Showing papers on "Ecosystem published in 1981"

Tropical Rain Forests: Are Nutrients Really Critical?

Abstract: Nutrient poor forests are more common in the tropics than in the temperate regions, but most of the work on nutrient cycling in the tropics has been carried out on nutrient rich sites such as those in Puerto Rico and Costa Rica rather than nutrient poor sites such as those in central and eastern Amazonia. Consequently, there has been confusion as to whether nutrients are critical in tropical forests. Productivity and nutrient cycling in nutrient rich and nutrient poor forest ecosystems do not differ greatly as long as the ecosystems are undisturbed. However, when the forests are cleared for agricultural purposes, the nutrient poor systems quickly lose their productive potential, whereas the nutrient rich systems do not. The nutrient poor ecosystem is able to maintain its productivity under undisturbed conditions through a variety of nutrient conserving mechanisms, the most important of which are associated with the humus and root layer on top of the mineral soil. These mechanisms are destroyed when the nu...

Organic Carbon Flow in a Swamp‐Stream Ecosystem

Abstract: An annual organic carbon budget is presented for an 8-km segment of Creeping Swamp, an undisturbed, third-order swamp-stream in the Coastal Plain of North Carolina, USA. Annual input of organic carbon (588 gC/m2) was 96% allochthonous and was dominated by leaf litter inputs (36%) and fluvial, dissolved organic carbon (DOC) inputs (31%). Although the swamp-stream was primarily heterotrophic, autochthonous organic carbon input, primarily from filamentous algae, was important during February and March when primary production/ecosystem respiration (P/R) ratios of the flooded portions were near one. Annual output of organic carbon via fluvial processes (214 gC/m2), 95% as DOC, was 36% of total annual inputs, indicating that the swamp-stream segment ecosystem was 64% efficient at retaining organic carbon. Respiration (327 gC/m2) accounted for most of this retention, or about 57% of annual inputs, and storage accounted for the remaining 7% of inputs. Organic carbon dynamics in the Creeping Swamp segment were compared to those reported for upland stream segments using indices of organic matter processing suggested by Fisher (1977) and a loading potential index suggested here. Creeping Swamp, while loading at a high rate, retains a much larger portion of its organic carbon inputs than two upland streams. Organic carbon loading potential in Creeping Swamp is very large, primarily because of its great width and complete canopy; however, its low gradient and dense vegetation enhance organic carbon retention, especially of coarse partic- ulate organic carbon (CPOC), by maintaining low water velocities with little erosive force, tortuous flow pathways, and debris dams. Most of the retention and oxidation of organic carbon in the flooded Creeping Swamp ecosystem takes place in the floodplain. It is suggested that floodplain exchanges should also be considered in budgets of higher gradient rivers and streams. Despite the high degree of retention and oxidation of organic inputs to Creeping Swamp, there is a net annual fluvial export of 21 gC/m2, mostly in the dissolved form. Watersheds drained by swamp- streams in the southeastern United States are thought to have large organic carbon exports compared to upland forested drainages, because the stream network covers a much greater proportion of the total watershed area.

Productivity of Desert Ecosystems

Abstract: Primary production in desert ecosystems is limited by precipitation, nutrient availability (especially nitrogen), and the species' production potential. Plant biomass provides food for consumers that occupy several trophic levels. The resultant transfer of energy and nutrients is also water-limited as are rates of decomposition and activities of decomposer organisms. (Accepted 20 February 1981)

Natural disturbance and the steady state in high-altitude balsam fir forests.

Abstract: Wind-induced, cyclic waves of death, regeneration, and maturation constantly move through the high-altitude balsam fir forests in the northeastern United States. Biomass and productivity relations, species diversity, and nutrient cycling patterns are closely tied to this cycle of disturbance. Disturbance is thus an integral part of the long-term maintenance of this ecosystem. Since forests of this type normally include all phases of the disturbance-regeneration cycle, they may constitute a steady-state ecosystem in equilibrium with the surrounding environment.

Evidence of temperature control of production and nutrient cycling in two interior Alaska black spruce ecosystems

Abstract: Selected indices of structure and function were used to evaluate the effect of differing soil thermal regimes on soil-permafrost-dominated (muskeg) and permafrost-free (north-slope) black spruce ecosystems in interior Alaska. The poorly drained, permafrost site displayed cooler soil temperatures and higher soil moisture content than were encountered on the well-drained north slope. Mineral soil nutrient pools generally were largest on the permafrost site. However, low soil temperature acted as a negative feedback control, suppressing soil biological activity, nutrient mineralization, and tree primary production to lower levels on the soil-permafrost-dominated site as compared with the permafrost-free site. Forty percent larger accumulation of tree biomass and 80% greater annual tree productivity occurred on the warmer site.

