of SOC with increasing altitude. The relationship of SOC content with soil group (Podzol vs. non-Podzol) has also been demonstrated. The greatest potential for long-term carbon sequestration in soils was shown in older stands (101-190 years) dominated by Norway spruce with lower density of stocking, located in forest vegetation zones (altitude range: 1010-1225 m a.s.l.) where natural mountain Norway spruce forests currently occur. According to our results, Norway spruce stands may perform a stable function of carbon sequestration in the soil at these sites, especially in the mineral soil horizon

Thin-film characterization of neutral p-associated assemblies incorporating putative pseudo-rotaxanes

Thin films of 1:1 and 1:2 stoichiometric mixtures of bis(1,5-naphtho)-38-crown-10 (1) with both N,N′-di-n-alkylpyromellitic diimide (2) and N,N′-di-n-alkyl-1,4,5,8-naphthalenetetracarboxylic diimide (3) have been prepared using both Langmuir-Blodgett (LB) and thermal evaporation techniques. For thermal evaporation, the substituted n-alkyl chains were CH (2a and 3a, respectively), while for LB deposition, they were CH (2b and 3b, respectively). LB monolayers of different stoichiometric mixtures of both 1.2b and 1.3b were studied using UV-visible spectroscopy, Brewster-angle microscopy, and angle-dependent X-ray photoelectron spectroscopy and revealed that in both cases a stoichiometric mix of electron-donating and electron-accepting aromatic moieties was necessary to achieve good film-forming properties. 1:2 mixtures of 1.2a and 1.3a were then deposited as thin films using thermal evaporation techniques and studied using atomic force microscopy. This showed that films of 1.2a consisted of large spheres ≤ ca. 300 nm in diameter whereas films of 1.3a were found to be relatively uniform, with the maximum surface roughness being less than a third of the total film thickness. Additional electrical conduction measurements made on both LB and thermally evaporated prepared metal/organic/metal devices resulted in only evaporated films of 1.3a giving any measurable resistance. Furthermore, films of this material displayed a Poole-Frenkel conduction mechanism. These experiments have shown that rudimentary electrical devices can be prepared from neutral π-associated assemblies