Host preferences and differential contributions of deciduous tree species shape mycorrhizal species richness in a mixed Central European forest

Mycorrhizal species richness and host ranges were investigated in mixed deciduous stands composed of Fagus sylvatica, Tilia spp., Carpinus betulus, Acer spp., and Fraxinus excelsior. Acer and Fraxinus were colonized by arbuscular mycorrhizas and contributed 5% to total stand mycorrhizal fungal species richness. Tilia hosted similar and Carpinus half the number of ectomycorrhizal (EM) fungal taxa compared with Fagus (75 putative taxa). The relative abundance of the host tree the EM fungal richness decreased in the order Fagus > Tilia >> Carpinus. After correction for similar sampling intensities, EM fungal species richness of Carpinus was still about 30–40% lower than that of Fagus and Tilia. About 10% of the mycorrhizal species were shared among the EM forming trees; 29% were associated with two host tree species and 61% with only one of the hosts. The latter group consisted mainly of rare EM fungal species colonizing about 20% of the root tips and included known specialists but also putative non-host associations such as conifer or shrub mycorrhizas. Our data indicate that EM fungal species richness was associated with tree identity and suggest that Fagus secures EM fungal diversity in an ecosystem since it shared more common EM fungi with Tilia and Carpinus than the latter two among each other.     

Repartition des flavonols dans l'epaisseur des feuilles de quelques vegetaux vasculaires

The tissue localisation of flavonoids has been studied in leaves of Betula, Corylus, Fagus, Fraxinus, Pisum, Platanus, Quercus, Spinacia and Tilia and scales of onion bulbs. All these species contain flavonols which are, for the most part, located in the upper epidermis of the leaves. In the onion bulb, flavonols are exclusively in the epidermis. The flavonols are glycosylated and dissolved in the vacuoles. The leaves were fractionated by an original technique of abrasion of the frozen material. The physiological significance of such a distribution of flavonoids in the adult leaves or scales is discussed.     

Studies on the Holocene history of vegetation in the region of lake Srebarna (northeast Bulgaria)

The results of pollen analysis of two sediment cores from lake Srebarna (northeast Bulgaria) are presented. On the basis of the palynological data and the radiocarbon dates a reconstruction of the past flora and vegetation is made. For the first time a continuous palaeosuccession is established for the area of the Danubian Dobrudza and the Ludogorie district of northeast Bulgaria: a dominance of mixed xero- and mesophilous oak woods with Carpinus betulus, Ulmus, Tilia, Corylus during the Atlantic period; mixed oak woods with increasing importance of Tilia, Ulmus, Acer and a considerable presence of Carpinus betulus and Fagus during the Sub-boreal period; degradation of the woodland vegetation and transition to secondary plant communities with Carpinus orientalis and herbs during the Sub-atlantic period. Received January 5, 2001 / Accepted March 13, 2001     

Pollen stratigraphy of coal-bearing deposits in the Neogene Jidong Basin,Heilongjiang Province,NE China: New insights on palaeoenvironment and age

The palaeoenvironment and age of coal-bearing lacustrine deposits in the Jidong Basin, Heilongjiang Province, is poorly understood. New pollen data from the Yongqing Formation and the overlying lower part of the Daqingshan Formation recovered in borehole 91-205 revealed a rich and diverse palynoflora representing approximately 70 taxa at the genus/family level. Of these taxa, Ulmus, Quercus, Carya, Liquidambar, Pinus, Tilia, Fagus, and Alnus are the main woody elements; these occur together with numerous pteridophytes, subordinate herbs, and rare algae and acritarchs. Abundant woody taxa suggest a mixed deciduous/conifer forest in the region in association with local shrubs, herbs and algal communities. Some of the pollen types, especially those of climate sensitive genera such as Ulmus, Carya, Liquidambar and Fagus, vary considerably in relative abundances, suggesting climate variability. The reflected climate shows an overall trend towards cooling or deterioration which is largely in agreement with global climate change during the Neogene.Comparisons of the pollen record with representative datasets from neighbouring areas, together with the appearance of the highly-evolved genus Artemisia, suggest that the Yongqing Formation and the lower part of the Daqingshan Formation are of Miocene age.     