Insect Herbivore Relationship to the State of the Host Plant: Biotic Regulation of Ecosystem Nutrient Cycling through Ecological Succession

Abstract: This paper provides a conceptual framework for increasing our understanding of the relationships between plant resistance to insect herbivores and insect herbivore influences on ecosystem nutrient cycling and succession. For a given plant species, adequate nutrient/light availability favors establishment and productivity; small insect herbivore populations regulated by plant biochemistry stimulate primary productivity and short-term nutrient cycling. As biomass and competition for nutrients and light increase during succession, plants become stressed as they approach their tolerance limits. Earlier successional plant species initially dominating the plant community have higher nutrient/light requirements and become stressed sooner than later successional plant species. Abundance and stress make the earlier plant species more apparent and susceptible, than later plant species, to insect herbivores. Insect herbivore populations increasing rapidly on stressed hosts tend to regulate long-term nutrient cycling patterns by accelerating changes in competitive relationships between plant species with different nutrient/light requirements.

Marine Fisheries Ecosystem: Its Quantitative Evaluation and Management

Abstract: Purpose and scope Ecosystem processes and approaches to quantitative simulation of the marine fish component Limitation of models based on primary production and comparison of biomass-based and number-based models Biomass parameters of fish population and distribution of biomass with age Major processes in the fish component of a marine ecosystem and their simulation Formulas and computation procedures of a biomass-based fisheries ecosystem Simulation of plankton and benthos, interactions of fish biota with them and the total carrying capacity of ocean regions Equilibrium biomasses and basic input data Equilibrium biomasses in the eastern Bering Sea at present and Bering Sea biomasses in natural state Environment - biota and interspecies interactions Natural fluctuations in the marine ecosystem Consumption of marine biota by marine mammals in the NE Pacific Ocean Verification and validation of ecosystem simulation Simulation of the fishery in marine ecosystem models Acceptable catch and its estimation Use of ecosystem simulation in fisheries management and research List of symbols.

Ecosystem Development on Naturally Colonized China Clay Wastes: I. Vegetation Changes and Overall Accumulation of Organic Matter and Nutrients

Abstract: (1) As a result of changes in mining operations and recessions in the china clay industry there are a number of abandoned waste tips in Cornwall ranging in age since last tipping from 16-116 years. These tips have been naturally colonized by vegetation. (2) The vegetation on a series of waste tips is described and four speciesassemblages-two pioneer groups, an intermediate group and a mature woodland group-are identified. It is clear that succession to a woodland ecosystem can occur on these waste tips. (3) The accumulation of organic matter and nutrients was measured and is discussed in relation to successional development. The central role of nitrogen in these new environments is suggested, and the potential inputs to the nitrogen budget examined.

Nutrient Cycling in Mediterranean Type Ecosystems

Abstract: This chapter reviews studies of nutrient pools and cycling processes in mediterranean type ecosystems of the world. Inter- and intrasystem cycles are compared to similar cycles in forest ecosystems.

Enigmatic Marine Ecosystem Metabolism Measured by Direct Diel ΣCO2 and O2 Flux in Conjunction with DOC Release and Uptake

Abstract: In an attempt to evaluate ΣCO2 changes as an index of net ecosystem metabolism, ΣCO2 and dissolved organic carbon (DOC) by infrared (IR) analysis and O2 by the Winkler method were followed over 12 diel cycles in a salt marsh, a simulated estuarine ecosystem, and the mixed layer of the northwestern Caribbean Sea. Each ecosystem exhibited replicable diel cycles, net production during the photoperiod, and a significant inverse correlation between ΣCO2 and O2 changes. Daily rates of system production and respiration calculated from ΣCO2, however, exceeded those from O2 by 1.5 to 3.5 fold in nearshore waters and by 2 to 6 fold in the open ocean. Net total system apparent production based on O2 and ΣCO2, respectively, were 2 345 and 3 604 mg C m-3d-1 for the salt marsh, 348 and 625 mg C m-3d-1 for the estuarine ecosystem, and 53 and 306 mg C m-3d-1 for the oceanic ecosystem, both parameters exceeding 14C data in the literature for similar environments by one to two orders of magnitude. The IR ΣCO2 productivity estimates are compatible with the diel cycles in DOC. In the marsh and Caribbean Sea, maxinium DOC concentrations were usually observed in the evening following a gradual accumulation during the photoperiod, while minimal values occurred in the early morning. In all ecosystems the average net release of DOC lagged CO2 uptake and O2 production and represented 22.7 and 43.3% of the carbon fixed as estimated from CO2 uptake and O2 production, respectively. If the consistently higher ΣCO2 measurements are not a systematic error nor due to atmospheric diffusion, then diel variation in O2 and CO2 may not always be quantitatively coupled due in part to habitat-dependent factors such as the nonphotosynthetic incorporation of CO2 and chemosynthetic removal of O2.

