Central European Tree Research Articles

How to quantify forest management intensity in Central European forests

Existing approaches for the assessment of forest management intensity lack a widely accepted, purely quantitative measure for ranking a set of forest stands along a gradient of management intensity. We have developed a silvicultural management intensity indicator (SMI) which combines three main characteristics of a given stand: tree species, stand age and aboveground, living and dead wooden biomass. Data on these three factors are used as input to represent the risk of stand loss, which is a function of tree species and stand age, and stand density, which is a function of the silvicultural regime, stand age and tree species. Consequently, the indicator consists of a risk component (SMIr) and a density component (SMId). We used SMI to rank traditional management of the main Central European tree species: Norway spruce (Picea abies [Karst.] L.), European beech (Fagus sylvatica L.), Scots pine (Pinus sylvestris L.), and oak (Quercus robur L. and Quercus petraea L.). By analysing SMI over their whole rotation period, we found the following ranking of management intensity: oak<beech<pine≪spruce. Additionally, we quantified the SMI of actual research plots of the German Biodiversity exploratories, which represent unmanaged and managed forest stands including conifer forests cultivated outside their natural range. SMI not only successfully separate managed from unmanaged forests, but also reflected the variability of forest management and stand properties across the entire sample and within the different management groups. We suggest using SMI to quantify silvicultual management intensity of stands differing in species composition, age, silvicultural system (even-aged vs. uneven-aged), thinning grade and stages of stand conversion from one stand type into another. Using SMI may facilitate the assessment of the impact of forest management intensity on biodiversity in temperate forests.

Annuality of Central European deciduous tree leaves delimits community development of epifoliar pigmented fungi

Communities of dark pigmented epifoliar fungi of various deciduous tree species from habitats in the surroundings of Bayreuth (Upper Franconia, Germany) were compared to those of evergreen plants overwintered in a greenhouse. The fungi were mainly assignable to the genera Aureobasidium , Cladosporium , Alternaria and Phoma , with most plants hosting more than one fungal genotype or taxon. While a host preference was not detected among the fungal taxa, the community composition significantly differed between annual and perennial leaves. The results indicate that the epifoliar fungal community found on leaves of deciduous Central European trees represents an early developmental stage of the same, but further developed community, found on older evergreen leaves. We therefore assume that the life-span of deciduous leaves is too short for the fungal community to reach a steady state. ► Epifoliar pigmented fungi differed between deciduous and evergreen trees. ► Aureobasidium pullulans dominated on annual and young perennial leaves. ► Predominance of Cladosporium cladosporioides was indicative for older leaves. ► Fungal communities on annual leaves represent an early developmental stage. ► Life-span of annual leaves is too short for the community to reach a steady state.

Phenols in Leaves and Bark of Fagus sylvatica as Determinants of Insect Occurrences

Beech forests play an important role in temperate and north Mediterranean ecosystems in Greece since they occupy infertile montane soils. In the last glacial maximum, Fagus sylvatica (beech) was confined to Southern Europe where it was dominant and in the last thousand years has expanded its range to dominate central Europe. We sampled four different beech forest types. We found 298 insect species associated with beech trees and dead beech wood. While F. sylvatica and Quercus (oak) are confamilial, there are great differences in richness of the associated entomofauna. Insect species that inhabit beech forests are less than one fifth of those species living in oak dominated forests despite the fact that beech is the most abundant central and north European tree. There is a distinct paucity of monophagous species on beech trees and most insect species are shared between co-occurring deciduous tree species and beech. This lack of species is attributed to the vegetation history and secondary plant chemistry. Bark and leaf biophenols from beech indicate that differences in plant secondary metabolites may be responsible for the differences in the richness of entomofauna in communities dominated by beech and other deciduous trees.

Transpiration of Pinus rotundata on a wooded peat bog in central Europe

Transpiration of a central European endemic tree species, Pinus rotundata Link, growing on a wooded peat bog in the Třeboň Basin, Czech Republic, was studied in 1999–2000. Transpiration was measured by sap flow techniques (heat field deformation method) on individual trees and scaled up to stand level. The radial patterns of sap flow density showed narrow peaks in the outer part of the xylem, sapwood accounted for 47–60% of the xylem radius and 72–84% of the xylem basal area. Adult trees tolerated well both short-term flooding during the growing season and drawdown of the water table to a depth of 60 cm below ground level. The maximum and mean daily transpiration rates were 3.0 and 1.8 mm per day, and were thus similar to published data for Scots pine. The seasonal total transpiration (25 April–20 October 2000, 180 days) amounted to 322 mm, or 62% of the potential evapotranspiration over this period. This canopy transpiration was compensated by 319 mm of precipitation. The difference between the accumulated precipitation and the accumulated transpiration (derived from seasonal sap flow measurements) closely mimicked the seasonal course of the water table.

