Showing papers on "Productivity (ecology) published in 1970"

Primary productivity of reef-building calcareous red algae

Abstract: Primary productivity of reef—building algae was studied by putting samples from the reef in a closed system and measuring oxygen exchange in the light and in the dark Gross productivity determined for 32 samples in full sunlight had a mean value of 0048 mg O2 cm—2 hr—1 Photosynthesis was found to increase with the logarithm of light intensity up to 1,000 ft—c and was constant between 1,000 and 8,000 ft—c Rates of gas exchange in flowing water showed no correlation with water velocity but were greater than rates in still water Daily patterns of photosynthesis were calculated for populations of calcareous algae living on the submarine faces of the windward sides of atolls During most of the daylight hours light is probably not a limiting factor for photosynthesis in these populations Calculated productivity of various calcareous algal zones indicates that these do not contribute significantly to overall reef production on atolls of the northern Marshall Islands Island reefs are less productive than previously studied inter—island reefs

Contemporaneous Disequilibrium, a New Hypothesis to Explain the „Paradox of the Plankton”

Abstract: The diversity of lake phytoplankton is unexpectedly high, since the epilimnion of a lake is continuously mixing and might be expected to have only one or at most a few niches for primary producers. However, a carefully replicated series of samples from Castle Lake, Calif., showed a high degree of patchiness for many phytoplankton species, indicating that the rate of mixing is slow enough relative to the reproductive rate of the algae for many different niches to exist simultaneously. Productivity per unit biomass ratios, measured at Lake Tahoe, California-Nevada, shows that the turnover times for carbon in even this ultraoligotrophic lake are often less than 1 day. High diversity is associated with high productivity per unit biomass and high zooplankton populations in this lake. A contemporaneous disequilibrium model to explain the diversity of the lake phytoplankton is therefore highly plausible. At any one time, many patches of water exist in which one species is at a competitive advantage relative to the others. These water masses are stable enough to permit a considerable degree of patchiness to occur in phytoplankton, but are obliterated frequently enough to prevent the exclusive occupation of each niche by a single species.

Relationships between Development Rate of Eggs and Older Stages of Copepods

Abstract: It has been argued (McLaren, 1963, 1965) that reproduction and development of copepods may be physiologically (rather than trophically) determined when food is sufficiently abundant: thus, under these conditions the rates of development and egg production, and the total number of eggs laid by a female in her lifetime vary only with the physical factors of the environment such as temperature, salinity and pressure, temperature being by far the most important. This paper is part of a continuing study of the physiological controls of growth and development as part of a general investigation on productivity of marine zooplankton.

Production, Mineral Accumulation and Pigment Concentrations in Typha Latifolia and Scirpus Americanus

Abstract: Shoot productivity was measured for Typha latifolia and Scirpus americanus. Samples were also subjected to chemical analyses. Tissue concentrations of chlorophylls a and b, carotenoids and most macronutrients declined as the plants aged. Net accumulation of these constituents per square meter usually continued during periods of dry matter increase, even though tissue concentrations were diminishing. Dry matter standing crop was the decisive factor determining quantities of chemical constituents per square meter. Uptake rates for macronutrients were generally not proportional to productivity rates. The most rapid uptake of several nutrients occurred earlier than maximum growth rates. See full-text article at JSTOR

Recent and Postglacial Production Rates of a Marl LAKE1

Abstract: Pigment degradation products were analyzed spectrophotometricaIly in postglacial, 14Cdated sediments from the central depression and a marl lakemount of Pretty Lake in northeastern Indiana. Fluctuations in pigment products were examined in relation to the development of the productivity of the lake and to enviromnentai parameters that might effect differential rates of preservation and deposition. Agreement was good between quantities of pigment degradation products and organic matter and other paleolimnological indices of productivity. There was a major peak of pigment products per gram of organic matter following the Boreal period, subsequent regression of productivity with several lesser peaks, especially during the millennium 6,500-5,500 B.P., and a slow increase in recent times. Contemporary rates of primary production were extrapolated to the inception of the lake. A general inverse relationship was evident between chlorophyll degradation products per unit organic content and carbonate levels. Changing levels of carbonate are discussed in relation to contemporary nutritional interactions and photosynthetic regulation. Rates of sedimentation at the central depression of the lake differed markedly from those of the httoral lakemount. While the rates in the central depression accelerated, those of the marl lakemount fluctuated sigmoidally, greatly accelerated during the interval D,OOO7,000 BP. The lakemount ceased accretion abruptly 1 m from the lake surface at 2,740 B.P. The probable ontogeny of marl lakemounts is discussed.

