1,721,589 research outputs found
Monospecific and mixed stands of Fagus and Nothofagus species in the temperate zones of the world
No full textMonospecific and mixed stands of Fagus and Nothofagus species in the temperate zones of the world
No full textAuswirkungen von Biodiversitätsmaßnahmen auf die Segetalflora auf intensiv bewirtschafteten landwirtschaftlichen Flächen - Ergebnisse aus dem F.R.A.N.Z.-Projekt
No full textComplementarity in the use of nitrogen forms in a temperate broad-leaved mixed Forest
No full textBackground: The complementary use of different forms of soil nitrogen (N) might lead to a higher productivity of mixed forests than monocultures, but convincing evidence for temperate mixed forests is scarce. Aims: We searched for species differences in N uptake rates and the preference for NH4+, NO3− or glycine among five temperate broad−leaved tree species (Acer pseudoplatanus, Carpinus betulus, Fagus sylvatica, Fraxinus excelsior, Tilia cordata) in a mature mixed stand. Methods: 15N tracer was added to the soil and its accumulation in fine root biomass was analysed after 10 min, 1 h and 1 d. Results: The estimated root uptake rates of the species were in the range of 5–46 µg N g−1 root h−1 for NH4+, 6–86 µg N g−1 h−1 for NO3− and 4–29 µg N g−1 h−1 for glycine during the first hour after tracer application. Carpinus, Tilia and Acer tended to prefer NH4+ over NO3−, while Fraxinus showed equal preference for both N forms and Fagus seemed to prefer NO3−. Conclusions: The five co-existing tree species differed in uptake rates and partly in their N form preference, but complementarity in the use of different N forms seems to be of minor importance in this forest because tree species appear to be rather flexible in their N form use
The in situ root chamber: A novel tool for the experimental analysis of root competition in forest soils
No full textCompetition between the roots of mature trees in mixed forests is not well understood because adequate methods for studying this interaction under field conditions are not yet available. We present a novel root chamber (size: 90 x 70 x 30 mm) that allows growth monitoring of individual tree fine roots in the soil while altering root competition situations experimentally. Fine roots of mature trees that were carefully uncovered from the soil were allowed to grow for several months in the chamber which contained soil material from the root's close proximity. Fine root increment was quantified by optical root length determination at the beginning and the end of the experiment. By placing individual fine roots of a tree species together with a second conspecific or allospecific root, the chamber allows one to simulate conditions of intra- and interspecific competition, and to test hypotheses on intensity and direction of root competition in the soil of mixed forests. We investigated the applicability of the root chamber in a mature beech-oak mixed forest in which beech is known to be a superior competitor above-ground. One-hundred and six chambers with different combinations of beech and oak fine roots were exposed in the soil for 180 or 438d. In two-species chambers, which contained one beech and one oak root allowing for interspecific competition, beech fine roots grew significantly faster than oak roots. Furthermore, beech roots tended to show a higher growth rate in two-species chambers than in single-species chambers (two beech roots: intraspecific competition). In contrast, oak roots tended to grow slower when placed together with beech than when growing together with oak. By expressing the competitive strength of beech and oak roots with the relative competition intensity (RCI) index, evidence of asymmetric interspecific root competition in favour of beech was obtained. The potentials of this technique are related to the fact that replicated experiments with fine roots of adult trees can be conducted in the field; a certain artificiality, which is inherent to all rhizosphere experiments, represents the main limitation. From this study we conclude that while there are some Limitations, in situ root chambers represent an important step towards the experimental analysis of root competition in forests. (c) 2005 Elsevier GmbH. All rights reserved
Consistent patterns of elevational change in tree taxonomic and phylogenetic diversity across Malesian mountain forests
