Die chronologische Liste zeigt aktuelle Veröffentlichungen aus dem Forschungsbetrieb der Hochschule Weihenstephan-Triesdorf. Zuständig ist das Zentrum für Forschung und Wissenstransfer (ZFW).
Prof. Dr. Andreas Rothe,
Prof. Dr. Jörg Ewald,
David E. Hibbs
Berechtigungen: Peer Reviewed
Do admixed broadleaves improve foliar nutrient status of conifer tree crops? (2003) Forest Ecology and Management 172 (2-3), S. 327-338.
DOI: 10.1016/S0378-1127(01)00800-3
We investigated three Douglas fir–red alder stands in Oregon, USA, and five Norway spruce–European beech stands in Bavaria, Germany, to test the hypothesis that admixtures of broadleaved trees improve nutritional status of conifers. At each site needle samples from 20 to 30 conifer trees with varying proportions of broadleaves adjacent to the sample trees were taken and analysed for needle mass and the macronutrients N, P, K, Ca and Mg. The neighbourhood of each tree was described by the proportion of deciduous basal area within an 8 m circle. Ordination methods (principal component analysis; redundancy analysis) were used to test the dependency of the multivariate nutritional pattern in conifers on deciduous neighbours and rank correlation and regression were used to analyse bivariate relationships between tree species composition and descriptors of needle status. The statistical analyses yielded no evidence that deciduous admixtures improve foliar nutrition of conifers. Alongside with other empirical studies this shows that beneficial effects of broadleave admixtures on conifer nutrition are less common than postulated. Future research investigating the whole causal path relevant for tree nutrition and growth is necessary to improve our knowledge in the complex field of nutrition of mixed species forests.
Prof. Dr. Jörg Ewald
Berechtigungen: Peer Reviewed
The sensitivity of Ellenberg indicator values to the completeness of vegetation relevés (2003) Basic and Applied Ecology 4 (6), S. 507-513.
DOI: 10.1078/1439-1791-00155
Ordination and calibration (indicator species analysis) are based on the taxonomic composition and richness of communities. How strongly does the performance of a widely used method like weighted averaging of Ellenberg indicator values depend on the completeness of samples? Based on a stratified random sample of coincident phytosociological relevés of forest understorey and environmental measurements (overstorey cover, elevation, moisture index, pH and C/N-ratio in topsoil) indicator values for light, temperature, moisture, soil acidity and nitrogen were tested. To simulate reduced sampling effort and uncomplete representation of plant diversity, the original compositional matrix was reduced by randomly deleting 1, 10, 20, 40 and 80% of species records with low abundance. The relationship between indicator values based on the full matrix and environmental variables was closest for temperature (R2 = 0.53) and lowest for soil nitrogen (R2 = 0.28). Deletion of low-abundance species records affected the correlations only weakly. With as little as 20% of the original species records (or 40% of gamma- and 20% of alpha-diversity) explained variance was still in a range of 0.26 to 0.37. The overall multivariate association between species composition and environment, as measured by Mantel statistics, was more strongly affected by the ommission of species records than the Ellenberg method. The relative resilience of Ellenberg indicator values to incomplete sampling is attributed to its predominant reliance on coarse structural information, i.e. the dominance pattern of relatively few plant species. Finely-tuned local indicator systems perform better by exploiting the idiosyncratic information of rare species. Choosing an optimal sampling scale involves a tradeoff between noise and completeness, an issue that has been largely neglected by environment-composition studies.
Prof. Dr. Jörg Ewald
Buchbesprechung von Hubbell, S. P.: The Unified Neutral Theory of Biodiversity and Biogeography (2002) Forstwissenschaftliches Centralblatt 121 , S. 152-153.
Prof. Dr. Jörg Ewald
Berechtigungen: Peer Reviewed
Book review of Hubbell, S. P.: The Unified Neutral Theory of Biodiversity and Biogeography (2002) Folia Geobotanica 37 , S. 355-356.
Dr. Helge Walentowski,
Hans-Jürgen Gulder,
Dr. Christian Kölling,
Prof. Dr. Jörg Ewald,
Winfried Türk
Regionale natürliche Waldzusammensetzung Bayerns (2002) Berichte aus der Bayerischen Landesanstalt für Wald und Forstwirtschaft, LWF-Wissen 32, 97 S. + Karte .
Prof. Dr. Jörg Ewald
Berechtigungen: Peer Reviewed
Multiple controls of understorey plant richness in mountain forests of the Bavarian Alps (2002) Phytocoenologia 32 (1), S. 85-100.
DOI: 10.1127/0340-269X/2002/0032-0085
The management of biodiversity in forests requires a basis derived from community ecology. In a transect representative of montane and subalpine forests at the northern fringe of the Alps, I studied the relative importance of the tree layer diversity and age, understorey cover and species pool size for species richness of vascular understorey communities. Regional species pools were estimated for seven community types represented in a large phytosociological database. Local species pool size was modelled for each community type on the basis of regional pools and grid cell data from floristic mapping. Tree-layer diversity was the only study variable unrelated to species richness. Understorey richness increased with understorey cover, species pool and stand age. Combined, these three predictors explained 46 % of the observed variation in richness in a regression model. When the species pool variable was partioned into its components, synecological information was a more powerful predictor of richness than variation in the local flora, which was likely due to the strength of site effects related to soil pH and to the relatively small geographic extent of the study. Species richness in mountain forests can be forecasted by maps of community types. Within the bounds of natural site-dependent diversity, extensive management practices allowing for moderate to high cover of understorey and the development of old growth stands favour the occurrence of forests rich in vascular plant species.
Prof. Dr. Jörg Ewald
Berechtigungen: Peer Reviewed
A probabilistic approach to estimating species pools from large compositional matrices (2002) Journal of Vegetation Science 13 (2), S. 191-198.
DOI: 10.1111/j.1654-1103.2002.tb02039.x
Species pools are increasingly recognized as important controls of local plant community structure and diversity. While existing approaches to estimate their content and size either rely on phytosociological expert knowledge or on simple response models across environmental gradients, the proposed application of phytosociological smoothing according to Beals exploits the full information of plant co‐occurrence patterns statistically. Where numerous representative compositional data are available, the new method yields robust estimates of the potential of sites to harbour plant species. To test the new method, a large phytosociological databank covering the forested regions of Oregon (US) was subsampled randomly and evenly across strata defined by geographic regions and elevation belts. The resulting matrix of species presence/absence in 874 plots was smoothed by calculating Beals' index of sociological favourability, which estimates the probability of encountering each species at each site from the actual plot composition and the pattern of species co‐occurrence in the matrix. In a second step, the resulting lists of sociologically probable species were intersected with complete species lists for each of 14 geographical subregions. Species pools were compared to observed species composition and richness. Species pool size exhibited much clearer spatial trends than plot richness and could be modelled much better as a function of climatic factors. In this framework the goal of modelling species pools is not to test a hypothesis, but to bridge the gap between manageable scales of empirical observation and the spatio‐temporal hierarchy of diversity patterns.
A. Zollner,
Prof. Dr. Jörg Ewald,
K. Ketterer
Die Abhängigkeit der Vegetation eines südostbayerischen Hochmoores von Entwässerung und sekundärer Bewaldung (2001) TELMA - Berichte der Deutschen Gesellschaft für Moor- und Torfkunde 31 , S. 231-247.
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Gerhard Radlmayr
Referent für Wissenstransfer und Forschungskommunikation
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