3,113 research outputs found
The estimation of aboveground biomass and nutrient pools of understorey plants in closed Norway spruce forests and on clearcuts
No full textThe estimation model PhytoCalc allows a non-destructive quantification of dry weight and nutrient pools of understorey plants in forests by using the relationship between species biomass, cover and mean shoot length. The model has been validated with independent samples in several German forest types and can be a useful tool in forest monitoring. However, in open areas within forests (e.g. clearcuts), the current model version underestimates biomass and produces unreliable nutrient pool estimations. Thus, tissue density, as approximated by leaf dry matter content (LDMC), is systematically higher under high light compared to low light conditions. We demonstrate that the ratio of LDMC under clearcut conditions to LDMC under forest conditions can be used to adjust the PhytoCalc model to clearcut conditions. We investigated the LDMC ratio of five exemplary species commonly occurring on clearcuts. Integrating the square of the ratio as a correction factor improved estimates of biomass to more than 70% fit between observations and predictions. Results also suggest this ratio can be used to correct nutrient concentrations modelled in PhytoCalc, which tend to be overestimated in clearcuts. As morphological groups of plant species exhibit significantly different ratios, we advise using group-specific correction factors for clearcut adjustments in the future
Nitrogen in forest communities: the alteration of its importance
No full textDuring the last decades the effect of nitrogen on forest ecosystems has totally changed: Formerly, vegetation growth was limited by nitrogen, today nitrogen must be seen as a pollutant. The increased deposition of nitrogen into forest-ecosystems affects not only the vegetation composition, but also endangers the meaning of forests as a source for drinking water. in the article the impact of increased nitrogen availability on forest ecosystems is shown. Especially the possibilities and advantages of using vegetation as an indicator for the impact of nitrogen are discussed and compared with methods of technical measurements. Based on these results it is strongly recommended to enhance the explanatory power of technical measurements by additionally carrying out vegetation analyses
High functional diversity is related to high nitrogen availability in a deciduous forest - evidence from a functional trait approach
No full textThe current study tested the assumption that floristic and functional diversity patterns are negatively related to soil nitrogen content. We analyzed 20 plots with soil N-contents ranging from 0.63% to 1.06% in a deciduous forest near Munich (Germany). To describe species adaptation strategies to different nitrogen availabilities, we used a plant functional type (PFT) approach. Each identified PFT represents one realized adaptation strategy to the current environment. These were correlated, next to plant species richness and evenness, to soil nitrogen contents. We found that N-efficient species were typical for low soil nitrogen contents, while N-requiring species occur at high N-contents. In contrast to our initial hypotheses, floristic and functional diversity measures (number of PFTs) were positively related to nitrogen content in the soil. Every functional group has its own adaptation to the prevailing environmental conditions; in consequence, these functional groups can co-exist but do not out-compete one another. The increased number of functional groups at high N-contents leads to increased species richness. Hence, for explaining diversity patterns we need to consider species groups representing different adaptations to the current environmental conditions. Such co-existing ecological strategies may even overcome the importance of competition in their effect on biodiversity
Herb-layer diversity in deciduous forests: Raised by tree richness or beaten by beech?
No full textWhere natural production capacity permits, modern silvicultural management in Central Europe frequently aims at the development of mixed broadleaved stands, instead of pure European beech (Fagus sylvatica) stands. It is crucial to study the effects of these tree-layer diversity variations on herb-layer vegetation, since herb-layer vegetation contributes significantly to ecosystem functioning in forests. In Hainich National Park (Thuringia, Germany), we conducted observational research in deciduous stands to investigate whether herb-layer diversity was related to canopy-layer diversity, and to ascertain possible causal mechanisms. We found that herb-layer vegetation of deciduous forest stands rich in canopy species appeared to be more diverse than herb-layer vegetation of beech-dominated stands. We surmise that herbaceous understorey diversity was indirectly influenced by canopy tree species through the medium of the altered environmental factors soil pH and litter layer thickness. Apparently, lower beech proportion had a more profound effect than the number of secondary tree species. There were no correlations between herb-layer diversity and light transmissibility of the canopy layer, indicating that the light factor was not crucial for herb-layer diversity. At least for the Hainich research sites, our results indicated that small-scale light and soil heterogeneity is insignificant for herb-layer diversity. We found several herb-layer species whose occurrence was particularly correlated with tree-layer diversity and environmental factors. Remarkably, all species positively correlated with soil pH were important for the phytosociological classification of the research sites. Beech-dominated research sites showed high tree-layer volumes, whereas research sites with high tree-layer diversity tended to feature lower tree-layer volumes. These findings could be the result of differing former silvicultural systems and varying soil clay contents affecting tree species composition. In contrast, herb-layer biomass was positively correlated with tree-layer diversity. Herb-layer productivity might be promoted in more diverse research sites by increased nutrient supply and base saturation. It is also possible that greater beech proportion interfered with herb-layer productivity. However, herb-layer biomass was also positively correlated with herb-layer diversity. Hence, our study hints that positive diversity-functioning relationships might occur in the herb-layer of the deciduous forest under investigation. (C) 2008 Elsevier B.V. All rights reserved
