3,539 research outputs found
Comparing the plant diversity of paired beech primeval and production forests: Management reduces cryptogam, but not vascular plant species richness
No full textConflicting evidence of the impact of forest management on biodiversity exists, either decreasing or increasing species richness. Variable diversity responses may result from the adoption of different unmanaged reference systems, ranging from stands with management abandonment in the recent past to true primeval forests. We compared the species richness of epiphytic bryophytes and lichens and vascular forest floor plants in three primeval forest/production forest pairs of Fagus sylvatica in Slovakia, adopting a replicated design and a reference system without any management legacy. Mean number of bryophyte and lichen species per 500 m2-plot tended to be higher in the primeval forests, while the mean α-diversity of vascular plants was higher in the production forests. In contrast, the β-diversity of the three plant groups as expressed by the Sørensen Dissimilarity Index was generally higher in the primeval forest plot sample, reflecting a higher heterogeneity of plant community composition and habitat diversity. Plotting cumulative species numbers against plot numbers suggests that the curves for bryophyte and lichen species richness may saturate at ca. 250 plots or ∼12.5 ha in the primeval forests, but already at 30–60 plots (50 plots (total area: 2.5 ha) were investigated, evidencing the importance of natural disturbance regimes for maintaining high forest biodiversity. Our results show that Fagus sylvatica primeval forests are inhabited by a species-rich epiphyte flora despite the species poverty of the tree layer. This evidences the outstanding value of primeval forest reserves for the conservation of temperate forest biodiversity
Redoxaktive Lewissäure und gemischt-valente borverbrückte Oligo(ferrocenylene)
No full textFerrocenbasierte Polymere stellen interessante Verbindungen dar. Sie weisen herausragende optische und/oder elektronische Eigenschaften auf, die sich auf die redoxaktiven Eisenionen sowie die kooperativen Effekte entlang des Polymerstrangs zurückführen lassen. Befindet sich Ferrocen in der Hauptkette und sind die Ferrocenbausteine jeweils über ein einzelnes Atom miteinander verbunden, so ist dieses Brückenelement maßgebend für die substanzspezifischen Merkmale des Makromoleküls. Während bereits effiziente Syntheserouten bekannt sind, auf denen sich Atome der Gruppen 14 bis 16 in die Brücke einführen lassen, bereitet die Synthese borverbrückter Poly(ferrocenylene) große Schwierigkeiten. Gerade diese Stoffklasse wäre aber besonders attraktiv, da Boratome sowohl dreifach als auch vierfach koordiniert vorliegen können und über diese Eigenschaft das Ausmaß der elektronischen Wechselwirkungen entlang des Polymerrückgrats ebenso wie die Struktur des Makromoleküls gezielt beeinflussbar ist. Vor diesem Hintergrund galt es im Rahmen der vorliegenden Arbeit, chemisch stabile Poly(ferrocenylene) mit tetrakoordinierten anionischen Boratbrücken darzustellen. Als Grundlage diente die Adduktbildung zwischen lewissauren 1 ,1'-fc(BRz)zDerivaten und dem lewisbasischen doppelt deprotonierten Ferrocen 1,1 '-fcLi2 x 2/3 TMEDA. Frühere Untersuchungen an BMez-verbrückten di- (35) und tri nuklearen (36) Ferrocenkomplexen haben gezeigt, dass diese Verbindungen extrem empfindlich gegenüber Luft und Feuchtigkeit sind. Auch mussten cyclovoltammetrische Messungen an 35 bzw. 36 bei tiefen Temperaturen (-78 Oe) durchgeführt werden, um zu verhindern, dass es zu einer Zersetzung der Moleküle im Zuge der Fe{fI)Oxidation kam. Im Rahmen dieser Arbeit sind Systeme dargestellt worden, bei denen die labilen BMe2-Gruppen durch BPh2- bzw. Borafluorenylbrücken ersetzt sind. An mononuklearen Verbindungen konnten (Diphenylboryl)ferrocen 57, 1, 1'MBis(diphenylboryl) ferrocen 58 und 9-Ferrocenyl-9-borafluoren 61 isoliert und voIlständig charakterisiert werden (Abb. 53). ...
forest
No full textAbstract Question Biodiversity surveys of epiphytic bryophytes and lichens on standing trees are mostly restricted to the lowermost 2 m, since sampling above this level is time‐consuming and therefore expensive. However, sampling only the stem base is likely to result in underestimation of forest epiphyte diversity, because microclimate and physico‐chemical site conditions, both of which vary with height above the ground, play important roles for poikilohydric organisms. We investigate variation in epiphyte diversity and composition along the vertical gradient in forests and discuss factors that may potentially account for height‐dependent distribution patterns. Location Montane primeval beech forest Havešová in the Carpathians, eastern Slovakia. Methods Ten circular plots, each 500 m 2 , were selected randomly in an area severely affected by windfall. Epiphytes were sampled along the stems of recently uprooted trees, from base to the canopy. Mean Ellenberg indicator values ( EIV ) for light, moisture, acidity and nitrogen availability were used as surrogate variables for environmental interpretation of compositional patterns for sampling segments of 2 m along the stem. Results By sampling only the lowest 2 m, 10% of the total bryophyte and 48% of the lichen species would have been missed. We detected systematic patterns of compositional variation for both groups along the vertical gradient. While pleurocarpous mosses and liverworts were mostly restricted to the stem base, acrocarpous mosses and crustose lichens occurred along the stem almost to the top. Foliose and fruticose lichens were concentrated at intermediate heights and in the upper canopy. Patterns of variation in EIV s suggested that increasing light availability, decreasing moisture and increasing inputs of acidic and nitrous substances are responsible for the compositional shifts along the vertical gradient. Conclusions Sampling only the stem base implies severe underestimation of the epiphyte diversity in temperate broad‐leaved forests. The middle and the upper parts of tree stems have distinctive compositions of epiphytic cryptogams, because microclimate and physico‐chemical site factors vary with height above the ground
Effects of natural forest dynamics on vascular plant, bryophyte, and lichen diversity in primeval Fagus sylvatica forests and comparison with production forests
No full textInnovative capacity development approaches for the ERA-ARD project
No full textThe aim of the present paper is: 1. To provide definitions and outline trends in capacity development in Agricultural Research for Development (ARD) 2. to summarize the findings and recommendations of recent documents on planning and conducting capacity development activities in ARD 3. to present a summary and a compilation of best practices and innovative capacity development approaches among ERA-ARD consortium members 4. to derive basic principles for capacity development in ARD and to define entry points for joint and/or transnational activities to strengthen capacity development in ARD
Vertical variation in epiphytic cryptogam species richness and composition in a primeval Fagus sylvatica forest
No full text- …