Stand-scale reconstruction of late Holocene forest succession on the Gdańsk Upland (N. Poland) based on integrated palynological and macrofossil data from paired sites

This study concerns the stand-scale palaeoecological reconstruction of the subsequent stages of late Holocene vegetation development on habitats recently covered by beech-dominated woodland in the southern Baltic region. The data, based on pollen, non-pollen palynomorphs, macrofossil and charcoal analyses from two close-lying sites, demonstrated that each of the subsequent late Holocene shifts in dominating forest communities took place because of human impact coupled with climatic events or episodic human-made disturbances. Shifts from the Tilia dominated forest to the Quercus-Corylus plant community at around 3300 bc was most probably driven by the coupled effect of climate change and human activity. Human impact was the primary driver of the final Corylus decline and concurrent major Carpinus expansion at c. 460 bc, and the Carpinus decline followed by Fagus expansion at c. ad 900. Carpinus had been lingering on the edge of a major expansion in the local forest for at least 2,500 years while Fagus had persisted in a small admixture for no fewer than 1,500 years before becoming important forest constituents. Our data illustrate the role of episodic disturbances as turning points that initiate long-term vegetation changes.     

Long-term history of land-use and vegetation at Ire,an agriculturally marginal area in Blekinge,south Sweden

Pollen records from a small lake and a small peatland at Ire in northern Blekinge, Sweden, reveal that until a.d. 300 there was a mixed deciduous type of woodland dominated by Quercus, Tilia and Corylus, with Betula, Pinus, Populus, Fraxinus, Ulmus and Acer as important constituents. The first, but weak, signs of human influence on the vegetation are detected around 2300 b.c. At this time, the area was probably used for woodland grazing. The regional expansion of Fagus occurred around 100 b.c.–a.d. 200, and later, at about a.d. 500, woods dominated by Fagus were common in the area. Around a.d. 600–700 an isolated farmstead may have been established in the area, as single pollen grains of Secale (rye) were found. This farmstead may represent the first permanent settlement in the area. A more widespread opening of the vegetation occurred around a.d. 1000, probably as an effect of a more pronounced use of the area, and an expansion of settlements in the region. The openness of the area seems to have peaked around a.d. 1400–1800, and during this period the vegetation was highly fragmented with small stands of woodland, intensively grazed pastures, and arable fields where Secale and Triticum were mainly cultivated. Around a.d. 1600 Fagus pollen percentages sharply decrease, most probably caused by a deliberate and selective felling of beech trees for the production of potash, which consumed enormous amounts of wood. Picea seems to have been established around a.d. 1600, but it did not become a regional dominant until the first part of the 20th century, when land use decreased and it became favoured by forestry.     

Vegetation history in the Eastern Romanian Carpathians: pollen analysis of two sequences from the Mohoş crater

Two sequences of about 10.5 m originating from a peat bog in Romania were analysed for pollen (202 and 127 pollen spectra). The vegetation history, supported by 24 ¹⁴C dates is described since the Late Glacial. At the onset of the Holocene Ulmus first appears, together with Betula. Among the main components of the Quercetum mixtum (Quercus, Fraxinus, Tilia, Corylus) that became established almost simultaneously by around 9000 B.P., Quercus frequencies rarely exceed 10%. The local establishment of Carpinus is about 6000 b.p. Its maximum occurred between 4500 and 3000 b.p. Fagus pollen is regularly recorded since 8000 b.p. Its absolute dominance tooks place at about 3000 b.p. Picea pollen is present since the Late Glacial. The first indications of human activities appear at around 6500 b.p.     

Some problems of forest transformation at the transition to the oligocratic/<Emphasis Type="Italic">Homo sapiens</Emphasis> phase of the Holocene interglacial in northern lowlands of central Europe

The paper discusses the main changes in the composition of mixed deciduous forests which occurred mostly between 5,000 and 2,000 b.p., based on selected pollen diagrams from the lowlands of Germany, Denmark and Poland, and including two pollen diagrams from varved sediments, used as reference sites, and on isopollen maps for Poland. The Ulmus retreat is shown on maps, and additional data for its pathogenic origin are presented. Corylus declines at ca. 3,500 b.p. at both reference sites, and its connection with Fagus expansion in the west and Carpinus expansion in the east is discussed. The nature of post-Atlantic transitory shrub–forest communities with dominant Corylus and Quercus is presented. Relationships between the history of Fagus and Carpinus and the development of human settlements are shown. Human impact has been admitted as one of the most important driving forces determining vegetational development since the time of fully developed Neolithic cultures. Other very important abiotic factors were the climate (particularly after 2,500 b.p.), and soil degradation.     

