Showing papers by "Swiss Federal Institute for Forest, Snow and Landscape Research published in 1991"

Impairment of gas exchange and structure in birch leaves (Betula pendula) caused by low ozone concentrations

Abstract: Injury caused by low O3 concentrations (0, 0.05, 0.075, 0.1 μl 1-1) was analyzed in the epidermis and mesophyll of fully developed birch leaves by gas exchange experiments and low-temperature SEM: (I) after leaf formation in O3-free and ozonated air, and (II) after transferring control plants into ozonated air. In control leaves, autumnal senescence also was studied in O3-free air (III). As O3 concentration increased, leaves of (I) stayed reduced in size, but showed increased specific weight and stomatal density. The declining photosynthetic capacity, quantum yield and carboxylation efficiency lowered the light saturation of CO2 uptake and the water-use efficiency (WUE). Carbon gain was less limited by the reduced stomatal conductance than by the declining ability of CO2 fixation in the mesophyll. The changes in gas exchange were related to the O3 dose and were mediated by narrowed stomatal pores (overriding the increase in stomatal density) and by progressive collapse of mesophyll cells. The air space in the mesophyll increased, preceded by exudate formation on cell walls. Ozonated leaves, which had developed in O3-free air (II), displayed a similar but more rapid decline than the leaves from (I). In senescent leaves (III), CO2 uptake showed a similar decrease as in leaves with O3 injury but no changes in mesophyll structure and WUE. The nitrogen concentration declined only in senescent leaves in parallel with the rate of CO2 uptake. A thorough understanding of O3 injury and natural senescence requires combined structural and functional analyses of leaves.

Yearly maps of summer temperatures in Western Europe from A.D. 1750 to 1975 and Western North America from 1600 to 1982: Results of a radiodensitometrical study on tree rings

Abstract: The primary purpose of this publication is to make available two series of historical maps showing 'summer' (April-September mean) temperatures over western Europe from A.D. 1750 and western North America from A.D. 1600. These maps have been reconstructed using networks of temperature-sensitive tree-ring chronologies as part of a continuing collaboration between the Swiss Federal Institute for Forest, Snow and Landscape Research (FSL) at Birmensdorf, Switzerland and the Climatic Research Unit (CRU) at the University of East Anglia, Norwich, U.K. The maps were reconstructed using relatively long maximum latewood density chronologies selected from the extensive networks of tree-ring data produced at the FSL. The reconstructions were produced using a spatial regression technique developed at CRU. The basis for the reconstructions are wood samples from various conifers growing at cool-moist sites close to the alpine or boreal timberlines. This material was analysed by x-ray densitometry and the resulting maximum latewood density chronologies were calibrated against meteorological data over a 100-year calibration period. These results emphasize the value of dendroclimatological research which can provide continentalscale reconstructions of past climate which represent a potential resource for climatologists, biologists, and historians with an interest in the spatial variability of summer temperatures over the middle to high latitudes.

Freeze-fracturing for conventional and field emission low-temperature scanning electron microscopy : the scanning cryo unit SCU 020

Abstract: SUMMARY A dedicated cryopreparation system, the SCU 020 (Balzers), is introduced and described in detail for use in low-temperature scanning electron microscopy (LTSEM). The basic unit consists of two parts: (i) a high-vacuum preparation chamber equipped with a cold-stage, motor-driven fracturing microtome, planar magnetron (PM) sputter source, quartz-crystal thin-film monitor, Meissner cold trap, and turbo molecular pump stand; and (ii) a second part (separated from the first by a sliding, high-vacuum valve) residing in the SEM chamber. This is equipped with an anti-contamination cold trap, a fully movable goniometer cold stage (having motor drives for x, y, and rotation) and replaces the SEM's original stage (Raith). The SCU 020 is entirely self contained allowing independence from, and synchroneity with, the SEM of choice. LTSEM micrographs of specimen (that are fully frozen hydrated or partially freeze-dried) surfaces or fracture faces, without or with various metal coatings, can be examined over a broad temperature range (-150 to +50°C). This is made possible by the combined application of the two, independently controlled, cold stages and the on-line, high-vacuum, specimen cryo transfer between them. In-situ etching is simple and straightforward. Intramembranous particles and membrane fracture steps, typically imaged in transmission electron microscopy (TEM), are resolved by PM sputtering with platinum at low specimen temperature and high-resolution LTSEM in a field emission microscope.

