The role of heterogeneity in spatial plant population dynamics

Ecological theory names interacting mechanisms that allow competing species to coexist in limited available space, some of them are perceive as antagonistic. Most prominent are niche differentiation, heterogeneity and neutrality (ecological equivalence). Species similarity is also influenced by two mechanisms: Habitat filtering selects for ecologically similar species, while niche differentiation reduces competitive pressure and thus prefers ecologically different species. The spatial arrangement of abiotic resources can determine the spatial pattern and competition framework for a pre-selected tree species ensemble. Spatial occurrence patterns of trees are formed by dispersal, growth and mortality which are influenced by the interacting abiotic and abiotic conditions. The relative impact of these mechanisms are underresearched in temperate forest trees, especially in Europe. We analysed a data set of a temperate old-growth forest with spatially explicit information about more than 15 000 individual trees of six tree species (90 % beech admixed with Ash, Hornbeam, Sycamore, Norway Maple, and Wych Elm) located in the central region of the Hainich National Park in central Germany. We tested space-related coexistence mechanisms under heterogeneous conditions. For this, we employed Point Pattern Analysis for testing several ecological hypotheses on inter- and intraspecific interactions of the species, varying from randomness to strict ecological niche. In order to identify the critical components of possible niches, we collected field data on the abiotic conditions such as the availability of water and light, and considered topography using a Digital Elevation Model. These field data were used for fitting suitability surfaces depending on tree species identity using spatial interpolation methods such as Kriging and Generalised Additive Models. We used Spatial Point Process Models to reconstruct the spatial distribution processes composed of purely biotic, abiotic or mixed covariates of the tree species. We found that spatial heterogeneity was important in all aspects we studied. Both, tree density and the distribution of the abiotic habitat components varied in space. Especially when species interacted with beech, abiotic heterogeneity played an important role: beech outcompeted the admixed species under most prevailing abiotic conditions. This way, beech influenced the spatial pattern of the six studied species by limiting available (niche) space via inter- and intraspecific competition. Here, Beech proved to be the superior competitor with no pronounced abiotic niche, but is mostly excluded from slopes. The remaining available niche space was often occupied by ecologically similar species, which formed typical associations in subregions of the study area less suitable for beech. We found spatial segregation between the three most abundant species Beech, Ash, and Hornbeam, coexistence by niches seem to be rather trait based rather than based on abiotic preferences. Habitat suitability and spatial distribution of Ash, Sycamore, and Norway Maple were more affected by the abiotic environmental condition than Beech, Hornbeam, and Elm. This indicates that the coexistence of rare species seems to be mediated by heterogeneity. Our study revealed that the difference in abiotic conditions, such as soil depth and plant-available water were relevant for habitat suitability at small spatial and temporal scales. When simulating the distribution pattern of the surveyed species, it became apparent that biotic interactions play an important part in shaping the scales at which aggregation or segregation happen in the abiotic environment. Beech and Sycamore both showed endogenous heterogeneity. For both species, point processes models incorporated several different interaction scales of intraspecific interaction. The interspecific interaction played only a minor role compared to the intraspecific one. All results together seem to underline that niche differentiation happens at the level of the individual allowing ecologically similar species to interact de facto neutrally within their niche space and thus, to coexist in presence of a strong competitor

THE SOILS OF THE MPANDAMATENGA PLAINS

This report presents results for the soil survey and mappi. indamatenga lacustrine clay plains in the Chobe district.The report has three chapters covering the following subjectsChapter 1 giros t, genera't description of the area covering such aspects as the location, population, communication, ,Climate, geology, geomorphology, natural vegetation and land use.Chapter 2 gives a systematic description of tje soils, soil classification systems, soil legend and soil units. In chapter 3, the phydiography of these lacustrine plains is described with some cross sectional illustrations.Finally, there are two appendices, one for soil chemical and physical analyses and the other tor selected representative soil profile descriptions and analytical data

Transcriptional co-expression and co-regulation of genes coding for components of the oxidative phosphorylation system

<p>Abstract</p> <p>Background</p> <p>The mitochondrial oxidative phosphorylation (OXPHOS) is critical for energy (ATP) production in eukaryotic cells. It was previously shown that genes coding for mitochondrial proteins involved in energy production co-express at the RNA level. Because the OXPHOS enzymes are multimeric complexes, we tested the hypothesis that genes coding for components of specific complexes are also co-regulated at the transcriptional level, and share common regulatory elements in their promoters.</p> <p>Results</p> <p>We observed for the first time that, not only OXPHOS genes as a group co-express, but there is a co-expression of genes within each of the five OXPHOS enzyme complexes, showing a higher degree of complexity in gene co-regulation. <it>In silico </it>analysis of homologous promoter sequences in mammals identified the likely core promoter elements for most genes encoding OXPHOS subunits/assembly factors. The results included a significant abundance of previously identified sites (e.g. NRF1, NRF2, ERRA and YY1), as well as several sites that had not been previously detected. Although we identified patterns that correlated to OXPHOS gene expression, we did not detect an OXPHOS complex-specific arrangement of transcription factor binding sites within the core promoter that could explain the tight co-expression of these functionally related genes.</p> <p>Conclusion</p> <p>This study mapped the core promoters of most OXPHOS related genes and provided an example of gene expression regulation based on the final protein arrangement within a linear metabolic pathway.</p

