Black alder swamps on forested peatlands in Latvia

The black alder (Alnus glutinosa (L.)Gaertn.) stands occupy 2.5% of the forest area in Latvia. The majority of its communities lie on peatlands; they have been studied in the whole of latvia using the Braun-Blanquet approach. One hundred and fifty alder dominated relevés selected from 334 forest areas have been analysed. Three associations (Carici elongatae-Alnetum, Sphagno squarrosi-Alnetum, andCircaeo-Alnetum), one with four subassociations have been recognized; these belong to the Eurosiberian alder swamps (cl.Alnetea glutinosae) and the European broad-leaved forests (cl.Querco-Fagetea). The phytosociological structure, distribution in Latvia and floristic features of these communities are reported. Results are compared with similar communities in the Baltic Sea states and neighbouring countries.     

An introduction to the phytosociology of the Whitlaw Mosses nature reserve

Summary

A first step in categorising the plant communities of the Whitlaw Mosses on a phytosociological basis has been made. The main communities belong to the classes Phragmitetea, Molinio-Arrhenatheretea, Caricetea nigrae and Alnetea glutinosae.     

Alder forests of Numidia (N.E. Algeria): floristic biodiversity, vulnerability and conservation

The phytoecological study of the alder forests of north-east Algeria shows that these habitats with boreal affinities harbour very high species richness (> 400 species) and complex structures, which suggest their ancient origin. They correspond phytosociologically to two syntaxa, the Campanulo alatae-Alnenion glutinosae (riparian alder forests) and the Rusco hypophylli-Alnetum glutinosae (peat-forming alder carrs), respectively. Their degraded state and their regressive dynamics, observed during the 14 years of the study, reveal their precarious situation and their rapid ongoing decline under the influence of human-induced uncontroled disturbances (cutting, burning, draining, dumping…). With regard to their ecological, historical and patrimonial importance, the alder forests of Algerian Numidia should be urgently protected, with the aim of assuring the perennity of their exceptional floristic corteges.     

The shore vegetation in selected lakeland areas in northeastern Poland

Phytosociological and habitat studies on the riparian vegetation in the river-lake systems of Krutynia River and upper Szeszupa River (north-eastern Poland) typical of the postglacial lakelands, were conducted. It was demonstrated that the riparian vegetation is composed of communities from the classes: Phragmitetea, Scheuchzerio-Caricetea fuscae, Artemisietea, Molinio-Arrhenatheretea, Alnetea glutinosae and Querco-Fagetea. In the land/water ecotone, these communities are spatially differentiated and often from a zonal pattern. In the waters from the rhizome-root layer (pore waters), the differences in nutrient concentration on transects from riparian plant communities reflect the communities' ability to modify the habitat. The decrease in nutrient concentration while passing through broad zones of either sedge communities or alderwóod and sedge communities may result from nutrient uptake by the components of those communities. The patterns in which sedge communities are forming floating mats, adjoined to the typical littoral or river bed, could be favourable for the protection of river and lake waters. The floating mats reacts elastically to wave action and changes in water level.     

Floodplain forests in Estonia: Typological diversity and growth conditions

Flooded forests in 79 sample areas were studied throughout the country. Using multivariate methods, six community types were established: (i)Tilia cordata-Mercurialis perennis, (ii)Ulmus laevis-Allium ursinum, (iii)Populus tremula-Convallaria majalis, (iv)Alnus incana-Cirsium oleraceum, (v)Alnus glutinosa-Filipendula ulmaria and, (vi)Alnus glutinosa-Carex acutiformis. The species composition of these types is partly overlapping but the abundance proportions of species are clearly different and all types have several significant (P < 0.05) indicator species. Communities of the first type grow mainly on temporarily overmoistened Dystri-Gleyic Arenosols on floodplain terraces but sometimes also in lower areas close to a riverbed on Eutric Gleysols or Gleyic Fluvisols. The second and third types embrace communities on levees where mainly Eutric Gleysols or Gleyic Fluvisols are represented. Communities of the fourth type are characteristic of low levees or flat areas with Mollic Fluvisols or Eutric Gleysols. The communities of the fifth and sixth types represent floodplain backswamp black alder forests on Eutric Gleysols, Molli-Histic and Histic Fluvisols. The convergence of communities, i.e., a situation where plant communities growing in various hydrological conditions and on different soils can have similar structure and belong to one community type is rather conspicuous for floodplain forests. In the conditions of Estonia, like in the Central European and Scandinavian countries, it is reasonable to consider as floodplain forest not only those growing on Fluvisolssensu stricto but all forests that are almost annually regularly covered with flood-water at least for a couple of weeks; the amount of alluvial sediments is not a decisive criterion in this case.     