Hylobius pine weevils adult host selection and antifeedants: feeding behaviour on host and non-host woody scandinavian plants

Abstract 1 We searched for antifeedant activity in predomonantly non‐host woody plants to find new compounds for seedling protection of Scots pine (Pinus sylvestris) and Norway spruce (Picea abies) against feeding by pine weevil Hylobius abietis. In total, 38 species from 25 families were compared in choice and no‐choice tests. 2 In choice tests with Empetrum, Juniperus, Ledum, Populus, Betula, Evonymus, Sorbus, Salix, Myrica and Pinus, the weevils preferred Pinus to all others. In no‐choice tests with the same species, the insects removed a similar or even greater area of the bark in three of 10 species than Pinus. The results were clearly different between the test modes. 3 In experiment 4, the areas of outer and inner bark (phloem) removed were quantified separately.The weevils removed significantly less of both outer and inner bark in Ilex, Evonymus, Populus, Syringa, Taxus, Tilia, Viburnum, Lonicera and Sorbus than Pinus. 4 Large areas of outer bark were removed in Juglans, Fraxinus, Sambucus, Aesculus, Quercus, Corylus, Fagus, Salix, Alnus and Acer. However, in the latter cases the insects stopped when reaching the inner bark. Thus, certain plant species have the outer bark removed by the insects but possessed an inner bark with antifeedant qualities.     

Late Miocene vegetation and climate reconstruction based on pollen data from the Sofia Basin (West Bulgaria)

The analysis of fossil palynomorh assemblages in the Late Miocene freshwater sediments of the Sofia Basin (West Bulgaria) was done to collect data on the vegetation and climate dynamics during the Late Miocene. On the basis of pollen data, we described the main palaeocomunities developed in the region. The mixed mesophytic forests dominated the vegetation in which species of Quercus, Ulmus, Zelkova, Fagus, Carpinus, Betula, Castanea, Corylus, Pterocarya, Carya, Juglans, and Eucommia played important roles. Swamp forests were also recorded, including Taxodiaceae, Alnus, Glyptostrobus, Nyssa, and Myrica. Herbaceous vegetation was distributed in the middle part of the section, with a maximum of 35.5%. The vegetation dynamic passes through several phases, which were associated with changes in paleoclimate and palaeoecological conditions. Coexistence Approach (CA) was applied to palynological data to calculate four climatic parameters. The values of coexistence intervals for mean annual temperatures are 13.6–16.6 °C, with winter temperatures being 3.7–6.6 °C and summer temperatures being 23.6–27.8 °C. Mean annual precipitation ranged most frequently between 828 and 1308 mm. The palaeoclimatic reconstruction illustrates existence of a warm-temperate and relatively humid climate with higher mean annual temperature than the present day climate.     

Unrestricted quality of seeds in European broad-leaved tree species growing at the cold boundary of their distribution

Background and Aims

The low-temperature range limit of tree species may be determined by their ability to produce and disperse viable seeds. Biological processes such as flowering, pollen transfer, pollen tube growth, fertilization, embryogenesis and seed maturation are expected to be affected by cold temperatures. The aim of this study was to assess the quality of seeds of nine broad-leaved tree species close to their elevational limit.

Methods

We studied nine, mostly widely distributed, European broad-leaved tree species in the genera Acer, Fagus, Fraxinus, Ilex, Laburnum, Quercus, Sorbus and Tilia. For each species, seeds were collected from stands close to optimal growth conditions (low elevation) and from marginal stands (highest elevation), replicated in two regions in the Swiss Alps. Measurements included seed weight, seed size, storage tissue quality, seed viability and germination success.

Key Results

All species examined produced a lot of viable seeds at their current high-elevation range limit during a summer ranked ‘normal’ by long-term temperature records. Low- and high-elevation seed sources showed hardly any trait differences. The concentration of non-structural carbohydrates tended to be higher at high elevation. Additionally, in one species, Sorbus aucuparia, all measured traits showed significantly higher seed quality in high-elevation seed sources.