Reliable and valid measurement scales for determinants of the willingness to accept knowledge

Before any acquired knowledge is used or adds value to the receiving project (members), it must be accepted by its recipients, leading to an increase in their positive attitudes towards, and intended use of, the acquired knowledge. To be willing to accept knowledge, the receiving project's team members must perceive it to have value and be easy to use. The focus of this exploratory paper is to develop and empirically test relevant sub-dimensions of perceived value and ease-of-use. The sub-dimensions were identified through a literature review, and measurement scales were developed empirically by applying a well-established scale development methodology

A reappraisal of the Carboniferous macrofloras of the Zonguldak – Amasra Coal Basin, north-western Turkey

The Zonguldak – Amasra Coal Basin in north-western Turkey has Carboniferous terrestrial deposits ranging in age from Arnsbergian to late Asturian or possibly early Cantabrian. They yield macrofloras that allow detailed biostratigraphical correlations with sequences in Europe. These correlations suggest there are substantial gaps in the Zonguldak – Amasra succession, with middle to upper Namurian, upper Langsettian, Duckmantian and lower Asturian strata apparently being missing. This in turn suggests the area was subjected to significant tectonic instability during Pennsylvanian (late Carboniferous) times and that this might have been instrumental in initiating the progressive change in composition and eventual collapse of the coal swamp biome across Variscan Euramerica during Westphalian times.</p

Transition Contour Synthesis with Dynamic Patch Transitions

In this article, we present a novel approach for modulating the shape of transitions between terrain materials to produce detailed and varied contours where blend resolution is limited. Whereas texture splatting and blend mapping add detail to transitions at the texel level, our approach addresses the broader shape of the transition by introducing intermittency and irregularity. Our results have proven that enriched detail of the blend contour can be achieved with a performance competitive to existing approaches without additional texture, geometry resources, or asset preprocessing. We achieve this by compositing blend masks on-the-fly with the subdivision of texture space into differently sized patches to produce irregular contours from minimal artistic input. Our approach is of particular importance for applications where GPU resources or artistic input is limited or impractical

Fongs de Gréixer

Fongs de Gréixer. Es presenten els resultats de l'estudi dels fongs que creixen a la vall de Gréixer, (Berguedà, Barcelona) en forma de catàleg florístic. Es fa una revisió crítica i l'actualització de les 62 citacions bibliogràfiques i s'amplia el catàleg de la vall fins els 214 tàxons diferents (4 mixomicets, 8 ascomicets i 202 basidimicets). Entre les espècies citades, destaquem: Entoloma Olidum NoordeI. et T. Borgen, E. Vernum S. Lundell, Pluteus phlebophorus Cooke, Hemipholiota Populnea (Pers.) Bon i Phylloporus rhodoxanthus (Schwein.) Bres.Fungi of Gréixer. As a result of the fungal study carried out in the valley of Gréixer (Catalonia, Spain), we present a floristic catalogue herewith. After a critical review of the 62 bibliographic citations, and once updated, the catalogue has been increased to 214 different taxa (4 mixomycetes, 8 ascomycetes and 202 basidimycetes) ; among those, we can stand out: : Entoloma Olidum NoordeI. et T. Borgen, E. Vernum S. Lundell, Pluteus phlebophorus Cooke, Hemipholiota Populnea (Pers.) Bon i Phylloporus rhodoxanthus (Schwein.) Bres

Contribució a la flora dels fongs del Parc Natural del Cadí-Moixeró (Catalunya). I. El gènere Entoloma (Fr.) P. Kumm

Contribució a la flora dels fongs del Parc Natural del Cadí-Moixeró (Catalunya). I. El gènere Entoloma (Fr.) P. Kumm. Es presenten els primers resultat s dels estudis micològics que s'han estat duent a terme els darrers tres anys al Parc Natural del Cadí-Moixeró (Catalunya, Espanya) . En concret, es descriuen i s'il•lustren set espècies del gènere Entoloma, de les quals Entoloma dichroum (Pers.) P. Kumm., E. Nitens (Velen.) Noordel. i E. Olidum Noordel. et T. Borgen creiem que són noves citacions per a Catalunya, mentre que les altres, E. Byssisedum (Pers.) Donk, E. Catalaunicum (Singer) Noordel., E. Hebes (Romagn.) Trimbach, E. Mougeotii (Fr.) Hesler, E. Sericatum (Britze lm.) Sacc. i E. Vernum S. Lundell ja eren coneguts al nostre país.Contribution to the flora of fungi in the Cadí-Moixeró nature park in Catalonia I. The genus Entoloma (Fr.) P. Kumm. We present the first results of mycological studies performed over the last three years in the Cadí-Moixeró nature park (Catalonia, Spain). We describe and illustrate seven species of the genus Entoloma, of which Entoloma dichroum (Pers.) P. Kumrn., E. Nitens (Velen.) Noordel. and E. Olidum Noordel. et T. Borgen are believed to be new citation s for Catalonia, while the others, E. Byssisedum (Pers.) Donk, E. Catalaunicum (Singer) Noordel., E. Hebes (Romagn.) Trimbach, E. Mougeotii (Fr.) Hesler, E. Sericatum (Britzelm.) Sacc. and E. Vernum S. Lundell were already known in this region