Showing papers on "Productivity (ecology) published in 1979"

Grazing as an Optimization Process: Grass-Ungulate Relationships in the Serengeti

Abstract: A substantial literature is reviewed which indicates that compensatory growth upon tissue damage by herbivory is a major component of plant adaptation to herbivores. Experiments in Tanzania's Serengeti National Park showed that net above-ground primary productivity of grasslands was strongly regulated by grazing intensity in wet-season concentration areas of the large ungulate fauna. Moderate grazing stimulated productivity up to twice the levels in ungrazed control plots, depending upon soil moisture availability. Productivity was maintained at control values even under very intense grazing, suggesting that conventional definitions of overgrazing may be inapplicable to these native plant-herbivore systems. A laboratory clipping experiment with a sedge abundant in one of the most intensely utilized regions resulted in a maximum net above-ground productivity of 11.6 g/m2 · day when clipped daily at a height of 4 cm. Few plant species have been reported with the ability to maintain a significant level of pr...

Structure and Primary Productivty of Lamto Savannas, Ivory Coast

Abstract: Lamto savannas (Ivory Coast) are characterized by the heterogeneity of their structure and by their dynamic evolution towards forest. Life-forms and phonological cycles of herbs, shrubs, and trees reflect the constraining factors of the environment. Biomass and productivity are largely dependent on soil and climate. The specific cycles of above- and belowground biomass allow an estimate of the primary productivity. Production of shrubs and trees, obtained from size-biomass correlations and growth measures, is compared with herb production to give an insight into the ecological balance of the savanna communities.

Structure and Function of the Zooplankton Community of Mirror Lake, New Hampshire

Abstract: An intensive study of the zooplankton community of Mirror Lake, New Hampshire, was undertaken over a 3-yr period. Our objectives in the lake study have included measurements of a number of attributes of the zooplankton community that integrate structure and function at the ecosystem level; among these are dispersion, biomass, productivity, respiration, and nutrient cycling. Eight species of rotifers and 3 species of cladocerans were successfully cultured. Generation time for planktonic rotifers was -8-10 days (170C). The effect of higher food levels on rotifers was to shorten generation time and to increase brood size. In cladocerans, high food levels caused an increase in length and brood size. A curvilinear relationship existed between zooplankton community respiration and temperature in Mirror Lake. Mean monthly zooplankton community respiration ranged from 96.0 kg C/ha/mo in June of 1969 to a low of 20.5 kg C/ha/mo in April of 1970. Over a 3-yr period, respiration was 79.9% of assimilation. The 0 to 4.5-m strata (;epilimnion) contributed 68.5% and 46.5% of the annual zooplankton production and biomass. Zooplankton community production ranged from 22.3 kg C/ha/yr to 29.3 kg C/ha/yr with a 3-yr mean of 25.2 kg C/ha/yr. The annual zooplankton biomass ranged from 1.4 to 2.6 kg C/ha with a 3-yr mean of 2.0 kg C/ha. A linear relationship was found to exist between net phytoplankton and zooplankton production in various lakes of the world. Ecological efficiency apparently increases with the trophic status of the lake. It is recommended that the term ecological efficiency be refined to include both autochthonous and allochthonous inputs of reduced carbon into the lake. Rotifers assume a major role in intrasystem nutrient cycling and energy transfer within the lake ecosystem. Of the total amount of P incorporated into the organic matter of zooplankton community each year, 33.5% is assimilated in rotifer tissue. The annual turnover rate of P by rotifers is 30.9 and is high compared to crustaceans (10.1). Copepods comprise 55.4% of the total zooplankton biomass. However, the copepods, with their slow growth over an entire year, represent only 19.3% of the zooplankton production, while rotifers account for 39.8% of the zooplankton production annually in Mirror Lake. Also, evidence is presented that rotifers play a major role in energy transfer in lakes of varying trophic status (oligotrophic to eutrophic).

