Abstract: The mineral nutrient requirements of Pinus silvestris L. and Picea abies Karst. were studied according to previously published methods applied to a series of various plant species. The optimum nutrient proportions are similar to those of Vaccinium, with a lower relative potassium requirement than birch and other broad-leaf species. Various ratios between ammonium and nitrate nitrogen were about equally efficient except for a minor growth reduction with pure nitrate, which gave a comparatively low nitrogen content and a high cation/nitrogen ratio. The rate of ammonium uptake was much higher than that of nitrate when both sources were supplied. The required total concentration in the nutrient solution for maximum growth is lower in pine than in spruce, but both fall within the low salt range. Both species, especially pine, are sensitive to high salt concentrations. Although pine and spruce grow on the same type of soils as Vaccinium— leached soils with low base saturation – accumulation of calcium or other cations is not as pronounced as in Vaccinium, especially not in pine. The results are compared with results from similar experiments with a series of other conifers. All the conifers have more flexible cation uptake mechanisms than Vaccinium but the results indicate tendencies to accumulation of anions, nitrate and phosphate. Recommended fertilizer compositions for forest fertilization and nurseries are discussed.

Abstract: Variability in the small-scale temporal and spatial patterns in nitrogenous nutrient supply, coupled with an enhanced uptake capability for nitrogenous nutrients induced by nitrogen limitation, make it possible for phytoplankton to maintain nearly maximum rates of growth at media nutrient concentrations that cannot be quantified with existing analytical techniques.

Abstract: Nutrient-cycling rates in ecosystems may be altered by translocation and transformation that result from the consumption process and/or the behavior of consumer organisms. Translocation by mobile consumers redistributes nutrients within and between subunits of the ecosystem. Migration of zooplankton and fishes carries nutrients across water-mass boundaries or retards net flux by sedimentation. Bioturbation of sediments and mixing of soil horizons by invertebrates similarly redistribute nutrients across system strata, facilitating utilization by primary producers. Transformation of particle size distribution alters rates of nutrient cycling in proportion to changes in surface/volume relationships. Through selective predation and comminution, consumers regulate rates of nutrient cycling. Nutrient pools comprised of large biomass units (e.g., tree boles, soil litter, lake zooplankton) may be transformed to smaller units, resulting in accelerated nutrient-cycling processes. Small units may be aggregated, for example, as macroarthropod feces or fish biomass, resulting in conservation of nutrients.

Abstract: Throughout the southeastern United States the hardwood Nyssa sylvatica (sensu lato) is distributed along a soil moisture gradient from upland sites, which are never flooded, to floodplains, which are periodically flooded and drained, to permanently flooded swamps. Population differentiation with respect to flood tolerance and related physiological attributes was investigated using 1-year-old seedlings grown in a greenhouse from seed collected along this gradient. Upland plants were very intolerant of flooded soils. Their root systems deteriorated, root respi- ration rates dropped and, after a year under such conditions, survival was poor and those that did remain were greatly stunted and had accumulated large concentrations of many nutrient elements. In contrast swamp plants were quite tolerant of flooded soils. Upon flooding, parts of the original root system were lost but new roots were initiated which had an increased capacity for alcoholic fermentation. Many of these new roots were more succulent, larger in diameter, and less branched than drained roots. Such succulent roots however were only a temporary response to short-term flooding; plants flooded for a year did not have such roots, rather the root system superficially resembled drained roots. Concomitant with this return to drained-like roots was an increase in internal oxygen transport to the roots and a drop in alcoholic fermentation. Floodplain plants under drained conditions allocated less biomass to roots than to shoots and had high respiration rates, traits similar to upland plants. Under flooded conditions they initiated new roots with medium respiration rates, allocated less biomass to roots than to shoots, significantly increased oxygen transport to the roots and had high survival, traits similar to swamp plants. Thus, the floodplain population produced a distinctly flood-tolerant phenotype; but not nearly as tolerant of flooded conditions as the swamp phenotype. Floodplain plants differed from swamp plants in transporting less oxygen to the roots under drained conditions, initiating fewer succulent-type roots and not accelerating alcoholic fermentation upon flooding and after a year under flooded conditions having less total biomass, less oxygen transport to the roots and a greater accumulation of Fe and Mn in the roots. The floodplain plants apparently have been selected to be similar to upland plants under drained conditions and swamp plants under flooding and one consequence of this is that their tolerance of flooded conditions is intermediate. It is argued that one of the more important trade-offs in adapting to flooded conditions is that high internal oxygen transport carries with it a "cost" in terms of excessive water loss under water stress conditions.