Relation between Biomass, Productivity, and Loss to Predators in a Population of a Marine Benthic Polychaete, Pectinaria hyperborea

Abstract: The changes in population density and individual size distribution in a population of the trumpet worm Pectinaria hyperborea Malmgren were observed on eight occasions in 20 months at a station 60 m deep on a soft muddy substrate in St. Margaret's Bay, N.S. Production proceeded rapidly during the early life stages while loss due to mortality (elimination) was low, so that biomass increased and reached a maximum at 170 days. Between 30 and 370 days the rate of elimination was nearly constant at about 0.9 g/m2 wet weight per 50-day period in spite of changing biomass. After 370 days the rate of production, rate of elimination, and biomass decreased. It was estimated that 80% of mortality was due to predation. Almost 90% of total production of the cohort took place in the first year of life. The ratio between annual production and biomass present in May 1967 in the study area was used to estimate annual production at 24 stations in the bay.

Soil respiration, litter fall and productivity of tropical rain forest.

Abstract: Since undisturbed equatorial rain forest is a climax community it should have a constant biomass per unit area. This implies a steady carbon cycle with a decomposition rate of organic matter equal to the primary production. If there is no appreciable consumption by direct grazing organic substances return to the soil mainly as litter fall, timber fall and dead roots. Their complete degradation by the soil fauna and flora results in a corresponding carbon dioxide evolution. The measurement of the rate of this soil respiration (Lundegardh 1924) should thus permit an indirect estimation of net primary productivity. Reliable productivity data are very scanty for tropical rain forest (Bray & Gorham 1964; Miller & Nielsen 1965; Rodin & Bazilevich 1967). Soil respiration measurements in tropical regions have been made in Africa by Birch & Friend (1956) and by Schulze (1967) in Costa Rica. No data are available for East Asian rain forests. Some preliminary observations are reported here which were made during a visit to Bogor and Tjibodas, Indonesia and Sarawak, North Borneo. The results are compared with available data for litter fall and productivity.

Studies on the productivity of tropical pasture plants. 2. Growth analysis, photosynthesis, and respiration of 20 species of grasses and legumes in a controlled environment.

Abstract: A previous study of one grass and one legume at early vegetative stages has been extended to include a further nine species of each. It confirms the superior relative growth rates (RW) of grasses, arising from very high net assimilation rates (EA), in turn dependent on high photosynthetic rates (P). Leaf area ratios (FA) varied over a similar range in both groups. RW values of grasses in the second week after sowing varied from 0.41 to 0.55 gg-1 day-1; for legumes, they were 0.31-0.36. Corresponding EA values were 1.5-1.9 g dm-2 wk-1 in grasses, and 1.1-1.8 in legumes. Within both grasses and legumes, comparisons between species can be made with less certainty. In grasses, variation in FA combined with generally uniform EA values resulted in variable RW values. Both FA and EA varied in the legumes but were usually compensatory, leading to uniformity in RW. Watson and Hayashi's method of separating EA into photosynthetic and respiratory components was used. Differences both between and within grasses and legumes were shown, but there are probably important errors in this technique, particularly where there are discrepancies between light and dark respiration.

Productivity of Macrophytes in Marion Lake, British Columbia

Abstract: The in situ productivity of both the phytoplankton and the macrophytes in Marion Lake, B.C., was determined from April 1966 through September 1966, by using 14C techniques. The uptake of NaH14CO3 was measured in selected macrophytes by enclosing them in Plexiglas chambers. These plants were then combusted in oxygen, and the 14CO2 was absorbed in toluene-POPOP-ethanolamine. Radioassay was accomplished by liquid scintillation. In addition to the 14C method, an organic weight method was used to measure macrophytic productivity.The productivity of the macrophytes was always higher than that of the phytoplankton. There was a considerable difference in the estimates of the macrophyte productivity arrived at by the two different methods, and reasons for this are discussed.The total productivity of the lake is very low when compared with lakes of similar latitudes because of low phytoplankton productivity. It is concluded that in Marion Lake the macrophytes are more important primary producers than the phytoplank...

Litter accumulation in selected forests of the Republic of Panama.

Abstract: Accumulated litter was collected from primary and secondary tropical moist forests, and from a primary, premontane wet forest in Panama during June to August 1967 (wet-season months), and in January 1968 (a dry-season month) Weights of litter and caloric contents were greatest in the premontane wet forest Litter accumulation and energy content increased during the dry season in two secondary, tropical moist forests THE NET RATE of change in energy stored in an ecosystem or its parts equals the rate of income minus the rate of loss (Olson 1963) These rates may be expressed for various trophic levels or species and also for accumulated organic matter In forests, both living and dead material accumulate large reservoirs of energy A substantial fraction, often one-third to one-half or more of the energy and carbon annually fixed in forests, is present on the forest floor as litter Because litter is generally related to the amount of photosynthetic machinery in the system, it can be a useful index of ecosystem productivity Since litter fall can serve as an indicator of forest production, it is feasible that the energy content of litter accumulated on the forest floor can be used to compare levels of productivity in various forest types Calorimetric methods, which involve measuring the amount of heat liberated by combustion of samples in oxygen-filled bombs, have been used frequently as a means of deriving energy contents of organic materials The purpose of this paper is to report the amounts of litter collected from several selected forests in the Republic of Panama and calorimetric analyses of the material