Sensitivity of marine phytoplankton to uv-b radiation: impact upon a model ecosystem

Abstract: Human activities may cause a 16% reduction of stratospheric ozone. The concomitant increase in solar UV-B radiation reaching the surface of the earth could detrimentally affect the phytoplankton that form the base of the food web in oceanic and estuarine ecosystems. In the current study acute exposure of seven species of marine phytoplankton to UV–B radiation depressed the radiocarbon estimate of primary production. A model of a marine ecosystem was constructed based on the differential sensitivities of the seven species of phytoplankton. Increasing the UV–B exposure within the model from 100 EffDNAJ/m2/day to 150 EffDNAJ/m2/day significantly altered the community composition of the ecosystem. In nature, alteration of the phytoplanktonic community structure could result in a significant impact upon successional patterns and primary producer–consumer trophodynamics.

Atmospheric concentration of ammonia in Massachusetts and deposition on vegetation

Abstract: Ammonia has an important role in atmospheric chemistry and the soil nitrogen cycle, and it has long been suggested that terrestrial ecosystems may be important sources and sinks for atmospheric ammonia in both gaseous and particulate form1–4. But there is relatively little information on the average atmospheric concentrations of NH3 gas and particulate NH+4 and their fluxes to and from ecosystems. Furthermore, much existing data are unreliable because of difficulties in separating gaseous NH3 from particulate NH+4 (refs 1, 5). We have used a new method5,6 which overcomes these difficulties and have made continuous measurements for a 1-yr period at a rural location in Massachusetts. From these data and from measurements of the rate of deposition of ammonium on plastic and natural leaves, we conclude that particulate NH+4 can be a significant nitrogen source for ecosystems, especially pine forests. In contrast, gaseous NH3 is probably of little importance as its concentration is very low.

Biological and environmental impacts of the insecticides malathion and parathion on nontarget biota in aquatic ecosystems.

Abstract: Pesticides-nontarget biota interactions are quite complex, requiring detailed analysis and critical interpretations. The effects of pesticides may be direct, resulting in the die-off and reduction in the numbers of the affected organisms in a short period of time. Another impact commonly encountered in the use of pesticides on nontarget organisms is that leading to secondary effects. These effects are visible after some period of time after exposure. The complete or partial impact of pesticides on the population of one species may lead to the imbalance of other interacting units of the ecosystem. Depending upon the severity and magnitude of these disruptions, there is always a tendency in the dynamics of the various components to return to their prestress state. The secondary effects could manifest themselves in a number of ways such as decreased density and intraspecific competition, emigration, recolonization, and in changes in diversity of the species in the system. Secondary effects may also result from pesticide-induced changes of the target species such as the development of resistance, necessitating higher dosages of a pesticide and thus disrupting the general homeostasis of the ecosystem.

Producers and the Fire Cycle in a Phryganic Ecosystem

Abstract: The severe summer drought combined with high temperatures leads to a high frequency of fires in mediterranean-type ecosystems. The relation of this climatic type with fire has been long ago noted (Griesebach, 1872). Shantz (1947) refers to the mediterranean-type ecosystems of California as “fire-type” or “fire-climax”. The numerous adaptations of plants dominating mediterranean-type ecosystems indicate that fire has been a strong selective force and that these systems can be considered as “fire-induced” or “fire-adapted” (Jepson, 1930; Naveh, 1973; Biswell, 1974).