Alnus glutinosa – dominated wetland forests of the Baltic Region: community structure,syntaxonomy and conservation

Community structure, syntaxonomy and conservation aspects of Alnus glutinosa-dominated forests in the Baltic States, Central Europe, southern Fennoscandinavia and north-western part of the Commonwealth of Independent States are surveyed. Communities of the black alder wetlands, subjected to cluster analysis (TWINSPAN, GROUPAGE) and correspondence analysis (CANOCO) and synsystematically treated following the Braun-Blanquet approach, belong to Alnion (Carici elongatae-Alnetum Schwick. 33 with two subassociations, Sphagno squarrosi-Alnetum Sol.-Gorn. ex Pried. 96) and Alno-Ulmion (mainly Circaeo-Alnetum Oberd. 53) forests in the Baltic Region. The indicator values sensu Ellenberg, site ecology, floristic assemblages and the phytogeographical features point at a high affinity of these forests in a wide geographical area. Eleven syntaxonomical approaches by classifying central and north-eastern European alderwoods have been analysed. These differ in Alnion classification and distinguish from 2 to more than 10 syntaxa at the level of association. The actual distribution of less disturbed black alder wetlands and areas under these forests in Europe suggests that the SE part of the Baltic Region could be the key area for Alnus glutinosa-dominated wetlands. Thus, it deserves an establishment of an international network of standard protected areas so as to maintain the diverse community samples and elaborate the principles of sustainable management. Abbreviations: In figures CLT PALU means Caltha palustris, CAL PALU – Calla palustris. Abbreviations of all other species follow first 3 and 4 letters of the genus and species name, respectively. Nomenclature: Tabaka et al. (1988) for vascular plants, Abolina et al. (1984) for mosses.     

Effects of invasive European bird cherry (Prunus padus) on leaf litter processing by aquatic invertebrate shredder communities in urban Alaskan streams

European bird cherry (Prunus padus) (EBC) is an invasive ornamental tree that is spreading rapidly in riparian forests of urban Alaska. To determine how the spread of EBC affects leaf litter processing by aquatic invertebrate shredders, we conducted complementary leaf pack experiments in two streams located in Anchorage, Alaska. The first experiment contrasted invasive EBC with three native tree species—thin-leaf alder (Alnus tenuifolia), paper birch (Betula neoalaskana), and black cottonwood (Populus trichocarpa)—in one reach of Chester Creek; finding that EBC leaf litter broke down significantly faster than birch and cottonwood, but at a similar rate to alder. The second experiment contrasted EBC with alder in four reaches of Campbell and Chester creeks; finding that while EBC leaf litter broke down significantly faster than alder in Chester Creek, EBC broke down at a similar rate to alder in Campbell Creek. Although EBC sometimes supported fewer shredders by both count and mass, shredder communities did not differ significantly between EBC and native plants. Collectively, these data suggest that invasive EBC is not currently exhibiting strong negative impacts on leaf litter processing in these streams, but could if it continues to spread and further displaces native species over time.     

