Showing papers by "Swiss Federal Institute for Forest, Snow and Landscape Research published in 1998"

Predicting the potential distribution of plant species in an alpine environment

Abstract: . The relationships between the distribution of alpine species and selected environmental variables are investigated by using two types of generalized linear models (GLMs) in a limited study area in the Valais region (Switzerland). The empirical relationships are used in a predictive sense to mimic the potential abundances of alpine species over a regular grid. Here, we present the results for the alpine sedge Carex curvula ssp. curvula. The modelling approach consists of (1) a binomial GLM, including only the mean annual temperature as explanatory variable, which is adjusted to species presence/absence data in the entire study area; (2) a logistic model restricted to stands occurring within the a priori defined temperature range for the species - which allows ordinal abundance data to be adjusted; (3) the two species-response functions combined in a GIS to generate a map of the species' potential abundance in the study area; (4) model predictions filtered by the classes of the qualitative variables under which the species never occur. Such a stratified approach used to better fit the variability within the optimal altitudinal zone for the species. Removing stand descriptions from altitudes too high or too low, where the species is unlikely to occur, enhances the global modelling performance by allowing the identification of important environmental variables only retained in the second model. The model evaluation is finally carried out with the γ-measure of association in an ordinal contingency table. It shows that abundance is satisfactorily predicted for C. curvula.

Trees tell of past climates: But are they speaking less clearly today?

Abstract: The annual growth of trees, as represented by a variety of ringwidth, densitometric, or chemical parameters, represents a combined record of different environmental forcings, one of which is climat...

Pollen and charcoal in lake sediments compared with historically documented forest fires in southern Switzerland since AD 1920

Abstract: Charcoal in unlaminated sediments dated by 210Pb was analysed by the pollen-slide and thin-section methods. The results were compared with the number and area of forest fires on different spatial scales in the area around Lago di Origlio as listed in the wildfire database of southern Switzerland since AD 1920. The influx of the number of charcoal particles > 75 µm2 in pollen slides correlates well with the number of annual forest fires recorded within a distance of 20-50 km from the coring site. Hence a size-class distinction or an area measurement by image analysis may not be absolutely necessary for the reconstruction of regional fire history. A regression equation was computed and tested against an independent data set. Its use makes it possible to estimate the charcoal area influx (or concentration) from the particle number influx (or concentration). Local fires within a radius of 2 km around the coring site correlate well with the area influx of charcoal particles estimated by the thin-section method measuring the area of charcoal particles larger than 20 000 µm2 or longer than 50 µm. Pollen percentages and influx values suggest that intensive agriculture and Castanea sativa cultivation were reduced 30-40 years ago, followed by an increase of forest area and a development to more natural woodlands. The traditional Castanea sativa cultivation was characterized by a complete use of the biomass produced, so abandonment of chestnut led to an increasing accumulation of dead biomass, thereby raising the fire risk. On the other hand, the pollen record of the regional vegetation does not show any clear response to the increase of fire frequency during the last three decades in this area.

Predicting the Effects of Atmospheric Nitrogen Deposition in Conifer Stands: Evidence from the NITREX Ecosystem-Scale Experiments

Abstract: The NITREX project, which encompasses seven ecosystem-scale experiments in coniferous forests at the plot or catchment level in northwestern Europe, investigates the effect of atmospheric nitrogen (N) deposition in coniferous forests. The common factor in all of the experiments is the experimentally controlled change in N input over a period of 4–5 years. Results indicate that the status and dynamics of the forest floor are key components in determining the response of forests to altered N inputs. An empirical relationship between the carbon–nitrogen (C/N) ratio of the forest floor and retention of incoming N provides a simply measured tool through which the likely timing and consequences of changes in atmospheric N deposition for fresh waters may be predicted. In the terrestrial ecosystem, a 50% increase in tree growth is observed following the experimental reduction of N and sulfur inputs in a highly N-saturated site, illustrating the damaging effects of acidifying pollutants to tree health in some locations. Few biotic responses to the experimental treatments were observed in other NITREX sites, but the rapid response of water quality to changes in N deposition, and the link to acidification in sensitive areas, highlight the need for N-emission controls, irrespective of the long-term effects on tree health. The observed changes in ecosystem function in response to the experimental treatments have been considered within the framework of the current critical-load approach and thus contribute to the formulation of environmental policy.