Adaptive Strategies at the Ecosystem Level: Examples from Two Benthic Marine Systems

Abstract: . Adaptive strategies on the ecosystem level are demonstrated using the properties of systems (community biomass, trophic level energy transfer). Development of stabilizing storages versus rapid turnover and energy transfer through the grazing food chain versus detritus food chain are shown to be adaptive processes leading towards an optimal performance of the system. A model of incorporation and processing of information in ecosystems is proposed which contains the essential features of evolution. The persistence of “interspecific altruism” is discussed.

Bird Communities along a Montane Sere: Community Structure and Energetics

Abstract: -We examined 11 of 24 ecosystem attributes that Odum (1969) proposed would change during succession in avian communities in meadow, aspen, fir, and spruce forests in northern Utah and southern Idaho. A total of 71 bird species was observed during the 30-month study, of which 43 were known to breed. Yearly energetic relationships were calculated for the breeding bird populations using an avian community energetics model. In the different avian communities, the ratios of annual secondary production/community respiration, secondary production/biomass present, and secondary production/consumption all tended to decrease with increasing plant succession; biomass present/"unit energy flow" tended to increase. All of these trends are consistent with those postulated by Odum for the entire ecosystem. These energetics ratios differed in 1977 from those in 1976 and 1978 due to a severe drought. They also fluctuated greatly during the course of a year. Avian species diversity was highest in the preclimax fir forest during the breeding season and fluctuated widely in the nonbreeding season. Species equitability tended to be relatively high in all avian communities, although it was slightly lower during the nonbreeding season. No trends were found in male body sizes, mean clutch size, and mean length of incubation period (a crude measure of parental investment). Thus, for the bird communities, we reject the postulated trends of increased species diversity, equitability, and organism size in the climax, quantity to quality production, and rto K-selection. During the drought of 1977 the spruce avifauna appeared more stable, so we cannot reject Odum's hypothesized trend of increased stability in the climax. We conclude that the vegetational characteristics of a given sere will in most cases determine the avian population response along that sere; this in turn will influence the correspondence of the avian communities to Odum's postulates. Incorporating these avian results with other studies within our subalpine sere, some of Odum's hypothesized trends are supported while others are not, suggesting that successional relationships are more complicated than would follow from Odum's relatively simple model. Received 20 February 1980, accepted 9 June 1980. ODUM (1969: Table 1) proposed trends in 24 ecosystem attributes that change as succession proceeds from early (pioneer) to late (mature or climax) stages. He divided these ecosystem attributes into six groups: community energetics, community structure, life history, nutrient cycling, selection pressure, and overall homeostasis. The trends Odum proposed were based on the following premises concerning succession: "i) It is an orderly process of community development that is reasonably directional and, therefore, predictable; ii) It results from the modification of the physical environment by the community . . . ; iii) It culminates in a stabilized ecosystem in which maximum biomass (or high information content) and symbiotic function between organisms are maintained per unit available energy flow" (Odum 1969: 262; see also Odum 1971: 251-267). This viewpoint has been widely criticized (see review in Connell and Slatyer 1977). Connell and Slatyer stated that Odum's scheme is based on analogy, not evidence, and Engleberg and Boyarsky (1979) argued that even the analogy is a poor one. Few studies have attempted to test the proposed attributes simultaneously on an ecosystem-wide basis. During 1975-1978 a study was undertaken to test empirically as many of Odum's 24 attributes as possible in a relatively simple subalpine sere. Data were collected on as many aspects of the plant and animal communities that were related to Odum's I Present address: Bodega Marine Laboratory, University of California, Bodega Bay, California 94923 USA. 8 The Auk 98: 8-28. January 1981 This content downloaded from 157.55.39.249 on Wed, 03 Aug 2016 04:13:55 UTC All use subject to http://about.jstor.org/terms January 1981] Montane Avian Community Structure 9 TABLE 1. Eleven attributes proposed by Odum (1969) that were tested by examining the spruce-fir avifauna along a subalpine sere. Ecosystem attribute Predicted trend (Odum 1969) Community energetics Production/respiration Approaches 1 Production/biomass High to low Biomass/unit energy flow Low to high Net community production High to low Community structure Total organic matter Low to high Species diversity-variety Low to high Species diversity-equitability Low to high

Catchment nutrient budgets and geological weathering in Eucalyptus regnans ecosystems in Victoria

Abstract: The movement of water and nutrients (N, P, K, Na, Mg, and Ca) through Eucalyptus regnans dominated catchments in the Maroondah catchment near Melbourne were determined. Nutrient fluxes in precipitation and streamflow are discussed and used to prepare simple precipitation input – stream flow output catchment budgets. These budgets are similar to those found elsewhere in Australia and overseas with the exception of nitrogen. This was probably due to errors in measurement and incomplete quantification of nitrogen fluxes. Catchment sodium budgets were used to estimate geological weathering rates by two different methods. Both methods yielded similar results. Data from two other studies in Victorian forested catchments yielded results similar to those obtained from Maroondah. It was concluded that the bedrock weathering rate at Maroondah was approximately 700 kg ha-1 year-1 which is very similar to that found elsewhere. Nutrient inputs from geological weathering were then estimated and possible errors discussed.