Nutrient limiting factors in an oligotrophic South Carolina pond

Abstract: Nutrient relationships were studied in a small oligotrophic pond. Dissolved nutrient levels were very low and marked seasonal changes in concentrations were not apparent. Rainfall nutrient input was large, but comparatively small quantities of nutrients entered the pond in leaf fall. Light and dark bottle productivity estimates were very low. The carbon-14 bioassay technique revealed that sulfate was the only single nutrient capable of increasing productivity. Combinations of nitrate and phosphate increased productivity as much as nitrate, phosphate, and sulfate. When calcium or potassium was added with these anions an additional increase in carbon-14 uptake was observed.

Studies on the production structure of forest. XVI. Primary productivity of Abies veitchii forests in the sub-alpine zone of Mt. Fuji.

Abstract: Generally speaking, there are four zones i.n the vertical distribution of plant communities in the Japanese Islands; the submontane, the montane, the subalpine and the alpine zones. The subalpine zone, lying bet\veen the montane zone and alpine zone or between the upper limit of montane zone and the forest line in the mountain region of central Japan, are represented by the forests consisting of evergreen coniferous species, such as Abies veitchii, Abies mariesii, Picea jezoeusis v. lzondoensis, Tsuga diversifolia, etc. mixed wilh deciduous ones, such as Betula ermauii, Larix leptolepis, etc. The climatic condition in the subalpine zone, corresponds to that in the subarctic zone, is severe in general because of low temperature, cold wind, sno\vfall, etc., so the regeneration and tending of forest stands in this zone come to be important problems in forestry as the felling area in this zone spreads. About twenty or more workers belonging to our Forest Experiment Station have carried out joint studies on the silvicultural treatments of the subalpine zone, which contains researches on the natural regeneration, the artificial regeneration, the forest dry matter productivity and the climatic condition. This paper deals with the primary productivity of several forests of Abies veitchii which is one of the typical tree species in the subalpine zone of central Japan. The studies were performed as a part of the joint studies mentioned above. The primary productivity in subalpine Abies forests has been studied by several workers. Especially, OsHIMA 'et al.12 l, KuRotwAs>-8), J(JMURA2> and KIMURA et at.3> have an interest in the peculiar structure of Abies forests on Mt. Shimagare, Nagano Prefecture, where all subalpine A.bies trees in the forest aged about 100 years die in stripes naturally, and the next generation grows in the stripes of dead trees, and their ecological and physiological studies on the structure and productivity have been reported in series. Also, AsADA and AKAI1) surveyed the productivity of many subalpine Abies forests in Nagano Prefecture from the vie\vpoint of silvics. This article was read in part at the 78th and 79th Annual Meetings of Japanese Forestry

The horizontal structure of reed stands (Phragmites communis) and its relation to productivity.

Abstract: Measurements along a transect through littoral stands of Phragmites communis sh ow that productivity and density are positively correlated . The density in these stand s decreases from the shore . This gradient can be attributed to the accumulation of old plant parts, producing more organic material in some regions of the stand. The spacing of individuals is contagious: the dimensions of the pattern are examined by block size analysis. The clumping is most pronounced in the most productive plots. Introduction Although there are many interesting features of horizontal structure and spacing of plants in crop stands, only those directly related to dry matter production are here considered. When assessing the amount of production in different plant stands from pot or field experiments, as is usually done, effects of variation in horizontal spacing are usually dominated by appropriate experimental design or selection of field site. In many natural stands, however, the effects of density must be taken into account. Changing density will affect many environmental factors: soil composition, light and temperature, specific conditions of tillering, competition, etc. These variations will affect the statistical significance of m ean production values obtained from random samples throughout the stand. Not only overall d en sity but pattern must be taken into account, since the scale of pattern and its nature will affect t h e size of sample required. Three main types of pattern may be distinguish ed: random, regular and contagious. If the distribution is contag10us, sample sizes must exceed those of cluster s , since the variance of samples of the same s ize a s clusters is very large. Density measur e ment s Density, its distribution and influence on productivity were studied in two stands of Phragmites communis in different ecotopes growing near each other and experiencing the same macroclimate. The first (site V) is a typical littora] ecotope of the South Bohemian region, forming an almost pure monospecific community along the shore of Opatovicky pond, a band about 25 30 m wide. The flooding level varies from 25 90 cm above soil surface, being shallowest on the shoreward side. The second limosal ecotope (site S) is never actually flooded, although the water table comes very cJose to the surface. Since this stand is not subject to wave erosion much more detritus accumulates on the bottom than in site V.