Showing papers on "Biodiversity published in 1986"

Effects of disturbance on diversity in mixed-grass prairie

Abstract: Seven grassland treatments representing different disturbance regimes were sampled within a large area of mixed-grass prairie in southwestern Oklahoma, USA. Species diversity was low on the undisturbed and most severely disturbed grasslands. The results also indicate, however, that grassland diversity was not a simple function of disturbance rate, size or intensity. Instead, species diversity was maximized under a combination of natural disturbances. To some extent, the increase in species diversity was the result of increased habitat diversity associated with a type of disturbance. That is, disturbances such as grazing and wallowing have a cumulative effect one grassland diversity. Overall, the structure one grassland communities can not be accurately determined without considering the structure of the natural disturbance regime.

Environmental Science: Working with the Earth

Abstract: Part I Humans and sustainability - an overview: environmental problems, their causes, and sustainability living sustainably growth and the wealth gap resources pollution environmental and resource problems - causes and connections cultural changes and sustainability is our present course sustainable?: economics, politics, ethics, and sustainability economic systems and environmental problems economic growth and external costs solutions - using economics to improve environmental quality solutions - reducing poverty solutions - converting to earth-sustaining economies politics and environmental policy environmental worldviews - clashing values and cultures solutions - living sustainably. Part II Scientific principles and concepts - science, systems, matter and energy science, technology, environmental science, and critical thinking: models and behaviour of systems matter - forms, structure, and quality energy - forms and quality physical and chemical changes and the law of conservation of matter nuclear changes the two ironclad laws of energy connections - matter and energy laws and environmental problems ecosystems and how they work - connections in nature ecology and life earth's support systems ecosystem concepts and components connection - food webs and energy flow in ecosystems connections - matter cycling in ecosystems how do ecologists learn about ecosystems?: ecosystem services and sustainability evolution, biodiversity, and community processes - life and its origins evolution and adaptation speciation, extinction, and biodiversity niches and types of species species interactions ecological succession ecological stability and sustainability climate, weather, and biodiversity weather and climate - a brief introduction biomes - climate and life on land desert and grassland biomes forest and mountain biomes saltwater life zones freshwater life zones population dynamics, carrying capacity, and conservation biology population dynamics and carrying capacity reproductive strategies and survival conservation biology - sustaining wildlife populations human impacts on ecosystems - learning from nature solutions - working with nature to help heal ecosystems risk, toxicology, and human health risks and hazards - toxicology, chemical hazards physical hazards - earthquakes and volcanic eruptions biological hazards - disease in developed and developing countries. (Part contents)

The sensitivity of australian animals to 1080 poison. IX: Comparisons between the major groups of animals, and the potential danger non-target species face from 1080-poisoning campaigns

Abstract: The sensitivity of a species to 1080 poison is difficult to predict from toxicity data for other, closely related species. LD*50s of practical use for evaluating the risk species might face from 1080-poisoning campaigns can be obtained for untested members of some groups by the use of either values for similar species, regression equations involving body weight, or the lower 95% confidence limits of the distribution of LD*50S of members in each group. Among the 171 species for which there are data there was considerable variability in the time until signs of poisoning became apparent (0.1 h- >7 days), the time to death (0.1 h- >21 days) and the time until animals began to show signs of recovery (2 h-18 days). Marsupial carnivores generally showed signs earlier and died or recovered quicker than eutherian carnivores, eutherian herbivores and the marsupial herbivores of eastern Australia, even though the last three groups have lower LD*5OS. Reptiles and amphibians generally were the slowest to show signs of poisoning, to die or to recover, and had the highest LD50s . All species in Australia for which toxicity data are available were ranked according to the percentage of their body weight they would have to eat of various poison baits to receive an LD*5O. Many non-target species require lower percentages than the target animals but the actual consumption of lethal bait may be affected by various factors. Finally, an evaluation is given of the major groups of animals potentially most at risk in 1080-poisoning campaigns in Australia, based on their susceptibility to 1080.

