Showing papers on "Productivity (ecology) published in 1987"

Wave energy and intertidal productivity.

Abstract: In the northeastern Pacific, intertidal zones of the most wave-beaten shores receive more energy from breaking waves than from the sun. Despite severe mortality from winter storms, communities at some wave-beaten sites produce an extraordinary quantity of dry matter per unit area of shore per year. At wave-beaten sites of Tatoosh Island, WA, sea palms, Postelsia palmaeformis, can produce > 10 kg of dry matter, or 1.5 × 108 J, per m2 in a good year. Extraordinarily productive organisms such as Postelsia are restricted to wave-beaten sites. Intertidal organisms cannot transform wave energy into chemical energy, as photosynthetic plants transform solar energy, nor can intertidal organisms “harness” wave energy. Nonetheless, wave energy enhances the productivity of intertidal organisms. On exposed shores, waves increase the capacity of resident algae to acquire nutrients and use sunlight, augment the competitive ability of productive organisms, and protect intertidal residents by knocking away their enemies or preventing them from feeding.

Comparative Analyses of Carbon Dynamics in Native and Cultivated Ecosystems.

Abstract: Plant productivity, litter decomposition rates, and soil organic matter accumulation for winter wheat and for unbroken tallgrass prairie in Central Missouri were analyzed and compared. As measured in this 3-yr study, annual production of dry matter above- and belowground for the cultivated system averaged slightly higher than that for the natural vegetation burned every 3-4 yr. Prairie was characterized by greater year-to-year fluctuation of productivity, which in some years exceeded productivity of the cultivated system. More litter and structural biomass older than 1 yr occurred in the prairie, reflecting the perennial nature of the root system. Principal pathways of carbon transfer in both ecosystems were modeled, and mean residence time in major storage compartments estimated. Combined CO2 losses from above- and belowground litter decay, expressed as a percentage of total soil respiration, were twice as great under wheat as for native prairie. A relatively greater fraction of net primary production was available for synthesis of soil organic matter in native prairie. Under equilibrium conditions, decomposition constants for this compartment, however, were similar. Contrasts in community structure and phenology, seasonal dynamics of litter decay, and levels of soil disturbance are suggested influences affecting transfer and storage characteristics.

The water masses of the east coast of Tasmania: seasonal and interannual variability and the influence on phytoplankton biomass and productivity

Abstract: The seasonal and interannual variability of the water masses, nutrients, phytoplankton biomass and primary productivity of the waters off the eastern coast of Tasmania are described. The seasonal and interannual variability in the water masses on the east coast could be explained by the varying influence of tropical and subantarctic waters and the presence of the northern edge of the subtropical convergence north-east from Maria Island. The physical oceanography was dominated by mesoscale events and the influence of the two parent water masses was highly episodic. Subtropical water rarely extended as far south as Tasman Island in summer and subantarctic water never extended as far north as Flinders Island. Data from satellite Advanced Very High Resolution Radiometer (AVHRR) images confirmed the hydrographic data and were used to interpret the seasonal and interannual variability. Interannual variability in maximum summer temperatures at Maria Island was correlated with the southerly extension of subtropical waters and with El Nino/Southern Oscillation events at least until the mid-1970s. There was evidence of a long-term warming at Maria Island and a cyclic fluctuation of 10-15 years in smoothed maximum summer temperatures. The decline in nitrate, and hence the phytoplankton spring bloom, occurred a month earlier inshore than offshore. Long-term data records from the inshore station at Maria Island showed strong interannual changes in the timing of the nitrate decline. The timing of the spring bloom varied from year to year by as much as 4 months. The seasonal cycle of phytoplankton biomass in 1984 and 1985 showed spring (October) and autumnal (April) blooms, with an early summer bloom in December. Low chlorophyll levels in February and March coincided with the influence of subtropical water. The seasonal cycle of phytoplankton biomass was therefore a complex function of seasonal and episodic events. Primary productivity data from the spring of 1984 showed low productivity on the west coast of Tasmania but high productivity on the east coast around Maria Island and the islands in Bass Strait.

The Temporal Scale of Variance in Limnetic Primary Production

Abstract: Substantial variability in the productivity of the world's lakes cannot be explained by methodology, weather, hydrology, or nutrient supply. A deterministic model shows that variable piscivory, cascading through the food web and causing fluctuations in planktivory, herbivory, and primary production, can bring about variability in primary production comparable in magnitude and time scale to the variability that cannot be explained by physical or chemical factors. The variance of productivity and the correlation between primary production and zooplankton biomass are functions of the time scale over which model results were averaged. The scatter of data around regressions of annual production versus nutrient loading represents internal system dynamics at a host of time scales, some of which may be regulated by fish populations. An important consequence of these dynamics is that variances and covariances of limnological variables are strongly related to sampling scale. Nutrient loading, hydrology, and spring ...