Underground biomass profiles and productivity in atlantic coastal marshes

Abstract: An underground biomass profile and productivity study involved year-long sampling programs in 18 stands of salt marsh plants in Georgia, Delaware, and Maine. As the result of the monthly or bimonthly marsh coring program three types of underground biomass profiles were found. In the first, the concentration of macro-organic matter (MOM) was uniform with depth; the notable example of this type was creekbank Spartina alterniflora in the southern part of the coast. A second type had a high MOM concentration at the surface which decreased with depth. This, the most common type of profile, was exemplified by Spartina patens, S. alterniflora from the high marsh along the southern coast (Georgia), and creekbank S. alterniflora from the northern part of its range (Maine). The third type of profile was seen where a large rhizome mat developed 15-20 cm below the surface. Spartina cynosuroides and Phragmites communis were typical examples of this type of profile, resulting in a low biomass at the surface, a higher biomass somewhat below the surface, and a low concentration at depth. The annual maxima and minima of MOM biomass were used to calculate annual increments, which can be considered minimum annual production values. These productivity values ranged from a low of 80 g C/m2 for creekhead S. alterniflora in Maine to a high of 1690 g C/m2 for Juncus gerardi in Maine. The mean for all plant stands was 650 g C/m2. Since the average carbon content of the MOM was 35.3%, this corresponds to 1850 g dry weight/m2 per year. As a measure of the relative activity of the total pool of macro-organic material in the soil, turnover times were calculated by dividing the total macro-organic matter by the annual increments. Within the MOM pool there are several components with turnover times varying from days to years. The turnover time for the entire pool ranged from 18 months in two Georgia salt marsh plant stands to 224 months for one in Maine. In the two instances where values for a species could be compared between Maine and Georgia, the turnover time was shorter at the more southerly site. These results can probably be attributed to slower microbial decay rates in the cooler climate. In Georgia and Maine where the turnover values for a species were determined for two elevations, the time was shorter at the lower elevation. SUFFICIENT SALT MARSH aboveground plant part dynamics and primary production studies have been reported in the literature to warrant several comprehensive reviews (Keefe, 1972; Turner, 1976). In spite of the fact that most of the fixed carbon reserves of salt marshes are in the soils (Gallagher, 1974) the underground portions of salt marsh plant dynamics has received relatively little attention (Valiela, Teal and Pearson, 1976; Stroud, 1976; de la Cruz and Hackney, 1977). In 1 Received for publication 24 March 1978; revision accepted 5 October 1978. This work was supported in part by grants from the Sapelo Island Research Foundation, Inc., Contract No. DACW3973-C-01 10 as part of the Dredged Material Research Program administered through the U.S. Army Engineer Waterways Experiment Station, and National Science Foundation grant OCE75-20842-A02. 2 Present addresses: U.S. Environmental Protection Agency, Corvallis Environmental Research Laboratory, 200 SW 35th Street, Corvallis, Oregon; and Department of Botany, University of Georgia, Athens, Georgia. Contribution No. 363 from the University of Georgia Marine Institute, Sapelo Island Georgia. the study reported here we conducted a sampling program aimed at identifying the types of underground macro-organic matter (material not passing a 1-mm sieve) profiles found within and between species in a given marsh and along the latitudinal gradient of the eastern coast of the United States. Further, we designed the program to examine the seasonal dynamics of the quantity of macro-organic matter (MOM), from which we computed minimum values for underground production. METHODS AND MATERIALS-Samples were collected along the U.S. Atlantic Coast gradient from March 1972 to April 1975 from sites in Georgia, Delaware and Maine (Table 1). In Georgia, Spartina cynosuroides was sampled on a small island near the mouth of the Altamaha River where water salinity was usually less than 3%o. Borrichia frutescens, Distichlis spicata, Spartina patens, and Sporobolus virginicus were sampled in marshes developed along creeks behind the dune complex on the eastern

Detritus and juvenile salmon production in the Nanaimo Estuary : I. Production and feeding rates of juvenile chum salmon (Oncorhynchus keta)

Abstract: Theories of food chain dynamics have important implications for the management of marine resources. As yet, however, there are few empirical studies of the food chain dynamics of resource species against which these theories can be judged. This paper compares the food requirements of juvenile chum salmon (Oncorhynchus keta) in the Nanaimo Estuary with the productivity of their principal food species. Chum were present in the estuary from March until June and the estuary population ranged up to 4.1 million in May 1975 and 2.4 million in April 1976. The average weight of chum was 0.66 g in 1975 and 0.65 g in 1976, and their rate of growth averaged ~6% body weight per day in both years. Food intake estimated by three independent methods ranged 4.4–18% body weight per day and was assumed to average 15% body weight per day. Annual fry production was 2381 kg in 1975 and 1122 kg in 1976. Food intake was 6184 kg in 1975 and 2815 kg in 1976. The principal dietary item in both years was harpacticoid copepods. In 19...

