Net Primary Production Rates Research Articles

Carbon sources and sinks in forest biomes of the former Soviet Union

The carbon budget of the forest biomes of the former Soviet Union (FSU) and their sequestration potential were assessed by considering (1) net ecosystem productivity (NEP) of different age forest stands and actual forest coverage, (2) carbon flux related to forest fires, (3) the rate of peat accumulation, and (4) anthropogenic influences. The area of forest biomes in the FSU was estimated at 1426.1 million hectares (Mha); forest ecosystems comprised 799.9 Mha, nonforest ecosystems and arable land comprised 506.3 and 119.9 Mha, respectively. The vegetation pool (phytomass and coarse woody debris) was 68.7 Gt C (carbon). The litter and soil carbon pools were 12.2 and 319.1 Gt C, respectively. The net primary productivity (NPP) of forest biomes ecosystems was 5.6 Gt C/yr, the rate of foliage formation was 2.3 Gt C/yr, the rate of humus formation was 161 Mt C/yr with 73 Mt C/yr in the stable form. The NEP of the forest biomes was assessed from the data on NEP of young, middle‐age, and premature forest stands. The NEP of the forest biomes was 825 Mt C/yr. Peat was accumulating at an average rate of 23 Mt C/yr. Carbon effluxes from mortmass, litter, and soil organic matter decomposition were calculated from the NPP, NEP, foliage, and humus formation rates. The efflux from mortmass decomposition was 2.6 Gt C/yr, from litter decomposition 2.1 Gt C/yr, and from soil organic matter decomposition 61 Mt C/yr. Peat combustion represented a carbon efflux of 30 Mt C/yr. The carbon efflux from forest fires and agricultural activities was 199 and 10 Mt C/yr, respectively. Carbon efflux from wood harvesting (carbon sequestration in regrowing vegetation was excluded) was 152 Mt C/yr. Considering all components of the natural carbon cycle and the anthropogenic influences, FSU forest biomes were a net sink of 485 Mt C/yr of atmospheric carbon. The Siberian and Far East forests represent approximately 82% of the net sink. The total carbon sink in FSU forests was equivalent to one half of the annual CO2 fossil fuel emissions in the FSU or one half the carbon released from deforestation in subtropical regions.

Canopy dynamics and aboveground production of five tree species with different leaf longevities.

Canopy dynamics and aboveground net primary production (ANPP) were studied in replicated monospecific and dual-species plantations comprised of species with different leaf longevities. In the monospecific plantations, leaf longevity averaged 5, 6, 36, 46 and 66 months for Quercus rubra L., Larix decidua Miller, Pinus strobus L., Pinus resinosa Ait. and Picea abies (L.) Karst., respectively. Specific leaf area, maximum net photosynthesis per unit mass (A/mass), leaf N per unit mass (N(leaf)/mass) and maximum net photosynthesis on a leaf N basis (A/N(leaf)) were inversely correlated to leaf longevity (r(2) = 0.92-0.97, 0.91, 0.88 and 0.80, respectively). Maximum net photosynthesis per unit area (A/area) was not correlated to leaf longevity, whereas leaf N per unit area (N(leaf)/area) was positively correlated to leaf longevity (r(2) = 0.95). For a similar-diameter conifer, species with long-lived foliage supported a greater foliage mass than species with short-lived foliage; however, Quercus rubra did not follow this pattern. At the stand level, total foliage mass ranged from 3.3 to 30.5 Mg ha(-1) and was positively correlated (r(2) = 0.97) to leaf longevity. Leaf area index (LAI) was also positively correlated (r(2) = 0.82) to leaf longevity. Production efficiency (ANPP/LAI) was inversely related to leaf longevity and positively related to A/mass. Aboveground biomass and net primary production differed significantly (P < 0.05) among the five species but were not correlated to leaf longevity, total foliage mass or leaf area. In monospecific plantations, stem NPP for Larix decidua was 17% greater than for Pinus strobus and 14% less than for Picea abies, but in mixed-species plantations stem NPP for Larix decidua was 62 and 85% greater than for Pinus strobus and Picea abies, respectively. Similar aboveground net primary production rates can be attained by tree species with different leaf longevities because of trade-offs resulting from different structural and physiological leaf and canopy characteristics that are correlated to each other and to leaf longevity.