Conclusions

For the broad-leaved tree taxa studied, the results are not in agreement with the hypothesis of reduced quality of seeds in trees at their high-elevation range limits. Under the current climatic conditions, seed quality does not constitute a serious constraint in the reproduction of these broad-leaved tree species at their high-elevation limit.     

Epiphytic microorganisms degrading aromatic hydrocarbons from the phyllosphere of urban woody plants

From the leaves of three urban trees (Tilia sp., Acer sp., and Fraxinus sp.), 180 strains degrading phenanthrene, naphthalene, and salicylate were isolated by direct plating and enrichment cultures. The leaves of each tree species were characterized by a specific profile of aromatic hydrocarbon-degrading microflora. Members of the type Actinobacteria were predominant in the case of direct plating on media with phenanthrene and naphthalene. Enrichment cultures with phenanthrene and salicylate were shown to yield microbial consortia, the composition of which changed with time. Members of the type Proteobacteria were predominant in these consortia. No plasmids of polycyclic aromatic hydrocarbon degradation of the P-7 and P-9 incompatibility groups were revealed in the studied strains.     

Spatial patterns of tree seedling establishment and their relationship to environmental variables in a cold-temperate deciduous forest of eastern North America

Patterns of seedling recruitment may have persistent effects on population and community processes. Assuming seed availability is not limiting, the environmental sieve (i.e., the suite of factors influencing seed germination and seedling emergence and survival) determines how many seedlings establish and, most importantly, where they do so. In this study, we identify the spatial structure of some resources and abiotic conditions known to be significant for tree seedling emergence and survival and determine how these environmental factors influence the establishment of Fagus grandifolia, Acer saccharum, Fraxinus americana, and Ostrya virginiana in a deciduous forest of southern Québec (Canada). We expect an increase from Fagus, through Acer and Fraxinus, to Ostrya in the control of environmental variables on seedling emergence and survival, because of differences in the seed size of these species. Density of newly-emerged seedlings of all four species showed positive spatial autocorrelation at distances of up to ca. 10 m. Environmental variables were also structured at the same spatial scale, except for soil moisture. Acer seedling emergence pattern was positively correlated to photosynthetic photon flux density (PPFD), and the pattern of Fraxinus to soil N and moisture. Seedling survival was not spatially autocorrelated for any of the four species, although it was positively density-dependent in Acer and Fagus. In only Ostrya was seedling survival correlated (positively) to one of the environmental variables studied, i.e., PPFD. Overall, environmental variables were spatially less heterogeneous than seedling emergence and survival. Either seed availability was not saturating or factors not considered here, such as competition and predation (the intensity of which often varies with resources and/or abiotic conditions), modified the influence that the physical environment had on patterns of seedling establishment. Our prediction of a greater environmental control on seedling emergence and survival in small-seed species was not totally confirmed.     

Palaeoecological studies at the Mesolithic site at Bedburg-Königshov near Cologne, Germany

The Late Glacial and early Holocene palaeovegetation is reconstructed by analysis of pollen and macroscopic plant remains from sediments of the lower river Erft valley, near Cologne, exposed by the Garzweiler opencast lignite mine. The study was carried out in parallel with the archaeological excavation of the Mesolithic site of Bedburg-Königshoven, located within a former meander of the Erft. During the Younger Dryas period, the study region was thinly wooded. Relatively open pine woods existed during the Preboreal, becoming more closed during the Boreal. Later in the Boreal,Corylus and taxa of the mixed oak woodland (Ulmus, Quercus, Tilia andFraxinus) appeared. The Atlantic period was characterised by mixed oak woods with dominantUlmus. At the beginning of the Subboreal,Ulmus declined andTilia became the predominant element of the woods. The Mesolithic settlement existed during the early and middle part of the Preboreal period. At that time, the woodland of the Erft valley was mainly composed ofPinits, Belula and somePopulus. The pollen results do not show any evidence of the activity of Mesolithic people. Local vegetational changes of the filling process of the Erft meander were described and interpreted. The vegetational development of the study region is compared with that of neighbouring regions.     

