Natural regeneration of the deciduous oak species Pedunculate Oak (Quercus robur L.) and Sessile Oak (Quercrus petraea Liebl.) – a literature review with focus on wood pasture

Auswertungen von Untersuchungen über frühere Waldnutzungen sowie Waldweide legen nahe, dass die Verjüngung der mitteleuropäischen laubabwerfenden Eichenarten Stieleiche (Quercus robur L.) und Traubeneiche (Quercus petraea Liebl.) ein episodischer Prozess ist, mit oft langen Phasen ausbleibender Verjüngung im Wechsel mit Phasen der erfolgreichen Etablierung einer neuen Generation. Eine Vielzahl von Faktoren wirkt sich auf die Verjüngung der Eichen aus. Als besonders bedeutsam werden genannt die Lichtversorgung; Prädation der Eicheln insbesondere durch Mäuse, Wildschweine und andere Tiere; Verbiss durch Wildtiere und Weidetiere; Befall der Blätter durch Mehltau (Microsphaera alphitoides); Konkurrenz durch die Bodenvegetation; Spätfrost; sowie der Wasserhaushalt des Standorts. All diese Faktoren wirken in einem komplexen Wechselspiel zusammen. Zur Ansamung und erfolgreichen Etablierung der Eichen im Wald sind eine Auflichtung des Kronendachs sowie eine niedrigwüchsige Bodenvegetation notwendig. Letztere können beispielsweise durch Beweidung erreicht werden. Verbiss wird bei guter Lichtversorgung durch die Jungeichen gut vertragen, es bilden sich bonsai-artige Krüppelbäumchen mit tiefreichendem Wurzelwerk heraus. Ein Höhenwachstum setzt jedoch erst dann ein, wenn der Weidedruck reduziert wird. Dies kann durch zeitliche oder räumliche Schwankungen des Verbissdrucks erreicht werden (Weideruhe). Die laubabwerfende Stiel- und Traubeneiche muss daher als Intermediärtyp zwischen Pionierbaumart und „stresstolerator“ sensu GRIME et al. (1978) eingestuft werden. In vielen Kulturlandschaften finden sich Bedingungen zur erfolgreichen natürlichen Eichenetablierung, also ohne unterstützende waldbauliche Maßnahmen, heute nur mehr an linienförmigen saum- und mantelartigen Randstrukturen von Wäldern, in Hecken und Gebüschen – dort trotz des Vorhandenseins von Wild. Naturschutzfachliche Gründe und zu erwartende Klimaänderungen legen jedoch eine stärkere Beachtung und Förderung der Eichenverjüngung nahe. Hierzu stellt Beweidung im Wechsel mit Weideruhe eine in Vergessenheit geratene und heute nur mehr wenig bekannte Möglichkeit dar.Studies of historic forest uses and wood pastures allow the conclusion, that the regeneration of the central European deciduous oak species Pedunculate oak (Quercus robur) and Sessile oak (Quercus petraea) is an episodic process. It must be assumed, that long-lasting phases without successful regeneration of young oaks change with phases of successful establishment of a new oak generation. A number of factors is influencing the regeneration of oaks. The literature mentions light supply; predation of acorns by rodents, wild pigs and other acorn eating animals; browsing pressure by wild and domestic animals; infection of leaves with the mildew fungus Microsphaera alphitoides; competition with ground vegetation; late frost; and water supply. All these factors are interrelated in a complex way. It seems, that germination and successful establishment of these oaks depend from an open canopy and a low ground vegetation. In cultural landscapes, the last can be facilitated through wood pasture. Browsing is tolerated by the young oaks, when light supply is high. Under browsing pressure, oaks on open sites are able to survive, forming “bonsai-like” dwarfed deeply rooting treelets. However, height growth only can start after the end of grazing. This can be achieved by temporal and spatial fluctuations of browsing pressure. In terms of their life form strategy, Quercus robur and Q. petraea can be classified as stress-tolerating pioneers. In many cultural landscapes today, optimal sites for a successful natural establishment of oaks, i.e., without silvicultural supporting measures, can be found only along forest edges, in hedges and shrubland, even under presence of browsing wildlife. Today, arguments of nature conservation and climate change recommend an increased effort to facilitate oak regeneration. For that, periods of grazing changing with periods of succession can be a successful approach, which was well known in the past, but is nearly forgotten today