Algal food supply and grazer demand in a very productive coral-reef zone

Benthic algal-community net primary productivity (NPP) and herbivore ingestion rates were quantified for the productive zone dominated by the aggressive surgeonfish Acanthurus lineatus (Linnaeus) on the windward crest of Davies Reef, Great Barrier Reef, northeastern Australia. The aim was to evaluate whether or not food supply could be a limiting factor for grazers. Grazing accounted for 65° o of NPP in carbon terms during summer, and 43° o in winter. The most important grazers were the resident territorial surgeonfish Acanthurus lineatus (41° o of NPP in summer) and damselfish Stegastes apicalis (De Vis) (15° o). Grazing rates increased 1.8-times, while NPP increased only 1.2-times, between winter (mean ambient temperatures 23°C) and summer (28°C), but in both summer and winter grazing was significantly less than NPP. NPP which was not accounted for by grazing may have been lost through secretion of dissolved organic matter by algae, export of algal fragments from the zone and decomposition in situ, processes which have been little studied.

Gross and net primary production in the Scotia-Weddell Sea sector of the Southern Ocean during spring 1988

Daily rates of gross and net primary production were calculated in the Scotia-Weddell Sea sector of the Southern Ocean during spring 1988 (EPOS, Leg 2) on the basis of kinetic experiments, which combine radiotracer technology and classic biochemical procedures, and by taking into account the light regime, the physical structure of the water column, the vertical distribution of chlorophyll a, and the protozoan grazing pressure. From these calculations, three distinct sub-areas were identified: the Closed Pack Ice Zone (CPIZ), characterized by the lowest average gross primary production (0.36 gC · m−2 · day−1); the Marginal Ice Zone (MIZ) with a maximum mean value of 1.76 gC · m−2 · day−1; and the Open Ocean Zone off the ice edge (OOZ) with an intermediate mean value of 0.87 gC · m−2 · day−1. Net primary production fluctuated nearly in the same proportions, averaging 0.55, 0.2 and 1.13 gC · m−2 · day−1 in the OOZ, CPIZ and MIZ respectively, representing 53% of the total photo-assimilated carbon under heavy ice cover (CPIZ) and 64% in the two other areas. Available light, strongly dependent on the ice cover, was shown to control the level of primary production in the sea ice associated sub-areas, whilst protozoa grazing on phytoplankton determined the moderate primary production level characteristic of the “well illuminated” OOZ area.

Aboveground production and canopy dynamics in sugar maple and red oak trees in southwestern Wisconsin

Aboveground net primary production, canopy allometry, growth efficiency, and sapwood volume were compared for early- to mid-successional red oak (Quercusrubra L.) and late-successional sugar maple (Acersaccharum Marsh.) co-occurring in young and mature natural stands in southwestern Wisconsin. For similar-diameter trees, shade-tolerant sugar maple supported a significantly greater (p &lt; 0.05) stem, branch, and foliage biomass and leaf area than mid-tolerant red oak. Red oak and sugar maple had similar stem net primary production rates over a 5-year period (1984–1988), but sugar maple had a significantly greater total aboveground net primary production than similar-diameter red oak. However, red oak had a significantly greater (p &lt; 0.0001) growth efficiency (stem net primary production per unit of leaf area) than sugar maple. The significantly greater sapwood volume, but equal stem volume, of sugar maple versus red oak suggests that annual stem maintenance respiration costs may be greater for sugar maple than for red oak. Possible causes for differences in stem net primary production and growth efficiency between early- and late-successional tree species are discussed.

