Showing papers on "Productivity (ecology) published in 1975"

Limnology: Lake and River Ecosystems

Abstract: Preface 1 Prologue 2 Water as a Substance 3 Rivers and Lakes - Their Distribution, Origins, and Forms 4 Water Economy 5 Light in Inland Waters 6 Fate of Heat 7 Water Movements 8 Structure and Productivity of Aquatic Ecosystems 9 Oxygen 10 Salinity of Inland Waters 11 The Inorganic Carbon Complex 12 The Nitrogen Cycle 13 The Phosphorus Cycle 14 Iron, Sulfer, and Silica Cycles 15 Planktonic Communities: Algae and Cyanobacteria 16 Plantonic Communities: Zooplankton and their Interactions with Fish 17 Bacterioplankton 18 Land-Water Interfaces: Larger Plants 19 Land-Water Interfaces: Attached Microorganisms, Littoral Algae, and Zooplankton 20 Shallow Lakes and Ponds 21 Sediments and Microflora 22 Benthic Animals and Fish Communities 23 Detrirus: Organic Carbon Cycling and Ecosystem Metabolism 24 Past Productivity: Paleolimnology 25 The Ontogeny of Inland Aquatic Ecosystmes 26 Inland waters: Understanding is Essential for the Future References Appendix Index

Vegetation of the santa catalina mountains, arizona. v. biomass, production, and diversity along the elevation gradient'

Abstract: Measurements were taken in 15 communities along the elevation gradient from fir forest at high elevations, through pine forest, woodlands, and desert grassland, to deserts at low elevations in the Santa Catalina Mountains, Arizona, and in a Cercocarpus shrubland on limestone. Eight small-tree and shrub species of woodlands and deserts were subjected to dimension analysis by the Brookhaven system. Aboveground biomass decreased along the elevation gradient from 36-79 dry kg/M2 in fir and Douglas-fir forest to 0.26-0.43 kg/M2 in the desert grassland and two desert samples. Net aboveground primary productivity similarly decreased from 1,050-1,150 g/m2 * yr in mesic high-elevation forests to 92-140 g/m2 - yr in desert grassland and deserts. Both biomass and production show a two-slope relation to elevation (and, probably, to precipitation), with a steeper decrease from the high-elevation forests to the mid-elevation woodlands, and a less steep decrease from dry woodlands through desert grassland into desert. The two groups of communities at higher vs. lower elevations also show different relations of leaf area index and chlorophyll to elevation and to productivity. The two groups may represent different adaptive patterns: surface-limiting, with low pro- ductivity in relation to precipitation but high production efficiency in relation to surface in the more arid lower elevations, vs. surface-abundant, with high productivity relative to pre- cipitation based on high community surface area, but lower production efficiency in relation to this area, in the more humid higher elevations. Vascular plant species diversity shows no simple relation to productivity, but decreases from high-elevation fir forests to the pine forests, increases from these to the open woodlands, and decreases from dry woodlands through the desert grassland and mountain slope desert to the lower bajada (creosotebush) desert.

Methods of Assessing Terrestrial Productivty

Abstract: Major contrasts between aquatic and terrestrial communities result from the short life spans and small accumulation of biomass in aquatic plants, and the longer life spans and substantial accumulation of biomass in land plants. The relationship can be expressed as the biomass accumulation ratio: the ratio of the standing crop or biomass present, to the annual net primary productivity. Such ratios are fractions of one in most aquatic communities, but range from one up to 50 or more in terrestrial communities. Significant differences in structure, function, and diversity of communities are related to this contrast between rapid turnover of the community’s organic matter in short-lived organisms, and accumulation of the productivity from several years in the complex structure of woody organisms (Whittaker and Woodwell, 1971b). The contrasts extend to the prevalent means of measuring productivity.

Brown pelicans: improved reproduction off the southern California coast

Abstract: Although still about 30 percent too low for population stability, productivity of California brown pelicans at their two northern colonies has improved significantly since 1971. Numbers of adults breeding probably reflect food supplies and recruitment from more successful colonies to the south, but improving fledging rates (up to 0.9 young per nest in 1974) reflect better egg survival and improving eggshell condition, with declining DDE contamination in anchovies, their major food source.

Mangrove Forests and Aquatic Productivity

Abstract: The connection between terrestrial primary production and aquatic secondary production has often been overlooked. In many streams, rivers, lakes, and even coastal waters, the most important source of plant energy is not phytoplankton or benthic algae, but detritus particles originating from trees, shrubs, sedges, and grasses in the watershed. This can occur in any situation where surplus production of plant vascular material drains into a body of water. Mangrove swamps appear to present such a situation.

A Production Model for Myriophyllum spicatum L.

