Distinguishing fossil Betula nana and B. pubescens using their wingless fruits: implications for the late-glacial vegetational history of western Norway

Principal components analysis of 7 size and shape variables measured on 154 modern fruit bodies of Betula species and hybrids shows that B. pubescens and B. nana can be distinguished from each other on the basis of their fruit bodies, and that B. pubescens ssp. tortuosa and hybrids either fall within the range of B. pubescens or have an intermediate position on PCA axes 1 and 2. Passive positioning on the modern PCA axes of fossil fruit bodies from late-glacial sediments at Eigebakken, south-west Norway, shows that only B. nana was locally present in the Allerød. This contradicts earlier inferences from pollen analyses alone of birch woodland development in the Allerød in south-west Norway. There is no macrofossil evidence for tree-birches in the Allerød near Eigebakken. The relatively large amounts of Betula pollen, including B. pubescens, at Eigebakken are thus probably derived by long-distance transport from tree-birches in Denmark, south Sweden, and Britain, whose presence is proved there by macrofossils. Consequently, earlier estimates of mean July temperature during the Allerød in southwestern Norway should be reduced to around 7.5–10°C. In contrast, the PCA shows that fruit bodies from Holocene sediments at Eigebakken and at Kråkenes, western Norway, are mostly derived from B. pubescens. Birch trees were able to spread quickly and effectively across Norway in the early Holocene.     

On the reputed decline in gastric carcinoma: necropsy study from western Norway.

Carcinoma of the stomach is said to be decreasing in many countries, Norway included. About 10% of all cases in Norway occur in the county of Hordaland. They do not differ in any known respect from cases in the rest of the country. A series of 575 cases coming to necropsy from Hordaland over 25 years was examined and the findings compared with the total number reported to the Norwegian Cancer Registry from the same district. Although the incidence of histological verification rose over the period from 49 to 85%, the number of histologically confirmed cases remained relatively constant, the considerable decline being confined to cases without such documentation. The results suggest that increased diagnostic effort has led to the exclusion of cases previously classified clinically as gastric carcinoma and that the incidence of the disease itself has not changed radically in the county of Hordaland.     

The occurrence of thermophilous trees in the Scandes Mountains during the early Holocene: evidence for a diverse tree flora from macroscopic remains

1 Macroscopic remains of the fairly thermophilous tree species Alnus glutinosa , Tilia cordata and Betula pendula were recovered in subalpine and adjacent boreal environments far above and beyond their present-day distributional limits. This establishes that the early Holocene tree flora of the Scandes Mountains in northern Sweden was indeed richer than it is today.
2 Dates ranged between c . 8600 and 7000 radiocarbon years bp . These are much earlier than previous estimates by conventional pollen stratigraphical analyses of the arrival of these species at their maximum geographical limits. This highlights problems in using only pollen data for vegetation reconstruction, and suggests re-evaluation of earlier records.
3 The results, together with similar macrofossils for Picea abies and Larix sibirica in northern Sweden, suggest that many tree species spread rapidly and became established at their most extended range limits during the early Holocene. Abundances have subsequently varied in accordance with the ecology of individual species as well as with climatic change.
4 Palaeoclimatic inferences may suggest a strongly continental climate, i.e. warmer and drier summers and possibly fairly cold winters between 8600 and 7000 bp relative to the present. Some change towards a more oceanic climate regime with less pronounced seasonal contrasts may have occurred towards the end of the period.     

The 'oriental' component of the Balkan flora: evidence of presence on the Thracian Plain during the Weichselian late-glacial