The effect of a seed source on primary succession in a forest ecosystem

Abstract: An analysis of the Relative Importance Value Index (RIVI) of later successional tree species and the Shannon diversity indexH′ of all tree and shrub species was undertaken on previously mined sites within a sparsely forested area in central Florida, USA. A comparative analysis of the distance to a seed source and the age of a site suggested that the distance to a seed source was the best predictor (R 2=0.85) of the regeneration of the later successional species and a good predictor of species diversity. Both theRIVI of the later successional species and the diversity index decreased with the distance from the seed source. The lack of a seed source containing climax species resulted in arrested succession at some sites. It is suggested that biological information is the causative means of succession and the dispersal of this information entails spatial dependency while its introduction and development are time dependent processes.

Measures of resilience: the response of coastal sage scrub to fire

Abstract: Measures of four components of resilience are developed and used to quantify the response of coastal sage scrub to fire in southern California: (1) elasticity (rate of recovery following disturbance), (2) amplitude (threshold of disturbance beyond which recovery to the original state no longer occurs), (3) malleability (extent of alteration of the new stable-state from the original) and (4) damping (extent and duration of oscillation in an ecosystem parameter following disturbance). Vegetation and soil properties measured before fire, and for the first 5–6 yr after fire on four coastal (Venturan association) and four inland (Riversidian association) sites of coastal sage were used to follow changes. In addition, results from a simulation model of post-fire succession in Venturan coastal sage scrub (the FINICS model of Malanson) were used to examine resilience behavior over a 200 yr period. Resilience behavior of coastal sage scrub is critically influenced by the presence of a competitive mix of inherently strongly and weakly resprouting species. Sites dominated by weak resprouters exhibit lower elasticity and less damping of year-to-year fluctuations in composition in the early post-fire years. Sites with a mixture of weak and strong resprouters have a lower threshold of disturbance (amplitude) before species extirpation occurs, a result intensified by a higher frequency of disturbance. Malleability is also greater in these systems under higher disturbance frequency.

The Breeding and Re-establishment of the Brush-Tailed Bettong, Bettongia penicillata, in South Australia

Abstract: The brush-tailed bettong formerly ranged over much of southern Australia, but is now extinct except in the south-west of Western Australia and northern Queensland. A small colony was obtained from the Perth Zoo in 1975 and these were bred successfully at the Para Wirra Recreation Park near Adelaide and provided stock for a re-establishment program in South Australia. Details of the breeding program are given. Bettongs were kept in small colonies, usually one male and two or three females; the young were removed when they reached 550 g, or, with very intensive breeding, at a lower weight. The animals were fed principally on commercial kangaroo pellets with a range of supplements. Usually two offspring per year were produced although up to three were produced with intensive breeding. Females commenced breeding when approximately 4 months old. Techniques for re-establishment were tested on small islands. One island, Island A in Venus Bay, provided apparently ideal habitat and the captive-bred stock released there established quickly. Bettongs bred in the wild on two small and two large islands. However, the introduction to St Francis I., their last stronghold before extinction in South Australia, was least successful. Possible reasons for this are discussed.

Successional changes in the morphology and ecological responses of a grazed pasture ecosystem in Central Spain

Abstract: Morphological characteristics related to spatial occupation, reproduction and adaptations to grazing were used to characterize the most frequent species in a therophytic pastureland of Central Spain.

The Habitat, Distribution and Conservation Status of the Tasmanian Bettong, Bettongia-Gaimardi (Desmarest)

Abstract: The Tasmanian bettong, Bettongia gaimardi, appears to be the most common member of its genus. Though formerly distributed on the Australian mainland, B. gaimardi is now found only in the open forest habitats of eastern Tasmania, the vast majority of which are susceptible to forestry operations, such as clearfelling, burning and the laying of 1080 poison. Unless carefully managed, all of these practices in the long term are likely to reduce bettong populations. This and the fact that only 5% of bettong habitat lies within National Parks, leads to the conclusion that the conservation status of this species should be regarded as 'vulnerable'.

