Showing papers on "Vegetation (pathology) published in 1992"

Vegetation Description and Analysis: A Practical Approach

Abstract: The Nature of Quantitative Plant Ecology and Vegetation Science. The Description of Vegetation in the Field. The Nature and Properties of Vegetation Data. Basic Statistical Analysis of Vegetation and Environmental Data. Ordination Methods I, 1950-1970. Ordination Methods II, 1970-1992. Phytosociology and the Zurick-Montpellier (Braun-Blanquet) School of Subjective Classification. Numerical Classification and Phytosociology. Computer Programs for Vegetation and Environmental Data Analysis. Quantitative Plant Ecology, Vegetation Science and the Future. References. Index.

GEMI: a non-linear index to monitor global vegetation from satellites

Abstract: Knowledge about the state, spatial distribution and temporal evolution of the vegetation cover is of great scientific and economic value. Satellite platforms provide a most convenient tool to observe the biosphere globally and repetitively, but the quantitative interpretation of the observations may be difficult. Reflectance measurements in the visible and near-infrared regions have been analyzed with simple but powerful indices designed to enhance the contrast between the vegetation and other surface types, however, these indices are rather sensitive to atmospheric effects. The ‘correction’ of satellite data for atmospheric effects is possible but requires large data sets on the composition of the atmosphere. Instead, we propose a new vegetation index which has been designed specifically to reduce the relative effects of these undesirable atmospheric perturbations, while maintaining the information about the vegetation cover.

Modeling the land surface boundary in climate models as a composite of independent vegetation stands

Abstract: An efficient strategy for modeling the land surface boundary in general circulation models (GCMs) is presented which accounts for the effects of vegetation on surface energy fluxes and allows for an arbitrary number of vegetation types to coexist in a grid square. The GCM grid square is depicted as a 'mosaic' of vegetation 'tiles', with each tile consisting of a single vegetation type. The energy balance equation for each tile follows closely that of a single vegetation version of the simple biosphere (SiB) model of Sellers et al. (1986) but is simplified enough to be written in Penman-Monteith form. Each tile in the square is coupled independently to the GCM atmosphere, and tiles affect each other only through the atmosphere. This coupling strategy differs conceptually from that of models such as SiB that assume a homogeneous mixture of vegetation types within a GCM grid square. A quantitative comparison of the two strategies is presented.

The Alaska vegetation classification.

Abstract: Viereck, L.A.; Dyrness, C.T.; Batten, A.R.; Wenzlick, K.J. 1992. The Alaska vegetation classification. Gen. Tech. Rep. PNW-GTR-286. Portland, OR: U.S. Department of Agriculture, Forest Service, Pacific Northwest Research Station. 278 p. The Alaska vegetation classification presented here is a comprehensive, statewide system that has been under development since 1976. The classification is based, as much as possible, on the characteristics of the vegetation itself and is designed to categorize existing vegetation, not potential vegetation. A hierarchical system with five levels of resolution is used for classifying Alaska vegetation. The system, an agglomerative one, starts with 888 known Alaska plant communities, which are listed and referenced. At the broadest level of resolution, the system contains three formations-forest, scrub, and herbaceous vegetation. In addition to the classification, this report contains a key to levels I, II, and III; complete descriptions of all level IV units; and a glossary of terms used.

A fuzzy sets approach to the representation of vegetation continua from remotely sensed data : an example from lowland health

Abstract: Conventional image classification routines are often inappropriate for the mapping of continuous phenomena suchy as heathland vegetation. To allow for the natural fuzziness of such an environment, a fuzzy sets algorithm may be used to model the heathland vegetation more appropriately than a classification. The results of this study show that the fuzzy c-means algorithm can be used to discriminate accurately between the end points of a set of continua, and that class membership functions derived from the analysis are sensitive to the botanical composition of the vegetation canopy. Mapping the fuzzy membership functions will therefore enable a more realistic portrayal of the healthland vegetation than a conventional classification.

Lead, Cadmium, and Zinc Contamination of Aspen Garden Soils and Vegetation

Abstract: The objective of this study, conducted in 1983, was to determine the source and the extent of Pb, Cd, and Zn contamination of Aspen gardens soils and metal concentrations in vegetables grown in contaminated gardens

Vegetation and dragonfly fauna―characteristics and examples of biocenological field studies

Abstract: Until now very few biocenological studies have been carried out on dragonflies This paper describes the various functions of vegetation for Odonata, especially in habitat selection

Vegetative characteristics of successful and unsuccessful nests of lesser prairie chickens