Biomass, Productivity and Energetics in Himalayan Alder Plantations

Biomass, net primary production and energy fixation in an age sequence of Himalayan alder (Alnus nepalensis D. Don) plantations were estimated in the Kalimpong forest division of the eastern Himalayas. Biomass in the plantations ranged from 106 t ha−1 (7-year stand) to 606 t ha−1 (56-year stand) demonstrating the potential of the alder for accumulating large biomass. Net primary production and net energy fixation rates of the plantations were reduced by nearly half in the 7-year stand (25 t ha−1 year−1; 421 × 106 kJ ha−1 year−1) compared with the 56-year stand (13 t ha−1 year−1; 215 × 106 kJ ha−1 year−1). Compartmental models of energy storage and flow rates were developed for the 7-year and 56-year stands. The production efficiency, energy conversion efficiency and energy efficiency in N2 fixation have inverse relationships with plantation age. These efficiencies, when treated with each other, showed significant exponential functions.

Effect of mangrove detrital outwelling on nutrient regeneration and oxygen fluxes in coastal sediments of the central Great Barrier Reef lagoon

The effect of tidal outwelling of mangrove detritus on sediment nutrient chemistry, nutrient regeneration and oxygen fluxes in a coastal area of the central Great Barrier Reef lagoon was examined. Organic carbon and total nitrogen concentrations ranged from 0·2 to 3·9% and 0·01 to 0·18% by sediment dry weight (DW), respectively, and were highest at stations receiving the greatest quantities of mangrove litter. Total phosphorus concentrations ranged from 0·013 to 0·048% by DW, but did not relate to outwelling. C:N:P. ratios ranged from 29:6:1 at the site receiving the least amount of detritus to a high of 397:17:1 at the station receiving the most litter. The effect of outwelling on dissolved inorganic nutrients in porewaters was less clear, with concentrations closely related to sediment type and obscured by contributions from continental runoff. Ammonium (range: 10–310 μM) and silicate (range: 10–315 μM) were in greatest concentration at most sites followed by phosphate (range: 1–12 μM) and nitrite and nitrate (0·07–6·0 μM). Directly measured fluxes of dissolved inorganic nutrients across the sediment-water interface were either undetectable or small [ΣN = −560 to +3503; PO43 = undetectable to +157; Si(OH)4 = undetectable to +6449 μmol m−2 day−1] and not related to outwelling. Addition of mangrove litter to ☐core samples incubated for 10 days in the laboratory did not affect rates of dissolved inorganic nutrient release. Oxygen consumption rates ranged from 8·7 to 60·2 mmol O2 m−2 day−1 and were highest at most sites closest to mangrove forests, in agreement with previous measurements of bacterial productivity. Rates of net community primary production were either undetectable or low (as were chlorophyll α and phaeopigments) ranging from 12 to 77 mg C m−2 day−1. It appears that much of the deposited mangrove litter is highly refractory, but the amount of sedimented material appears to be great enough to significantly enrich bulk concentrations of particulate carbon and nitrogen, and rates of oxygen consumption. Benthic nutrient regeneration contributes only a small proportion to the daily nitrogen (6%) and phosphorus (9%) demand of coastal phytoplankton, implying supplementation from continental runoff and/or high rates of pelagic recycling.

Effect of aeration on the primary productivity of phytoplankton in experimental tanks

Six experimental tanks were used to examine the effect of artificial aeration on the primary productivity of phytoplankton under four different treatments: 5 and 2.5 h aeration day −1 each with a carp fingerling stocking density of 60 000 ha −1; 5 h aeration day −1 with a stocking density of 100 000 ha −1 and the control system (no aeration) with a stocking density of 60 000 ha −1. All the four treatments were duplicated during three experiments carried out during the period from June 1982 to April 1984. The results of this study revealed that aeration induced the net photosynthetic activity of the phytoplankton by substantially reducing their demand for oxygen for respiration. Since the rates of net primary productivity (NPP) and the abundance of phytoplankton were markedly reduced under high density culture compared with normal density culture with the same aeration, it suggests that the high density of fish caused intense grazing on the phytoplankton and was, thus, responsible for the lower rates of NPP.