Distribution of suspended bacteria in neritic waters south of Long Island during stratified conditions1

Abstract: Ahstruct Bacteria (direct counts) averaged 1.85 x 10” cells * ml-’ in highly stratified waters south of Long Island during September 1976. The vertical distribution of bacteria was related to the location of the thermocline and the bottom, the horizontal distribution to distance from shore indicating longshore continuity. The average numbers of bacteria (X 10” cells * ml-l) in neritic water were 2.14 nearshore, 1.96 midshelf, and 0.67 near the shelf break. Overall the number of bacteria was positively correlated with chlorophyll and ammonium concentrations but not with mcasurcments of heterotrophic activity. The location of a large, relatively inactive population of bacterial cells near the surface of the highly stratified midshelf water corresoonds to the approximate location of unusually persistent phytoplankton blooms observed during March-f&e 1976. The importance of suspended heterotrophic bacteria in seawater has been recognized for many years. Their role includes decomposition of both particulate (Waksman 1934) and dissolved (ZoBell and Grant 1943) organic matter and transformation of such substances into bacterial biomass. Krizcncky and Podhradsky in 1927 (cited in ZoBell 1954) stressed the potential importance of bacteria as a food source for aquatic animals. Necessary steps in evaluating the role of bacteria in the overall productivity of marine ecosystems are determination of their biomass, in situ rates of decomposition of organic matter, and secondary productivity. We discuss here the’ distribution of bacteria and their activity relative to concurrent (September 1976) and historical data on the distribution of chlorophyll in neritic waters south of Long Island, New York.

Analysis of heterotrophic microplankton in an upwelling area

Abstract: The role played by heterotrophic microplankton in the synthesis and flux of organic matter was studied in the Punta San Juan Coastal upwelling region off Peru in April and May 1977. The data from a drogue study show that the main component of the planktonic community in the freshly upwelled water is the microheterotroph component. The biomass of bacteria (49 mg C/ m3) in the newly upwelled water exceeded by two orders of magnitude the biomass of phytoplankton. Total respiration of the microheterotrophs (3.35 g C/ m2/ day) exceeded by three-fold the primary production, indicating that the heterotrophic respiration was dependent on the content of organic matter preexisting in the upwelling waters. In the upwelling at Punta San Juan the biomass of protozoa was 1 g/ m3 (wet weight) at the depth of the maximum concentration; this concentration is the highest ever observed in sea water. During transects on a section normal to the coastline an abundant population of dinoflagellates (5 to 40 × 103 /1) of the genera Gymnodinium and Prorocentrum were found in anoxic waters at 50 to 100 m. Strong red tide water coloration was observed as a result of a bloom of the autotrophic ciliate Mesodinium rubrum; the biomass of the ciliate at the surface in calm weather reached 50 to 70 g/ m3 (wet weight) and the cell density was 2 to 4 × 106/l.

In situ measurements of net primary production in a Colorado mountain stream

Abstract: Six stations were established on a Colorado mountain stream, and net primary productivity was measured in situ during all seasons. For 24-hour periods the dissolved oxygen and temperature of the water were electronically monitored over an undisturbed 1 x 1 m section of rubble bottom enclosed by a large plastic dome tightly fitted to the substrate. A submerged pump maintained a current within the dome, and the whole apparatus was submerged below the stream level. The bottom community net metabolism varied between heterotrophy and autotrophy with no correlations with altitude, season, light, water chemistry, and temperature. Readings were all very low and ranged from -27.38 to 35.59 grams of carbon fixed per square meter per year. There were no correlations between biomass of the bottom fauna and net community productivity.