Aim To obtain palaeobotanical evidence enabling evaluation of the viability of the hypothesis that the ‘oriental’ element of the Balkan flora reached south‐east Europe from Turkey prior to the Holocene, probably via the Thracian Plain during a late Quaternary glacial stage but no later than the late Weichselian. Location Ezero wetland, northern Thracian Plain, Bulgaria. Methods We undertook analyses of pollen and microspores, plant macrofossils, wood fragments and molluscs recovered from sediments deposited in the Ezero wetland during the late Weichselian and Weichselian late‐glacial. Sediment chronology was determined using radiocarbon age estimates. Results Six metres of sediments were recovered from the basin, of which the lower 3 m, extending from c. 15,450 cal yr bp to the early Allerød, was analysed. A major hiatus occurred after c. 13,900 cal yr bp , the overlying sediments being of late Holocene age. Palaeobotanical evidence indicates predominantly open vegetation during the Weichselian late‐glacial, although macrofossil remains of woody taxa demonstrate the local presence of patches of wooded steppe and gallery forest. Changes in the composition of the steppe vegetation, and in the nature of the sediments deposited in the basin, indicate changes in climatic conditions, especially in the hydrological regime and in the moisture available to vegetation. After an initially relatively moister phase, the final centuries of the late Weichselian were drier, as was a short interval that may correlate with the Older Dryas. Moister conditions characterize intervals corresponding to the Bølling and Allerød sub‐units of the Weichselian late‐glacial interstadial. Although the pollen evidence is thus consistent with that from previous studies of this period in south‐east Europe and south‐west Asia, indicating predominantly open steppe vegetation, the macrofossil evidence indicates the persistent local presence of woody taxa. The woody taxa recorded include Celtis tournefortii‐type and Juniperus cf. J. excelsa, two taxa today characteristic of the wooded steppes of Anatolia and members of the ‘oriental’ element of the southern Balkan flora, as well as Rosaceae Subfams. Maloideae and Prunoideae, Alnus and Fraxinus. Main conclusions The late Weichselian vegetation of the northern Thracian Plain included patches of wooded steppe that supported members of the ‘oriental’ element of the modern Balkan flora. The presence of such taxa renders viable the hypothesis that they could have reached south‐east Europe from Turkey via the Thracian Plain during glacial times. Such hypotheses in historical biogeography can be evaluated critically using the evidence obtained from plant macrofossil analyses in combination with that from pollen analysis.     

Biodiversity and vegetation dynamics in the coastal heathlands of western Norway

The heaths of Lygra, western Norway, were investigated, and 19 communities at the association level were distinguished. Distinct ecotypes of Ranunculus acris and Poa humilis and microspecies of Euphrasia were restricted to the grass heaths. No distinct ecotypes were found in the Calluna -dominated vegetation. It is suggested that the regular burning, which has been part of the management of the area, has activated the seed bank of the ericaceous heath, and thus maintained genetic diversity and slowed down ecotype differentiation. The grass heaths, with no combustible material, have been unaffected in this way. Permanent plots in the two dominant heath types, dry heath (Vaccinio-Callunetum) and wet heath (Ericetum tetralicis) were followed over six years and the data analysed using a modification of Jaccard's index, allowing for species abundances.     

Mast-producing trees and the geographical ecology of western scrub-jays

We analyzed the relationship between population abundance and variability of western scrub-jays Aphelocoma californica based on 48 yr of Audubon Christmas Bird Counts and the resources on which they depend as indexed by the diversity and abundance of mast-producing oaks and pines and, for California, estimates of acorn production based on a statewide survey. In general, populations of A. c. californica along the Pacific coast were related to oaks, with populations being more abundant and more stable in areas with more oak species and greater oak abundance. In contrast, populations of A. c. woodhouseii in the Great Basin were correlated with pines/conifers, again with higher abundance and greater stability with increased number of pine species and greater abundance of pines/conifers. The presumed driver of these patterns is increased resource abundance with greater habitat abundance and increased resource stability with increasing species diversity due to asynchrony in seed production among different species of trees. Asynchrony in acorn production is particularly high among oaks that require different number of years to produce acorns, but we failed to confirm that populations with access to both types were more stable than those with access to only one type after controlling for oak diversity. However, we did find a strong positive correlation between overall mean scrub-jay abundance in California and overall acorn production one year earlier, suggesting that acorns benefit scrub-jay populations primarily by increasing reproductive success the following year. These patterns demonstrate the strong dependence between population dynamics and resource stability as well as how different these relationships can be within closely related taxa.     