Rare earth elements in soil and in soil-grown plants

Abstract: Concentrations of the rare earth elements (REEs) La, Ce, Nd, Sm, Eu, Gd, Tb, Yb and Lu were determined in leaves of 6 plant species (Norway spruce, silver fir, maple, ivy, blackberry, and wood fern), and in pertinent soils and soil extracts, also taken from the same site. The distribution of the individual REEs in plants showed little or no agreement with that in the soil or the soil extracts. Ce had a negative anomaly with respect to the soil in all plants. The REE distribution patterns of fir and spruce were almost identical, but differed profoundly from that of the other species. In most cases, concentration ratios between species were a smooth function of the atomic number of the REE. Very similar results were obtained at 2 additional sites.

Analysis of the temperature dependent development of the spruce bark beetle Ips typographus (L) (Col., Scolytidae)

Abstract: Following individual development by means of the ‘sandwich method’ the duration of egg, larval, and pupal stages, as well as of adult maturation feeding of the spruce bark beetle (Ips typographus) was measured at constant temperatures in the range between 12° and 33° C. At 20° C complete development from egg to adult emerging from pupa averaged 29 days. The proportion of the duration of larval development relative to total preimaginal development increased with temperature. Developmental rates, i.e. the speed of development increased linearly with temperature in a range between 15° and 25°C. Based on linear regressions, lower developmental thresholds were calculated to be 10.6°C (eggs), 8.2°C (larvae), 9.9°C (pupae), and 8.3°C (preimaginal development egg to pupa), respectively. Differing heat sums reported in the literature matched ours when recalculated with our developmental thresholds. A nonlinear model (Logan/Lactin) was fitted to the data which allowed to describe development in the entire temperature range. It further permits to identify lower and upper (≅ 40°C) developmental thresholds as well as optimum temperatures (30–33°C) of the instars.

Modelling floristic species richness on a regional scale: a case study in Switzerland

Abstract: In this paper a multivariate linear regression model is proposed for predicting and mapping regional species richness in areas below the timberline according to environmental variables The data used in setting up the model were derived from a floristic inventory Using a stepwise regression technique, five environmental variables were found to explain 489% of the variability in the total number of plant species: namely temperature range, proximity to a big river or lake, threshold of minimum annual precipitation, amount of calcareous rock outcrops and number of soil types A considerable part of the unexplained variability is thought to have been influenced by variations in the quality of the botanical inventory These results show the importance of systematic floristic sampling in addition to conventional inventories when using floristic data as a basis in nature conservation Nevertheless it is still possible to interpret the resulting diversity patterns ecologically Regional species richness in Switzerland appears to be a function of: (i) environmental heterogeneity; (ii) threshold values of minimum precipitation; and (iii) presence of calcareous rock outcrops According to similar studies, environmental heterogeneity was the strongest determinant of total species richness In contrast to some studies, high productivity decreased the number of species Furthermore, the implications of this work for climate change scenarios are discussed

Forest biodiversity and its assessment by remote sensing

Abstract: Several international conventions and agreements have stressed the importance of the assessment of forest biodiversity. However, the methods by which such assessments can be made remain unclear. Remote sensing represents an important tool for looking at ecosystem diversity and various structural aspects of individual ecosystems. It provides a means to make assessments across several different spatial scales, and is also critical for assessments of changes in ecosystem pattern over time. Many different forms of remote sensing are available. While lately the emphasis on laser scanner and synthetic aperture radar data has increased, most work to date has used photographs and digital optical imagery, primarily from airborne and spaceborne platforms. These provide the opportunity to assess different phenomena from the landscape to the stand scale. Remote sensing provides the most efficient tool available for determining landscape-scale elements of forest biodiversity, such as the relative proportion of matrix and patches and their physical arrangement. At intermediate scales, remote sensing provides an ideal tool for evaluating the presence of corridors and the nature of edges. At the stand scale, remote sensing technologies are likely to deliver an increasing amount of information about the structural attributes of forest stands, such as the nature of the canopy surface, the presence of layering within the canopy and presence of (very) coarse woody debris on the forest floor. Given the rate of development in the technology, even greater usage is likely in the future.

