Different Types Of Ecosystems Research Articles

Closed Artificial ecosystems as a means of ecosystem studies for Earth and space needs.

Closed Artificial ecosystems (CAES) have good prospects for wide use as new means for quantitative studies of different types of both natural ecosystems and man-made ones. The paper deals with the discussion of three points of CAES applications. The first one is of importance for theoretical ecology development and is connected with bringing together "holistic" and "merological" approaches in ecosystems studies. Using CAES, we can combine both approaches, taking into account the biotic turnover of limiting substrates which few in number even for complicated natural ecosystems. The second CAES use concerns the development of "ecosystems health" concept and application of a key-factor-approach for the indication and measurement of healthy unhealthy state and functioning of ecosystems or their links. The third use is more of an applied nature, oriented to the intensification of bioremediation or biodepollution processes in different types of ecosystems, including the global biosphere. Grant numbers: N 99-04-96017, N25.

Compounded Perturbations Yield Ecological Surprises

All species have evolved in the presence of disturbance, and thus are in a sense matched to the recurrence pattern of the perturbations. Consequently, disturbances within the typical range, even at the extreme of that range as defined by large, infrequent disturbances (LIDs), usually result in little long-term change to the system's fundamental character. We argue that more serious ecological consequences result from compounded perturbations within the normative recovery time of the community in question. We consider both physically based disturbance (for example, storm, volcanic eruption, and forest fire) and biologically based disturbance of populations, such as overharvesting, invasion, and disease, and their interactions. Dispersal capability and measures of generation time or age to first reproduction of the species of interest seem to be the important metrics for scaling the size and frequency of disturbances among different types of ecosystems. We develop six scenarios that describe communities that have been subjected to multiple perturbations, either simultaneously or at a rate faster than the rate of recovery, and appear to have entered new domains or “ecological surprises.” In some cases, three or more disturbances seem to have been required to initiate the changed state. We argue that in a world of ever-more-pervasive anthropogenic impacts on natural communities coupled with the increasing certainty of global change, compounded perturbations and ecological surprises will become more common. Understanding these ecological synergisms will be basic to environmental management decisions of the 21st century.

Environmental relaxation in response to reduced contaminant input: The case of mercury pollution in Haifa Bay, Israel

Environmental relaxation, defined as the rate of return of a polluted environment to an acceptable state following a reduction in the input of contamination, was evaluated for the case of mercury pollution in northern Haifa Bay (Israel) on the basis of the long-term record of mercury levels in sediment cores and biota. Mercury was found to decrease with a half-time of 2, 5 and 6–33 years in filter-feeding bivalves, fish and sediments, respectively, after the influx of mercury into the area (from a chlor-alkali plant) was drastically reduced. The present levels of mercury in edible fish do not represent a risk to human health. The removal of mercury from the sediments is probably by particle resuspension and subsequent seaward transport. Although the mercury concentrations in the sediments will probably remain above background for a long time, the associated ecological risk does not appear to be high. It is concluded that evaluations of the environmental relaxation of different types of ecosystems, with respect to various contaminants, may provide important input to decision-making on marine waste disposal.

Potential impacts of climate change on ecosystems: a review of implications for policymakers and conservation biologists

CR Climate Research Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsSpecials CR 06:179-191 (1996) - DOI: https://doi.org/10.3354/cr006179 Potential impacts of climate change on ecosystems: a review of implications for policymakers and conservation biologists Markham A Climate change represents a significant threat to global biodiversity and ecosystem integrity. The UN Framework Convention on Climate Change (UNFCCC), which has been ratified by 118 nations and came into force in 1994, has amongst its aims the protection of ecosystems. This paper reviews the relevant text in the Convention and gives an overview of scientific efforts to provide policymakers with the necessary information on ecosystem impacts. The sensitivity of different types of ecosystem to climatic change is discussed and the concepts of ecological limits and thresholds are addressed and examples given. The paper concludes there is a need for a better understanding of the impacts of climate change on ecosystem resilience in order to maintain biological diversity and respond to the needs of policymakers in implementing the UNFCCC. Recommendations are made for increased research effort, including increased resolution of climate models, better predictive capacity at a regional level for within- and between-year rainfall patterns, seasonality and extreme events. Collaborative monitoring programs, including long-term ecological research along climate gradients, are proposed for 4 biomes: coastal wetlands, montane ecosystems, coral reefs and Arctic ecosystems. Adaptation · Biodiversity · Climate · Conservation · Critical levels · Ecosystem impacts · Global warming · Protected areas · UNFCCC Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in CR Vol. 06, No. 2. Publication date: February 19, 1996 Print ISSN: 0936-577X; Online ISSN: 1616-1572 Copyright © 1996 Inter-Research.