Single Crystal X-ray Structure Analyses of Thallides: Halide Incorporation and Mixed Alkali Sites in A8Tl11X (A = K, Rb, Cs; X = Cl, Br)

A8Tl11 (A = alkali metal) compounds have been known since the investigations of Corbett et al. in 1995 and still are matter of current discussions as the compound includes one extra electron referred to the charge of the Tl117− cluster. Attempts to substitute the charge by incorporation of a halide atom succeeded for the lightest homologue of the group, Cs8Ga11Cl, and powder diffraction experiments for the heavier homologues also suggested the formation of analogous compounds. However, X-ray single crystal studies on A8Tl11X to prove this substitution and to provide a deeper insight into the influence on the thallide substructure have not yet been performed, probably due to severe absorption combined with air and moisture sensitivity for this class of compounds. In our contribution we present single crystal X-ray analyses of the new compounds Cs8Tl11Cl0.8, Cs8Tl11Br0.9 and Cs5Rb3Tl11Cl0.5. It is shown that a (partial) incorporation of halide can also be indirectly determined by examination of the Tl-Tl distances for low resolved data sets, e.g., for Cs5.7K2.3Tl11Cl?. Mixed occupied sites by two different alkali metals indicate a dependence on the cesium content, the systems K/Rb–Tl–Br and K/Rb–Tl–Cl only gave rise to the formation of the higher reduced (K/Rb)8Tl11 and the less reduced by-product (K/Rb)15Tl27. We have not been able to prove the formation of halide including thallides in the absence of cesium

Comparison of four different programs for the analysis of hemispherical photographs using parameters of canopy structure and solar radiation transmittance

There have been many studies involving the use of hemispherical photographs to indirectly estimate canopy structures and forest light environments. A variety of commercial and free software packages are available for the analysis of hemispherical photographs. The costs of investment might represent an advantage of the free programmes over the commercial, but as yet little has been documented about the differences in their outputs and in the technical applications from a user (ecologist and forester) perspective. The objective of the study was to compare the canopy structure variables (canopy openness and effective plant area index) and solar radiation transmission estimates (direct, diffuse and global solar radiation transmittances) from digital hemispherical photographs taken under two forest canopy conditions (gap and closed canopy) in three different broadleaf forest regions (Chile, Germany, Venezuela) and calculated using four different programmes. The hemispherical photographs were analysed using one commercial (HemiView) and three free programmes (Gap Light Analyzer, hemIMAGE and Winphot). The results obtained revealed that all of the programmes computed similar estimates of both canopy structures and below-canopy solar radiation. Only the results relating to the effective plant area index with an ellipsoidal leaf angle distribution made with HemiView and Winphot deviated significantly. Other user aspects are also discussed, such as costs, image formats, computer system requirements, etc.In vielen Studien werden Hemisphärenphotos genutzt um indirekt die Kronenstruktur und die Belichtungsverhältnisse zu schätzen. Verschiedene kommerzielle und kostenfreie Softwarepakete sind zu Analyse von Hemisphärenphotos verfügbar. Es gibt bisher keine umfassende Vergleichsstudie zu Ergebnissen oder technischer Handhabung aus Sicht der Nutzer dieser Programme (Ökologen und Forstwissenschaftler). Das Ziel dieser Studie war der Vergleich der Schätzungen von Kronenstrukturvariablen (Kronenöffnung und effektiver Pflanzenflächenindex) Solartransmission (direkte, diffuse und Global-Strahlung) aus digitalen Hemisphärenphotos berechnet mit vier verschiedenen Programmen (kostenpflichtig: Hemi- View und frei: Gap Light Analyzer, hemIMAGE and Winphot). Die verwendeten Photos stammen aus drei verschiedenen Laubwaldregionen (Chile, Deutschland und Venezuela) und repräsentieren jeweils Verhältnisse unter geschlossenem Kronendach und in Lücken. Die ermittelten Schätzungen für die verschiedenen Strukturvariablen und Einstrahlungsverhältnisse zeigten eine sehr hohe Übereinstimmung. Einzig der effektive Pflanzenflächenindex basierend auf ellipsoider Blattwinkelverteilung unterschied sich signifikant zwischen den Programmen. Weitere für Nutzer interessante Aspekte wie Kosten, Bildformate, Systemvoraussetzungen und mehr wurden verglichen und diskutiert