Abstract: The mathematical model WEED was derived to study the productivity of the submerged macrophyte Myriophyllum spicatum in the littoral of Lake Wingra, Madison, Wisconsin. The model coordinates four biomass compartments with selected physiological processes evaluated for a stratified meter—squared water coloumn. Light and temperature are the primary environmental forcing functions. The model considers growth form (depth distribution of biomass), total biomass/meter—squared, the depth profile of photosynthesis and macrophyte contributions to dissovled and particulate organic matter pools in the water column. The model output was tested against field data for seasonal patterns of standing crop, depth distribution of biomass and depth profile of photosynthesis for a rooting depth of 150 cm. WEED has permitted the simulation of macrophyte growth response to changes in environmental conditions and has outlined areas of needed research. See full-text article at JSTOR

Effects of Species Removal on an Old‐field Plant Community

Abstract: The effect of removing the dominant grasses on the net productivity of subordinate forb species was investigated in the perennial—grass stage of old—field succession. Removing the dominants increased the net productivity of subordinate species from 0.49 g/m2°day to 1.44 g/m2°day. The increased net productivity of subordinates was due to increased productivity by almost all subordinate species. This increase was not sufficient to equal the total net productivity of the unaltered community (2.26 g/m2°day). Net productivity by subordinates in the absence of dominants was less than that reported for earlier successional stages where the forbs are the dominant producers. However, this difference might have been caused by relatively low rainfall at the time of this experiment. See full-text article at JSTOR

A fifteen-year record of biotic metabolism in the Northern Hemisphere

Abstract: THE health and productivity of the biosphere are essential to man's welfare. Several scientists have speculated that global productivity and/or biomass should be increasing because of such factors as plant fertilisation from industrially derived atmospheric CO2 enhancement1,2. Others have maintained that global primary production and biomass must be decreasing because of pollution effects, such as from acid rain, and forest cutting3,4. There are some (rather controversial) tree-ring data that may support this view5,6. If one or the other of these trends is true, there would be a shift in the absolute and relative rates of global photosynthesis, respiration and their ratio (the PR ratio). Earlier attempts to ascertain any such trends from long term changes in atmospheric CO2 concentration have been frustrated by difficulties in distinguishing changes in biospheric retention from changes in the uptake or discharge of other reservoirs, principally the sea and industrial sources7,8. We present here a new model for the examination of such trends that we believe avoids such problems by focusing on potential changes in yearly patterns of atmospheric CO2.

Dynamics and productivity of two populations of the benthic tube-dwelling amphipod Ampelisca brevicornis (Costa) in Helgoland Bight

Abstract: Population dynamics of the amphipod Ampelisca brevicornis were investigated from 1969 to 1972 at two sublittoral (28 m) fine sand stations. Juveniles appear between the end of July and the end of September; they reach maturity in the following year. Females propagate once. Numerical abundance and biomass (up to 2.8 g wet weight per m2) are highest from October to December. In winter the population density is low, and a further decrease occurs in spring. Biomass values between June and August are below 0.3 g per m2. Productivity was calculated on the basis of monthly abundance and biomass figures, and on the basis of monthly size class distributions. The second procedure gives somewhat higher values: a mean annual biomass of about 1 g wet weight per m2, an annual production of about 4 g per m2 , and a turnover ratio of about 4. Of the annual production 60–70 % is consumed in October, November and December, 15–23% in May, and only 8–22 % during the remaining 8 months of the year. A turnover rate of...

Mineral Nutrient Pool and Cycling in a Missouri Forest

Abstract: This paper reports on part of an investigation of the composition, structure, productivity, biomass and nutrient cycling in an oak-hickory forest in the Ashland Wildlife Area (AWA) in central Missouri, U.S.A. The study area has been described in previous papers (Rochow 1972, 1974a). Much of the soil consists of 'steep stoney land' derived mainly from limestone on 7-23? slopes or Weldon soils derived mainly from loess on 2-5? slopes. The main forest-type is dominated by Quercus alba L.; however, the steeper slopes and bottomlands are composed of various tree species depending on the aspect. Estimates of biomass, productivity and litter fall have already been published (Rochow 1974a, b). Estimates are presented here for the amounts of macro-nutrients in the above-ground standing crop and for some of the rates of cycling in the ecosystem.

