Showing papers on "Ecosystem published in 1969"

The ecology of marine microbenthos IV. Structure and function of the benthic ecosystem, its chemical and physical factors and the microfauna commuities with special reference to the ciliated protozoa

Abstract: The paper describes the ecosystem constituted by marine sediments and their microfiora and fauna but with special emphasis on the ecology of ciliated protozoa. This description is based on quantitative studies of the vertical and horizontal distribution of the fauna, the physicochemical factors (O2, H2, S, Eh, pH, grain size, organic matter, salinity) and the microfiora, and on model experiments with artificial and natural sediments. Factors controlling the oxidation-reduction properties of sediments, the O2-uptake of reduced sediments and the respiration and photosynthesis of undisturbed sediments were studied. Among other things it is demonstrated that the microfaunal communities can be correlated with the oxidation-reduction properties of sediments and with their mechanical composition and that the endproducts of anaerobic decomposition (notably H2S) are of large trophic significance to the sediment ecosystem through the activity of cherno- and photoautotrophic bacteria. The energetic role of ...

Biotic regulation of particulate and solution losses from a forest ecosystem

Abstract: Particulate matter losses from the Hubbard Brook watershed-ecosystems show seasonal variations, with the bulk of the material being exported during the spring runoff period. However, a single autumnal storm of unusual intensity accounted for 54% of the total particulate matter output during a 2-year period. Total particulate matter losses amounted to 2.5 metric tons/km2/year. This value is appreciably less than values reported for other similar regions. Total output of dissolved substances was 14 metric tons/km2/yr. This is about 25% of the dissolved load predicted for such areas by Langbein and Dawdy (Leopold et al., 1964). The relatively small losses of dissolved substances and particulate matter indicate that the Hubbard Brook ecosystem is very stable. This is also supported by the biotic structure of the ecosystem. Chemicals may be exported from various compartments of the ecosystem as particulate or dissolved organic material from the organic compartment, dissolved inorganic substances from the available nutrient compartment, and inorganic particulate matter from the soil and rock mineral compartment. The route of export an element follows is a function of its geochemistry, its utilization by the biological components, and its differential accumulation within the ecosystem. Although debris avalanches are not an important consideration at Hubbardmore » Brook, our data suggest that at higher elevations in the White Mountains avalanches are probably a more important denudational force by an order of magnitude than solution and slower mass movements. Secondary ecological successions following severe disturbance of forest ecosystems result in significant conservation of nutrients lost from the ecosystem. This effect is achieved by a complex interaction of biomass accumulation, alteration of the hydrolic cycle, reduction of erodibility of the system, and changes in concentration of dissolved substances in drainage waters.« less

Concepts of ecology

Abstract: I. ECOLOGY AND ECOSYSTEMS. 1. Ecology as a Science. 2. The Nature of Ecosystems. II. THE ABIOTIC ENVIRONMENT. 3. Minimums, Tolerances and the Medium. 4. Insolation, Precipitation and Climate. 5. Soils, Nutrients and Other Factors. III. ENERGY FLOW IN ECOSYSTEMS. 6. Energy Fixation by Autotrophs. 7. Energy Flow Beyond the Producers. IV. BIOGEOCHEMICAL CYCLES AND ECOSYSTEMS. 8. Gaseous and Sedimentary Nutrient Cycles. 9. Nutrient Budgets and Ecosystems. V. POPULATION ECOLOGY. 10. Population Growth and Structure. 11. Population Regulation. VI. COMMUNITY ECOLOGY. 12. The Structure and Function of Communities. 13. Stability and Change in Communities. VII. MAJOR ECOSYSTEMS OF THE WORLD. 14. Biomes, The Major Terrestrial Ecosystems. 15. Aquatic Ecosystems. VIII. HUMAN ECOLOGY. 16. The Nature of Human Ecology. 17. The Human Population. 18. Anthropogenic Impact on Aquatic Ecosystems. 19. Anthropogenic Impact on Terrestrial Systems. 20. Anthropogenic Impact on the Atmosphere.

Accumulation and Cycling of Calcium by Dogwood Trees

Abstract: Chemical analyses of plants and soils have helped explain agricultural productivity since the 17th century (Davies 1940) and productivity of forest trees since the 19th century (Ebermayer 1876; Rennie 1955). Because calcium is the element removed in greatest quantity when tree crops are harvested, it received much of the attention in the latter studies. The desire to understand ecosystem functioning reinforces the motivation for studies of nutrient circulation in forests. Circulation of elements within the plant-soil system is exceedingly complex. Remezov (1959) classified nutrient cycles as subannual cycles, annual cycles, and those consisting of successive annual cycles; he stated that it is impossible to list all minor cycles and that, "The biological cycle of elements in a forest is a complicated polycyclic process depending on the combination of many factors." There are inputs of elements to the plant-soil system by, e.g., precipitation, dust, and weathering of parent material, and losses due to, e.g., drainage waters and plant and animal harvests; these incomes and exports have been discussed by Ovington (1962, 1965). Auerbach (1965) summarized the needs for cycling studies and concluded that additional tracer investigations should be undertaken to measure cycles in various ecosystems. Flowering dogwood (Cornus florida L.) has been acknowledged for several decades as a nutritionallybeneficial understory species due to accumulation of calcium in its leaves and rapid decomposition of its litter, thus releasing -calcium for use by other species.

