Natural age and size of Pinus sylvestris and Picea abies on a mire in the inland part of northern Sweden

The investigation was carried out on a sparsely forest covered poor fen 350 m a.s.l. in the inland pan of northern Sweden (64°32'N, 18°55'E). On the investigated mire the natural regeneration of pine Pinus sylvestris has been relatively successful from the 1920's up to the beginning of the 1970's. Natural regeneration of spruce Picea abies has taken place throughout the period 1938-1970, whereafter no establishment at all has occurred. The age and size structures of the pine and spruce stands on the mire vary in pattern according to the particular type of vegetation in which they are growing. Both the climatic amelioration during the first half of the present century and the successional stage of the mire vegetation were found to be important in regard to present-day age and size structures of the pine and spruce. Root competition and snow conditions arc probably important determinants of the size structure of pine stands in the mire environment.     

黑长臂猿栖息地旱冬瓜和潺槁木姜子种群分布格局和动态

旱冬瓜（Alnus nepalensis）和潺槁木姜子（Litsea glutinosa）是云南省无量山黑长臂猿（Nomascus concolor）栖息地中的两种常见乔木.利用最近邻体法和Heygi单木竞争指数模型,对两个种群的分布格局和竞争情况进行分析.结果表明,旱冬瓜在不同生长阶段均呈现随机分布,而伴生的潺槁木姜子种群则呈现随机分布 聚集分布 均匀分布的变化趋势.种间竞争和物种自身生物学特性对两个种群的分布格局具有显著影响.旱冬瓜种群的龄级结构为衰退型,潺槁木姜子种群则为成长型.     

Sleeping sites of black-and-white snub-nosed monkeys (Rhinopithecus bieti) at Baima Snow Mountain, China

Data on sleeping sites of a group of black-and-white snub-nosed monkeys Rhinopithecus bieti (Colobinae, Primates) were collected between April–July and September–December 2001 to try to determine the factors affecting site selection at Nanren (99°04'E, 28°34'N, Baima Snow Mountain, China). Sleeping trees were tall emergents (27.5±3.2 m) with large diameter at breast height (57.9±16.9 cm) and broad crown diameters (6.3±1.4 m), and significantly larger than other trees. The use of large sleeping trees could provide effective shelters from attacks of terrestrial and aerial predators, heavy snow and rain. Sleeping sites were changed nightly and located at significantly lower altitudes in winter months than in other seasons, which might be a thermoregulatory adaptation or related to snow covering. Such sites tended to be at the middle of sun-oriented slopes, possibly trading off predator avoidance and foraging efficiency.     

Restriction pattern analysis of deoxyribonucleic acid isolated from callus and cell suspension of actinorhizal and non-actinorhizal Betulaceae

Using cell suspensions, a method was elaborated to isolate high-molecular-weight genomic deoxyribonucleic acid (DNA; 65 MDa or more) from members of the Betulaceae: Alnus incana (L.) Moench, Alnus glutinosa (L.) Gaertn. and Betula papyrifera Marsh. The method was also effective for isolation of DNA from callus cells. Based on the chemical lysis of protoplasts, this procedure yielded 130 μg (callus) to 250 μg (cell suspension) of DNA (g fresh cells)⁻¹, with a ratio A₂₀₀/A₂₈ of 1.7–2.0. The purified DNA obtained, formed distinct bands when restricted fragments were electrophoresed. Among the 10 endonucleases used for restriction analysis of Alnus glutinosa, Alnus incana and Betula papyrifera genomes, PvuI1 (EC 3.1.23.33) was unique in giving identical patterns for the two Ainus species. An unusual pattern occurred when Al-2 DNA was restricted with Ava II (EC 3.1.23.4). It formed a ladder with a repeating fragment unit of 181 base pairs long. With the enzymes tested, no differences in restriction patterns were observed among clones of Alnus incana (AI-2 vs AI-2), Betula papyrifera (BP-4 vs BP-8) and subclones of Ainus glutinosa AG-1 (PLFJ709 vs LF1709), suggesting genetic stability of the Betulaceae cultures.     