Ecological Observations in the Dwarf Cloud Forest of the Luquillo Mountains in Puerto Rico

Five species accounted for 95 percent of the stems of at least 10 cm DBH on three plots totaling 0.22 ha in the dwarf cloud forest of the Luquillo Mountains in Puerto Rico. Mean density for stems of at least 10 cm DBH was 3671 ? 516 stems/ha, and mean basal area was 49.1 ? 8.2 m2/ha. The aboveground woody biomass on two small plots of 0.0036 ha, one located on a ridge and the other 100 m to the leeward, was 48 and 110 t/ha, respectively. Leaf area index on the ridge was 1.99 m2/m2, leaf biomass was 288 g/m2, and specific leaf weight was 14.5 mg/cm2. Mean annual litterfall rates averaged only 0.85 g/m2/day (3.10 t/ha/yr), of which 79 percent was leaf litter, 9 percent wood litter, and 12 percent miscellaneous material. The rate at which nutrients returned to the soil (kg/ha/yr) averaged 23.9 for nitrogen, 0.7 for phosphorus, 4.3 for potassium, 16.3 for calcium, and 7.6 for magnesium. The annual increment in tree diameter was low, averaging only 0.03 ? 0.01 cm/yr. For trees at least 2.5 cm in diameter, aboveground biomass accumulated at an average rate of 45 g/m2/yr. Net primary productivity was 3.84 t/ha/yr. ZONATION OF FORESTS WITHIN MONTANE HABITATS on tropical islands is condensed into a narrow altitudinal range, a phenomenon known as the Massenerhebung effect. One example is the Luquillo Mountains of northeastern Puerto Rico, which abruptly rise to 1060 m in only 15 km. As elevation increases, the number of arborescent stems/ha increases, while decreases occur in average height of dominants, average DBH, basal area/ha, and number of species per unit area (White 1963). The dwarf forest, an association in the lower montane rain forest (sensu Holdridge 1967, Ewel & Whitmore 1973) on the upper slopes and summits of the Luquillo Mountains, is short, frequently contorted, and densecovered with epiphytes including bromeliads, liverworts, and mosses-and includes only a few species of trees (Beard 1949, Wadsworth 1951, Howard 1968). The climate is wet, with nearly 5000 mm/yr of rainfall. Mean monthly temperatures range from 18 to 20?C (Weaver et al. 1973). The vegetation is commonly saturated with moisture and frequently enveloped in clouds. Both aerial and superficial roots are common (Lyford 1969). Saturated soils, impeded root respiration, physiological drought, high winds, high soil leaching, low nutrient availability, low temperatures, high fog incidence, reduced solar insolation, high humidity, reduced transpiration rates, and shallow soil have all been suggested as causal agents in stunting, either individually or in combination (Gleason & Cook 1927, Beard 1944, Wadsworth & Bonnet 1951, Holdridge 1967, Odum 1968, Baynton 1969, Grubb 1971, Weaver et al. 1973). Similar forests elsewhere in the Caribbean and Central America have been discussed by La Bastille and Pool (1978). Despite the abundance of hypotheses regarding the cause of dwarf cloud forests, little information is available on their growth rates, net primary productivity (NPP), and nutrient cyding. The purpose of this study is to determine species composition and standing biomass of the dwarf forest, and to estimate the rates of NPP, litterfall, and diameter and biomass growth of arborescent species. Rates of nutrient return to the soil are also in-

Benthic-pelagic coupling and nutrient cycling across an experimental eutrophication gradient

Sediment-water exchange rates of dissolved inorganic nitrogen (NH:, NO;, NO;) and phosphorus (PO:-), water column concentrations of both dissolved and particulate forms of N and P, and net primary production (14C) were measured during a summer period in large (13 m3) experimental mesocosms that had been subjected to continuous daily nutrient additions (N, P, Si) for over 1 yr. The concentrat~on of combined dissolved inorganic plus particulate nutrient forms (N, P) was linearly related to the nutrient input rate across a loading range from 596 to 34,100 mmols N m-2 yr-l. Benthic nutrient regeneration generally increased, although not uniformly, with loading. Average summer fluxes for treatments ranged from about 150 to 1200 pmols NH: m-2 h' , 188 to 989 pmols DIN m-2 h' , and 8 to 76 pmols PO:m-2 h' , with highest rates being I-ecorded at the 2 highest loading levels. Benthic nutrient regeneration d ~ d not increase in direct proportion to loading, but appeared strongly related to net primary production rates across the enrichment gradient. Comparison, across the experimental gradient, of the external nutrient supply rate with the benthic feedback of dissolved nutrients to the water column indicated that beyond a loading of about 2000 to 5000 mmols N m-? yr-' the water column nutrient dynamics became dominated by the external supply. Results suggest that the importance of benthic-pelagic interactions to biogeochemical and ecological cycles of coastal areas may decrease markedly with nutrient enrichments which exceed the needs of the autotrophic components of the ecosystem.