Landbird productivity in central coastal California: the relationship to annual rainfall and a reproductive failure in 1986

Abstract: The avian productivity of 51 locally breeding species in coastal grassland, coastal scrub, and mixed evergreen forest habitats was estimated from 11 years of standardized mist-netting data collected between 10 May and 17 August at Point Reyes Bird Observatory’s Palomarin Field Station. A relationship between the number of young birds banded per 100 net hr and the amount of annual (winter) rainfall during the previous season was apparent for the 10 years 1976 to 1985: productivity was low (19 to 32% below the 1 Oyear mean) in years of extremely low rainfall, increased to a maximum (21 to 39% above the IO-year mean) in years of average or slightly above average rainfall, and decreased substantially (20% below the IO-year mean) in years of very heavy rainfall. The number of young birds banded per 100 net hr in 1986, however, was 62.3% below the previous loyear mean and fell well outside the above relationship. This high level of reproductive failure occurred in most of the 51 locally breeding species and was independent of migratory behavior, habitat choice, and nest location. It was not independent of foraging behavior, however, as swallows and woodpeckers, species that feed their young on insects produced in decomposeror detritus-based food chains rather than in primary production-based food chains, showed no significant reduction in productivity. Timing of the decrease in young birds suggests that the onset of reproductive failure occurred in mid-May, well after the nesting season began. Such a large-scale reproductive failure of virtually an entire landbird community has not been reported before and no obvious weather factors appear to explain it. Preliminary data indicate that the reproductive failure was not confined to the vicinity of Palomarin or to central coastal California but rather extended over much of northern California even to the west slope of the Sierra Nevada. It is interesting, but perhaps only coincidental, that several circumstances of this phenomenon, including its timing, appear to coincide remarkably well with the passage of a radioactive “cloud” from the Chernobyl nuclear power plant accident and associated rainfall.

A Model for Evaluating Climatic Productivity and Water Balance of Irrigated Rice and Its Application to Southeast Asia

Abstract: A physiology-oriented dynamic model incorporating crop physiological data on IR36 rice was proposed for the evaluation of climatic productivity and water balance of irrigated rice. The model explained well the location-to-location variations ofactual rice yield in Japan and the U.S.A. The climatic productivity per crop at Bangkok (Thailand) and Los Banos (Philippines) was evaluated to be approximately 9.0 and 11.0 ton/ha for the wet- and dry-season crops, respectively. These values were significantly lower than the 19.3, 15.6 and 13.9 ton/ha evalu­ ated for California, Milano and Niigata, respectively. The lower productivity in tropical Southeast Asia is mainly attributable to the too rapid development ofthe crop due to the higher temperature. Since three to four crops per year are possible in tropical monsoon regions, the annual climatic productivity in tropical monsoon Asia was estimated to be at least twice as high as in the most temperate regions. The climatic water balance at Bangkok and Los Banos was evaluated to be about -460 mm per dry-season crop, implying that at least this amount of irrigation water is necessary for the dry-season rice crop there.

Productivity of the Ecklonia cava community in a bay of Izu Peninsula on the Pacific Coast of Japan

Abstract: Net production of theEcklonia cava community was monitored on a monthly basis for a year, and annual net production was estimated. Growth rate of blades reached a maximum of about 13 g dry wt·m−2·day−1 in spring and a minimum of about 2 g dry wt·m−2·day−1 in late summer. Annual production of blades was calculated to be 2.84 kg dry wt·m−2·year−1. If the growth of stipes is taken into account, annual net production is estimated to be about 2.9 kg dry wt·m−2·year−1. Standing crop was monitored monthly for two and a half years, and a close negative correlation was found between seasonal change in standing crop and net production. Standing crop reached a maximum of about 3 kg dry wt·m−2 in summer and a minimum of about 1 kg dry wt·m−2 in winter. Low productivity in summer at a period of maximum biomass may be explained by the dense canopy and the large area of reproductive portion occupying a blade, which diminish net assimilation.

The dynamics of benthic microbial communities at Davies Reef, central Great Barrier Reef