Genetic variation of the bud and leaf phenology of seventeen poplar clones in a short rotation coppice culture

Abstract: Leaf phenology of 17 poplar ( Populus spp.) clones, encompassing spring phenology, length of growth period and end-of-year phenology, was examined over several years of different rotations. The 17 poplar clones differed in their latitude of origin (45°30'N to 51°N) and were studied on a short rotation experimental field plantation, situated in Boom (province of Antwerpen, Belgium; 51°05'N, 04°22'E). A similar, clear pattern of bud burst was observed during the different years of study for all clones. Clones Columbia River, Fritzi Pauley, Trichobel (Populus trichocarpa) and Balsam Spire (Populus trichocarpa × Populus balsamifera) from 45°30'N to 49°N reached bud burst (expressed as day of the year or degree day sums) almost every year earlier than clones Wolterson (Populus nigra), Gaver, Gibecq and Primo (Populus deltoides × Populus nigra) (50°N to 51°N). This observation could not be generalised to end-of-season phenology, for which a yearly returning pattern for all clones was lacking. Late bud burst and early leaf fall of some clones (Beaupré, Boelare, IBW1, IBW2, IBW3) was brought about by increasing rust incidence during the years of observation. For these clones, the variability in leaf phenology was reflected in high coefficients of variation among years. The patterns of genetic variation in leaf phenology have implications for short rotation intensive culture forestry and management of natural populations. Moreover, the variation in phenology reported here is relevant with regard to the genetic mapping of poplar.     

Muskrat life history: a comparison of a northern and southern population

Muskrats Ondatra zibethicus were studied at Old Crow flats Yukon Territory (68°05'N, 140°05W) and Tiny Marsh, Ontario (44°35'N, 79°52'W) during the summers of 1985 and 1986 Life–history traits of these two populations were compared Litter size was not significantly different between the two sites However average annual productivity was significantly greater at Tiny Marsh where individuals produced more litters per season Growth rates of juvenile and adult muskrats were significantly greater at Tiny Marsh, as was juvenile and adult weight However overwinter survival of juvenile muskrats was significantly greater at Old Crow than at Tiny Marsh We suggest that the shorter growing season and proximate energetic limitations on growth and reproduction favour a conservative reproductive strategy by the northern muskrat population For the southern muskrat population a long growing season and high quality food resources allow for a more productive reproductive strategy     

Red-listed lichens in Sweden: habitats, threats, protection, and indicator value in boreal coniferous forests

The three major threats to lichens in Sweden; forestry, air pollution, and structural changes in the agricultural landscape, are outlined. Forestry is the most serious. The majority of the red-listed lichens in forests are found in productive forests with a continuity in tree growth, but nearly 70% of the protected area in Sweden consists of alpine landscapes. Examples of important habitats with red-listed lichens are described, e.g. Alnus glutinosa marshes, alvar-vegetation, broad-leaved deciduous forests and different Picea abies forests. The use of selected indicator species of lichens and macrofungi (mainly red-listed species) in boreal coniferous forests provides information on continuity in tree growth of an area, and on earlier influences of forestry. Examples of indicator species for different types of forest are presented and discussed. In spite of the Swedish right of common accesso, collecting of lichens is forbidden without permission from the land-owner. Collecting in protected areas is allowed only with a permit obtained from the authorities.     