Abstract: The hydrological, thermal, and chemical characteristics of two small streams flowing through relatively undisturbed, low-elevation mountain watersheds in southwestern British Columbia were investigated. All observations and chemical analyses of ecosystems were consistent with the hypothesis that stormflow originated mainly from flow of water through soil macrochannels to groundwater and thence to streams. Water budgets indicated unmeasured groundwater losses. The streams exhibited annual chemical cycles for most parameters, with maximum values in late summer and early autumn and minimum values in winter and early spring. Nitrate concentrations displayed no consistent seasonal variation, whereas potassium and sulphate concentrations were relatively uniform throughout the year. Most chemical parameters decreased with increasing discharge, whereas dissolved oxygen concentrations increased. Potassium concentrations exhibited some increases and some decreases, and chloride, nitrate, and sulphate concentrations were generally not significantly related to discharge. Concentration-discharge relationships were used to infer the origin of stormflow water. Differences in the chemistry of the two very similar streams have important ramifications for the design of watershed nutrient studies. Nutrient budgets were very similar to those of other watersheds in humid temperate regions, with net losses of calcium, sodium, magnesium, potassium, chloride, and sulphur. Nitrogen and phosphorus exports in dissolved or particulate organic form were not measured. Based on dissolved inorganic measurements, nitrogen was accumulated, while any gains or losses of phosphorus were extremely small.

Abstract: : Both the basic aspects of flood tolerance in plants and the applied aspects of establishing vegetation on reservoir shorelines are discussed through a comprehensive literature review. Flooding imposes complex stresses on many vascular plants, most of which arise from the depletion of oxygen in the flooded soil. Soil anoxia results in conditions that favor reduction reactions and anaerobic metabolism, which lead to the formation of ions in reduced valence states and organic acids and gases in concentrations exceeding those in aerobic soils. Changes in pH accompanying soil reduction may also alter nutrient availability. Plants avoid or mitigate these flooding stresses by either transferring oxygen into their roots via anatomical modifications in the shoot and/or by utilizing anaerobic respiration pathways in their roots. In addition to a plant's ability to withstand soil anaerobiosis, plant age, plant size, flood depth, flood duration, flood timing, substrate composition, wave action, and other factors determine survivorship when plants are flooded. Studies are reviewed that correlate these factors with species tolerances. A detailed summary of research relating directly to reservoir revegetation is provided, and species tolerances are assessed for each of the Army Corps of Engineers Divisions. Techniques for the establishment of vegetation around reservoirs are discussed, as are examples of species mortality prediction and impact assessment.

Abstract: Cotton (Gossypium hirsutum L. cv. H14) seedlings were raised in soil of differing soil water content in specially designed pots in which the roots had access to freely available water and nutrients located 2.5 cm below the base of the soil core. The time for root emergence from the soil core and the rate of root growth were measured daily from sowing to harvest. The root and shoot dry weight and leaf water potential were measured at the final harvest 16 days after sowing. As soil water content decreased, the root emerged from the soil earlier and the initial rate of root elongation was faster. In spite of the availability of freely available water, the plants in the soil at low water contents had significantly lower leaf water potentials than those in soil at high water contents. The root: shoot ratio increased as the soil water content decreased. This arose from an absolute increase in root weight, with shoot weight not being significantly affected.

Abstract: N, (C,H,) fixation and primary production were measured in communities of Thalassia testudinum at two sites in Bimini Harbor (Bahamas). Production was determined by uptake of [14C]NaHC03, by leaf growth measurements, and by applying an empirical formula based on leaf dimensions. The last two methods gave similar results but the 14C method gave higher values. Anaerobic sediment Nz fixation supplied about ‘/4 to % of the nitrogen demand for leaf production (by leaf growth method) and there was a significant correlation between Nz fixation and CO2 fixation rates when all components of the communities were considered (macrophyte, phyllosphere epiphytes, and detrital leaves). N2 fixation is important to production in Thalassia communities and the plant and its leaf epiphytes may be distinct entities in terms of nitrogen and carbon metabolism. Thulassia testudinum is the most prominent sea grass in the tropical and subtropical regions of the Atlantic Ocean, where it covers extensive portions of the subtidal zone (Moore 1963; Phillips 1960). These notably productive communities (Westlake 1963; McRoy and McMillan 1977) flourish in nutrient-poor waters (Smith et al. 1950). The source of nutrients for Thalassia communities has been the subject of several studies and some debate. Patriquin (1972), working in Barbados, observed a direct relationship between leaf growth and the concentration of interstitial NH4+ in the root zone. He suggested that, because reserves of av’ailable nitrogen were low in the sediments, bacterial NB fixation probably maintained the interstitial