Comparative Analysis of Different DNA Extraction Protocols: A Fast, Universal Maxi-Preparation of High Quality Plant DNA for Genetic Evaluation and Phylogenetic Studies

Abstract: Four DNA extraction protocols were compared for ability to produce DNA from the leaves or needles of several species: oak, elm, pine, fir, poplar and maize (fresh materials) and rhododendron (silica dried or frozen material) With the exception of maize and poplar, the species are known to be difficult for DNA extraction Two protocols represented classical procedures for lysis and purification, and the other two were a combination of classical lysis followed by anion exchange chromatography The DNA obtained from all procedures was quantified and tested by PCR and Southern hybridisationTest results indicated superiority of one of the four protocols; a combination of CTAB lysis followed by anion exchange chromatography which enabled DNA extraction from all seven species A second protocol also produced DNA from leaves or needles of all species investigated and was well suited for PCR applications but not Southern hybridisations The remaining protocols produced DNA from some but not all species tested Abbreviations: CTAB, hexadecyltrimethylammonium bromide; EtOH, Ethanol; TBE, tris-borate-EDTA

Measurement of atmospheric deposition under forest canopies: some recommendations for equipment and sampling design

Abstract: Quantification of the forest water flux provides valuable information for the understanding of forest ecosystem functioning. As such, throughfall (and stemflow to a lesser extent) has been frequently measured. Although throughfall collection may seem relatively simple, the requirements to obtain reliable estimates are often underestimated. This review addresses the criteria to take into account when working out the sampling procedure, from the selection of equipment to implementation in the field. Sound sampling of the forest water flux is difficult due to its high spatial and temporal variation. The high costs entailed by the ideal sampling design often prohibit its implementation. Different procedures are available, some of which are compromises between the aim of the study (monitoring or experimental study, short or long term objectives, absolute or relative estimates, quality of the assessment to be achieved) and the available means.

Comparison of vegetative compatibility types in Italian and Swiss subpopulations of Cryphonectria parasitica

Abstract: Summary Tester isolates of 20 vegetative compatibility (vc) types from 11 Italian subpopulations and tester isolates of 26 vc types from five Swiss subpopulations of Cryphonectria parasitica were compared by two different vc test methods. A total of 31 different vc types was identified; 15 vc types were common to both countries, five Italian vc types were not found in Switzerland and 11 Swiss vc types were not found in Italy. These 31 vc types were labelled with the acronym EU, followed by progressive numbers and may constitute the base for a common European nomenclature. The vc type EU-2 was the most common vc type in both countries and dominated in all Swiss and in seven Italian subpopulations. The vc types EU-1 and EU-5 were found primarily in northern Italy and Switzerland, while EU-10 and EU-12 were most common in southern Italy. The diversity of vc types was greater in the subpopulations of Switzerland and northern Italy than in the subpopulations of southern Italy. The geographical distribution of vc types in Europe should therefore be taken into consideration for biological control measures of chestnut blight and quarantine regulations.

Effects of elevated CO2 and soil quality on leaf gas exchange and above-ground growth in beech-spruce model ecosystems

Abstract: Responses of leaf gas exchange and above-ground growth of beech (Fagus sylvatica L.) and Norway spruce (Picea abies Karst.) to atmospheric CO2 enrichment (374 μl l−1 vs. 590 μl l−1) and increased wet deposition of N (5 vs. 50 kg N ha−1 a−1) in combination with two natural forest soil types (‘acidic’ and ‘calcareous’) were studied in large open-top chambers. Eight juvenile beech and spruce trees from different provenances, together with a ground cover composed of five understorey species, were established in each of 32 model ecosystems. Both beech and spruce showed sustained enhancement of photosynthesis in response to atmospheric CO2 enrichment during the first 2 yr of treatment. Nevertheless, switching measurement CO2 concentrations revealed partial downward adjustment of photosynthesis in trees grown in elevated CO2, beech generally showing more pronounced downward adjustment than spruce. The responsiveness of photosynthesis to CO2 enrichment did not vary significantly among trees from different provenances. Stomatal conductance was reduced under elevated CO2 in both tree species. In spruce, the radial growth of the main stem and the annual production of wood (shoot-wood dry mass of current-year lateral shoots), needle dry mass, and assimilation area per tree were stimulated both by CO2 enrichment and increased N deposition, but were not significantly affected by soil type by year 2. In contrast, in beech, the radial growth of the stem and the total leaf number, foliage dry mass, and assimilation area per tree were all not significantly affected by elevated CO2 and increased N deposition when responses of the two soil types were pooled, but were greater on calcareous than on acidic soil by year 2. However, CO2 interacted with soil type in beech: irrespective of the N deposition rate, saplings showed growth stimulation on the calcareous soil but responded negatively to CO2 enrichment on the acidic soil (where growth was slower). Our results suggest that complex interactions between CO2, species and soil quality need to be accounted for when attempting to predict forest development in a future CO2-rich world.