Unexpected early extinction of the European pond turtle (Emys orbicularis) in Sweden and climatic impact on its Holocene range

Using ancient DNA sequences of subfossil European pond turtles ( Emys orbicularis ) from Britain, Central and North Europe and accelerator mass spectrometry radiocarbon dating for turtle remains from most Swedish sites, we provide evidence for a Holocene range expansion of the pond turtle from the southeastern Balkans into Britain, Central Europe and Scandinavia, according to the 'grasshopper pattern' of Hewitt. Northeastern Europe and adjacent Asia were colonized from another refuge located further east. With increasing annual mean temperatures, pond turtles reached southern Sweden approximately 9800 years ago. Until approximately 5500 years ago, rising temperatures facilitated a further range expansion up to Östergötland, Sweden (approximately 58°30'N). However, around 5500 years ago pond turtle records suddenly terminate in Sweden, some 1500 years before the Holocene thermal maximum ended in Scandinavia and distinctly earlier than previously thought. This extinction coincides with a temporary cooling oscillation during the Holocene thermal maximum and is likely related to lower summer temperatures deteriorating reproductive success. Although climatic conditions improved later again, recolonization of Sweden from southern source populations was prevented by the Holocene submergence of the previous land connection via the Danish Straits that occurred approximately 8500 years ago.     

Ectomycorrhizal root development in wet Alder carr forests in response to desiccation and eutrophication

Effects of desiccation and eutrophication on ectomycorrhizal (ECM) root development in wet Alder carr forests in The Netherlands were studied. In northwestern Europe, wet Alder carr forests are found mostly in peatlands and along streams, forming an important component of wetland ecosystems. The dominant tree species in wet Alder carr forests is Alnus glutinosa (L.) Gaertn. (Black alder), which associates with ectomycorrhizal fungi. During recent decades, wet Alder carr forests in Europe have declined because of desiccation and eutrophication, particularly in The Netherlands. In the present study, the number of root tips of A. glutinosa trees was highest in an undisturbed wet Alder carr forest in a peatland area. Eutrophication in the peatland area significantly inhibited ectomycorrhizal (ECM) root development of A. glutinosa. In the eutrophied forest, ECM root tips were observed only close to A. glutinosa trees growing on hummocks. The concentrations of nitrate and potassium in soil water of the eutrophied forest were significantly higher than in the undisturbed forest, while magnesium and iron concentrations and the pH were significantly lower. The number of ECM root tips of A. glutinosa in a desiccated forest along a stream was generally lower than in an undisturbed wet Alder carr forest on waterlogged soil in the same area. The sulphate concentration in soil water in the desiccated forest was significantly higher than in the forest on waterlogged soil. ECM root development of A. glutinosa may have been negatively affected by the chemical composition of the soil water.     

Canopy gaps and establishment patterns of spruce (Picea abies (L.) Karst.) in two old-growth coniferous forests in central Sweden

The spatial pattern of seedlings, saplings and canopy trees was studied in two spruce (Picea abies (L.) Karst.) forests in central Sweden. Canopy and forest structure were determined in five 0.25 ha plots. Life stage classes were distinguished on the basis of age and size distributions. Ripley's K-function (1977) was used to analyze the spatial patterns within each class. A random distribution of seedlings gave way to a more aggregated pattern on a small scale during the establishment phase. Saplings and sub-canopy trees were strongly aggregated and canopy trees were again randomly distributed within the plots. The proportion of individuals growing in gaps was used as an index of association between the spatial pattern in saplings and sub-canopy trees and the occurrence of small (50–350 m²) canopy gaps. Under the null hypothesis of independence the expected value of this statistic would equal the canopy gap ratio for the stand. Monte Carlo simulation of this statistic, using fixed sapling positions and randomly repositioned canopy gaps, confirmed the importance of canopy gaps for the final success of establishment of spruce. The association of understorey trees with gaps suggest that small gaps are typically closed by recruitment of new saplings from a sapling bank rather than by the release of larger suppressed trees.     