Abstract: Crop plants accumulated chromium from nutrient solutions labelled with either 51CrIII or 51CrVI and retained approximately 98 % of the elements in the roots. Of the 9 crop species examined, cauliflower plants accumulated the most chromium in both shoots and roots and mung bean seedlings the least. Species differences of approximately 10-fold in the tops and 5-fold in the roots were recorded. The roots of each species supplied with 51CrIII contained more chromium than those supplied with 51CrVI but the reverse was found in the shoots. There was a greater proportion of soluble chromium in plants supplied with 51CrVI than in those supplied with 51CrIII, the major soluble compound being tentatively identified as trioxalato-CrIII. Little chromium was associated with cell organdies or soluble proteins.

Abstract: The purpose of this work was to determine the relative importance of mass flow and diffusion in supplying nutrients to wheat plants and to calculate nutrient uptake rates by roots (inflow). Winter wheat was grown in the field and measurements of plant Na, K, Ca, Mg, P, S and N contents, root length, plant water uptake and soil solution concentration made at regular intervals during growth. The apparent contribution of mass flow to plant uptake of nutrients between mid- April and mid-June was greater than the measured plant uptake for sodium, calcium, magnesium and sulphur (14, 9, 2 and 4 times respectively); however, only 50 % of the measured plant uptake of nitrogen and potassium and 5% of the phosphorus was supplied in this way. There were some 7 day periods when mass flow was able to supply the measured uptake of nitrogen and potassium, and it is possible that for these nutrients the importance of mass flow and diffusion may change during growth. Mean inflows (uptake in mol/cm root/sec) were calculated from sowing until mid- June. Inflow decreased for all nutrients from high initial values to low values during the winter and rose again in mid-April and May before falling in June. The increase in inflow in mid-April was concomitant with increased shoot growth but the precise factors controlling plant demand for nutrients and uptake in the field are still ill-defined.

Abstract: Current literature review and discussion of the N status of plants as related to their growth and yield and quality of produced product.

Abstract: (1) Lupinus arboreus rapidly colonizes micaceous china clay wastes, which are deficient in nitrogen, phosphorus, calcium and potassium. (2) Nitrogen accumulated at rates of about 180 Kg ha-1 y on areas where L. arboreus was established. The concentration of total, inorganic and mineralizable nitrogen increased in these soils. Non-legume species colonized the soil beneath L. arboreus and apparently benefited from the increased soil nitrogen status. (3) L. arboreus is tolerant of soils with low concentrations of major plant nutrients; this, and its ability to fix atmospheric nitrogen, makes it a suitable pioneer species for reclaiming wastes of low fertility. Trees and shrubs may be introduced in about the third year.

Abstract: The stability, regulating factors, and dynamics of an experimental community of pro- tozoans are examined here. The predator Didinjium nasutumn is found to coexist in microcosms with its prey, Colpidiunm campyl/um. Prey are limited by the quantity of bacteria and nutrients available. Didiniumn proves to be an ineffective predator and is limited by the availability and/or quality of prey as food. Enrichment of this community with bacteria or nutrients results in the extinction of prey and starvation of the predator. Increasing diversity of the lower trophic level by adding alternative prey species destabilizes this community, also causing extinction. Stability depends here on the charac- teristics of the particular species serving as prey and not simply the diversity of species present.