Abstract: Most descriptions of vegetation at lesser prairie chicken (Tympanuchus pallidicinctus) nests do not differentiate between those that are successful or unsuccessful. Consequently, we used radio telemetry and ground searching to analyze vegetative characteristics around 36 lesser prairie chicken nests in areas where vegetation was dominated by a mixture of shinnery oak (Quercus havardii) and grassland in eastern Chaves County, New Mexico

Man and vegetation in the Pollen diagrams from Wolin Island (NW Poland)

Abstract: Pollen, charcoal and ash content data complemented by 26 C dates from three small (4-5 ha) basins on Wolin Island (NW Poland) enabled a detailed chronological reconstruction of human impact on vegetation during the last 8000 years. Locally, woodland was already actively changed in the Mesolithic. Animal husbandry and cereal cultivation were probably initiated by the people representing the Erteb~lle culture. The first Ulmus decline is radiocarbon dated in two profiles at ca. 5800 BP and seems to be caused mainly by human activity. In the Neolithic and Bronze Age coppicing changed the forest structure; animal husbandry was the main form of farming at that time. Cultivation increased in importance in the Lusatian culture and in the Iron Age, but the considerable extension of arable land did not take place until the early Middle Ages. On the poor sandy soils Calluna heath developed in the Neolithic due to intensive burning and grazing in the Pinus-Quercus-Betula forest. Several palaeohydrological events are analysed with respect to anthropogenic forest disturbances, climatic changes and fluctuations in the level of the Baltic Sea.

Predicting Influence of Bank Vegetation on Channel Capacity

Abstract: A theoretically based method for taking into account the effects of bank vegetation on channel-flow parameters is outlined. It can be used to predict what effect changes in bank vegetation will have on the discharge capacity of a channel and to make comparisons of bank-vegetation effects between channels. Using the analysis on individual channels may aid in gauging the true impact of bank vegetation on in-bank flow capacity and in deciding whether the beneficial effects of bank vegetation in stabilizing banks outweigh any adverse effects that result from the potential reduction in discharge capacity. Using this method, the effect bank vegetation has on channel discharge capacity is shown to decline rapidly as the width-to-depth ratio of channels increases. When seasonal growth of vegetation is simulated the effect on channel discharge capacity is shown to be less than 10% for channels with a width-to-depth ratio greater than 16.

The Transient Response of Vegetation to Climate Change: A Potential Source of CO2 to the Atmosphere

Abstract: Global climate change as currently simulated could result in the broad-scale redistribution of vegetation across the planet. Vegetation change could occur through drought-induced dieback and fire. The direct combustion of vegetation and the decay of dead biomass could result in a release of carbon from the biosphere to the atmosphere over a 50- to 150- year time frame. A simple model that tracks dieback and regrowth of extra-tropical forests is used to estimate the possible magnitude of this carbon pulse to the atmosphere. Depending on the climate scenario and model assumptions, the carbon pulse could range from 0 to 3 Gt of C yr-1. The wide range of pulse estimates is a function of uncertainties in the rate of future vegetation change and in the values of key model parameters.

Life Cycles and Fire-Stimulated Flowering in Geophytes

Abstract: Fire-stimulated flowering (hereafter FSF) is a common trait in herbaceous plants in fire-prone vegetation (Gill 1981a; Rundel 1981a). FSF of geophytes occurs in all the mediterranean shrublands of the world (Naveh 1974; Gill and Groves 1981; Trabaud 1981; Keeley 1986). The Cape flora is renowned for its rich and diverse geophytic flora (Table 8.1), and there are many anecdotal accounts of the profuse flowering of geophytes for one or more years after fire (Levyns 1966; Martin 1966; Goldblatt 1978; Frost 1984), but few quantitative studies.

A dielectric model of the vegetation effects on the microwave emission from soils

Abstract: A layer of vegetation over the soil surface absorbs some of the radiation emitted from the soil and emits at its own temperature. This results in a reduction of the information in the microwave radiation about the soil surface. To study this problem further the authors use the model of F.T. Ulaby and M.A. El-Rayes (1987) for the dielectric constant of vegetation to estimate the absorption loss and optical depth, tau , of plant canopies for frequencies between 1 and 40 GHz. The authors treated tau as the product of a vegetation parameter b and vegetation water content, VW. They compared both the linear and square root (refractive) mixing models with the observed data in terms of the b parameter. These data were obtained from published reports on the values of tau and VW for crops ranging from prairie grass to corn and soybeans. The data fit the curve for the refractive model quite well. For the refractive model the value of b was independent of VW, while for the linear model there was some dependence on VW. For both models b is roughly proportional to the frequency. >