Airborne pollen in Bahía Blanca,Argentina: seasonal distribution of pollen types

The composition and seasonal distribution of airborne pollen grains in the atmosphere of Bahía Blanca, Argentina, has been studied between June 2001 and December 2003 using the Rotorod sampler (model 40). The results show that the main pollen types during this period were Cupressaceae, Fraxinus, Myrtaceae, Poaceae, Amaranthus/Chenopodiaceae, Pinus, Urticaceae, Ulmus, Olea and Styphnolobium. The highest concentrations occurred from August to December (end of winter and spring), accounting for 80% of the total annual pollen count. The greatest diversity was found in the spring, with the major of pollen coming from short-flowering plant types, such as Populus, Acer, Platanus, Juglans, Tamarix, Ailanthus and Typha. The potential sources of pollen from woody ornamental species are Cupressus sempervirens, Eucalyptus camaldulensis and Fraxinus pennsylvanica. whereas those from herbaceous species are the Chenopodiaceae and Poaceae, which are found within the city and also in the surrounding natural vegetation, and the Urticaceae, which are only present in the city. Marked annual differences were noted during the study period. The increase in 2002 may have been due to the abundant rainfall that occurred prior to the spring season, which would have favored the vegetative stage and flower development of plants. The decrease in pollen concentration in 2003 was mainly due to low rainfall throughout the year.     

Leaf Survival and Evolution in Betulaceae

Studies on the changes in leaf number of 12 species of Betulaceaewere carried out by repeated observations during several years.The inner structure of the winter buds of these species wasalso examined. The periods of leaf emergence were long in Alnusand Betula, intermediate in Corylus and short in Ostrya andCarpinus. A heavy summer leaf fall is characteristic only ofthe Gymnothyrsus subgenus of Alnus. One lamina and two stipulesis the basic unit constituting the winter buds. Only the budsof Gymnothyrsus are composed of several of these units. In theAlnaster subgenus of Alnus, Betula and Corylus, there are oneor two scales that seem to have originated from the two stipulesremaining after reduction of the lamina. Eight and 24 scalesof similar origin were found in Ostrya and Carpinus respectively.A common ancestral species having the following primitive charactersis proposed: shoot constituted only of the equal-sized units,period of leaf emergence long, and leaf fall usually occurs.Alnus (Gymnothyrsus) is assumed to be the most primitive typeas it has many characters similar to those of the proposed ancestralspecies. Carpinus is assumed to be the most advanced group.The leaf survivorship curve is assumed to have changed fromthe primitive bell-shaped to an advanced trapezoid concurrentwith an increase in the number of bud scales. Betulaceae, Alnus, Betula, Carpinus, Corylus, Ostrya, leaf survival, leaf emergence, stipules, winter buds, evolution     

Lichen diversity and red-listed lichen species relationships with tree species and diameter in wooded meadows

This study provides a unique large dataset of total epiphytic lichen diversity (fruticose, foliose and crustose species) and composition on 1,294 trees of 17 tree species in wooded meadows in Sweden and Estonia, the Baltic region. The inventory (25,380 observations and 246 lichen taxa) clearly illustrated that Ulmus minor, Quercus robur and Fraxinus excelsior contributed most significantly to epiphytic lichen richness and number of red-listed species. In Sweden, average single tree α richness was 22.2 on Ulmus (only in Sweden), 21.6 on Quercus (25.0 in Estonia) and 19.8 on Fraxinus (16.7 in Estonia), respectively. Ulmus hosted on average one red-listed species per tree, compared with 0.7 on Fraxinus (0.6 in Estonia), 0.4 on Quercus (0.7 in Estonia) and only 0.05 on Betula (same in Estonia). Lichen species composition and the average number of red-listed lichens were influenced by tree diameter on Fraxinus and Quercus, whilst no such pattern was evident on Ulmus. Randomized species accumulation curves of the dominating tree species illustrated that Fraxinus, Quercus and Ulmus supported α dominated lichen communities where individual trees hosted a substantial part of the total richness. Betula, on the other hand, supported β dominated communities where individual trees tended to be dissimilar and, therefore, more of the total richness existed as species turnover among host trees. Lichen species composition was influenced by tree species, and most notably, lichen species on Ulmus had a strong consistent clumping in ordination graphs, with many rare and red-listed lichens. The broadleaved deciduous trees within the wooded meadows clearly contribute greatly to the biodiversity of the Baltic region.     

Crown responses to neighbor density and species identity in a young mixed deciduous stand

Key message

Density was more important in shaping crown structure than neighbor species identity. Both species showed high crown plasticity at alternative levels, which may explain species coexistence in mixed broadleaved forests with functionally similar species.