Leaf water relations of black alder [Alnus glutinosa (L.) Gaertn.] growing at neighbouring sites with different water regimes

 The tree species black alder [Alnus glutinosa (L.) Gaertn.] typically inhabits wet sites in central Europe but is also successful on well drained soils. To test the physiological adjustment of the species in situ, conductances, transpiration rates and water potentials (Scholander pressure chamber) of black alder leaves were investigated at two neighbouring sites with different water regimes: alder trees at an occasionally water logged alder forest and alder shrubs in a nearby, much drier hedgerow. Additional experiments with alder cuttings in nutrient culture showed that leaf conductances and gas exchange were both strongly influenced by the substrate water potential. In situ however, there was little spatial variability within the different parts of a crown and we found that physiological regulation at leaf level was hardly influenced by different site water regimes or different tree sizes. Diurnal courses of leaf water relations as well as their regulation at the leaf level (e.g. the hyperbolic relationship between conductances and ΔW) were strikingly similar at both sites. Leaf water potential in black alder was shown to be a consequence of immediate transpiration rates, which were high in comparison to other tree species (up to 4 mmol H₂O m^–2 s^–1), rather than the water potentials being a factor that influenced conductance and, therefore, transpiration. The always high leaf conductances and consequent high transpiration rates are interpreted as a strategy to maximise productivity through low stomatal limitation at sites where water supply is usually not limited. However, at the same time this behaviour restricts black alder to sites where at least the deep-going roots can exploit water. Received: 10 September 1998 / Accepted: 12 January 1999     

Migration of herbaceous woodland flora into post-agricultural black alder woods planted on wet and fertile habitats in south western Poland

Because post-agricultural black alder woods have not been the subject of studies on forest recovery, the aim of the research was to investigate the process of colonization of their herb layer by woodland flora. Migration rates of 51 forest plant species in the herb layer of alder woods planted on abandoned meadows, bordering meso- and eutrophic forests, were studied. Mean migration rates calculated for typical wet alderwoods reached 1.20–1.60 m yr⁻¹, for oak-hornbeam forests 1.17–1.63 m yr⁻¹, and for alder-ash carrs 0.79–1.26 m yr⁻¹, exceeding those reported in studies conducted in less fertile, drier sites. Although migration rates for many species exceeded 2 or 3 m, there was a group of slow colonizing species, mainly ancient woodland indicators. Species migration patterns fitted either the model based on the establishment of isolated individuals, or the model of a wave front. The age of the recent forests and the presence of Urtica dioica in their herb layer are the main factors explaining the species composition in post-agricultural black alder woods.     

Kragge-woodlands in the Netherlands as a new community-type within the Alnion glutinosae

In the low-lying parts of The Netherlands peat-cutting in the past resulted in many large and small lakes. The larger ones were often reclaimed and turned into arable land. In smaller ones a process of secondary succession led to the establishment of reed and sedge fens. Due to changes in the management many of the still existing fens have been left over to natural developments over the last decades. Here succession rapidly led to woodland communities. These woodlands are initially often dominated by Salix species, soon followed by Alnus glutinosa and Betula pubescens. In species composition these young woodlands are closely related to the Carici elongatae-Alnetum glutinosae. There are, however, considerable differences in species composition. This woodland type as found in the western parts of The Netherlands was also recognized in relevés from Belgium, western Germany and Norfolk in the UK. As it also differs in ecological conditions from the brooks and rivulets accompanying forms of the Alnion glutinosae elsewhere in western Europe, it is here proposed to treat these communities as a separate community-type within the Alnion glutinosae.     

N2 fixing alder (Alnus viridis spp. fruticosa) effects on soil properties across a secondary successional chronosequence in interior Alaska

Green alder (Alnus viridis ssp. fruticosa) is a dominant understory shrub during secondary successional development of upland forests throughout interior Alaska, where it contributes substantially to the nitrogen (N) economy through atmospheric N₂ fixation. Across a replicated 200+ year old vegetation chronosequence, we tested the hypotheses that green alder has strong effects on soil chemical properties, and that ecosystem-level N inputs via N₂ fixation decrease with secondary successional stand development. Across early-, mid-, and late-successional stands, alder created islands of elevated soil N and carbon (C), depleted soil phosphorus (P), and more acidic soils. These effects translated to the stand-level in response to alder stem density. Although neither N₂ fixation nor nodule biomass differed among stand types, increases in alder densities with successional time translated to increasing N inputs. Estimates of annual N inputs by A. viridis averaged across the upland chronosequence (6.6 ± 1.2 kg N ha^?1 year^?1) are substantially less than inputs during early succession by Alnus tenuifolia growing along Alaskan floodplains. However, late-succession upland forests, where densities of A. viridis are highest, may persist for centuries, depending on fire return interval. This pattern of prolonged N inputs to late successional forests contradicts established theory predicting declines in N₂-fixation rates and N₂-fixer abundance as stands age.     