Nutrients, biomass and primary productivity of nannoplankton in eutrophic Lake Vombsjon, Sweden

Abstract: Seasonal variations of physical and chemical factors were studied in the eutrophic, usually totally-circulated, Lake Vombsjon in South Sweden, 1970 through 1973. Biomass and primary productivity of nannoplankton (< 20 jm) and of the total phytoplankton community were investigated 1971 through 1973. Nannoplankton biomass, estimated as chlorophyll a, was highest in early spring (3040 mg m-3) and averaged 20 mg m-3 in summer. A 10-fold variation of nannoplankton biomass occurred throughout the year, compared with a 25-fold variation for netplankton biomass. During late summers, when temperature was high and the surface water enriched with nutrients, blue-green algae (netplankton) dominated. Productivity of nannoplankton and of the total phytoplankton community was 3-193, and 8-550 mg C m-2 h-1, respectively. Correlations between biomass and productivity were established. A significant difference in the photosynthetic capacity of nannoplankton, as compared with netplankton, was found. Mean annual productivity of the total phytoplankton community was 525 g C m-2 yr-1, of which about 50%. was photosynthesized by nannoplankton.

Biomass and Productivity of an Alder Swamp in Northern Michigan

Abstract: Total aboveground dry weight biomass and annual production were determined for two sites of different soil texture in an alder swamp of Michigan's upper peninsula. The more poorly drained site A av...

Lake Trummen restoration project II. Bacteria, phytoplankton and phytoplankton productivity: With 8 figures and 1 table in the text

Abstract: The number of aerobic heterotrophic bacteria in the water did not change after the restoration of Lake Trummen. A marked decrease of protein, starch and glucose decomposing bacteria was observed. I...

Historical Survey of Primary Productivity Research

Abstract: From a recent paper on the history of the discovery of photosynthesis (Rabinovitch, 1971), it appears that many biologists equate photosynthesis with productivity and identify the raw materials of photosynthesis (water, carbon dioxide, and sunlight energy) as the direct controls of productivity. Photosynthesis and primary productivity are not so simply identical. Indeed, primary productivity—the actual energy bound into organic matter—is the product of photosynthesis. Yet primary productivity requires more than photosynthesis alone. The uptake and incorporation of inorganic nutrients into the diverse organic compounds of protoplasm are essential to the photosynthesizing organism. Temperatures govern annual productivity in various ways that do not result from temperature dependence of the photosynthetic process. On land, productivity is strongly affected by the availability of water, not primarily for use in the photosynthetic process itself, but to replace the water lost through the stomata that are open to allow carbon dioxide uptake.

The Natural History, Ecology and Production of the Crayfish, Pacifastacus leniusculus, in a Subalpine Lacustrine Environment

Abstract: Author(s): Flint, Robert Warren | Abstract: The natural history and ecology of the California Crayfish, Pacifastacus leniusculus (Dana}, was investigated in a portion of subalpine Lake Tahoe from March 1974 through February 1975. Three specific areas of the lake were chosen for study because of their variability in bottom contour, substrate type and primary production. Population estimates in these areas ranged from 16,561 to 192,448 crayfish with almost equal distribution of sexes. Mean standing crop and annual production of the population were estimated at 99.77 and 30.56 g/m2 respectively.Both sexes matured in their fourth year, mating took place from late Sep­tember through October, and hatching occurred in July. Reproductive performance was 78% of the potential capacity.Age structure of the crayfish population varied in the three areas. The avnilable cover in one of these areas was identified as the limiting factor responsible for slower growth rate and smaller mean size at onset of sexual maturity. Mortality rate was also much higher at this location. The population age structure consisted of at least 9 age classes. At recruitment carapace length of the young was 3.25 mm and the largest adult taken was 57.0 mm (C.L.}.Crayfish occupied shallow water during the summer and fall months. Decreasing water temperatures and sunlight were identified as the major stimuli causing the population to move into deeper water (to 100 m) where they remained until the following June. Frequent storms with high winds in late fall caused high mortality rates among those crayfish-that did not move to deeper water. Nocturnal activity prevailed and nightly they left their crevices and burrows on the slopes and fed on the open sand flats or in the boulder zones near shore. Adult P. leniusculus fed mostly on "aufwuchs", macrophytes, and detritus while the juvenile diet consisted of 47% animal material.The role of crayfish grazing intensity on periphyton primary productivity was investigated in field and laboratory enclosures where the ratio of crayfish to substrate was varied (in artificial microcosms). Primary productivity was enhanced in a low density crayfish field site and inhibited in a high density site. These results were duplicated in laboratory trials, where grazer biomasses less than 131 g/m2 stimulated productivity while it was inhibited by overgrazing when crayfish exceeded 204 g/m2. Grazing effects were also estimated on higher aquatic plant beds found in the littoral area of Tahoe by inclusion-exclusion experiments. Nutrients contributed from feces of the crayfish significantly stimulated algal primary productivity.