Structural Chemistry of Halide Including Thallides A8Tl11X (A=K, Rb, Cs; X=Cl, Br)

A(8)Tl(11) (A = alkali metal) compounds have been known since the investigations of Corbett et al. in 1995 and are still a matter of current discussions as the compound includes one extra electron referred to the charge of the Tl-11(7-) cluster. Attempts to substitute this additional electron by incorporation of a halide atom succeeded in the preparation of single crystals for the lightest triel homologue of the group, Cs8Ga11Cl, and powder diffraction experiments for the heavier homologues also suggested the formation of analogous compounds. However, X-Ray single crystal studies on A(8)Tl(11)X to prove this substitution and to provide a deeper insight into the influence on the thallide substructure have not yet been performed, probably due to severe absorption combined with air and moisture sensitivity for this class of compounds. Here, we present single crystal X-Ray structure analyses of the new compounds Cs8Tl11Cl0.8, Cs8Tl11Br0.9, Cs5Rb3Tl11Cl0.5, Cs5.7K2.3Tl11Cl0.6 and K4Rb4Tl11Cl0.1. It is shown that a (partial) incorporation of halide can also be indirectly determined by examination of the Tl-Tl distances, thereby the newly introduced cdd/cd(av) ratio allows to evaluate the degree of distortion of Tl-11(7-) clusters

[Tl7]7– Clusters in Mixed Alkali Metal Thallides Cs7.29K5.71Tl13 and Cs3.45K3.55Tl7

Investigations in the ternary system Cs–K–Tl resulted in the unexpected formation of new ternary thallides Cs7.29K5.71Tl13 and Cs3.45K3.55Tl7. Single crystal X-ray structure analyses of both compounds reveal the presence of isolated Tl cluster units. Cs7.29K5.71Tl13 crystallizes in the monoclinic space group C2/c (a = 30.7792(9) Å, b = 11.000(2) Å, c = 14.0291(4) Å, β = 112.676(4)°, Z = 4) and contains [Tl6]6– and [Tl7]7– clusters as thallium subunits. Cs3.45K3.55Tl7 crystallizes in the tetragonal space group I41/a (a = 13.6177(2) Å, c = 25.5573(8) Å, Z = 8) and contains [Tl7]7– clusters exclusively. The formation of Cs7.29K5.71Tl13 is obtained after slow cooling in addition to that of Cs3.45K3.55Tl7 and can be suppressed by quenching the stoichiometric mixture. First dissolution experiments in liquid ammonia suggest thallium and amide as final oxidation products. Full relativistic band structure calculations of Cs4K3Tl7 and Cs8K5Tl13 showed a (pseudo) band gap around EF for both compounds

The Role of Different Alkali Metals in the A15Tl27 Type Structure and the Synthesis and X-ray Structure Analysis of a New Substitutional Variant Cs14.53Tl28.4

Alkali metal thallides have been known since the report of E. Zintl on NaTl in 1932. Subsequently, binary and ternary thallides of alkali metals have been characterized. At an alkali metal proportion of approximately 33% (A:Tl~1:2, A = alkali metal), three different unique type structures are reported: K49Tl108, Rb17Tl41 and A15Tl27 (A = Rb, Cs). Whereas Rb17Tl41 and K49Tl108 feature a three-dimensional sublattice of Tl atoms, the A15Tl27 structure type includes isolated Tl11 clusters as well as two-dimensional Tl-layers. This unique arrangement is only known so far when the heavier alkali metals Rb and Cs are included. In our contribution, we present single-crystal X-ray structure analyses of new ternary and quaternary compounds of the A15Tl27 type structure, which include different amounts of potassium. The crystal structures allow for the discussion of the favored alkali metal for each of the four Wyckoff positions and clearly demonstrate alkali metal dependent site preferences. Thereby, the compound Cs2.27K12.73Tl27 unambiguously proves the possibility of a potassium-rich A15Tl27 phase, even though a small amount of cesium appears to be needed for the stabilization of the latter structure type. Furthermore, we also present two compounds that show an embedding of Tl instead of alkali metal into the two-dimensional substructure, being equivalent to the formal oxidation of the latter. Cs14.53Tl28.4 represents the binary compound with the so far largest proportion of incorporated Tl in the structure type A15Tl27