Differences in transpiration of Norway spruce drought stressed trees and trees well supplied with water

The paper focuses on the evaluation of transpiration as a physiological process, which is very sensitive to drought stress. Reactions of 25-year-old Norway spruce (Picea abies (L.) Karst.) trees to drought were examined during 2009 summer. Sap flow rate (SF), meteorological and soil characteristics were measured continually. Vapour pressure deficit of the air (VPD) and cumulative transpiration deficit (KTD) was calculated. During the second half of the vegetation period, the decrease in soil water content was observed and irrigation was applied to a group of spruce trees, while the second group was treated under natural soil drought. On the days, when the differences in transpiration between irrigated (IR) and non-irrigated (NIR) trees were significant (21 days), transpiration of NIR trees was only 23% of the transpiration of IR trees. We found significant differences in transpiration when the soil water content (SWC) of NIR variant at a depth of 5–15 cm ranged from 10.4 to 13.7%. Under both regimes of water availability, daily transpiration significantly responded to atmospheric conditions. However, the influence of all assessed meteorological parameters on SF of NIR trees was significantly lower than on IR tree. The dependency of transpiration on evaporative demands of atmosphere decreased with the decreasing soil moisture. Cumulative transpiration deficit of the stand during the entire evaluated period was 50.9 mm. The difference between the transpiration of the mean NIR tree and of the mean IR tree was 278.8 L over the assessed period of 47 days (5.9 L per day). The transpiration of NIR trees was 40.3% from the transpiration of IR trees during this period.     

Dominance of non-native riparian trees in western USA

Concern about spread of non-native riparian trees in the western USA has led to Congressional proposals to accelerate control efforts. Debate over these proposals is frustrated by limited knowledge of non-native species distribution and abundance. We measured abundance of 44 riparian woody plants at 475 randomly selected stream gaging stations in 17 western states. Our sample indicates that Tamarix ramosissima and Elaeagnus angustifolia are already the third and fourth most frequently occurring woody riparian plants in the region. Although many species of Tamarix have been reported in the region, T. ramosissima (here including T. chinensis and hybrids) is by far the most abundant. The frequency of occurrence of T. ramosissima has a strong positive relation with the mean annual minimum temperature, which is consistent with hypothesized frost sensitivity. In contrast the frequency of occurrence of E. angustifolia decreases with increasing minimum temperatures. Based on mean normalized cover, T. ramosissima and E. angustifolia are the second and fifth most dominant woody riparian species in the western USA. The dominance of T. ramosissima has been suspected for decades; the regional ascendance of E. angustifolia, however, has not previously been reported.     

The drift of zooplankton and microzoobenthos in the river Strandaelva,western Norway

The drift of zooplankton (rotifers, cladocerans, cyclopoid copepods) and microscopical zoobenthos (mainly bdelloid rotifers and small chironomid larvae) was investigated by filtering samples of river water. The number of drifting benthic rotifers varied between 1 000 and 6 000 ind. m^–3 in the lake inlet, and between 30 and 500 ind. m^–3 in the lake outlet, without any seasonal trend. The number of drifting insect larvae was approx. equal in the lake inlet and outlet, with a maximum in summer (250–300 ind. m^–3) and minimum in winter (ca. 10 ind. m^–3). Increasing water flow resulted in an increasing number of drifting zoobenthos. Downstream from the lake, the number of drifting benthic rotifers was increasing from approx. 300 ind. m^–3 in the outlet to 6 500 ind. m^–3 3.4 km downstream, while the number of insect larvae was ca. 100 ind. m^–3 in the outlet and leveled off at approx. 300 ind. m^–3 after 200 m. The number of drifting zooplankton in the lake outlet varied between 20 and 2 000 ind. m^–3 for crustaceans, and between 300 and 20 000 ind. m^–3 for rotifers, both with a maximum in late summer/autumn and a minimum in winter. The number of drifting zooplankton decreased by some 45% in the first 200 m from the lake outlet, but some zooplankton was still found in the drift 3.4 km downstream. The largest species was removed first from the drift. The diurnal variation in the number of drifting zooplankton in lake outlets appear to be related to the vertical migration in the lake, i.e. the largest number drifting when most animals are in the upper water layers.Contribution from the Voss Project, University of OsloContribution from the Voss Project, University of Oslo     