Effects of diet, climate and physiology on nitrogen isotope abundances in terrestrial foodwebs

Variations in nitrogen isotope ratios in terrestrial foodwebs are described, and alternative models for variation in the enrichment between trophic levels are evaluated. Nitrogen isotope ratios in bone collagen have been used to determine trophic levels and differentiate marine from terrestrial resource consumption among prehistoric humans. However, recent research in terrestrial ecosystems has revealed significant variation in nitrogen isotope ratios between habitats, and within trophic levels in the same environment. Foodwebs in hot, arid environments tend to have higher nitrogen isotope ratios than cool, wet ones. Within ecosystems, the stepwise enrichment between trophic levels is often greater in hot, arid environments. Within ecosystems, herbivore species with physiological adaptations to water conservation have higher nitrogen isotope ratios than water-dependent species. The nitrogen isotope ratios of human bones may be affected by climate and physiology and thus cannot be directly compared between different types of ecosystems without first determining the isotopic composition of the local foodweb and the stepwise enrichment between trophic levels.

MARINE PLANKTON FOOD CHAINS

The view on the ecology of marine plankton has changed significantly within the last decade. In some respects the is sufficiently dramatic to make some authors speak about a change in paradigm (84). The new picture of plankton dynamics includes the recognition that phototrophic and heterotrophic microorganisms play a substantial and sometimes dominating role in the cycling of matter in the sea, that plankton food chains include a higher number of trophic levels than hitherto believed, and that a large fraction of the primary production is not consumed directly by herbivorous consumers but is channelled through a pool of dead organic matter before it becomes available-via bacterial production-to phagotrophic organisms. In this latter respect the structure of planktonic systems resembles benthic and terrestrial systems. This changing view is remarkable for more than one reason. Among different types of ecosystems, that of the open sea was long considered the simplest and best understood. Many ecology textbooks used marine plankton to introduce the concept of food chains. A graphical presentation might be in the form of a pyramid with its base representing primary producers; above them two hori-zontal layers represented zooplankton and fish, respectively; and at the top a fisherman (or a whale) represented the highest trophic level. While this essentially remains correct, it has certainly proven to be an incomplete picture of pelagic food chains. Modem biological oceanography began at the turn of the century. During the following decades it developed into an established discipline which successfully explained fundamental aspects of plankton dynamics. Organic

Parasites as indicators of host populations

The literature on parasites as indicators of populations of aquatic hosts is reviewed, with the emphasis on work published since about 1980. General guidelines are proposed for the selection of tag parasites, with a discussion of earlier criteria in the light of recent knowledge. The use of parasites for different types of population study, for different types of ecosystem and for different taxonomic groups of hosts is discussed. Some promising future application of parasites in population studies of aquatic hosts are suggested.

Field measurements of emission of nitric oxide from fertilized and unfertilized forest soils in Sweden