Reaction of Sn44− in liquid ammonia: the formation of Rb6[(η2-Sn4)Zn(η3-Sn4)]·5NH3

The reaction of Rb4Sn4 with ZnPh2 in liquid ammonia in the presence of [2.2.2]-cryptand yielded crystals of Rb6[(η2-Sn4)Zn(η3-Sn4)]·5NH3, which could be characterized by single crystal X-ray diffraction. This is the first example of a successful solution reaction of the highly charged tetrahedral Sn44− anions. The homoleptic [E4ZnE4]6− complex (E = tetrel element) was previously known only for E[double bond, length as m-dash]Ge and Si/Ge

Single Crystal X‐Ray Structure Analyses of Binary and Ternary Compounds A 49 Tl 108+x ( A =K, Rb, Cs; x=0–1.76) Related to the K 49 Tl 108 Type Structure

The structural chemistry of alkali metal thallides shows a broad range of type structures. At an alkali metal : thallium proportion A : Tl 1 : 2 the perceived dependency on the alkali metal involved is conspicuous. Two main structure types are reported with A15Tl27 (A=K, Rb, Cs) and K49Tl108. The compound K49K108 with a 3-dimensional Tl-substructure has been known since 1993 from Cordier and Müller but so far only with potassium. We here present single crystal X-Ray structure analyses of the compounds K49-yRbyTl108, and K49-yCsyTl108 (urn:x-wiley:00442313:media:zaac202200117:zaac202200117-math-0001 belonging to the K49Tl108 type structure. Additionally, structures of Rb49Tl109.67, Cs3.35Rb45.65Tl109.71 and Cs7.49Rb41.51Tl109.76 are introduced, which prove the possibility of Tl incorporation in the Tl12 icosahedra in K49Tl108 type structures. The effects of the change in alkali metals on the thallium substructure are discussed as well as the preferred Wyckoff sites of the different alkali metals

Na₇RbTl₄ – A New Ternary Zintl Phase Containing [Tl₄ ] ⁸⁻ Tetrahedra

Na7RbTl4 has been prepared by solid state reaction from the elements. Single crystal X-ray structure analysis suggested the presence of pseudo-merohedral twinning. The final model could be derived in space group Pbam (a=16.3584(4) Å, b=16.3581(4) Å, c=11.3345(3) Å, V=3033.04(14) Å3, R1/wR2 0.0282/0.0402) and proved the presence of isolated [Tl4]8− anions, which are only known from two other solid state thallide phases so far. The structure of Na7RbTl4 is compared to the long-known Na2Tl and the similarities and differences in the three-dimensional arrangement within the crystal structures are reported on. DOS calculations revealed a pseudo-band gap at EF. Dissolution experiments in the style of the chemistry of group 14 and group 15 Zintl anions in liquid ammonia yielded degradation of the thallides. Subsequent characterization of the reaction products by powder X-ray diffraction allowed for the determination of alkali metal amide and elemental thallium as products

Turning Seashell Waste into Electrically Conductive Particles

Biomaterials such as seashells are intriguing due to their remarkable properties, including their hierarchical structure from the nanometer to the micro- or even macroscopic scale. Transferring this nanostructure to generate nanostructured polymers can improve their electrical conductivity. Here, we present the synthesis of polypyrrole using waste seashell powder as a template to prepare a polypyrrole/CaCO3 composite material. Various synthesis parameters were optimized to produce a composite material with an electrical conductivity of 2.1 x 10(-4) +/- 3.2 x 10(-5) S/cm. This work presents the transformation of waste seashells into sustainable, electronically conductive materials and their application as an antistatic agent in polymers. The requirements of an antistatic material were met for a safety shoe sole