Shoot Production and Biomass Transfer of Big Sacaton [Sporobolus wrightii

The annual pattern of above-ground live biomass, recent dead standing biomass, old dead standing biomass, and standing crop of big sacaton (Sporobolus wrightii Monro) grassland community in semiarid Arizona was studied over a 3-year period. Live biomass was produced throughout the year but peak production, over the 3 2 years, was in August. Peak biomass production was 296 g m in 1 wet summer and averaged 133 g mover 2 dry summers. Recent dead standing biomass was greatest in spring and least in summer, over the 3 years. Transfer of recent dead standing biomass to old dead standing biomass was precipitation and temperature dependent. Old dead standing biomass was greatest in summer, least in winter, and was primarily composed of dead seed stalks. Livestock management of big sacaton grasslands should possibly be distinct from adjacent upland areas. Big sacaton (Sporobolus wrightii Monro) is a robust perennial warm-season bunchgrass that begins growth in early spring and usually produces a limited amount of green herbage in winter (Haferkamp 1982). The species grows on low alluvial flats and flood plains (Wooten and Standley 1912). It usually is excluded from alkaline and saline playas and lowlands dominated by alkali sacaton [Sporobolus airoides (Torr.) Torr.]. Big sacaton is distributed from southeastern Arizona to central Texas and Author is range scientist, Arid Land Ecosystems Improvement, USDA, Agricultural Research Service, 2000 East Allen Road, Tucson, Ariz. 85719. Appreciation is extended to R.M. Madrigal and B.B. Buck for field assistance; Drs. H.L. Morton and T.N. Johnsen, Jr., for technical assistance; the Donaldson family at the Empire Range for their cooperation; and ANAMAX Mining Company for permission to use their land. Manuscript received August 17, 1983. south into the northern Mexican Frontier States; however, stand development is greatest in southeastern Arizona (Kearney and Peebles 1960). Dense stands of big sacaton formerly dominated alluvial flats and bottomlands along the Santa Cruz and San Pedro Rivers in Southeastern Arizona and supported more than a million cattle in 1890 (Humphrey 1958). Big sacaton bottoms have been, and continue to be burned and grazed (Bock and Bock 1978), plowed and sown to agricultural crops (Griffiths 1901), channelized to provide irrigation water and drainage (Cooke and Reeves 1976), and covered with houses and asphalt (Renard et al. 1983). Today the species occupies less than 5% of its original area (Humphrey 1960). Big sacaton stands were usually associated with perennial, surface water and new growth was readily consumed by livestock in spring when upland grasses were dormant (Thornber 1910). Dead standing big sacaton biomass is coarse and stands have been burned or mowed in either late fall, winter, or early spring for at least the past 100 years (Thornber 1910, Humphrey 1970). The animal-carrying capacity of semiarid grazing lands is dependent on net primary production and the amount of plant biomass which is available to be converted into animal biomass. Previous investigators have been interested in big sacaton production after natural and man-caused fires (Humphrey 1960, Bock and Bock 1978, Gavin 1982). However, net primary production rates under nonburned conditions have not been measured. The first step in a program to evaluate carrying capacity should be to quantify the annual accumulation and decomposition characteristics of live biomass and standing litter in big sacaton grassland communities. JOURNAL OF RANGE MANAGEMENT 37(4), July 1984 377 This content downloaded from 157.55.39.223 on Wed, 24 Aug 2016 05:07:16 UTC All use subject to http://about.jstor.org/terms This paper reports on studies in which the above-ground live biomass production, recent dead standing biomass, and old dead standing biomass were examined over 3 years. The relative differences in yield accumulation and decomposition in response to climate were also studied.