Abstract: The dynamics of benthic microbial communities were examined within different functional zones (reef crest, reef flat, lagoon) of Davies Reef, central Great Barrier Reef, in winter. Bacterial numbers did not change significantly across the reef with a mean abundance \((\bar x{\text{ }} \pm {\text{ 1 SE)}}\) of 1.3 (±0.6) x 109 cells g-1 DW of sediment. Bacterial production, measured as thymidine incorporation into DNA, ranged from 1.2 (±0.2) to 11.6 (±1.5) mg C m-2h-1 across the reef and was significantly lower in a reef crest basin than in the other zones. Bacterial growth rates (μ) across the reef (0.05 to 0.33 g-1) correlated only with sediment organic carbon and nitrogen. Protozoan and meiofaunal densities varied by an order of magnitude across the reef and correlated with one or more sediment variables but not with bacterial numbers or growth rates. Nutrient flux rates were similar to those found at other reefs in the central and southern Great Barrier Reef and are significantly lower than rates measured in temperate sand communities. In the front lagoon, bioturbation and feeding acitivity by thalassinid shrimps (Callianassa spp.) negatively influenced microbial and meiofaunal communities with a net import of organic matter necessary to support the estimated rates of bacterial productivity. In lagoonal areas not colonized by shrimps, primary productivity (400–1100 mg C m-2d-1) from algal mats was sufficient to support bacterial growth. It is suggested that deposit-feeding macrobenthos such as thalassinid crustaceans play a major role in the tructuring and functioning of lower trophic groups (bacteria, microalgae, protozoa, meiofauna) in coral reef sedments, particularly in laggons.

Productivity and abundance of large sponge populations on Flinders Reef flats, Coral Sea

Abstract: Large populations of flattened sponges with cyanobacterial symbionts were observed on the shallow reef-flats of the Flinders Reefs, Coral Sea. Estimates of these populations indicated as many as 60 individuals with a total wet biomass of 1.2 kg per m2 in some areas. Along a metre wide transect across 1.3 km of reef flat the population was estimated at 530 kg wet weight sponge (mean 411 g m-2). The four prominent species had instantaneous P/R ratios between 1.3 and 1.8 at optimum light such that photosynthetic productivity was calculated to provide between 61 and 80% of sponge energy requirements in summer and 48 to 64% in winter. While such sponge beds are a prominent feature of these reefs, they appear to contribute less than 10% of gross reef-flat productivity.

Intertidal habitats and benthic macrofauna of the Forth estuary, Scotland

Abstract: The intertidal habitats of the Forth estuary are dominated by fine-grained muds, which experience a salinity range of 0–32%, j over the length of the estuary from Stirling to Queensferry. The current total area of the intertidal zone is 23.3 km2, the majority of which is found in the three central bays of Skinflats, Kinneil and Torry Bay. Over the centuries, agricultural and industrial reclamation has reduced by almost 50% the size of the Forth estuary intertidal habitat. The upper estuary has narrow intertidal shores, inhabited almost exclusively by oligochaete worms, which are very abundant due to organic enrichment of the area. The middle estuary is responsible for the greatest biomass and production of the intertidal benthic macrofauna. The lower estuary has a greater diversity of species than the upper and middle estuary, but has a lower biomass and abundance of macrofauna. It is shown that the production/biomass (P/B) ratio of several species in the Forth estuary is lower than that of the same species in other estuaries. This depression cannot be explained by natural environmental variables, and is suggested as being due to the levels of pollutants throughout the area. Despite this depressed productivity, and the threats from further reclamation, the Forth estuary retains abundant populations of intertidal animals, which are an important food source for birds and fish.

Response of Subarctic Pacific diatom fluxes to the 1982–1983 El Niño disturbance

Abstract: Time series sediment trap samples were collected during October 1983 to August 1984 (second year) at 3800 m at station PAPA (50°N, 145° W; water depth 4200 m) in the northeastern North Pacific. Components of diatom fluxes have been measured and compiled with previously published 1982–1983 records (first year). Most diatom species showed significantly lower cumulative fluxes in the second year than in the first. Second-year seasonal flux patterns were also notably different from those in the first year. Many of the differences are attributed to the second year's hydrographic change in density structure in the upper 100 m, resulting in a poor nutrient supply to the euphotic layer. The changes in the density structure were coincidental with the 1982–1983 El Nino disturbance. Such an observed flux decrease was analogous to notable changes in hydrography and biota reported elsewhere in the eastern subarctic Pacific which were reported to be due to the El Nino. Diatom fluxes clearly responded to this unusual climate change as well as to normal seasonal cycles. The valve percentages of each species within total centric diatoms showed monotonous values throughout year 2, when productivity was generally low. The percent values were similar to those of year 1's low production period, consistently indicating that these are low productivity signals. High diatom fluxes were accompanied by high percentages of Chaetoceros, suggesting high productivity signals. This strongly supports the contention that diatoms are sensitive climatic and productivity indicators. Maximum diatom carbon flux is mainly contributed by two taxa, Denticulopsis seminae, the smallest sized and most numerous taxon, and Rhizosolenia styliformis, the largest sized taxon. A sizable contribution of carbon flux by R. alata f. gracillima was observed in year 1, but this was not repeated in year 2 due to the El Nino disturbance.