The importance of alder to hazel grouse in Fennoscandian boreal forest: evidence from four levels of scale

Buds and staminate catkins of alder (Alnus spp) form an important winter food for hazel grouse Bonasa bonasia in the Fennoscandian boreal forest Alder was found to be highly preferred over other deciduous trees, particularly alders ≥ 10 m tall and ≤15 m from spruce forest Winter territories were probably feeding territories, as size was correlated negatively with alder density and almost significantly correlated negatively with competitor density All winter territories were found to contain ample winter food resources for hazel grouse However, the distribution of territories was associated significantly with the distribution of alders at two levels of scale, the territory level and the landscape level Moreover, relationships between the abundance of alders and hazel grouse were found at two additional levels of scale the local patch level and the biogeographic region level This agreement of the results from four levels of scale strongly suggested that the abundance and distribution of alder was a major factor limiting hazel grouse winter territories within dense Norway spruce Picea abies forests in the boreal zone of Fennoscandia Alder was relatively uncommon and exhibited a clumped dispersion pattern at the local and landscape scales, being associated with wet and rich soils The close relationship to alder implies that hazel grouse winter habitats, even in natural forests, also should be distributed patchily Hazel grouse may select the catkins and buds of alder because it is a very nutntous food source, and small species, such as the hazel grouse, require more nutritious food than larger species     

Response of green alder (Alnus viridis subsp. fruticosa) patch dynamics and plant community composition to fire and regional temperature in north‐western Canada

Aim Feedbacks between climate warming and fire have the potential to alter Arctic and sub‐Arctic vegetation. In this paper we assess the effects and interactions of temperature and wildfire on plant communities across the transition between the Arctic and sub‐Arctic. Location Mackenzie Delta region, Northwest Territories, Canada. Methods We sampled air temperatures, green alder (Alnus viridis ssp. fruticosa) cover, growth, reproduction and age distributions, and overall plant community composition on burned and unburned sites across a latitudinal gradient. Results Mean summer temperature across the study area decreased by 3 °C per degree of increasing latitude (6 °C across the study area). In the northern part of the study area, where seed viability was low, alder was less dominant than at southern sites where seed viability was high. The age structure of alder populations across the temperature gradient was highly variable, except in the northern part of the forest–tundra transition, where populations were dominated by young individuals. Alder growth and reproduction were significantly greater on burned sites (38–51 years following fire) than on unburned sites. North to south across the temperature gradient, vegetation changed from a community dominated by dwarf shrubs and fruticose lichens to one characterized by black spruce (Picea mariana), alder and willows (Salix spp.). Regardless of the position along the temperature gradient, burned sites were dominated by tall shrubs. Main conclusions Temperature limitation of alder abundance and repro‐duction, combined with evidence of recent recruitment on unburned sites, indicates that alder is likely to respond to increased temperature. Elevated alder growth and reproduction on burned sites shows that wildfire also has an important influence on alder population dynamics. The magnitude of alder’s response to fire, combined with observations that burns at the southern margin of the low Arctic are shrub dominated, suggest that increases in the frequency of wildfire have the potential to alter northern vegetation on decadal scales. By creating new seedbeds, fire provides opportunities for colonization that may facilitate the northward movement of tall shrubs. Feedbacks between the global climate system and low Arctic vegetation make understanding the long‐term impact of increasing fire frequency critical to predicting the response of northern ecosystems to global change.     