Abstract

Understanding crown response to local competition is essential to predicting stand development in mixed stands. We analyzed data from an 8-year-old field experimental plantation mixing two species according to a crossed gradient of density and species proportion to quantify the effect of a broad range of local neighborhood conditions on the development of young trees at multiple crown levels. We used Fagus sylvatica and Acer pseudoplatanus, as two model deciduous species. They are considered functionally equivalent at the young stages, but with contrasting architectural patterns. For both species: (1) changes in density explained more of the variation on crown development than species proportion (2) much of the effect of competition was accounted for by variables at the stem level, while branch and leaf development within crowns were not directly altered by competition. Both species were able to modify their crowns at the stem level to compete with intra- and inter-specific neighbors: Acer and Fagus were taller with a highest proportion of Fagus as neighbors; Fagus displayed a lower crown base when the proportion of Fagus decreased, while Acer had a lower crown base when the proportion of Fagus around it increased. Both species showed common shapes in allometric relationships but contrasting responses at alternative crown levels. Acer exhibited broader intra-specific variation in its height–diameter relationship and in its crown length, while Fagus displayed higher individual variation of branch development and leaf area than Acer. This study demonstrates that differences in crown development strategy of each species in response to changes in local neighborhood conditions are an important factor in maintaining species coexistence in broadleaved forests and designing mixtures that persist over time.     

Fruit-bearing branchlets are carbon autonomous in mature broad-leaved temperate forest trees

In order to evaluate the degree of carbon autonomy for fruit development, the carbon source-sink relationship in fruit-bearing branchlets of mature deciduous forest trees was manipulated in situ. The tests included half and complete defoliation, girdling or the combination of both treatments, which were applied on fruiting branchlets by using a canopy crane. Concentrations of non-structural carbohydrates (NSC) were analysed in different branchlet tissues and fruits, to identify situations of carbon imbalances induced by the treatments. NSC concentrations of branchlets were generally lower under treatments resulting in decreased fruit growth. All three investigated species (Carpinus betulus, Fagus sylvatica and Tilia platyphyllos) exhibited complete carbon autonomy of fruiting at the level of whole, undisturbed branchlets, since neither a decrease of total infructescence biomass, nor of individual fruit mass occurred on girdled, un-defoliated branchlets. On girdled, 100% defoliated branchlets, fruit biomass relative to controls decreased by approximately 50% in Carpinus and Tilia, but by almost 80% in Fagus, which can be explained by different proportions of photosynthetically active infructescence tissues among the species. In contrast to the other two species, Tilia branchlets did not import carbon to compensate for assimilate loss after defoliation.     

Codominance of <Emphasis Type="Italic">Acer saccharum</Emphasis> and <Emphasis Type="Italic">Fagus grandifolia</Emphasis>: the role of <Emphasis Type="Italic">Fagus</Emphasis> root sprouts along a slope gradient in an old-growth forest

We studied how the unusual capacity of mature Fagus grandifolia to form clumps of clonal stems from root sprouts can contribute to its frequent codominance with Acer saccharum in southern Quebec, Canada. In an old-growth forest, the degree of dominance by the two species shifted along topographic gradients spanning a few hundreds of meters, with Fagus more frequent on lower slopes and Acer on upper slopes. The frequency distribution of Fagus stem diameter had an inverse J distribution at all slope positions, which is indicative of continuous recruitment. Acer stem diameter also had an inverse J pattern, except at lower slope positions where size structure was discontinuous. For stems <2 m tall, Fagus regenerated mainly by sprouts at the upper and mid-slopes, while regeneration from seed was more pronounced on the lower slope. This change of regeneration mode affected the spatial pattern of Fagus stems. Understory trees of Fagus were positively correlated with conspecific canopy trees on upper and mid-slopes, but not on lower slopes where Fagus regenerated mainly by seedlings. Understory trees of Acer were positively correlated with conspecific canopy trees only on the mid-slope. There were many Fagus seedlings around Acer canopy trees at the lower slope, suggesting the potential replacement of Acer canopy trees by Fagus. This study suggests that the regeneration traits of the two species changed with slope position and that Fagus patches originating from root sprouts can contribute to the maintenance of Acer–Fagus codominance at the scale of local landscapes.