深圳市大鹏半岛蕨类植物区系及其生态特点

深圳市大鹏半岛的蕨类植物共有105种,它们隶属于35科、65属。其中含5种以上的科有水龙骨科(Dryopteridaceae)、金星蕨科(Thely pteridaceae)、凤尾蕨科(Pteridaceae)、卷柏科(Selaginellaceae)、鳞毛蕨科(Dryopteridaceae)、蹄盖蕨科(Athy riaceae)、铁角蕨科(Aspleniaceae)、鳞始蕨科(Lindsaeaceae)。其区系具有较强的热带性质,科、属、种的分布区类型均以热带至亚热带为主,分别占总科数的54.26%,总属数的92.86%以及总种数的70.87%。单属科和单种属的比例较高,分别占总科数的54.26%,总属数的69.23%。按生长基质的不同,将大鹏半岛的蕨类植物划为土生、石生、水生和附生四种生态类型,其中以土生类型为主。     

Primary succession of subarctic vegetation and soil on the fast‐rising coast of eastern Hudson Bay,Canada

Aim The objectives of the study are: (1) to evaluate the dynamics of the maritime tree line and forest limit of white spruce, Picea glauca, within the dual framework of primary succession induced by the rapid post‐glacial land emergence on the eastern coast of Hudson Bay and the impacts of recent and past climate changes; and (2) to determine the time lapse between land emergence and seedling, tree, and forest establishment in the context of the primary chronosequence occurring on rising, well‐drained sandy beaches and terraces. Location The study area was located on the eastern coast of Hudson Bay (56°20′ N, 76°32′ W) in northern Québec, Canada. Methods We evaluated the colonization dynamics of white spruce as seedlings, tree‐line trees and primary‐forest trees at eight sites distributed along a 200‐km latitudinal gradient based on a mean land emergence rate of 1.2 m century^?1. A 30‐m wide by 140–300‐m long quadrat was positioned at random at the centre of each site. The elevation above sea level, position and age of all individuals of spruce present in the quadrat areas were determined, and the soils of each chronosequence were described. Results The main stages of primary succession along the emerging coast were common to all the sites, regardless of latitude, but occurred at different elevations above sea level (a.s.l.). White spruce seedlings colonized near‐shore beaches 2 m a.s.l., whereas the tree line and forest limit tended to form only at about 3–4 m and 4–8 m a.s.l., corresponding approximately to 180–825 years and 310–1615 years after land emersion, respectively. White spruce establishment at the tree line occurred about 50 years ago. Climatic conditions at this time were probably more favourable to tree colonization than when the species established at the forest limit. Soil formation was influenced primarily by distance from the seashore and elevation above sea level, with podzolization being accelerated by white spruce cover. Main conclusions The current tree‐line and forest‐limit positions on the rising coast of eastern Hudson Bay correspond to ecological limits established during the course of primary succession within a context of changing climatic conditions. The recent establishment of trees at the tree line and forest limit at relatively old coastal sites is associated with warmer conditions over the last 100 years. Although white spruce was present nearby, coastal sites were devoid of trees before the 20th century.     

Changes of adenine nucleotide and orthophosphate concentrations in buds of deciduous trees during spring reactivation

Summary Concentrations of AMP, ADP, ATP, and inorganic phosphate (Pi) were determined in buds of five deciduous tree species (Acer pseudoplatanus, Alnus glutinosa, Fagus sylvatica, Fraxinus excelsior, Quercus robur) during spring reactivation from February to the middle of May. In closed buds of diffuse-porous wood trees (Acer, Alnus, Fagus), the content of adenine nucleotides (AdN) increased temporarily between the middle of February and the middle of March. The main increase of AdN concentration appeared either when buds became swollen (Fraxinus, Fagus, Quercus), or at the time of bud-break (Acer, Alnus). Pi content in general decreased during the course of reactivation. It was almost zero in buds of Quercus at bud-break and afterwards, but in Fraxinus Pi concentration rose when bud-break took place. The extremely low AdN content in Quercus buds is contrasted by a steep increase in AdN content in Fraxinus following bud-break. The decrease of AdN content in emerging leaves of Quercus and Fagus could be related to the high age of these trees.Abbreviations AdN adenine nucleotide(s) - DTT dithiothreitol - EDTA ethylenediaminetetraacetic acid - PEP phosphoenolpyruvate - Pi orthophosphate Supported by Deutsche Forschungsgemeinschaft and by Bundesministerium für Forschung und Technologie, Federal Republic of Germany.     