Changes in sunshine duration are correlated with changes in daily temperature range this century: An analysis of Swiss climatological data

Abstract: Analyses of the relationship between trends in daily temperature range and those of sunshine duration in the Swiss Alps show a strong correlation at lower elevation sites. The decrease in daily temperature range is associated with a corresponding decrease in sunshine duration. At high elevations, however, this relationship is absent. The decrease in daily temperature range observed this century at lower elevation sites is inferred to be a consequence of an increase in low-level cloudiness. Higher elevation sites lie above the low-level cloud layers and the moisture-laden lower atmospheric boundary layer and as a result do not exhibit the same trends.

Biodiversity: A Diversity in Definition

Abstract: A quantitative and qualitative assessment of the international scientific literature of the past ten years indicates major differences in the definitions and use of the term biodiversity. This in part reflects a steady increase in the number of occurrences of the term in the titles of scientific articles from year to year, as shown by a search of various online literature databases.

The Rietveld method applied to the quantitative mineralogical and chemical analysis of a ferralitic soil

Abstract: Summary The analysis of X-ray diffraction (XRD) patterns by the Rietveld method was tested for characterizing quantitatively the mineralogical composition of a ferralitic soil from southern Mali. Quantitative analysis of two samples from this soil revealed kaolinite and quartz as major components and smaller amounts of haematite, goethite and anatase. Despite a strong overlap of the peaks, precise and reliable cell parameters and Al for Fe substitutions were determined. The quantitative results of the Rietveld refinement were verified by chemical analysis. This comparison revealed a strong influence of sample preparation on the quantitative mineralogical analysis by XRD.

Dark septate hyphomycetes in swiss conifer forest soils surveyed using Norway-spruce seedlings as bait

Abstract: Soil samples were collected under Norway-spruce trees (Picea abies (L.) Karst.) on 72 sites throughout Switzerland, passed through a disinfected sieve and put into autoclaved clay pots. Surface-sterilized Norway-spruce seeds were sown into these pots and the seedlings were reared in a growth cabinet for 4 months. The root systems of nine seedlings per site were surface-sterilized and one 2–3 mm long segment of each of two root-diameter classes (class 1: dia

Hearing and hunting in red bats (Lasiurus borealis, Vespertilionidae): audiogram and ear properties.

Abstract: We examined aspects of hearing in the red bat (Lasiurus borealis) related to its use of biosonar. Evoked potential audiograms, obtained from volume-conducted auditory brainstem responses, were obtained in two bats, and the sound pressure transformation of the pinna was measured in three specimens. Field-recorded echolocation signals were analysed for comparison. The fundamental sonar search calls sweep from 45 to 30 kHz (peak energy at 35 kHz), approach-phase calls sweep from 65 to 35 kHz (peak 40 kHz) and terminal calls sweep from 70 to 30 kHz (peak 45 kHz). The most sensitive region of the audiogram extended from 10 kHz to 45-55 kHz, with maximum sensitivity as low as 20 dB SPL occurring between 25 and 30 kHz. A relative threshold minimum occurred between 40 and 50 kHz. With increasing frequency, the acoustic axis of the pinna moves upwards and medially. The sound pressure transformation was noteworthy near 40-45 kHz; the acoustic axis was closest to the midline, the -3 dB acceptance angles showed local minima, and the pinna gain and interaural intensity difference were maximal. These results are related to the known echolocation and foraging behavior of this species and match the spectral components of approach- and final-phase calls. We conclude that co-evolution with hearing prey has put a higher selective pressure on optimizing localization and tracking of prey than on improving detection performance.