Diel Patterns of Phytoplankton Productivity and Extracellular Release in Ultra‐Oligotrophic Lake Tahoe

Abstract: Phytoplankton in Lake Tahoe is dominated by diatoms and chrysophytes. High water transparency permits photosynthesis to a maximum depth of over 100 m. Average annual primary production rates in the entire trophogenic zone are 0.5–0.6 g C m−3 year−1. Nutrient concentrations and biomass parameters showed little diel variation. Photosynthesis in mixed water columns decreased in the afternoon. This decline can be attributed to inactivation of algae by overoptimal light during mid-day hours. As the summer season progressed, algae became adapted to high light intensities and thus were less susceptible to light inhibition. Extracellular release by algae averaged 12.5 ± 7.4% of assimilated carbon without significant vertical differences. Damage of cells by light thus can be excluded. Respiratory losses overnight comprised at least 30% of the carbon assimilated during the preceding day. Integral photosynthesis showed a logarithmic relationship to incident light which can be used to predict daily production rates from mid-day incubation with an error of well below 10%.

Marine production mechanisms

Abstract: 1. Introduction M. J. Dunbar 2. Primary production in Frobisher Bay, Arctic Canada E. H. Grainger 3. Primary production in some tropical environments S. Z. Qasinm 4. Biological productivity of some coastal regions of Japan K. Hogetsu 5 Factors determining the productivity of South African coastal waters J. R. Grindley 6 The Strait of Georgia Programme T. R. Parsons 7. Biological production in the Gulf of St Lawrence M. J. Dunbar 8. Patterns of the vertical distribution of phytoplankton in typical biotopes of the open ocean H. J. Semina 9. The Dutch Wadden Sea M. van der Eijk 10. Seaweed utilization in the Philippines G. T. Velasquez 11. Trophic relationships in communities and the functioning of marine ecosystems: I Studies on trophic relationships in pelagic communities of the Southern Seas of the USSR and in the tropical Pacific T. S. Petipa 12. Trophic relationships in communities and the functioning of marine ecosystems: II Some results of investigations on the pelagic ecosystem in tropical regions of the ocean E. A. Shushkina and M. E. Vinogradov 13. Soviet investigation of the benthos of the shelves of the marginal seas A. A. Neynian 14. Studies of trophic relationships in bottom communities in the southern seas of the USSR E. A. Yablonskaya 15. Studies of the pattern of biotic distribution in the upper zones of the shelf in the seas of the USSR A. N. Golikov and O. A. Scarlato.

Populationsdynamik, produktivität und energiehaushalt des wattwurmsArenicola marina (Annelida, Polychaeta)

Abstract: Dispersion, abundance dynamics, size-frequency, mortality, growth, biomass, productivity, energy flow, germ-cell development, sex ratio, breeding season, natality and fertility ofArenicola marina were investigated from 1975 to 1977 at four intertidal study areas near Roscoff (Brittany, France). Numerical abundance is highest in the upper shore. Here the population consists chiefly of small immature worms. Towards the lower shore, abundance decreases whereas individual size increases. Annual variations in abundance are greatest in the upper shore. Variation in abundance is essentially influenced by wave movement. There is evidence supporting the view that, in spring, small lugworms migrate from the upper part of the shore all over the tidal flat area. Growth rates vary significantly within the areas examined. Generally they increase with increasing duration of submersion.A. marina is the most important producer among the polychaetes so far examined. Productivity is highest in sheltered flats and decreases with increasing disturbance by water movement. Energy budgets of lugworms are estimated. Energy requirements and energy supply are discussed, particularly the extent to which filtration in the headshaft of the burrow may cover food requirements. A brief description of gametogenesis is given. In 1975 at Penpoul the breeding season began in October and lasted two months. At the other study areas— Le Pouldu, Le Guillec and Le Dossen — spawning began in October and lasted one month. In 1976 spawning began earlier but terminated at the same time as in 1975.

Annual and Seasonal Variation of Individual Weights of Adult Water Insects. Schlitz Studies on Productivity, No. 36

Abstract: Annual and seasonal variations of individual weights of dominant species of aquatic insects in Breitenbach, Germany, are described and the probable reasons of variations are discussed. Variations are not correlated in different species, and there appears to be no uniform explanation of the phenomenon.

