Showing papers on "Ecosystem published in 1968"

Nutrient Loss Accelerated by Clear-Cutting of a Forest Ecosystem

Abstract: The forest of a small watershed-ecosystem was cut in order to determine the effects of removal of vegetation on nutrient cycles. Relative to undisturbed ecosystems, the cut ecosystem exhibited accelerated loss of nutrients: nitrogen lost during the first year after cutting was equivalent to the amount annually turned over in an undisturbed system, and losses of cations were 3 to 20 times greater than from comparable undisturbed systems. Possible causes of the pattern of nutrient loss from the cut ecosystem are discussed.

Primary Production in Terrestrial Ecosystems

Abstract: Results to date have established general ranges of such paometers of ecosystems as total biomass, total surface area of leaves and of stems and branches, rates of decay of organic matter in soils, rates of production of roots, and rates of photosynthesis and respiration under clifferent environmental conditions. In the Brookhaven forest net primary production is 1124 dry g/m2/yr (with an energy equivalent of 492 cal/cm2/yr), and gross production is about 2550 dry g/m2/yr; the producers or green plants thus respire 56% of their gross production. Net ecosystem pro? duction is 422 dry g/m2/yr in this young forest. The ratio of total respiration to gross produc? tion is a convenient expression of successional status; a value of 0.82 for the Brookhaven forest indicates that this is a late successional community, but not in steady-state or climax condition (1.0). A leaf surface area of 3.8 m2 per m2 of ground surface intercepts sunlight energy, and the ratio of net primary production to incident visible sunlight energy gives a net efficiency of pri? mary production of 0.0088. These and other functional characteristics of ecosystems are currendy important topics of research?involving understanding of communities as biological systems, evaluation of the potential of environments to support life and man's harvest; and understanding of the fundamental meaning and consequences of man's alteration, exploitation, and pollution of ecosystems.

Caloric Values of Bryophytes

Abstract: Thirteen bryophyte species from various ecosystems on Mt. Washington, New Hampshire, were combusted in an oxygen-bomb calorimeter to determine caloric values. Mean caloric values for the ten species studied immediately following collection varied from 4305 callg dry weight for Thuidium delicatulum to 3747 for Dicranella heteromalla, with an overall mean of 4002 calig dry weight for bryophytes in general. Bryophytes rank among the lower caloric components of the ecosystem. Species transplanted to, a high-humidity and high-temperature regime lost an average daily of 6.4 cal/g dry weight over a 27-day period. Unexpectedly, species in the coniferous and northern hardwoods ecosystems in all cases had higher caloric values than those in either the higher alpine ecosystem or the lower oak woods ecosystem. Ecosystem analysis has taught ecologists that no component of the ecosystem should be overlooked; even the smallest component may play a key role in an integrated system. The bryophyte component appears small in some ecosystems while in otherssuch as many tundra, boreal, temperate rain forest, and tropical ecosystems-the component generally is quite prominent. Yet, with few exceptions (e.g., Bliss, 1962, 1966), ecosystem studies have either ignored the mosses and liverworts or afforded them only token mention. The importance of bryophytes in mineral cycling is frequently noted and sometimes measured (e.g., Marchenko, 1968; Tamm, 1953), but little is known of their role in the energy flow and trophic dynamics of ecosystems. The caloric values3 of some dominant bryophyte species were determined as part of a study of the energy dynamics of bryophytes in nine ecosystems on Mt. Washington, New Hampshire, in 1967 and 1968. It is hoped that these data may aid certain ecosystem studies.

Application of the Second Law of Thermodynamics and Le Chatelier's Principle to the Developing Ecosystem

Abstract: “LIVING organisms (biota) and their non-living (abiotic) environment are inseparably interrelated and interact on each other. Any area of nature that includes living organisms and non-living substances interacting to produce an exchange of materials between the living (biotic) and the non-living (abiotic) parts is an ecosystem” (modified after Odum1). The driving force which causes this exchange is the energy incident on the given area. That part of the energy which is fixed by the photo-synthetic biomass is either used by the respiring biomass or is stored in chemical form as standing crop, extracellular produce, humus or peat.

Studies on littoral and sublittoral ecosystems

Abstract: The results of 93 phytosociological descriptions of five types of kelp forest from a number of phyto geographically distinct regions are presented. Methods are described for the measurement of a complex of meaningful ecosystem parameters which fall into three groups; individual performance, ecosystem performance and ecosystem potential. The results of such measurements in the phytosociologically defined units are presented." The validity of these results and the phytometer approach is discussed and tentative conclusions are drawn from the results regarding the biotic and abiotic components of the ecosystems.