Effects of Two Types of Nutrient Enrichment on the Structure and Function of Contrasting Old-field Communities

Effects of 4 years of sewage sludge and commercial fertilizer applications on producer and primary consumer populations in a 3-year-old and a 7-year-old field were investigated in 1981. Three 0.1-ha enclosures in each old field received five monthly applications of sludge annually from 1978 through 1981. An equivalent nutrient subsidy in the form of urea-phosphate fertilizer was applied to three enclosures in each old field. Two enclosures in each old field were left untreated as controls. Nutrient enrichment did not significantly increase primary productivity or standing crop biomass in either old field. Species diversity was lower in sludgeand fertilizertreated enclosures in the 3-year-old field. The species composition of both types of nutrient-enriched enclosures became dominated by early successional plants in both old fields. Live trapping of meadow voles indicated that vole population densities were not affected by treatment. Tissue samples of plants and meadow voles were assayed for heavy metal content by atomic absorption spectroscopy. Sludge treatment significantly elevated cadmium, copper, and zinc concentrations in plants and cadmium concentrations in vole livers and kidneys. Voles accumulated cadmium in these organs at levels in excess of plant concentrations, i. e., biological magnification of cadmium occurred. INTRODUCTION Numerous studies have investigated the effects of nutrient enrichment on terrestrial ecosystems. Several researchers (Mellinger and McNaughton, 1975; Kirchner, 1977; Reed, 1977; Bakelaar and Odum, 1978; Magdoff et al., 1980; Willems, 1980) reported increases in net primary productivity in grassland communities following fertilizer application. Kirchner (1977) and Bakelaar and Odum (1978) found species diversity decreased as a result of fertilization. Thus, nutrient enrichment appears to favor high net productivity and low plant species diversity. According to Odum (1969), these structural and functional responses should be characteristic of early successional stages of community development. However, Mellinger and McNaughton (1975) and Bakelaar and Odum (1978) reported increased dominance by later successional species following short-term fertilizer application. Although these studies raise questions about the relationship of nutrient enrichment and succession, there is a paucity of information concerning how contrasting successional communities might differ with respect to the effects of nutrient enrichment on community structure (e.g., plant species diversity and standing crop biomass) and function (e.g., rates of net primary productivity and mammalian reproduction). Recently, there has been considerable interest in municipal sewage sludge as a source of nutrient enrichment (Baker et al., 1979). Sludge disposal has become an increasingly troublesome problem. The application of digested sludge to land as a fertilizer and soil conditioner is an attractive method of disposal. Studies have established that sludge treatment can enhance plant productivity and increase available nutrient levels (e.g., Pomares-Garcia and Pratt, 1978; Magdoff et al., 1980). Application of sludge is not without potential environmental hazards, however. The accumulation of trace elements (e.g., cadmium) in plant tissue and the resultant availability of these elements to the food chain is of ecological concern. Trace element composition of sewage sludge varies with site of origin (Furr et al., 1976). SludgeI Present address: Department of Biology, Virginia Polytechnic Institute and State University, Blacksburg 24061.

Nitrogen fixation and net primary production in a young Sitka alder stand

Biomass, net primary production and nitrogen fixation rates were measured in a 5-year-old Sitka alder (Alnus sinuata (Regel) Rydb.) stand. Acetylene reduction assays yielded a nitrogen fixation estimate of 35 kg N ha−1 year−1. The biomass of leaves, stems, roots, and nodules was 13 720 kg ha−1 and aboveground net primary production was 6000 kg ha−1 year−1.