Localities of great significance to conservation of India's biological diversity

Abstract: We provide estimates of the extent to which each of the 43 vegetation types of India still persist as forest formations and at various stages of degradation, as also the extent to which these are represented in the present day network of wild life sanctuaries and national parks. Based on this analysis, we suggest a series of localities which should be accorded the highest priority in our attempts to conserve the whole spectrum of India's biological diversity.

An empirical test of the mass effect determinant of species richness

Abstract: The mass effect determinant of species richness proposed by Shmida & Wilson (1985) was empirically tested at the interface of undisturbed, native vegetation with recovering vegetation on a reclaimed surface mine. The observed decrease in native species richness with distance away from the source area was consistent with the predicted pattern based on Shmida & Wilson's (1985) model.

Dynamics of young Pinus pinaster vegetation in a Mediterranean area: diversity and niche-strategy

Abstract: This study is an attempt to interpret a mediterranean climatic gradient. It is based on 5-year observations of the dynamics of young plant communities dominated by Pinus pinaster in the hills of Provence, on permanent plots set up after the destruction of the pine forest by the introduction of Matsucoccus feytaudi. After a short description of the transect, including a classification of the plant communities and their relationship with environmental factors, we discuss the diversity pattern in relation to the niche concept. It is useful to explain diversity with the concept of resource distribution in order to construct models for the productivity of the communities and possible changes in the process of dominance. However, the acquisition of dominance by some species, the variation of habitat-niche breadth and the level of productivity of an environment are inferences from the models rather than the result of a process. As an alternative, we interpret the diversity gradient on the basis of the morphological and demographic characteristics of the species. We here consider Raunkiaer's life forms, including vegetative or offspring regeneration, leaf size and morphology as type of adaptive resistance to limiting factors such as frost, drought, competition, and as strategies used by the species to colonize or to survive.

Digestibility of alpine pasture on the bogong high plains of victoria

Abstract: The digestibility of the diet of cattle on the Bogong High Plains, in Victoria, was above 70% from the beginning of the grazing season in December 1982 until mid-March 1983, then fell to 63.5% at the end of the season in late March. Nitrogen content declined steadily from 1.60% to 0.99% in shrubland, 1.40% to 0.93% in grassland, 1.28% to 0.85% in mossbeds. The management implications are discussed.

The fossil record of evolution: Data on diversification and extinction

Abstract: Understanding of the evolution of complex life, and of the roles that changing terrestrial and extraterrestrial environments played in life's history, is dependent upon synthetic knowledge of the fossil record. Paleontologists have been describing fossils for more that two centuries. However, much of this information is dispersed in monographs and journal articles published throughout the world. Over the past several years, this literature was surveyed, and a data base on times of origination and extinction of fossil genera was compiled. The data base, which now holds approximately 32,000 genera, covers all taxonomic groups of marine animals, incorporates the most recent taxonomic assignments, and uses a detailed global time framework that can resolve originations and extinctions to intervals averaging three million years in duration. These data can be used to compile patterns of global biodiversity, measure rates of taxic evolution, and test hypotheses concerning adaptive radiations, mass extinctions, etc. Thus far, considerable effort was devoted to using the data to test the hypothesis of periodicity of mass extinction. Rates of extinction measured from the data base have also been used to calibrate models of evolutionary radiations in marine environments. It was observed that new groups, or clades of animals (i.e., orders and classes) tend to reach appreciable diversity first in nearshore environments and then to radiate in more offshore environments; during decline, these clades may disappear from the nearshore while persisting in offshore, deep water habitats. These observations have led to suggestions that there is something special about stressful or perturbed environments that promotes the evolution of novel kinds of animals that can rapidly replace their predecessors. The numerical model that is being investigated to study this phenomenon treats environments along onshore-offshore gradients as if they were discrete habitats. Other aspects of this investigation are presented.