No full textAim In order to investigate the relative importance of ecological (habitat specialization) and biogeographical (speciation, geographical dispersal limitation) processes as causes of non‐random spatial distribution of tree species in the mountain forests of Malesia, we analysed the elevational change in the taxonomic and phylogenetic diversity of tree assemblages in different biogeographical subregions. Location Malesia (Borneo, Java, Sulawesi and the Philippines). Methods Tree inventory data of 12 old‐growth forests from a wide elevational range (650–3080 m a.s.l.) were taxonomically harmonized and standardized (50 random draws of 245 individuals each per plot), and the phylogeny of 204 genera was resolved and scaled to its evolutionary origin. The taxonomic and phylogenetic diversities were calculated using effective generic measures, and the diversity patterns analysed by regression, ordination and classification. Results The primary factor determining the diversity patterns of the tree assemblages was elevation, whereas the influence of region was surprisingly low. This results in common elevational patterns in taxonomic and phylogenetic community structure across western and central Malesia. The major clades of the contemporary mountain forest trees must therefore have evolved before the formation of the Malay Archipelago in its present form (sympatric speciation). Taxonomic richness and phylogenetic diversity exhibited opposite trends with elevation. Generic richness decreased linearly with elevation; the phylogenetic structure of high‐elevation forests revealed overdispersion, indicating convergent trait evolution towards higher elevations, whereas the submontane and colline assemblages showed clustering with a considerable number of confamilials. The upper montane forests of Borneo and Sulawesi were characterized by the dominance of Southern Hemisphere conifers, which differentiated them from lower‐elevation communities. Main conclusions Our results indicate that ecological, evolutionary and biogeographical processes (environmental filtering, sympatry and long‐distance dispersal) have shaped the contemporary community structure of Malesian mountain forests. Wallace's Line may represent a significant barrier between the lowland tree floras of Borneo and Sulawesi, but this is not true for those at higher elevations. The uniqueness of high‐elevation forests in terms of their high phylogenetic diversity and of their unusual structure calls for a high priority in conservation programmes
Air humidity, soil moisture and soil chemistry as determinants of the herb layer composition in European beech forests
No full textWhat role does air humidity play as an environmental factor for the abundance and distribution of temperate woodland herbs? Beech forests on calcareous soils in southern lower Saxony, central Germany. The abundance of woodland herb species and total herb cover were investigated in 60 plots with contrasting exposure, slope angle and relief type. On all plots, air humidity, air temperature, soil moisture, photosynthetically active radiation, pH (H(2)O) and concentration of salt-exchangeable Ca, Mg and K were measured. Species-environment relationships were analysed with multiple regression analysis and CCA. Air humidity (RH), soil moisture and the concentration of exchangeable Ca and K, but not light, C/N ratio and the concentration of exchangeable Mg were identified as the most important abiotic factors influencing the cover of the most abundant plant species and total herb cover. RH varied substantially across the different forest floor site types and influenced species abundance independent of soil moisture. In several species (including Mercurialis perennis and Impatiens noli-tangere), RH was found to be a key environmental factor. Other species such as Aegopodium podagraria and Lamiastrum galeobdolon depended more on elevated soil moisture, while RH was less important. This study showed that the distribution of widespread temperate woodland herb species depends on high air humidity, and that certain sensitive species do not occur at sites with reduced air humidity even though soil moisture is high. Thus, high air humidity and ample soil moisture are key abiotic factors in beech forests on calcareous soils. Shade level (PAR) was found to be of secondary importance
Ein struktureller und funktionaler Vergleich
No full textThis article compares tropical rainforests and temperate broad-leaved deciduous forests with respect to forest structure, above- and belowground biomass, carbon in soil and deadwood, and net primary production based on a literature review. We test the widely held opinion that tropical forests are taller, richer in biomass and more productive than temperate forests. The comparison shows that tropical forests are not principally taller and richer in biomass (this is true for certain Paleotropical forests but not for Neotropical forests), they do not store more carbon in soil and deadwood, do not have higher leaf area indices and are not more productive on a daily basis than temperate broad-leaved deciduous forests. However, tropical forests harbor an exuberant biodiversity with ~ 85 % of the world’s tree species and 59-84 % of all vascular plants on less than 12 % of the earth’s land surface area
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