Wood formation in urban Norway maple trees studied by the micro-coring method

Intra-annual wood formation in healthy and affected Norway maple (Acer platanoides L.) street trees in the City of Ljubljana, Slovenia, was studied by the micro-coring method. Samples were taken with a Trephor instrument at weekly intervals during the 2005 growing season. The beginning of wood formation corresponded to the initiation of cambial activity in the middle of April in all investigated Norway maple trees. In healthy trees, the period of wood formation was finished in mid-September, persisting 7 weeks longer than in affected ones. Small destructivity and sufficient quality of micro-cores confirmed that sampling with a Trephor is a convenient method for the study of wood formation in diffuse-porous hardwoods, growing in the harsh conditions of an urban environment.     

Adaptive genetic diversity of trees for forest conservation in a future climate: a case study on Norway spruce in Austria

Genetic resources of forest trees are considered as a key factor for the persistence of forest ecosystems because the ability of tree species to survive under changing climate depends strongly on their intraspecific variation in climate response. Therefore, utilizing available genetic variation in climate response and planting alternative provenances suitable for future climatic conditions is considered as an important adaptation measure for forestry. On the other hand, the distribution of adaptive genetic diversity of many tree species is still unknown and the predicted shift of ecological zones and species’ distribution may threaten forest genetic resources that are important for adaptation. Here, we use Norway spruce in Austria as a case study to demonstrate the genetic variation in climate response and to analyse the existing network of genetic conservation units for its effectiveness to safeguard the hotspots of adaptive and neutral genetic diversity of this species. An analysis of the climate response of 480 provenances, clustered into 9 groups of climatically similar provenances, revealed high variation among provenance groups. The most productive and promising provenance clusters for future climates originate from three regions that today depict the warmest and driest areas of the natural spruce distribution in Austria. Gap analysis of the Austrian genetic conservation units in the EUFGIS Portal suggests adequate coverage of the genetic hotspots in southern parts of Austria, but not in eastern and northern Austria. Therefore conservation measures and sustainable utilization of the valuable genetic resources in these regions need to be expanded to cover their high adaptive genetic variation and local adaptation to a warmer climate. The study shows that current conservation efforts need to be evaluated for their effectiveness to protect genetic resources that are important for the survival of trees in a future climate.     

Recent cooling and recession of Norway spruce (Picea abies (L.) Karst.) in the forest—alpine tundra ecotone of the Swedish Scandes

Abstract. Repeated crown condition surveys, 1974–94, of subalpine clonal groups of Norway spruce ( Picea abies (L.) Karst.) were carried out in the Swedish Scandes. Complementary analyses concerned radial and vertical growth, sexual regeneration and range limit responses of other plant species. Significant defoliation of spruce progressed linearly over the period of study, reaching cumulative values of about 85%. It is inferred that defoliation was preconditioned by decreasing radial growth since the thermal climax in 1937 and was proximately initiated by the extremely cold winter of 1965/66 and paralleled by consistently declining radial growth and staggering vertical increase. It appears that severe and prolonged ground freezing invoked winter desiccation (xylem cavitation), extensive needle loss and reduced radial growth. Hypothetically, from circumstantial evidence, these processes are interrelated in a positive feedback system, implying increasing sensitivity to climatic stress and decreasing ability to take advantage of positive climatic anomalies. Thus, the total demise of the supranival stems is cautiously predicted, by linear regression of the 20-yr defoliation pattern, to be less than a decade ahead. The recession of P. abies , clearly relevant in a landscape perspective, conforms with analogous responses of Pinus sylvestris L. and Betula pubescens Ehrh. ssp. tortuosa (Ledeb.) Nyman and a significant altitudinal range-limit retraction of certain silvine field-layer species. The structural development examined in this study concurs with long-term climate cooling and cold events and strongly contrasts with simulations of the performance of this system in response to a putative enhanced'greenhouse'effect.