Wesolowski T.,Wroclaw University
Biological Conservation | Year: 2012
Numerous forest organisms rely on non-excavated tree-holes, which are often limited in managed European woods. Holes' supply depends on formation rates and persistence times. I use 30. years of data from a primeval forest (strictly protected reserve, Białowieża National Park, Poland) to determine how long non-excavated holes persist, whether their persistence varies across forest types, tree species and conditions, or bird species using them. From 1979 to 2010, I followed the fate of 1794 holes, used by 14 non-excavator bird species. Almost half of them were destroyed during this time, most often (40%) due to tree fall or break off of the hole-bearing section, growing over injury (28%) or decay of walls (24%). Holes were retained for a median of 12. years, longer in deciduous habitats (11-13. years) than in coniferous forests (4.4. years). These differences were due to different sets of tree species used in different habitats. Lifespan of holes varied by tree species, ranging from 5 (Populus tremula) to 16.5. years (Quercus robur). Persistence was much lower for holes in dead (5. years) than in living (14. years) substrates. It increased with increasing tree size. Differences in persistence times of holes used by various bird species was mostly a by-product of them selecting trees of different qualities. Holes in large living trees, with relatively hard wood, persisted longest. Their retention should become a conservation priority. Current forestry policies should be modified, to assure that hole-bearing trees are retained, and trees in which replacement holes could be formed are maintained. © 2012 Elsevier Ltd.
Wojaczynska E.,Wroclaw University of Technology |
Wojaczynski J.,Wroclaw University
Chemical Reviews | Year: 2010
Various achievements in the field of enantioselective synthesis of sulfoxides in years 2000-2009 are compiled. A series of (4-X-benzyl) p-tolyl sulfoxides was prepared in both enantiomeric forms using the Andersen method. Diastereomers of S-oxidized N-protected S-methyl or S-propyl-L-cysteine methyl ester were prepared using the DAG methodology and was found that the diastereomeric ratio is stongly dependent on the combination of solvent and base. While identifying the best method for the preparation of nonracemic modafinil derivatives, it was found that chiral oxaziridines give better results than metal-based systems. Studies on the sulfoxidation of the series of 2-arylsulfanylpyrroles demonstrated that the synthetic Kagan and Modena protocols could be applied with success if the electron-withdrawing groups differentiated the two substituents of the sulfur atom.
Pawlik T.,Wroclaw University
Earth-Science Reviews | Year: 2013
Forested hillslopes form a special geoecosystem, an environment of geomorphic processes that depend strongly on forest ecology, including the growth and decay of trees, changes in structure, disturbances and other fluctuations. Hence, the following various functions of trees are reviewed here: their role in both biomechanical and biochemical weathering, as well as their importance for the hillslope geomorphic subsystem and for transport of soil material via tree uprooting and root growth. Special attention is paid to tree uprooting, a process considered the most efficient and most frequent biogeomorphological indicator of bio-physical activity within forest in complex terrain. Trees have varied implications for soil formation in different environments (boreal to tropical forests) and altitudes. In this paper an attempt has been made to emphasize how trees not only modulate geomorphic processes, but also how they act as a direct or indirect agent of microrelief formation, the most striking example of which being widespread and long-lasting pit-and-mound microtopography. Based on the analyzed literature it seems that some problems attributed to forest ecology can have a fundamental effect on forested hillslope dynamics, a relationship which points to the need for its integration and interpretation within the field of geomorphology. The biology of individual trees has a key influence on the development of e.g. rock faces, weathering front migration and changes in the soil biomantle within upper and lower forest belts. Additionally, forms and sediments depend largely on the horizontal and vertical extent, volume and structure of root systems, as well as on active processes taking place in the root zone and rhizosphere. Furthermore, although trees to a large extent stabilize slope surfaces, their presence can also have a dual effect on slope stability due to tree uprooting, a process which in some circumstances can trigger mass movements (e.g. debris avalanches). So far, several attempts at quantifying the influence of trees on slopes have been made via the use of mathematical equations, enabling researchers to calculate: 1) the root plate volume of uprooted trees, 2) the amount of soil displacement due to tree root growth, and 3) rates of erosion, sedimentation and soil creep. In light of the reviewed literature, the most urgent issue appears to be the need for a thorough study of the interactions and feedbacks occurring between trees and geomorphic systems (e.g. soil mixing and biotransport by trees) in different climate zones, altitudes and time frames, especially in terms of the development of forest ecosystems during the Holocene. © 2013 Elsevier B.V.
Lisowski J.,Wroclaw University
Inorganic Chemistry | Year: 2011
The controlled formation of lanthanide(III) dinuclear μ-hydroxo-bridged [Ln2L2(μ-OH)2X2]n+ complexes (where X = H2O, NO3-, or Cl -) of the enantiopure chiral macrocycle L is reported. The 1H and 13C NMR resonances of these complexes have been assigned on the basis of COSY, NOESY, TOCSY, and HMQC spectra. The observed NOE connectivities confirm that the dimeric solid-state structure is retained in solution. The enantiomeric nature of the obtained chiral complexes and binding of hydroxide anions are reflected in their CD spectra. The formation of the dimeric complexes is accompanied by a complete enantiomeric self-recognition of the chiral macrocyclic units. The reaction of NaOH with a mixture of two different mononuclear lanthanide(III) complexes, [Ln1L]3+ and [Ln2L]3+, results in formation of the heterodinuclear [Ln1Ln2L2(μ-OH)2X 2]n+ complexes as well as the corresponding homodinuclear complexes. The formation of the heterodinuclear complex is directly confirmed by the NOESY spectra of [EuLuL2(μ-OH)2(H 2O)2]4+, which reveal close contacts between the macrocyclic unit containing the Eu(III) ion and the macrocyclic unit containing the Lu(III) ion. While the relative amounts of homo- and heterodinuclear complexes are statistical for the two lanthanide(III) ions of similar radii, a clear preference for the formation of heterodinuclear species is observed when the two mononuclear complexes contain lanthanide(III) ions of markedly different sizes, e.g., La(III) and Yb(III). The formation of heterodinuclear complexes is accompanied by the self-sorting of the chiral macrocyclic units based on their chirality. The reactions of NaOH with a pair of homochiral or racemic mononuclear complexes, [Ln1L RRRR]3+/[Ln2LRRRR]3+, [Ln1LSSSS]3+/[Ln2L SSSS]3+, or [Ln1Lrac] 3+/[Ln2Lrac]3+, results in mixtures of homochiral, homodinuclear and homochiral, heterodinuclear complexes. On the contrary, no heterochiral, heterodinuclear complexes [Ln1L RRRRLn2LSSSS(μ-OH)2X 2]n+ are formed in the reactions of two different mononuclear complexes of opposite chirality. © 2011 American Chemical Society.
Skarzynska A.,Wroclaw University
Coordination Chemistry Reviews | Year: 2013
The paper gives a short survey on the coordination properties of H-spirophosphoranes towards transition metals. The emphasis is on the application of H-spirophosphorane complexes in catalysis. Spirophosphoranes supported by transition metals, palladium or rhodium, have been identified as ligands in metal-catalysed enantioselective catalysis; connected to palladium centres, they exhibit catalytic properties in cross-coupling reactions. Rhenium complexes incorporating spirophosphoranes appear to act as excellent co-catalysts in oxidation reactions. It is demonstrated how fine tuning within the structure of phosphorus ligands can determine the catalytic properties of transition metal complexes. © 2012 Elsevier B.V.