Abstract: An electromagnetic method was adapted to quantitatively measure blood flow through an external pudic artery of the udder in lactating cows during several months. Blood flow through the ipsilateral external pudic vein was blocked while blood was taken from a subcutaneous abdominal vein. Blood flow to milk yield ratio amounted to a mean value of 507:1 in three cows. Peak milk yield occurred before the time of our experiments. There was a high correlation (r = .73) between mammary arterial blood flow and milk yield. Arterio-venous differences (AV) across the udder demonstrated that essential amino acids (EAA) were taken up by the mammary gland in sufficient amounts to account for the EAA secreted as milk protein. Uptake of valine, isoleucine, lysine and particularly that of arginine was in excess of that for milk protein synthesis. There was a highly significant correlation (P<.01) between AV differences of several amino acids and their corresponding arterial concentrations. Uptake of glucose was

Abstract: Summary Nutrient influx across the soil-root interface (rate of uptake per unit of root surface area) is influenced by the demand of the plant for the nutrients required for additional growth. Size of influx will depend on the relation between area of active root surface and the demand of the shoot. Nutrient demand per unit of root, surface varies with many factors including plant species, cultivars within species, nutrient, plant age, root age, nutrient status of the plant, and light and temperature conditions. Interactions between these factors as well as changes within the plant to compensate for a low rate of supply of a particular nutrient make specific characterization of nutrient influx difficult. Average nutrient influx is usually greatest during the first two weeks of growth and then decreases as the plant matures. While effect of root age on influx differs with nutrient and plant species, influx of some nutrients continues even after root suberization. Split-root experiments indicate that increasing requirement of phosphate and potassium by the plant per unit of root does not increase influx until there is a reduction in the concentration of these nutrients in the shoot. Control of influx within the plant appears to reside in the shoot rather than the root. Limited data indicate that 60 per cent or more of the roots need to be absorbing at their maximum rate in order that influx of phosphate or potassium does not limit plant growth. Plants have a capacity to compensate for deficiencies and when nutrients become limiting they may increase root size relative to shoot demand, increase root hair density and length.

Abstract: Plants are sensitive to sulfur dioxide and they are affected by it both directly and indirectly. The direct effects may be acute or chronic, depending on the duration and intensity of the exposure. Sulfur dioxide inhibits photosynthesis by disrupting the photosynthetic mechanism. The opening of the stomata is promoted by sulfur dioxide, resulting in an excessive loss of water. The cumulative effect of sulferous pollution is to reduce the quantity and quality of plant yield. Generally, its impact is more severe when in combination with other pollutants such as oxides of nitrogen, fluorides, and ozone. At the ecosystem level, sulfur dioxide affects species composition by eliminating more sensitive species. This reduces primary productivity and alters trophic relationships which have far‐reaching implications for the animal and microbial populations in the community. Another indirect effect results from the acid rain which leaches out nutrients from plant canopy and soil. The acidic run‐off changes the pH of...

Abstract: Interrelations between plankton communities and dissolved carbohydrates and amino acids were investigated under near-natural conditions in sea water enclosed in plastic tanks. In summer 1972 the development of a natural plankton population was followed in a 3-m3 plastic tank for 28 d. In the course of this experiment, concentrations of dissolved neutral carbohydrates and free amino acids were determined. Results are in the range of published data for the open sea with respect to concentrations (0.2-2.5 pnoles dm-3 total sugar; 0.2-3.1 pnoles dm3 total amino acids) and qualitative composition. A plankton succession was observed during the experiment; this was accompanied by distinct alterations in the concentrations of dissolved amino acids and carbohydrates. Glucose and lysine occurred in highest concentrations. Maximum rate of increase was 29 nmoles dm3 h-' for glucose, and 25 nmoles dm3 h-' for lysine. The rates of decrease are in the same range as bacterial uptake rates determined by various authors employing tracer methods. Numerous positive, highly significant correlations suggest heteropolysaccharides as one source of individual carbohydrates. Relations between certain species within the plankton succession and occurrence of dissolved organic substances were observed. Significant positive correlations existed between glucose and diatoms as well as between glucose, galactose, mannose, arabinose and ribose and phytoplankton biomass. There were also several significant positive correlations of amino acids, especially of valine, leucine and isoleucine with other biological parameters.

Abstract: Thalassiosira gravida was rapidly displaced from ammonium-limited chemostats at moderate (D = 0.03. h-‘) and low (D = 0.01 *h-l) dilution rates by Skeletonema costatum or Chaetoceros septentrionalis. Reduced temperature or reduced light did not favor Thalassiosira. Chaetoceros displaced Skeletonema at D = O.O3*h-’ but the two species coexisted at D = 0.01-h-‘. A brief temperature increase triggered changes in population densities in chemostats with coexisting species, leading to an increase in the less abundant species. Reduced turbulence did not change the pattern of coexistence. Nutrient-dependent growth-rate kinetics for the three species were deduced from rates of displacement in competition experiments and from published uptake kinetic and chemical composition data. The kinetics deduced by the two methods were qualitatively similar. Nutricrit kinetics apparently do not explain the survival of natural populations of T. gruvida in the field. On the basis of these results, a nutrient-based functional group of phytoplankton is defined to include S. costatum and C. septentrionalis and exclude T. gravidu.