Low-temperature scanning electron microscopy of birch leaves after exposure to ozone

Abstract: SUMMARY Comparison of different harvesting and preparation pathways showed that low-temperature SEM is an adequate method to conserve the stomatal aperture for SEM. Both critical point drying and freeze drying cause considerable artefacts. Exposure to site-relevant concentrations of ozone led to reduced width of the stomatal aperture. Moreover, unetchable droplet-like exudates were found on the outer face of mesophyll cells of leaves where the trees had been exposed to ozone. These exudates were later followed by collapsed mesophyll cells and ended in necrotic zones before premature leaf loss.

Chestnut blight (Cryphonectria parasitica) north of the Swiss alps

Abstract: Chestnut blight (Cryphonectria parasitica) was found in several stands in the Swiss plateau. At each site only one or two compatibility (vc) groups were present. The vc-group I was the most common. At a heavily infested site also young oaks (Quercus petraea) were infected.

Comparative studies on ectomycorrhizae synthesized with various in vitro techniques using Picea abies and two Hebeloma species

Abstract: Various in vitro synthesis techniques with Picea abies and two Hebeloma species showed that structures of the mantle and Hartig net of synthesized ectomycorrhizae within the given two fungus species are stable. However, thickness of mantle, and penetration depth and number of hyphal cell rows between cortical cells of the Hartig net are dependent on techniques and substrates. Porous glass balls as substrate in the Erlenmeyer technique seem to suppress or delay mantle and Hartig net formation. With the other techniques (growth pouch, open cuvette, Erlenmeyer with a vermiculite-peat moss mixture) development of the mantle is simultaneous with or shortly in advance of Hartig net formation. The ectomycorrhizae of the two tested Hebeloma species are similar and cannot be morphologically differentiated by the in vitro techniques used.

19 Root Window Technique for in vivo Observation of Ectomycorrhiza on Forest Trees

Abstract: Publisher Summary This chapter discusses one of the techniques of ectomycorrhiza on forest trees—root window technique. Soil core sampling, the most common method for studying root systems and mycorrhiza, is certainly useful for observing conditions at any given time, but has the great disadvantage of being destructive and thus precluding continuous observation of particular microsites, so that it does not allow conclusions about developments or changes in the mycorrhiza. These problems can be largely overcome through the installation of root windows, which allow continuous, long-term observation with minimum disturbance. Photographs can be used to register morphological changes. The root window is not a new concept. Numerous methods, such as installation, are reviewed. The root window is installed by ramming a sharp-edged 40cm steel plate about 20 cm into the soil tangentially to, and about 2 m from, the tree trunk. One of the technical methods is photography. Furthermore, another technique for in vivo observation-though only applicable to seedlings-involves the use of special folding containers, for instance the root-trainers. Yet another technique is to lay root windows horizontally on the soil surface, but this has the disadvantage that it hinders precipitation from penetrating into the soil.

Flexible Gradient Analysis: A Note on Ideas and an Application

Abstract: The standard approach to the study of vegetation is discussed in which sampling represents a first and data analysis a second step An alternative is suggested where sampling and analysis run concurrently An example is given to demonstrate possible gains in efficiency and flexibility

Sampling with Multiple Objectives and the Role of Spatial Autocorrelation

Abstract: The handling of mixed type multivariate data sets is discussed on an example from the ‘Man and Biosphere’ project, Davos, Switzerland. The data comprise variables of different spatial resolution, aggregation and reliability. Correlo-grams are computed for data subsets describing different landscape features on differing scales. Some variables show spatial independence, others exhibit correlation among adjacent sampling localities. Periodicity is detected in the distribution pattern of some animal species, and soil types form coenoclines. While some results derived by previous modelling reflect local patterns, others suggest wide ranging relevance. Optimum sampling intensity therefore should not only depend on the aims of the study, but be also influenced by the nature of the variables. For investigations with multiple objectives, the simultaneous use of a combination of sampling designs is suggested. Quadrat size, grid width, and even investigation areas may vary. The commensurability of the designs can be achieved by simultaneously running the operations at the different aggregation levels for the relevant variables.

MULVA-4, a Processing Environment for Vegetation Analysis

Abstract: In plant ecology, large data collections have been a traditional means to back and document patterns observed in the field. Because natural systems are complex and structures and processes obliterated by interactions and noise, data analysis with advanced statistical methods became a standard research tool (Orloci 1978, Pielou 1977, 1984). In the early years of electronic data processing, computer programs were written mainly to automatize hitherto manual data screening. This turned out to be of limited scope for several reasons:

The Relational Model for Data Bases in Community Studies

Abstract: Different data base models are considered and compared to the relational model. File structures are described and examples are given to illustrate the differences.