The invertebrate fauna of grassland and its influence on productivity. 1. The composition of the fauna

Abstract: The invertebrate groups which are of most significance in grassland are briefly reviewed. Factors influencing the abundance and composition of the fauna are considered together with the types of damage caused in grassland, the economic importance of such damage and beneficial effects on soil fertility.

Cattle productivity and nutrient fluxes on an amazon pasture

Abstract: Cattle grazing, defecation and urination rates, growth, and mortality were studied on pasture formed from rain forest in the Amazon territory of Venezuela. Cattle consumed 12-16 percent of total aboveground plant productivity on two pasture sites. The nutrients in this vegetation were recycled to the soil in dung (N, P, Ca, and Mg) and in urine (N and K). Nutrients recycled in cattle excreta were more available to plants and more spatially concentrated than nutrients in litterfall. The stocking rates on two pasture sites were 0.43-0.89 animal units/ha, and cattle productivity ranged from 21 to 42 kg live wt/ha/yr. Nonharvested mortality was 20 percent per year, and there was no successful reproduction. The low growth rates, reproductive failure, and part of the mortality may result from low phosphorus concentration in the grass.

Standing stocks and productivity of phytoplankton off Westland, New Zealand, February 1982

Abstract: In February 1982 there was an intense bloom of dinoflagellates close inshore off West‐land, New Zealand, and dinoflagellates also formed a large proportion of the phytoplankton offshore. Diatoms were present only at the bottom of the photic zone inshore off Wanganui Bluff, where dissolved nitrate‐nitrogen levels were elevated. Most biomass and production parameters were at least twice as large as in winter except for offshore biomass which was larger in winter. Weighted average chlorophyll a concentrations were negatively correlated with the depth of the mixed layer. The relative contribution which the vertical distribution of chlorophyll a, the production per unit chlorophyll a at optimal light intensities, and the initial slope of the light saturation curve made to the relationship between water column production per unit chlorophyll a and incident solar irradiance in inshore and offshore waters is discussed. In the non‐senescent inshore populations dominated by Prorocentrum micans, 91% of the ...

Structure, Dynamics and Production of Mesozooplankton Community in the Bothnian Bay, Related to Environmental Factors

Abstract: Studies on the zooplankton community of the Bothnian Bay (BB), the northernmost basin of the Baltic Sea, were carried out in 1976–78. Only 8–14 taxa dominated in the zooplankton community. The highest abundances and biomasses occurred during the warmest period or immediately afterwards, in July–September. The production of zooplankton was estimated to be 3.1–7.8 g C · m−2. a−1 in the coastal area and 2.5–3.6 g C · m−2 · a−1 in the open sea. During the short growing season (June–September) the biomass turnover took place in about 11 days. The productivity of zooplankton is discussed in relation to available food of both autochthonous and allochthonous origin and compared with the other parts of the Baltic Sea.

Some climatic aspects of biomass productivity of white spruce stem wood

Abstract: Biomass productivity was determined for white spruce (Piceaglauca (Moench) Voss) in the boreal forests of Alberta, the Northwest Territories, and Manitoba. Comparisons were made between southern and northern locations, between eastern and western transect locations, and between older (200 + years) and younger (110 years) trees. At 13 sampling locations, X-ray densitometric tree ring data were obtained from the base of the stem, breast height, and from five points equidistant along the stem. Markedly higher stem wood biomass productivity was found for the 110-year-old trees than for the 210-year-old trees in Alberta; average ring weights were 3.8 and 1.2 g for the first 100 years of growth in 1 cm thick disks at breast height. These results suggest that climatic warming since the end of the Little Ice Age (ca. 1850) has resulted in higher biomass productivity in the Canadian boreal forest.

Limnological characteristics, water quality and conservation measures of a high altitude bog and rivers in the Maluti Mountains, Lesotho

Abstract: Bogs occur in cirque-shaped riverheads above 2 500 m above sea level in the Maluti and Drakensberg Mountains. Numerous streams drain these bogs and pools occur on some of them. These are temporary shallow waters which fill in the wet summer months. A benthic community of macrophytes with epiphytic algae usually covers the bottom of the waters. The ionic content which was low, is influenced by the high rainfall, erosion of the basalts and seepage from the soil and peat deposits. The waters were moderately acidic, with an ionic dominance order of Ca > Mg > Na > K : HCO3 > SO4 > Cl and low concentrations of N and P. The precipitation was acidic with a low ionic content, which was dominated by edaphic and anthropogenic sources. According to the primary productivity and nutrient contents, the streams were oligotrophic and the pools mesotrophic. Productivity of the benthic communities was much higher than that of the pelagic zone. The quality of the waters is good, being low in dissolved salts, nutrients and clear. Overgrazing and the presence of burrowing ice-rats has led to erosion and conservation measures are needed to protect these important filters and regulators of water in this important catchment area of southern Africa.