Closed apparatus system for improving irrigation and method for its use

Abstract: A method and apparatus are described for providing improved irrigation to vegetation in open areas such as parks and golf courses, including providing improved microbiotic and nutrient supplies to such vegetation in a non-sterilized environment. In its method aspects, the invention comprises combining in an aqueous slurry effective amounts of first and second microorganisms, enzymes and nutrients, allowing the combined microorganisms to grow in a closed reservoir to reach levels of concentrations of the first and second microorganisms effective for irrigation, enhancement and nutrition of vegetation, and then applying the concentrated materials to the vegetation in a water slurry in quantities sufficient to effectively irrigate and provide nutrition to the vegetation and to provide it with protection against harmful microorganisms. Apparatus is described for the performance of the method, and includes an enhancement vessel adapted to retain the combined materials for a time sufficient for the first and second microorganisms to increase in concentration to provide a significant degree of nutrition and protection against harmful microorganisms to vegetation to which they are applied; and a conduit to convey the slurry to the vegetation and to apply it to the vegetation in effective quantities. Typical of the applications for which this invention can be used is the irrigation, protection and nutrition of vegetation for golf course, parks and other landscaped areas, to enhance the growth and physical condition of the vegetation of the course or park.

Accuracy of estimating the leaf area index from vegetation indices derived from crop reflectance characteristics, a simulation study

Abstract: The canopy radiation model EXTRAD was used to quantify the accuracy of leaf area index (LAI) estimations from vegetation indices (Vis), derived from green and infra-red crop reflectance. The Vis we...

Vegetation Ecology of Fiji: Past, Present, and Future Perspectives

Abstract: The Fiji Archipelago comprises a Tertiary island arc with several hundred small and a few large mountainous islands near the northeastern corner of the Australian tectonic plate, 3000 km from continental Australia-New Guinea. Despite contrary prevailing winds and ocean currents, the flora is very largely derived from that of Malesia, and the largest component was probably dispersed by frugivorous birds or bats, of which several taxa are established in Fiji. About 25% of the native vascular plant species are endemic and, with exceptions such as the relictual Degeneria, most have apparently diverged from overseas conspecifics. There are a few cases where speciation has occurred within Fiji but virtually none where reproductive isolation is established, permitting cohabitation. Until the arrival of humans, perhaps 4000 and certainly by 3000 yr B.P., the vegetation was predominately rainforests with stunted cloud forest at high altitude, though some more open communities might have occurred in drier areas. The forests have a mixed species composition, including most of the 1769 native species, and demographic observations indicate peak population fecundities after several hundred years for canopy trees and 80 years for several subcanopy taxa. Flowering phenology offorest species is seasonal with predominately synchronous annual or, in a few species, biennial frequency, while fruit maturation is spread throughout the year. Cyclones cause frequent minor damage and infrequent major damage, especially to coastal and ridge vegetation, and cause landslides. Insect-induced dieback has been recorded but there are no extensive single-species rainforests, except swamp forests, so the effects are diffuse. The impact of humans has been to convert much of the drier forest to frequently burned sedge-fern-grasslands, to create garden-forest successional mosaics around settlements in wetter areas, and, more recently, to selectively log much of the remaining accessible forest. Many plants have been introduced and established in cultivated or disturbed areas, increasing the flora by about 50% and largely excluding native taxa from those areas. Habitat conversion is thus the major threat to the conservation of Fijian native vegetation. I Manuscript accepted 2 May 1991. 2 Botany & Zoology Division, Australian National University, GPO Box 4, Canberra, ACT 2601, Australia. a volcanic base. The larger, older islands have mountainous interiors rising to 1320 m, comprising dissected volcanic landforms, uplifted marine sediments, and limestones. Taveuni is the product oflate Quaternary vulcanism and has a mountain range with scoria cones, craters, surface ash layers, and Holocene lava flows (most recently 2000 yr B.P.). Some islands in the eastern Lau group are raised coral reefs and have little or no surface exposure of the underlying volcanic rocks. Rotuma, a small island 500 km to the north, is not considered in this review. Alluvial coastal plains extend from valleys, and their shores III THE FIJI ARCHIPELAGO LIES in the seasonal tropics, with most islands between 16° and 19° Sand 176° E to 178° W, about 3000 km east ofcontinental Australia-New Guinea (Figure 1). The total land area of 18,376 km is largely in the islands of Viti Levu (56%) and Vanua Levu (30%), with a further 300 islands exceeding 2.6 km , numerous smaller rocky islets, and sand cays on reefs. The surrounding ocean is 2-4 km deep, and all the islands have

The distribution and ecology of the vegetation of ultramafic soils in Italy

Abstract: The vegetation, geology and distribution of serpentinized-ultramafic areas in Italy are described and the investigations on serpentine vegetation briefly outlined. The recent ecophysiological research on serpentine vegetation, including the endemic nickel accumulator Alyssum bertolonii Desv., is reported.