Some effects of agricultural development and fluctuations in water level on the phytoplankton productivity and zooplankton of a New Zealand reservoir

Abstract: Summary In Lake Mahinerangi, a New Zealand hydro-electric supply reservoir, phytoplankton productivity increased from an annual average of 76 mg earbon m−2 day^−1 in 1964–66 to 210 mg carbon m−2 day−1 in 1968–70. It is likely that the increase was due partly to water levels being higher in 1968–70. Results of multiple regression analyses on the annual productivity curves for 1964–66 had suggested that water level, with temperature, was a major factor influencing the productivity at near-optimal light intensity. In the interval between the two studies the first agricultural land-development, amounting to 3% of the drainage basin, was carried out, and there is evidence that this development also contributed to the increase in phytoplankton productivity. Streams which drain the developed land were richer in phosphate and nitrate than the unmodified ones. Phosphate concentrations in the lake increased, but other chemical changes were slight. There were no major changes in the species composition of the phyto-plankton. None of the three dominant species of zooplankton increased, but there were substantial increases in two less abundant taxa, Daphnia carinata King and Cyclopoida. The relative increase in Daphnia is consistent with the hypothesis that large zooplankton enjoy a competitive advantage over smaller species. Similar changes are noted from elsewhere.

A Model Explaining Successional Change in Standing Crop of Thermal Blue‐Green Algae

Abstract: The gross productivity and changes in the standing crop of both biomass and chlorophyll a were measured during ecological succession in a thermal blue-green algal com- munity. The rate of gross production (Pg) in gC * m-2 * h-1 was directly related to the chloro- phyll a (Chl) in mg m-2 and independent of light intensity (Pg 0.018 Chl051). In turn we found a log-log relationship of chlorophyll a (mg * m-2) to biomass (x) in g * m-2 (Chl = 0.59 x140). The respiration rate (R) in gC * m-2 * day-1 of the algal mat was directly proportional to the biomass (R 0.0164 x). The increasing concentration of chlorophyll a per unit bio- mass as succession proceeded in these thermal ecosystems contrasted with the decreasing chlorophyll concentration noted in other ecosystems. The equations were combined into a nonlinear model, and algal growth during succession was predicted on the basis of algal density, free CO2 concentrations in the water, and day length. These predictions agreed closely with the field data on biomass increase during succession.

Organization and Dynamics of Collembola Populations on Hardangervidda

Abstract: The present study is part of the Norwegian International Biological Programme (IBP) concerning productivity of tundra ecosystems in alpine regions in central southern Norway. Three different habitats were examined: a wet meadow, a dry meadow and a dry lichen heath, as described by Sonesson et al. (1975), and Solhoy (1972).

Effects of Forest Fertilization on Two Southeast Alaska Streams

Abstract: Four streams in southeast Alaska were studied to determine the effects of forest fertilization with urea on basic productivity and water quality. An initial, short-term increase in ammonia-nitrogen was observed in the treated streams, and nitrate-nitrogen levels increased and remained high compared to control stream levels during the year following treatment. Concentrations did not approach those considered toxic to aquatic life or unsafe for human consumption. Changes in biomass of periphyton and benthic fauna as a result of fertilization were not detected.

Secondary productivity of Leptodora kindtii in Lake George, N. Y

Abstract: Biomass and turnover rates were used to estimate secondary production of Leptodora kindtii in Lake George, N. Y., during 1970 and 1971. Maximum values for production during both years were measured in mid-July. The average annual production was 55 percent greater in 1970 than in 1971. In 1970, there was a S-N gradient in productivity with the southern basin being 1.5 times as productive as the northern basin. However, the opposite was true in 1971 when there was an increase in production along the S-N gradient. Variation between the data sets was most likely due to localized annual variation in prey and/or predator densities. It was concluded that although there may be localized seasonal or annual variations, Leptodora production did not exhibit a gradient of production within Lake George as had been reported for lower trophic levels. (auth)

Exchange of carbon, nitrogen and phosphorus in Lavaca Bay, Texas marshes. Volume II. The role of plants in nutrient exchange in the Lavaca Bay brackish marsh system. Final report

Abstract: The role of plants in nutrient exchange in the Lavaca Bay saltmarsh was studied. The rate of nutrient exchange, the comparative magnitude of the contributions of the various components of the marsh system to the exchange, and the effects of summer drying periods were studied. The rates of nutrient exchange varied with water level and were influenced by the effect of previous water levels on the productivity of the system. Algal mat communities released more phosphorus and nitrogen than did marsh grass communities but released less carbon. The release of nutrients from the system is attributed primarily to the products of decomposition. The sediments are an important source of nitrogen and phosphorus and serve as the primary site for nitrification processes. Periods of drying cause an abnormally high nutrient release when flows initially reinundate the area. The high productivity of the saltmarsh enables the marsh to export nitrogen, phosphorus, and carbon to the estuary.