Esophageal, fecal and exclosure estimates of cattle diets on a longleaf pine-bluestem range.

Abstract: Microhistological analysis of esophageal or fecal materials provides an accurate and efficient method for evaluating botanical compositions of cattle diets on native longleaf pine-bluestem range. For practical purposes fecal analysis is the preferred method. Plant species that were most important to cattle during the present study were the bluestems and panicums. Southern pine ecosystems serve as range for livestock and wildlife. These forest ranges have potential for high production of red meat with minimum inputs (Pearson and Whitaker 1974; Pearson 1975; Sternitzke and Pearson 1975). Cattle impact on ecosystems is related to the animal’s dietary needs, preferences, and available forage. The purpose of this study was to estimate cattle diets on longleaf pine-bluestem range. Specific objectives were to contrast cattle diets estimated from esophageal and fecal samples with estimates obtained from exclosures. Study Areas

Dissolved oxygen and pH relationships in northern Australian mangrove waterways

Abstract: Consistent, highly significant linear correlations (R2 greater than or equal to 0.8) between pH and dissolved oxygen levels have been found in northern Australian mangrove waterways. These properties seem to be influenced by dissolved organic matter, mainly polyphenolic compounds, present in the creeks and tidal channel waters.

Effects of Reservoirs Releases on Tailwater Ecology: A Literature Review.

Abstract: : This document presents a review of the often contradictory literature describing the effects of release waters on the tailwater environment and biota. The physical and chemical conditions found in tailwaters downstream from warmwater and coldwater discharge impoundments are compared and contrasted to those found in natural streams. Reservoir discharges modify the physical, chemical, and biological characteristics of the stream ecosystem. Physical and chemical characteristics in tailwaters are primarily determined by the depth, volume, and schedule of water releases. The magnitude of change is related to the type of reservoir and to the design and operation of outlet structures. The structure of the biotic community reflects the physical and chemical conditions existing in a particular tailwater. The community is composed of organisms, including nonnative species, that are adapted to this environment. The effects of the tailwater environment on the life history, physiology, and abundance of selected species are described. This information will aid in the development of reservoir discharge guidelines that will enhance the quality of the tailwater environment to increase project benefits. (Author)

Metabolism of a Florida lake ecosystem1,2

Abstract: Ecosystem and plankton community metabolism were Inc asured for 1 year in a central Florida lake. Values of ecosystem production and respiration were similar throughout the year, suggesting that little net production accumulates seasonally or annually. Gross production and respiration were 3,071 and 3,180 g 02*m-2*yr-‘. The plankton community was responsible for 44% of the gross production; the remainder was attributable to submersed macrophytes and associated epiphytes. Of the annual respiration, 54% was due to the plankton. Measurements of metabolism suggested that submersed plant photosynthesis and respiration were severely diminished for 1 month in summer, p lssibly as a result of high temperature.

Sensitivity analysis of a coastal marine ecosystem

Abstract: An ecosystem with four compartments, i.e. PO4-P, phytoplankton, zooplankton and detritus, in a coastal region was considered. Sensitivity analysis of a phosphorus flow model in well-mixed water without currents concludes that (1) the maximal photosynthetic rate,V m , in Michaelis-Menten relation plays an important role in the distribution of biomass among compartments but the half saturation constant,K s , is not so important, (2) the natural death rate of phytoplankton is important for the ecosystem, (3) the natural death rate of zooplankton is also effective on the ecosystem. A numerical experiment was also performed on the ecosystem with four compartments are also studied using a dynamical barotropic model of tidal currents of Mikawa Bay (Japan). Diffusion coefficient in diffusion equation plays the role of a linear smoothing parameter in the horizontal distribution of compartment. On the other hand, perturbations of biological parameters cause nonlinear variations in the horizontal distribution of compartment.