The spontaneous flora around street trees in cities—A striking example for the worldwide homogenization of the flora of urban habitats

Cities are well known as rich in vascular plant species. To evaluate the importance of this richness for global biodiversity it is necessary to know the degree of homogenization of the city flora at a continental or even worldwide scale. Therefore, we looked for a habitat type that is typical urban and which is represented in nearly all cities of the world: the area around street trees (“ Baumscheiben”). The spontaneous flora of this habitat was recorded in seven West and Central European metropolises situated in six countries and in Baltimore (USA). To test for floristic homogenization, the dissimilarity among the Baumscheiben Flora in the European cities was compared with dissimilarity among relevés of the potential natural vegetation in the cities. On average 81 species were found growing on Baumscheiben in each of the European cities. 29 species (i.e. more than one third of the total) were found in every city, 59 species (i.e. 74%) were represented in at least four of the seven cities. The obvious homogenization of the flora of this habitat is confirmed by low total variation among European Baumscheiben. Furthermore, the dissimilarity among Baumscheiben was much lower than among the potential natural vegetation (forests) around these cities. There is not only low variation between the Baumscheiben flora of the seven European metropolises analyzed, but also great similarity to the Baumscheiben flora of Baltimore: 80% of the species found on Baumscheiben in Baltimore also belong to the spontaneous flora of most European cities and 26% even belong to the group of the most common species of West and Central European tree bases.

Rapid change in adaptive performance from one generation to the next in Picea abies—Central European trees in a Nordic environment

Seedlings of open-pollinated Picea abies families from Norwegian and Central European parent trees standing at three sites in Norway were tested for timing of bud set at the end of the first growth season together with seedlings from control provenances producing seeds at their geographical origin. The parental origins were confirmed with a maternally inherited mitochondrial marker that distinguishes trees of the Northern European range from those of the Central European range. The seedlings from the families of Central European mother trees producing seeds in Norway had on average a bud set more similar to the families of local Norwegian origin producing seeds at the same site than the provenance of the same Central European origin. It is argued that the rapid change in this adaptive trait from one generation to the next can be explained by recent research results demonstrating that day length and temperature conditions during embryo formation and maturation can influence the phenotypic performance of seedlings in Norway spruce. This effect may influence the fitness of naturally regenerated plants produced in plantations of Central European trees in Norway.

Abundance, niche breadth, and niche occupation of Central European tree species in the centre and at the margin of their distribution range

How abundance, niche breadth and niche occupation of species change within the distribution range remains unresolved for tree floras. We compared populations of three common and three rare European tree species in the distribution centre and at the eastern margin with respect to abundance, niche breadth, and preferential occurrence along several soil-related niche axes. We hypothesised: (i) that abundance is higher, and niche breadth greater, in the distribution centre than at the margin, (ii) that the occupied niche differs between central and marginal populations with species being restricted to more favourable soils at the margin, and (iii) that common and rare species show different patterns. We characterised the occupied niche and niche breadth in a semi-quantitative way and discuss the role of human impact on tree abundance in the light of evidence from paleoecology and forest dynamics research. Five of the six species are more abundant in the centre than at the margin, at least in the natural vegetation prior to human intervention. In contrast to soil niche breadth, the preference for soil chemical and hydrological properties differed between centre and margin. Contrary to expectation, a shift to less fertile and partly also drier sites at the margin was observed, although bedrocks which give rise to the development of fertile soils were more frequent in Slovakia (ca. 49% of the total area compared to 20% in Central Germany) and bedrock types which produce infertile soils were more abundant in Central Germany (about 23% vs. 2% in Slovakia). While the abundant-centre-distribution hypothesis is supported by our data, we found no conclusive evidence of competitive displacement of weaker competitors and of a niche shift of superior competitors to more favourable sites at the range margin. Factors other than competition must be responsible for the observed niche shifts. Higher drought stress does not seem to be a limiting factor at the eastern margin, where dry sites were occupied more frequently compared to the centre.

The relationships between abundance, range size and niche breadth in Central European tree species

AbstractAim Range size and niche breadth have been found to be positively related to abundance in many plant and animal groups. We tested these two relationships for the tree species flora of Central Europe; that is, for all 25 species that have their distribution centre in this region.Location Eurasia, with a focus on Central Europe.Methods We devised an abundance and niche variable classification system to transform the existing literature data into a semi‐quantitative assessment of abundance and niche breadth (in terms of soil chemical and physical variables, and temperature) for each of the 25 tree species. Regression analyses between abundance, range size and niche breadth were conducted for the entire species sample and for subsets of species defined by their ecology or phylogeny.Results The relationship between abundance in the distribution centre and range size was weak for the Central European tree species. However, significant abundance–range size relationships were found for phylogenetically or ecologically more homogenous species groups (for example for trees of the order Rosales and for mid‐successional tree species). Realized niche breadth was positively related to range size in the case of temperature, but not for soil‐related variables. No relationship existed between niche breadth and abundance in the distribution centre.Main conclusions We hypothesize that the weak relationship between abundance and range size is primarily a consequence of substantial ecological and phylogenetic heterogeneity within this rather species‐poor assemblage. The positive relationship between realized temperature niche breadth and range size emphasizes the strong influence of climatic variables on plant distribution patterns over continental or global scales.

Variable desiccation tolerance in Acer pseudoplatanus seeds in relation to developmental conditions: a case of phenotypic recalcitrance?