Phytoplankton Population Dynamics and Productivity in a Sewage-Enriched Tidal

Abstract: Calico Creek differs from neighboring estuaries in that it receives sewage effluent, and its waters therefore contain ample nutrients. High nutrient levels enable the phytoplankton population, which is probably light-limited, to reach densities of 109 cells. 1- during the summer, 2 to 3 orders of magnitude higher than the surrounding, nutrient-limited populations. At cell densities greater than 108 cells. 1- the number of dominant species is greatly reduced, and the level of diversity drops sharply. Calico Creek also differs by being very shallow; the population can be drastically affected by high runoff. The productivity of both the phytoplankton and the surrounding Spartina marsh is much higher than the neighboring unpolluted estuaries. Unlike the larger and more stable estuaries nearby, the dependence of the population on the effluent for nutrients, the possibility of toxic materials entering the creek with the effluent, and its small size make Calico Creek subject to sudden change.

Limnology of nine Westland beech forest lakes

Abstract: Lakes in the beech (Nothofagus sp.) forest foothills between Greymouth and Hokitika, Westland, are characterised by amber‐coloured waters. Microbiological, biochemical, and chemical analyses of samples from nine such lakes during March 1976 indicate that they are unproductive. Microbial biomass was intensively investigated in heavily stained Lakes Haupiri and Lady and in least‐stained Lake Brunner. A combination of adenosine triphosphate assays, Utermohl phytoplankton counts, and autoradiographic biomass determinations revealed a greater bacterial than algal biomass in heavily stained lakes, a highly unusual phenomenon which suggests that most of the production of organic matter was allochthonous. Autochthonous productivity was low, probably because biologically available phosphorus was very scarce and because discoloration reduced the transparency of the water. Hypqlimnetic oxygen depletion was slight during this period of maximum thermal stratification; decomposition of organic matter was apparently inc...

Aquatic productivity and water quality at the upland-estuary interface in barataria basin, louisiana

Abstract: Three fresh- to brackish-water coastal lakes and streams at the upland-estuary interface of Barataria Basin, Louisiana, were studied for a one-year period. Measurements of community production and metabolism, chlorophyll a, and water column nitrogen and phosphorus were used to assess the functional relationship the upland connection has with the estuary. Aquatic community gross production was highest in the lake immediately adjacent to the New Orleans West Bank uplands (696 g C m-2 yr-1). A pattern of decreasing community hetero- trophy was exhibited in the lakes from upland to the lower estuary. Active chlorophyll a, nitrogen, and phosphorus were also highest in the streams and lake adjacent to the upland area. Chlorophyll a averaged over 55 mg m-3 at these locations; remaining stations averaged only 11 mg m-3. Nutrient levels were lowest in lakes, suggesting incorporation into plant biomass and sediments. Dissolved carbon and nutrient components made up an average of 78% of total concentrations.

Phytoplankton population dynamics and productivity in a sewage-enriched tidal Creek in North Carolina

Abstract: Calico Creek differs from neighboring estuaries in that it receives sewage effluent, and its waters therefore contain ample nutrients. High nutrient levels enable the phytoplankton population, which is probably light-limited, to reach densities of 109 cells·1−1 during the summer, 2 to 3 orders of magnitude higher than the surrounding, nutrient-limited populations. At cell densities greater than 108 cells·1−1 the number of dominant species is greatly reduced, and the level of diversity drops sharply. Calico Creek also differs by being very shallow; the population can be drastically affected by high runoff. The productivity of both the phytoplankton and the surroundingSpartina marsh is much higher than the neighboring unpolluted estuaries. Unlike the larger and more stable estuaries nearby, the dependence of the population on the effluent for nutrients, the possibility of toxic materials entering the creek with the effluent, and its small size make Calico Creek subject to sudden change.