温州地区黑荆树入侵群落的竞争与动态

黑荆树作为一种入侵植物在国外已经引起了相当的重视,被作为经济植物引入我国以后,目前在很多地区也形成了黑荆树天然更新林.但至今其对于我国生态系统的入侵风险的研究仍然很少.以温州地区6个黑荆树群落为样本,对黑荆树和其它树种的竞争强度、空间关系和群落中物种的相互替代进行了分析,结果表明:(1)黑荆树在群落竞争中并没有体现出优势;(2)黑荆树与其它物种在空间上基本是独立的,这可能是由于竞争强度比较弱,并不能造成明显的竞争性死亡;(3)除马尾松外各群落中物种都维持较高的自我替代,但是在PY04、CN02和RN01群落未来黑荆树仍可能替代其它物种变成主要优势种,而由于其存在幼苗更新困难这种优势不会长久;(4)黑荆树的入侵风险不高,保持群落的生物多样性能够有效地防止黑荆树成为优势物种,因此今后要尽力维持本地群落的生物多样性.     

Native forest metacommunity structures in Uruguay shaped by novel land‐use types in their surroundings

We explore the effect of land‐use change from extensively used grasslands to intensified silvi‐ and agricultural monocultures on metacommunity structure of native forests in Uruguay. We integrated methods from metacommunity studies, remote sensing, and landscape ecology to explore how woody species distribution was influenced by land‐use change from local to regional scale. We recorded richness and composition of adult and juvenile woody species from 32 native forests, created land‐use maps from satellite image to calculate spatial metrics at landscape, class, and patch levels. We also analyzed the influence of land use pattern, climate, topography, and geographic distance between sites (d) on metacommunity, and created maps to visualize species richness and (dis)similarity between communities across the country. Woody species communities were distributed in a discrete pattern across Uruguay. Precipitation and temperature seasonality shaped species distribution pattern. Species richness and community dissimilarity increased from West to East. Latitude did not influence these patterns. Number of patches, landscape complexity, and interspersion and juxtaposition indexes determine woody species distribution at landscape level. Increasing areas covered by crops and timber plantation reduced species richness and increased community dissimilarity. The spatial metrics of native forest fragments at patch level did not influence metacommunity structure, species richness, and community dissimilarity. In conclusion, Uruguayan native forests display a high range of dissimilarity. Pressure of neighborhood land uses was the predominant factor for species assemblages. Conserving landscape structures that assure connectivity within and among native forest patches is crucial. On sites with rare target species, the creation of alliances between governmental institution and landowner complemented by incentives for biodiversity conservation provides opportunities to advance in species protection focused on those less tolerant to land‐use change.     

Vegetationsverhältnisse und Naturumwelt des Beckens Jestřebská kotlina am Ende des Spätglazials und im Holozän (Doksy-Gebiet)

The method of pollen analysis was used to study a profile sample taken from the Jest?ebské blato mire, the Doksy District (northern Bohemia). The aim of the palacobotanical analyses was to perform a reconstruction of vegetation and environment for geobotanical and archaeological research purposes. Sediments dating back to the end of the Late Glacial and to both the Early and Middle Holocene were pollenanalytically studied. The results of the pollen analyses recorded the development of vegetation during the end of the Late Glacial, Preboreal, Boreal and Atlantic Periods. Parkline pine stands of the end of the Late Glacial developed to closed pine forests, during the Preboreal. Even during the Boreal, the dominant pine formed forest communities were typical of the area under study, though trees with greater demands on temperature and moisture conditions continued to penetrate the existing communities. During the Lower and the first half of the Upper Atlantic Period, spruce forests and alder woods formed the dominant forest communities in mire. Nevertheless,Pinus was still dominant on extreme sites (both from the edaphic and geomorphological points of view). An early occurrence ofAlnus andPicea is another characteristic feature of the studied area. The conclusions drawn from pollenanalytical results were used for the reconstruction of the past environment of the Mesolithic and Neolithic Ages.     

Pre-climax epiphyte communities of bryophytes and lichens in Mediterranean forests from the Central Plateau (Spain)

The pre-climax epiphytic communities of forests from the Spanish Mediterranean region (Central Plateau) were studied by numerical and traditional floristic methods. One hundred phytosociological relevés were analyzed through a classical numerical approach based on hard partitions improved by PCoA — Principal Coordinates Analysis — ordinations. Two groups easily related to two different suballiances included in Frullanion dilatatae Lecointe 1975, Ulotenion crispae (Barkman 1958) Lecointe 1975 and Fabronienion pusillae Barkman 1958 were detected. Two new syntaxa within the ass. Ortotrichetum lyellii (Allorge 1922) Lecointe 1975 are proposed. Phytogeography, syntaxonomy and ecology of these communities are discussed.     