Patterns and mechanisms of transpiration in a large subalpine Norway spruce (Picea abies (L.) Karst.)

Abstract: In situ water relations of a large subalpine Norway spruce (Picea abies) were analyzed by simultaneous measurements of sap flow at different crown positions. In the diurnal scale, transpiration varied greatly, both spatially and temporally. Over longer periods, however, different parts of the crown transpired in fairly constant proportions. The average estimated transpiration was about 3.5 times greater in the upper than in the lower half and decreased 1.6-fold from south to north. Water intercepted from rain, fog and dew buffered and significantly decreased the transpiration. The effect was strongest in those parts which were least coupled to the free atmosphere. The top of the crown seemed to experience a regular shortage of water shortly after starting transpiration, when it was forced to switch from internal reserves to sources in the soil. Further, lower branches then started transpiring, which may have led them to compete for the water. An enhanced nocturnal sap flow during warm and dry winds (Foehn) indicated that the tree also transpired at night. Shaded twigs had more capacity to intercept water externally than twigs in the sun. The significance of the crown structure for interaction with water in both liquid and vapour phases is discussed.

The cinnamyl alcohol dehydrogenase gene structure in Picea abies (L.) Karst.: genomic sequences, Southern hybridization, genetic analysis and phylogenetic relationships

Abstract: Based on PCR technologies, we have isolated three genomic cinnamyl alcohol dehydrogenase (CAD) clones from Norway spruce, Picea abies (L.) Karst., revealing about 99% identity within their protein coding regions. All clones contain five introns with an identity of 97–100% for intervening sequences II, III and IV, whereas intron V sequences revealed only 87–89% identity. Intron I sequences share an identity of 85–98% among all three clones. Intron IV is only present in Norway spruce and not found in published genomic CAD sequences of angiosperms. Tandem repeats between 24 and 49 bp were discovered within intervening sequences I and V. Southern hybridization of seedling DNA and PCR-based intron analyses using diploid leaf buds and haploid megagametophytes indicate the existence of a small CAD gene family within the spruce genome, consisting of at least two loci. Evolutionary analyses of CAD encoding sequences using distance matrix- and parsimony-based methods revealed that CADs from angiosperms form a clade distinct from those of gymnosperms. Confirmed by maximal bootstrap values of 100%, a gene duplication gave rise to two different groups of angiospermous CADs and this duplication may have occurred in an early stage of angiosperm radiation, certainly before the separation of the Dilleniidae and Rosidae lineages. Phylogenetic investigations suggest angiosperm CAD II sequences to have evolved more rapidly than angiosperm CAD I genes. On the other hand, CAD gene evolution appears to be significantly slower in conifers than in angiosperms.

Variation of the rare earth element concentrations in the soil, soil extract and in individual plants from the same site

Abstract: Samples of various types (spruce needles, blackberry leaves, soils, and soil extracts) have each been taken at 6 places from the same site. In addition, 4 whirls each from 2 spruce trees were sampled. Rare earth elements (REEs) were determined in these samples by neutron activation analysis with a chemical group separation. Variations between places were found to be small with soils and soil extracts, but large with plants. Variations between whirls were small. Plants neither reflected the soil nor the soil extract. Both plant species were dissimilar, but the logarithm of their ratio was a linear function of the atomic number of the REE. A negative Ce anomaly (with respect to soil) was found in both plant species.

An assessment of the use of crown structure for the determination of the health of beech (Fagus sylvatica)

Abstract: Summary Considerable difficulties exist with the standardization and interpretation of assessments of crown defoliation, the most commonly used index of tree health in Europe. A variety of other measures of crown condition exist and one that has received considerable attention, particularly for beech (Fagus sylvatica L.), is crown architecture. Four stages of crown development are generally recognized, termed the exploration, degeneration, stagnation and resignation phases. An analysis of the available literature suggests that there are a number of problems surrounding the use of these classes to describe trees. Although the classes probably reflect the progressive deterioration of the crown of a tree, there are many factors that affect the assessment and interpretation of the scores, as is the case for defoliation estimates. Measurements of shoot elongation in the upper crown provide a more useful measure, but involve destructive sampling and are very time-consuming. Consequently, while crown architectural assessments should only be incorporated into large-scale inventories of forest health with great care, they may be useful for case studies involving the detailed examination of a small number of sites.