Application of nitrate fertilizers on two types of forest soils led to a marked increase in the NO emission rate indicating a large potential for NO production in these soils. The largest fluxes on the fertilized plots were up to 60 ng NO−N m−2 s−1. About 0.35% of the applied nitrogen was lost as NO within about 14 days after fertilization. The fluxes from the unfertilized forest soils were in the range 0.1 to 0.8 ng NO−N m−2 s−1 with a median value of 0.3 ng NO−N m−2 s−1. If this value, obtained during June and August to September, is representative for the growing season (150 days), it corresponds to an annual emission of 0.04 kg NO−N ha−1. This is about 30% of the value obtained for an unfertilized agricultural soil. Because of the large areas occupied by forests in Sweden the flux of NO from forest soils represents a significant contribution to the total flux of NO from soils in Sweden. Earlier observations of equilibrium concentrations for NO have been verified. These were found to range from 0.2 to 2 ppbv for an unfertilized forest soil and up to 170 ppbv for a fertilized soil. At the rural site in Sweden where these measurements were performed the ambient concentrations where found to be less than this equilibrium concentration, and consequently there was generally a net emission of NO. There are still large uncertainties about the global flux of NO from soils. Using direct measurements on three different types of ecosystems and estimates based on a qualitative discussion for the remaining land areas, a global natural source for NO of the order of 1 Tg N a−1 was obtained. If 0.35% of the total annual production of fertilizer nitrogen is lost as NO, fertilization of soils may contribute with 20% to the natural flux from soils.

The Physical Geography (Geomorphology) of William Morris Davis

Canadian north and centre, an area larger than that of Quebec and the Maritime Provinces combined. Their depth is variable but may extend to about 100 feet (c. 30 m). Muskeg is thus a significant feature of the landscape and is also an important organic resource, so that the problem of its wise development is associated with many other aspects of the northern environment, such as water supplies, forest resources and the exploitation of petroleum, natural gas and other mineral deposits. The scope of this multidisciplinary work is extensive: there are papers dealing with the post-glacial history and origin ofthe muskeg, the classification ofthe different types of ecosystems, their chemistry and physical properties, their hydrology and soils. Further contributions discuss industrial utilization and the impact of economic development, particularly the effect of pipeline construction and human settle ents. A final section considers the wildlife of muskeg in relation to conservation and recreation. Each chapter reviews what is known, draws attention to limitations in knowledge and contains an extensive bibliography. The book is illustrated by many photographs, both ground and aerial, and also maps, diagrams and tables and is an essential reference text for all students of the physical environment ofthe Canadian north. W. W. Newey

Abundance, Biomass and Contribution to Energy Flow by Soil Nematodes in Terrestrial Ecosystems

A review is made of quantitative estimations on abundance and biomass of nematode faunas from different ecosystems. A great dispersion of the values from different authors is probably to some extent caused by differences in the efficiency of the extraction methods. The mean values of numerical abundance for different types of ecosystems ranged from 7.6 -10 m-2 for semideserts to 9.2 106 m-2 for temperate grasslands. The respiratory metabolism in more productive sites corresponded to an energy emittance of about 20-60 kcal m-2 and year whereas in cold or dry sites it amounted to 7-10 kcal m-2 and year. The contribution of nematodes to the total soil respiration is rather slight; probably in many cases under 1%. The accuracy of estimations on the total energy flow through the soil populations is discussed. Probably the microbial feeders have a high assimilation efficiency whereas the production efficiency is more varying depending upon the food supply which in the soil possibly

Study of a mediterranean type phytocenose subjected to chronic gamma radiation

A phytocenose of a natural Mediterranean ecosystem (wood and garrigue * ), undisturbed by man for a third of a century, has been subjected to chronic gamma radiation (source 137caesium) since July 12th 1969. This experiment has been set up at the Nuclear Research Centre at Cadarache. Some similar experiments have already been carried out, but with different types of ecosystems. The first results obtained up till the date of writing agree with the results obtained on different types of ecosystems, at least in the fields of morphology (leaf malformation and stem shortening), anatomy (meristem inhibition, tissue distortion) and radiosensitivity (the herbaceous plants are more resistant than ligneous plants). It should also be noted that surviving foliage which had grown before the radiation began displayed a high radiosensitivity in general, and that thallophytes (lichens) showed an increased rate of growth in the space left free by the death of higher plants (especially ligneous plants). The authors noted that the typical Mediterranean species were more resistant, while the submediterranean species appeared more sensitive, and this is apparent in the classification of the species by degree of sensitivity. It appears that in this case, the ecological environmental characteristics are as important as the standard factors already known, if not more so, in determining a plant's radiosensitivity.