An ectomycorrhizal fungus,Cenococcum geophilum,in a coastal pine forest has a high tolerance for an insecticide used to control pine wilt disease

Cenococcum geophilum Fr., one of several ectomycorrhizal species associated with black pine (Pinus thunbergii Parl.), is dominant in the coastal forests of Japan, even under adverse abiotic environmental conditions. In these forests, many tonnes of Sumipine® (fenitrothion) are applied every year to protect P. thunbergii from pine wilt disease, which is transmitted by a beetle. Here, we examined the effect of this insecticide on the species of fungi found as ectomycorrhizae on naturally regenerated P. thunbergii seedlings collected from coastal forest sites that had or had not been sprayed with fenitrothion. The proportion of C. geophilum ectomycorrhizae on black pine root tips was significantly higher in areas where fenitrothion had been applied than in areas where it had not. We measured the in vitro mycelial growth of C. geophilum as well as other ectomycorrhizal fungi of coastal black pine, Rhizopogon roseolus (Corda) Th. Fr. and Pisolithus arhizus (Scop.) Rauschert, at three levels of fenitrothion (density: 1.32 g/cm³), i.e., 0, 0.1 and 0.2 mL L^?1. The growth of all three species decreased significantly as the fenitrothion dosage increased. However, the reduction of mycelial growth in response to fenitrothion was lower in C. geophilum than in the other two species. These results suggest that C. geophilum has a high tolerance for fenitrothion, which may explain its dominance over other ectomycorrhizal species in coastal forests in Japan where fenitrothion is routinely sprayed.

     

Epiphytic macrolichen communities along regional gradients in northern Norway

Abstract. Question: What are the relative influences of human impact, macroclimate, geographic location and habitat related environmental differences on species composition of boreal epiphytic macrolichen communities? Location: Troms county in northern Norway. Methods: Detrended Correspondence Analysis revealed the main gradient structure in lists of epiphytic macrolichen species from deciduous forests. By Canonical Correspondence Analysis with variance partitioning, the relative amount of variance in macrolichen species composition attributable to human impact, macroclimate, spatial context and environmental differences was quantified. Results: There was no significant effect of human impact on species composition of epiphytic macrolichens of deciduous forests. Macroclimate was the most important factor determining epiphytic macrolichen communities, which were also strongly influenced by ecological differences such as forest stand properties. Conclusions: Epiphytic macrolichen communities are determined by a macroclimatic gradient from the coastline to the interior of central north Norway. In marked contrast, the species composition of epiphytic macrolichen communities seems to be unaffected by human impact in the study area, where air pollution was marginal.     

Community structure of polypores (Basidiomycota) in Andean alder wood in Argentina: Functional groups among wood‐decay fungi?

Abstract The polypores (Aphyllophorales s.l., Basidiomycota) are very effective wood decayers. Different species differ in their capacity to decay wood; therefore, many functionally different species can be found decaying different substrate conditions (decay stages and log diameter). This study aimed to describe the structure of the wood‐decay polypore communities that occur on different states of wood of the Andean alder (Alnus acuminata) within Argentina and to identify groups of polypore species that share the same substrate condition, and thus might have a similar functional role in the decay processes. We found 16 polypore species, among which Trametes versicolor, Bjerkandera adusta and Trametes cubensis were dominant species, showing the highest relative frequency in alder wood. Species richness was lower on trunks of living trees and higher on dead branches. Based on preferential occurrence on different wood conditions, a cluster analysis distinguished three groups, each of them containing one of the three dominant species. This corresponds to the situation of other groups of organisms, where each functional type consists of a dominant species that accounts for most of the ‘function’ and several subordinate species with similar functions. Albeit preliminary, our results provide a formal classification of wood‐decay fungi into functional types.