Preliminary analysis of root exudates of in vitro-micropropagated Alnus glutinosa clones

Biochemical analysis at Alnus glutinosa (L.) Gaertn. root exudates was carried out in order to investigate the probable role of these exudates in the establishment of the Alnus-Frankia symbiosis. Sufficient amounts of sterile root exudates were collected from plants originating from five in vitro-micropropagated A. glutinosa clones (AG1, AG2, AG3, AG4, AG8) grown under aerobic conditions in nutrient solution with Ballotini glass beads. Cytological controls showed good preservation of roots at the end of the collecting period. The total protein and sugar contents of crude root exudates were determined and related to the dry root weight. These results showed a provenance effect. Soluble high molecular-weight fractions (i.e. the mucilage) were isolated following rigorous purification of the crude root exudates and within this fraction proteins were characterized by isoelectric focusing. The protein pattern of the five clones tested showed major bands in common and some minor specific ones. These experimental data will serve as a useful basis for future physiological investigations.     

Characterization of a Casuarina glauca nodule-specific subtilisin-like protease gene, a homolog of Alnus glutinosa ag12

In search of plant genes expressed during early interactions between Casuarina glauca and Frankia, we have isolated and characterized a C. glauca gene that has strong homology to subtilisin-like protease gene families of several plants including the actinorhizal nodulin gene ag12 of another actinorhizal plant, Alnus glutinosa. Based on the expression pattern of cg12 in the course of nodule development, it represents an early actinorhizal nodulin gene. Our results suggest that subtilisin-like proteases may be a common element in the process of infection of plant cells by Frankia in both Betulaceae (Alnus glutinosa) and Casuarinaceae (Casuarina glauca) symbioses.     

Growth–mortality relationships as indicators of life-history strategies: a comparison of nine tree species in unmanaged European forests

Forest succession depends strongly on the life history strategies of individual trees. An important strategic element is the ability to survive unfavourable environmental conditions that result in strongly reduced tree growth. In this study, we investigated whether the relationship between growth and mortality differs among tree species and site conditions. We analysed 10 329 trees of nine tree species (Picea abies , Taxus baccata , Fagus sylvatica , Tilia cordata , Carpinus betulus , Fraxinus excelsior , Quercus robur , Betula spp. and Alnus glutinosa ) from unmanaged forests of Europe: the continental Białowieża forest (Poland) and several oceanically influenced Swiss forest reserves. For each species, we calculated a set of flexible logistic regression models with the explanatory variables growth (as measured by relative basal area increment), tree size and site. We selected the species-specific model with the highest goodness-of-fit and calculated its discriminatory power (area under the receiver operating characteristic curve, AUC) and calibration measures. Most models achieved at least a good discriminatory power (AUC>0.7) and the AUC ranged from 0.62 to 0.87; calibration curves did not indicate any overfitting. Almost all growth–mortality relationships differed among species and sites, i.e. there is no universal growth–mortality relationship. Some species such as F. excelsior showed reduced survival probabilities for both unfavourable and very good growth conditions. We conclude that the growth–mortality relationships presented here can contribute to the life-history classification of trees and that they should also help to improve projections of forest succession models.     