Reflexionen über Geschichte und historisches Lernen. Festschrift für Ulrich Mayer zum 65. Geburtstag
No full textDiverse tree layer - rich regeneration? Natural regeneration of species-rich deciduous forests in Hainich National Park
No full textIn Hainich National Park (Thuringia, Germany), an area with broad deciduous forests rich in tree species, we investigated relationships between tree-layer and regeneration diversity in consideration of deer browsing. In the 21 stands under investigation, which were characterised by closed canopies and a gradient from pure beech (Fagus sylvatica) stands to mixed stands with Lip to 11 deciduous tree species, we found that tree-layer and regeneration diversity were positively correlated (Tab. 3, Tab. 4, Fig. 4). But the composition of both strata differed considerably. In beech-dominated stands regeneration was more diverse than the tree layer, while in highly diverse stands the Situation was contrary (Fig. 2). Main tree species in the regeneration were sycamore (Acer pseudoplatanus), ash (Fraxinus excelsior), Norway maple (Acer platanoides), and beech (Fagus sylvatica) (Fig, 3). Oaks (Quercus spp.), hornbeams (Carpinus betulus), and limes (Tilia spp.), which became more abundant in the canopy with increasing tree-layer diversity, were nearly absent in the regeneration. Quality and quantity of the regeneration were obviously negatively affected by increasing litter layer thickness and soil acidity, which varied due to canopy-species effects. Particularly beech foliage, which decomposes poorly and results in acid soil conditions, had a limiting effect oil regeneration. There were no significant correlations between quality and quantity of the regeneration and the irradiance transmitted through the closed canopy (Tab. 5). A secondary stand including higher regeneration was missing between canopy layer and small growing regeneration (Fig. 1). Presumably it was too dark for further growing of regeneration under the canopy of all investigated stands; deer browsing had intensified this effect. Browsing intensity was neither quantitatively nor qualitatively correlated with regeneration supply, but it was strongly related to vertical and horizontal tree-layer diversity (Fig. 5). Particularly former coppices with standards and selection stands with high tree-species richness offer protection from unpleasant weather in winter (thermal cover). This is made possible by Suppressed trees with low-set branches, which are a key stimulus for the habitat choice particularly of roe deer (Capreolus capreolus)
Diverse tree layer - rich regeneration? Natural regeneration of species-rich deciduous forests in Hainich National Park
No full textIn Hainich National Park (Thuringia, Germany), an area with broad deciduous forests rich in tree species, we investigated relationships between tree-layer and regeneration diversity in consideration of deer browsing. In the 21 stands under investigation, which were characterised by closed canopies and a gradient from pure beech (Fagus sylvatica) stands to mixed stands with Lip to 11 deciduous tree species, we found that tree-layer and regeneration diversity were positively correlated (Tab. 3, Tab. 4, Fig. 4). But the composition of both strata differed considerably. In beech-dominated stands regeneration was more diverse than the tree layer, while in highly diverse stands the Situation was contrary (Fig. 2). Main tree species in the regeneration were sycamore (Acer pseudoplatanus), ash (Fraxinus excelsior), Norway maple (Acer platanoides), and beech (Fagus sylvatica) (Fig, 3). Oaks (Quercus spp.), hornbeams (Carpinus betulus), and limes (Tilia spp.), which became more abundant in the canopy with increasing tree-layer diversity, were nearly absent in the regeneration. Quality and quantity of the regeneration were obviously negatively affected by increasing litter layer thickness and soil acidity, which varied due to canopy-species effects. Particularly beech foliage, which decomposes poorly and results in acid soil conditions, had a limiting effect oil regeneration. There were no significant correlations between quality and quantity of the regeneration and the irradiance transmitted through the closed canopy (Tab. 5). A secondary stand including higher regeneration was missing between canopy layer and small growing regeneration (Fig. 1). Presumably it was too dark for further growing of regeneration under the canopy of all investigated stands; deer browsing had intensified this effect. Browsing intensity was neither quantitatively nor qualitatively correlated with regeneration supply, but it was strongly related to vertical and horizontal tree-layer diversity (Fig. 5). Particularly former coppices with standards and selection stands with high tree-species richness offer protection from unpleasant weather in winter (thermal cover). This is made possible by Suppressed trees with low-set branches, which are a key stimulus for the habitat choice particularly of roe deer (Capreolus capreolus)
Geschichtswissenschaft, Geschichtskultur, Geschichtsunterricht – Einführung in die Reihe.
No full textReflexionen über Geschichte und historisches Lernen. Festschrift für Ulrich Mayer zum 65. Geburtstag
No full textHistorisches Lernen für das 21. Jahrhundert : Festschrift für Markus Bernhardt zum 65. Geburtstag
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