Ceanothus megacarpus chaparral: A synthesis of ecosystem processes during development and annual growth

The evergreen sclerophyll shrub,Ceanothus megacarpus, dominates the chaparral in many areas of the Santa Ynez Mountains, Santa Barbara County, California, USA. Often occurring in pure stands,C. megacarpus chaparral accumulates large amounts of aboveground live biomass during growth after fire as a result of high rates of net primary productivity (850 g/m2/yr) compared to other chaparral areas and Mediterranean scrublands of the world. Populations ofC. megacarpus are even-aged, growing from buried seed which requires heat treatment for germination. During the early years of stand development after fire, competition for water among the shrubs results in mortalities of up to 50% of the initial population. This competition is evident by changes in the population size-structure and dispersion pattern of the living shrubs. Water potential measurements during the summer drought show that smaller individuals are more severely stressed than larger individuals. Similarly, shrubs in younger stands develop lower water potentials than shrubs in older stands. There is little mortality after 15 to 20 years of growth; competition for water is alleviated in older stands presumably because the surviving shrubs have developed more extensive root systems. Leaf area reaches a steady-state of 1.6 m2/m2 in 20-year-old stands. At this stage of development, competition for light is manifest in shrub physiognomy, particularly in the death of lower branches.

Particulate organic carbon flux in the oceans—surface productivity and oxygen utilization

Organic detritus passing from the sea surface through the water column to the sea floor controls nutrient regeneration, fuels benthic life and affects burial of organic carbon in the sediment record1–3. Particle trap systems have enabled the first quantification of this important process. The results suggest that the dominant mechanism of vertical transport is by rapid settling of rare large particles, most likely of faecal pellets or marine snow of the order of >200 μm in diameter, whereas the more frequent small particles have an insignificant role in vertical mass flux4–6. The ultimate source of organic detritus is biological production in surface waters of the oceans. I determine here an empirical relationship that predicts organic carbon flux at any depth in the oceans below the base of the euphotic zone as a function of the mean net primary production rate at the surface and depth-dependent consumption. Such a relationship aids in estimating rates of decay of organic matter in the water column, benthic and water column respiration of oxygen in the deep sea and burial of organic carbon in the sediment record.

Vegetation and arthropod responses to wastewater enrichment of a pine forset.

The effects of spraying secondary-treated wastewater on a young pine forest were studied in South Carolina, U.S.A. Soil, herb-shrub layer vegetation and arthropods were analyzed in control, low-spray and high-spray areas to determine the overall impact of four years of chronic nutrient and water enrichment. Spraying had no significant effect on soil organic matter and cation exchange capacity. Soil cation buildups did not occur and cation leaching was evident.Wastewater application produced a more mesic environment and the herb-shrub layer vegetation shifted to an earlier stage in succession. Plant diversity decreased significantly as a few rapidly-growing opportunistic species (e.g., Erechtites hieracifolia, Polygonum pensylvanicum) replaced the more diverse perennial herbshrub layer vegetation of the pine forest. Peak vegetation biomass levels doubled and net primary production rates were 10 times greater in high spray areas. Litter biomass levels, however, did not change significantly. Litter decomposition rates were significantly greater in treated areas which apparently offset the added litter resulting from increased plant production.Arthropod production increased 3-fold in treated areas. All herbivore guilds had higher biomasses that reflected seasonal changes in producer phenology. Total arthropod diversity increased despite the lower vegetation diversity in spray areas. Arthropod diversity apparently increased because of greater resource availability in treated areas.

The effect of sewage and industrial waste discharges on the primary production of a shallow turbulent river

Sewage and industrial waste discharges have been found to have a deleterious effect on the primary productivity of the shallow turbulent tropical river Khan (Indore) India. Even though net primary production rates have exceeded the respiration rates in the early recovery zone, the industrial wastes and sewage discharges have been found to decrease the overall productivity of the river. The above studies have been compared with other investigations in the temperate regions of the world, which generally refer to the effects of organic pollution on the primary productivity of the running waters. The present investigations lead to a generalized observation that in tropical running waters, toxic industrial wastes and sewage discharges have a depressing effect on the overall production rates. However, comparable studies in the temperate regions are nonexistent, as the studies in the temperate regions mainly refer to organic pollution and do not take into account the effects of toxic industrial waste and sewage discharges.