Nine seedlots of the widely planted southern and central European native tree species Acer pseudoplatanus L. were collected along a north-south gradient spanning 21° of latitude in Europe. We investigated how the heat sum during seed development influences seed maturity as assessed by physical, physiological and biochemical traits. Using principal component analysis we found predictable and consistent patterns in all traits, which correlated with heat sum. For example, compared with fruits from their native range (Italy and France, heat sum >3000°C d), fruits from the coldest location (Scotland; heat sum of 1873°C d) were shorter (c. 30 v. 42 mm), germinated over a narrower temperature range (5-20 v. 5-35°C) and had smaller embryos (28 v. > 70 mg) with a higher water content (c. 63 v. 48%), less negative solute potentials (c. -2.4 v. -4.1 MPa) and were more desiccation sensitive (critical water potential of -20.2 v. -55.4 to -60.7 MPa). The observed level of desiccation-tolerance for the French and Italian seedlots is more consistent with the intermediate category than the previous classification of A. pseudoplatanus as recalcitrant. Our results demonstrate that a lower heat sum causes fruits from northern Europe to be dispersed before maximum potential seed quality is achieved.

Modified dispersal‐related traits in disjunct populations of bird‐dispersed Frangula alnus (Rhamnaceae): a result of its Quaternary distribution shifts?

Many European tree species survived Pleistocene glaciations in Mediterranean refugia and rapidly recolonized temperate Europe afterwards. Inter‐ and postglacial migration processes are assumed to have catalized evolutionary optimizations of dispersal‐related traits, but up to now empirical evidence is lacking in vertebrate‐dispersed plants. We investigated if south Iberian glacial relict and central European “colonizer” populations of the bird‐dispersed treeFrangula alnushave experienced differentiations of dispersal‐related traits which increase the mobility of northern populations. A comparison of lifetime reproductive strategy, disperser guilds, ripening phenology, and fruit design revealed considerable differences. Compared to south Iberian conspecifics, central European plants were considerably smaller and experienced a highly accelerated generation turnover. In south Iberian populations seed dispersal was carried out almost completely by resident birds which occurred in constant abundances throughout the ripening season. In contrast, central European seeds were dispersed by migrants whose abundances changed considerably during the ripening season. Several bird species were involved in both study areas but rendered different importance for seed dispersal. The fruit ripening pattern was highly asynchronous throughout the ripening season in south Iberia, while central European trees showed a complex ripening sequence which resulted in a significant correlation between fruit abundance and changing disperser availability. Central European fruits were smaller and showed a considerably smaller seed load than south Iberian fruits, thus presumably being more attractive for their small‐sized main dispersers (Sylvia warblers). Chemical analyses revealed significant differences in contents of water, glucose, fructose, proteins, ash. and phenolic compounds. The extensive differentiation of dispersal‐related traits inF. alnussuggests that even weak selective pressures by frugivores may induce evolutionary adjustments of dispersal traits over large time scales. We suggest that the differences we observe today evolved during the species' distribution shifts in the Quaternary.

Environmental Archaeology of Prehistoric NW Crete

The occurrence of Central European tree-types no longer growing on Crete indicates that Neolithic and Bronze Age climates were moister than at present. Of equal significance is the appearance of large quantities of olive pollen in Late Neolithic levels, suggesting the practice of olive cultivation. Early Bronze Age levels show a disappearance of some Central European tree pollen and an increase in Mediterranean tree types, suggesting that the climate became somewhat drier. The pollen findings are used along with other environmental and archaeological data to reconstruct landscapes for the Neolithic and Bronze Age of NW Crete.

The bark of trees: thermal properties, microclimate and fauna.

The thermal properties of four different types of bark were investigated on twentyfour central European tree species using thermocouples. Tree species with white bark avoid overheating of their surface by reflection of the radiation. Species with fissured and scaly barks shade inner parts of their bark. Some tree species with fissured barks show high insulation across the bark. Smooth and thin barks show no adaptation to avoid overheating. These tree species (in central Europe e.g. Fagus sylvatica) have to form closed stands and are not able to occur in open stands as tree species with structured or white bark types.The arthropod fauna of the same bark types was studied on six tree species using three collecting methods. The microclimate on the bark determines the number per cm2 of some species, some are active during winter, and other tend to aptery and reproduce parthenogenetically. On smooth bark one species dominates, whereas a highly diverse fauna lives on fissured barks. The occurrence of species on bark is determined by the microstructure, microclimate and consistence of the epiphyts. If tree species alter within forest ecosystems the dominant species on bark will persist. Specialists of fissured barks will die out if tree species with smooth bark (Fagus sylvatica) form the central European forest.

Symposium on the glacial refugia and migration paths of Central and North European trees

A symposium on the glacial refugia and migration paths of Central and North European trees was sponsored by the Løvenholm foundation and held at Løvenholm Castle in Jutland, Denmark, in July 1981. Twenty invited lectures were given by participants from twelve European countries. The symposium showed that it may be possible to identify the migration centres and the origin of local populations of the