Frankia in acid soils of forests devoid of actinorhizal plants

The capacity of some acid forest soils to induce nodulation on a hybrid between Alnus incana (L.) Moench and A. glutinosa (L.) Gaertn. was investigated. Soil was sampled from tree stands devoid for decades of actinorhizal hosts. Seven-week-old Alnus seedlings growing m liquid culture were inoculated with soil dilutions. The nodules were counted after 6 weeks and classified as Sp⁻, if they lacked spores, or as Sp⁺. if spores were present, according to microscopy of microtome sections. Frankia was found in all the forest soils studied, apart from a soil from a Betula swamp. The highest nodulation capacities on Alnus , caused predominantly by Frankia of the Sp⁻ type. were observed in mineral soil sites with Betula stands — even higher than in soil from an A. incana stand. A positive correlation was found between the pH and the noduiation capacity of the soil.     

Identification and subgrouping of Frankia strains using sodium dodecyl sulfate-polyacrylamide gel electrophoresis

Polypeptide patterns of soluble proteins from 35 Frankia strains from different plants of various geographical origins, belonging to Alnus and Elaeagnus host-specificity groups were determined by one-dimensional sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The polypeptide pattern was qualitatively the same for each strain whatever the number of subcultures or the age. Two gel electrophoresis groups A and E were observed which matched with the Alnus and Elaeagnus host-specificity groups, but with some exceptions. The polypeptide patterns of the 35 Frankia strains tested were separated into 13 gel electrophoresis subgroups. Five Frankia strains were inoculated separately or in 3 mixed combinations of 2 strains on Alnus glutinosa (L.) Gaertn. plants. The polypeptide patterns of the re-isolates obtained from 5-month-old nodules were identical to the corresponding strains used initially in the inoculum. Dual infection was observed on single plantlets.     

A structural analysis of three Irish wooded wetlands

Abstract. Transect analyses emphasize the differences in tree species composition and structure of three different wooded wetland tracts in Co. Kerry, Ireland. These are variously dominated by Alnus glutinosa, Betula pubescens, Fraxinus excelsior, Quercus robur and Salix cinérea ssp. oleifolia. Stand density ranged from 16 to 54 live trees per 100 m², tree height did not exceed 15 m, mean individual basal area ranged from 78 to 165 cm² and the average total basal area per hectare was between 3.6 and 4.1m². The sites were quite different in a number of the characteristics recorded. The Irish forests were smaller in stature and denser than others in both temperate zones (Continental Europe, North America, Japan) and the tropics. Crown area indices were also lower than for other areas, ranging from 1.15 to 1.79. The height: diameter relationships may reflect the state of sylvige-nesis of each stand. Death by blowdown appears to be less frequent in the younger stands than death by suppression. Gaps are therefore formed gradually, not suddenly, allowing neighbouring suppressed trees to develop into the spaces formed.     

Seasonal and interannual variation in fish assemblages of northern temperate rocky subtidal habitats

Fish assemblages on two inshore rocky subtidal sites on the west coast of Scotland, were studied using diver visual surveys on a monthly basis between September 1995 and December 1999. A total of 17 689 fishes and 26 species were recorded from the two sites, Saulmore Point (056°27'N; 005°24'W) near Oban and Davy's Rock (055°46'N; 004°53'W) on the Isle of Great Cumbrae. The gobiid Thorogobius eppiphiatus , dominated the Saulmore Point site; six fish species accounted for >93% of total abundance at that site. At Davy's Rock four species contributed at least 93% of total fish abundance, and the dominant species was the labrid Ctenolabrus rupestris . Total abundance of the dominant species displayed a clear seasonal trend, and this was significantly related to recorded daily average seawater temperature. A maximum abundance of 4.9 fishes m⁻² was recorded in November 1998 at Davy's Rock and 2.5 fishes m⁻² at Saulmore Point in October 1998. Multivariate analysis indicated a degree of variation in assemblage structure between winter and summer at both sites. A number of species showed some degree of interannual variation, in particular the gobiid Gobiusculus flavescens whose abundance increased by over 300 times over a 5 month period in 1998. Correlation analysis showed that variation in annual winter seawater temperature could act as an indicator of interannual variation in abundance of some of the dominant species utilizing rocky subtidal habitats.