The Structure and Function of Ten Western North American Grasslands: IV. Compartmental Transfers and Energy Flow Within the Ecosystem

1) Seasonal and daily rates of inputs to and outputs from the various primary producer compartments of ten North American grassland sites are presented. (2) Net accumulation rates of total net primary production (TNP) ranged from c. 1 g m-2 day-1 in the desert grassland to over 11 g m-2 day-1 in the mountain grassland. The average average net accumulation rate of TNP was 4.4 g m-2 day -1 for ungrazed grasslands, and slightly more for the grazed grasslands. A significant amount of the variability in mean daily accumulation rates of TNP for ungrazed and grazed grasslands was related by regression analysis to variations in long-term mean annual temperature and long-term mean annual precipitation. (3) Above-ground net primary production (ANP) accumulated at rates of c. 1.4 and 1.2 g m-2 day-1 for ungrazed and grazed grasslands respectively. Variations in annual precipitation explained 60% and 76% of the variability in ANP rates for ungrazed and grazed grasslands respectively. (4) The amount of live material transferred during the growing season to the standing dead compartment averaged 182 g m-2 for the ungrazed treatment and 162 g m-2 for the grazed treatment. The desert grassland had the smallest amount of live material transferred to the standing dead compartment, while the tallgrass prairie had the greatest amount. (5) Transfers of standing dead material into the litter compartment during the growing season averaged 165 g m-2 for ungrazed grasslands and 134 gm-2 for grazed grasslands. Net disappearance of litter during the growing season averaged 147 g m-2 for both the grazed and ungrazed treatments, giving an average rate of litter disappearance of c. 0.9 g m-2 day-1 across these North American grasslands. (6) All grasslands, except the desert grassland, had higher mean rates of net accumulation of dry matter below-ground in the grazed treatment as compared with the ungrazed treatment. Generally, the rate of net accumulation of dry matter below-ground increased with decreasing mean annual temperature, and, within a particular temperature regime, with increasing aridity of habitat. (7) The percentage of incident solar energy captured in the ungrazed and grazed grasslands was 0.64 and 0.69% respectively. On the ungrazed grasslands there was three times more energy trapped in the below-ground compartment than in the above-ground compartment; for grazed grasslands, six times more energy was trapped below-ground compared to the above-ground vegetation compartments.

A limnological study of the Afram arm of volta lake

A two year's limnological study of the Afram arm of the Volta Lake is reported. This arm of the lake is shallow; it receives frequent winds, which together with the floods of June-September create near isothermal conditions. The upper io m is well oxygenated with some oxygen, about 2 mg/l, reaching the bottom for most part of the year. It is poor in nutrients, values of total dissolved solids lying between 40–60 mg/l. But frequent algal blooms of Oscillatoria curviceps, O. princeps and Mycrocystis aeruginosa occur and the net primary production rate in some areas range between 8.4 and 142.5 mg C/m3/hr. It is suggested that the high tropical temperatures encourage quick recycling leading to relatively high organic production, thus making this arm non-oligotrophic.

Assessments of primary and bacterial production in three large mountain lakes in Alberta, Western Canada

AbstractPreliminary studies on production by phytoplankton and bacteria in three large mountain lakes in Alberta, Canada (two in Waterton Lakes National Park and one in Jasper National Park) were concluded mainly through the use of the 14C technique. The main experiments were conducted in August, 1974, and some were repeated in August, 1975. Net primary production rates varied little from 1974 to 1975, even though there were drastic changes in the phytoplankton composition. Production in the largest lake (max. depth 135 m; mean phytoplankton production 206.5 mgC.m−2.d−1) was approximately twice that for each of the two smaller lakes (max. depths 19 and 27 m: average phytoplankton production 109 mgC.m−2.d−1). Bacterial production estimates averaged 3.8 times those for the phytoplankton production, after a proportionalety large error in the dark‐uptake technique was subtracted. High production rates in the largest lake are probably due to enrichment. Bacterial production rates are comparable to those in smaller oligotrophic lakes in Europe.