Arctic Plants, Ecosystems and Strategies

Abstract: Reviews and develops a perspective of what is known about the structure, function, and adaptive strategy of arctic tundra ecosystems, with emphasis on plants, the primary biological producers of an ecosystem. The short-term change in plant arrays following disturbance of the natural assemblage, due to ecological succession, is poorly understood in the tundra. Distribution and migrations of tundra flora give insight into Pleistocene events and evolutionary strategies, one clue to which is frequently of polyploidy. Implicit in understanding tundra dynamics or vegetation associations is study of topographic microrelief, soils and thaw depths, as well as description of the flora. Progress is noted in knowledge of the structure and function of vegetation in arctic ecosystems: the morphological adaptation, carbohydrate cycle, chlorophyll content, physiologic processes in adaption to severe environments such as photosynthesis, respiration, light saturation, photoperiodic requirements and temperature tolerance.

Ecotypes and Ecosystem Function

Abstract: ecotype in ecosystem function is primarily one of allowing a community of organisms to adjust to its habitat." The second: "The simultaneous selection of ecotypic variants within different kinds of organisms occupying a given area results in harmonious functions of a particular ecosystem." The third: "The selection of eco-genetic gradients results in the continuity of an ecosystem-type over geographic diversity." These three statements, modified here with reference to ecosystems, were made originally with respect to "ecotypes and community function" (McMillan, 1960). Their application here in reference to ecosystem function was facilitated by the use of the same basic concepts: (a) that ecotype, ecotypic differentiation, eco-genetic gradient refer to genetically-based variation that is habitat correlated; (b) that community is applied to the sum total of organisms in a given area; (c) that population is applied to the one or more individuals of a close genetic lineage in a given area; (d) that ecosystem is applied to the sum total of organisms (the community and its included populations) and to their relations with their environmental surroundings in a given area; and (e) that ecosystem-type results from the lumping or sorting of certain ecosystems into a particular kind. To these basic concepts, a time relation is indicated: at a given time. The modified application from the community to the ecosystem has changed the focus from the

Ecology of soil arthropod fauna in tropical forests: A review of studies from Puerto Rico

Abstract: The majority of ecological studies in the tropics deal with organisms participating in grazing food webs, while few deal with the diversity of invertebrates in the soil, leaf litter or dead wood that participate in detrital food webs For tropical forests, the status of information on soil animal diversity is limited, especially when compared to other ecosystems such as temperate forests, grasslands, and deserts Given the high rate of forest conversion and persistence of deforestation in the tropics, it is important to study the diversity of its fauna and assess how global changes will affect the linkages between soil biota and ecosystem functioning This review article focuses on surveys and studies conducted in Puerto Rico, a tropical Caribbean island where a significant number of ecological investigations have focused on the characterization of the edaphic fauna, and how they influence ecosystem processes in forested sites Results from experimentations suggest that soil fauna is an important determinant of decay and nutrient cycling in these forests Likewise, this article highlights the importance of methodological constraints in studies that compare these organisms at sites with differing climatic conditions, and focuses on the description of ecological studies related to the effects of microarthropods on litter and wood decay

Seasonal changes in biotic diversity and in Margalef's pigment ratio in a small pond: With 8 figures in the text

Abstract: Although MARGALEF'S pigment ratio would be a very useful ecological tool if it accurately reflected the biotic diversity of an ecosystem, very few data have been presented in the literature to subs...

Patterns of Numerical Abundance of Animal Populations

Abstract: An ecosystem is a natural unit composed of abiotic and biotic elements interacting to produce an exchange of materials. Actions of the abiotic environment and coactions between biotic components result in a characteristic assemblage of organisms. The complex of individuals belonging to the different species in the ecosystem is referred to as community structure. Natural biotic communities typically are characterized by the presence of a few species with many individuals and many species with a few individuals. An unfavorable limiting factor such as pollution results in detectable changes in community structure. The assumption that natural communities represent meaningful assemblages has prompted a diverse series of graphic and mathematical analyses to analyze community structure. Certain of these methods of analysis are described in Hairston (1959) and in Odum, Cantlon, and Kornicker (1960). An earlier paper (Wilhm 1967) described the use of a population sampling board to demonstrate some basic statistical measures and the concept of numerical abundance patterns in ecological communities. The present paper describes a technique to demonstrate these patterns in a natural situation.