Phytoplankton and Primary Production of Lakes in the Matamek Watershed, Quebec

Abstract: The productivity of three Shield lakes on Quebec's North Shore was found to be comparable with that of the most oligotrophic lakes known. Factors contributing to this condition may be that the moderately sized lakes of this study are deep relative to their surface areas, highly stained by humic substances, of very low conductivity, and contain little dissolved CO2. Standing crops of phytoplankton are very low, never exceeding 600 mg/m3. Chrysophyceae are dominant over all other classes of algae in both biomass and numbers, comprising approximately 50% of the fresh weight throughout the season. The abundance of micro-flagellates implies a large surface area to volume ratio and the ability to move are an advantage in a nutrient poor environment. Much of the phytoplankton present may grow heterotrophically and energy additions from the terrestrial environment may be extremely important to the productivity of northern lakes when photosynthetic production is not significant.

The energy potential of forest biomass in Ireland.

Abstract: Wood has several important advantages over other biomass sources for energy production. Vigorous juvenile growth, low moisture content and the capacity to coppice are the ideal characteristics of species grown for this purpose. The Forest and Wildlife Service is participating in an EEC Energy Project with the aim of investigating the energy potential of forest biomass. The first phase of this project, consisting of growth trials of a range of woody species at four representative forest sites (western blanket bog, midland raised bog, old red sandstone podzol and drumlin-gley) was established in 1977. Plant spacing was narrower than that used in conventional forest management practice in order to increase productivity per unit area. Early results of plant survival and dry matter production from the growth trials indicate that, of the species being investigated, lodgepole pine, Sitka spruce and Eucalyptus are performing best. Above average forest land is required for satisfactory growth of species capable of coppicing and, of the four sites, only the drumlin-gley appears to fulfil this requirement. The possibility of direct seeding reducing the establishment costs of the successful, though non-coppicing conifers, is being tested. Preliminary results from these trials, of seedling emergence, are encouraging. Yields of forest biomass ranging from 25-40 tonnes dry matter/ha/year have been obtained on productive forest lands in the United States; this is a productivity almost competitive with coal at 1974 prices. Similar yields are possible in Ireland on comparable sites. Estimates of the possible energy contribution of forest biomass, as waste materials and as pure energy plantations, are made. It is postulated that the energy import demands of this country could be reduced by 27% based on 1977 imports and assuming the equivalent of half the total forest area were managed on a 20 year rotation.

Dissolved glucose in a bayou estuary, possible sources and utilization by bacteria

Abstract: Surface and bottom samples were collected twice a month over a period of one year from three stations in Bayou Texar, Pensacola, Florida. Samples were analyzed for primary productivity, inorganic carbon, bacterioplankton heterotrophic productivity, dissolved glucose, and bacterial numbers. Dissolved glucose concentrations were generally high and displayed a seasonal pattern with variations being accompanied by corresponding changes in rates of glucose uptake by bacteria. A relationship between dissolved glucose and carbon fixation was found to exist at the upper station but diminishes toward the lower stations. It is believed that this is most likely the result of increased mixing by wind action.

II. Productivity under grazing

Abstract: New Zealand paspalum selections were compared with commercially available lines in mixed pastures under sheep grazing. Dry matter production, species contribution, persistence, soil moisture levels, weed ingress, and herbage digestibility were assessed. All pastures containing paspalum produced more than those sown with ryegrass alone. Those containing the selections had substantially greater dry matter production during summer than those with the commercial lines. There was also a carry-over effect of the selections into autumn, but no effect in winter and spring. The selections were never less persistent than the commercial lines. The significance of including a more productive paspalum component in mixed pasture is discussed.

Effects of habitat on stand productivity in the White Mountains of New Hampshire

Abstract: Mean annual biomass production of sapling stands was higher on washed tills, which have a hardwood climax, than on habitats having a softwood climax. However, biomass production of poletimber stands did not differ significantly among habitats. Apparently, differences among habitats in characteristics species composition tends to mask differences in biomass productivity. Demanding species growing on a good site will produce about the same biomass as less demanding species growing on a medium site. Mean diameter growth of sugar maple and yellow birch was much better on fine till and enriched habitats than on the other habitats covered by the study; and preliminary results from older stands indicate that board-foot production is much higher on the better habitats. In conducting intensive silvicultural operations, it is important to favor species well adapted to habitat.

Aboveground productivity and floristic structure of a high subalpine herbaceous meadow

Abstract: This is the publisher's version, which may also be found at: http://instaar.colorado.edu/AAAR/journal_issues/abstract.php?id=586