Abstract: The general pattern of nutrient distribution in the Gulf of St. Lawrence results from regeneration processes being superimposed on the physical processes of estuarine circulation within the Gulf. This leads to a general increase in nutrient concentration with depth and with distance into the Gulf from Cabot Strait. Nutrient concentrations in the Laurentian Channel are higher inside the Gulf than at equal or even greater depths in the Atlantic Ocean some distance outside Cabot Strait. Summer nutrient concentrations in the surface layer are generally low. However, during the winter when biological activity is low, quite high concentrations of the nutrients are found in the surface waters of the Gulf. A balance exists between inward and outward fluxes of all three nutrients through Cabot Strait in the winter. However, in the summer the influxes of both nitrate and silicate at Cabot Strait greatly exceed the outgoing fluxes. Losses of biogenic silica to the sediments may account for the silicate imbalance. Ex...

Abstract: The influence of community and edaphic variables on tissue nutrient concentration was assessed for 6 species occupying a Scirpus-Equisetum emergent aquatic wetland in southern Quebec, Canada. Potassium and nitrogen (12.0-23.5 mg/g) had by far the highest tissue concentrations followed by Ca > Na > P > Mg. Micronutrient concentrations (Fe > Mn > Zn > Cu) ranged from .003-.532 mg/g. Macronutrients were 1.3-6 times and micronutrients 2-20 times as great as reported in Carex, Fagus, and Quercus dominated ecosystems. Mean tissue concentrations of N, P and K were consistent between species. Variation was ?3 (24%) that observed in Ca, Mg and the micronutrients (74%). All elements except Cu, Na, and Zn had closely similar patterns of interspecies variation. Chelation, ion antagonism and increased solu- bility of micronutrients in flooded soils were possible mechanisms accounting for the unique patterns of Cu, Na, and Zn accumulation. Equisetum fluviatile had the highest level of total nutrients in green tissue. This was over twice that in Phragmites communis which had the lowest level. Moderate tissue nutrient concentrations were observed at both pioneer and mature extremes of a species primary successional gradient. However, compared to the community average, element concentrations were 22.3% higher in pioneer species and 21.9o lower in mature species. Species ordinated by principal components analysis showed wide differences between species. No species occupied a median position in the model. Edaphic parameters were 4 to 5 times more important than community structural attributes in varying tissue element concentrations. Soil potassium concentration was the foremost or second most important parameter in 9 of 12 elements tested by multiple regression. It was concentrated in plant tissue 79-fold over levels measured in the soil. This was 4 times the enrichment noted for phosphorus and 12-34 times the enrichment of other micronutrients. Among soil elements, potassium had the highest correlation with tissue P, K, Ca and Mg concentration. Soil calcium had the highest correlation with tissue nitrogen and the micronutrients Cu, Fe and Mn. The concentration of any soil element, however, never explained more than 64% of the variation in any tissue element.

Abstract: The effects over a wide range of interaction of sulfur (S) (5 levels) × phosphorus (P) (5) × nitrogen (N) (6) on nodulation and development of the soybean growing in a nutrient-deficient soil are described for three growth stages: flowering, pod-fill and seed maturity. There were consistent main effects for all three nutrients, but interactions changed from nil at flowering to a few P × N and P × S at pod-fill; and then to predominant P × S at maturity for the principal plant parts. Nodulation was extremely sensitive to levels of nutrient combination, with extremes of nutrient imbalance reducing nodulation almost to zero. Conversely, well-balanced combinations favoured nodulation right through growth until maturity, the best nodulation occurring at high levels of all three nutrients. The yield of seed was not affected by nitrogen supply when sulfur and phosphorus were adequate for an effective nitrogen symbiosis. Introduction

Abstract: Changes in tissue nutrient concentration and nutrient uptake of a C, native grassland and a sown C4 buffel grassland community, growing on infertile sandy red earth soils near Charleville, were studied. The seasonal pattern of litter production of grasslands in the grazed and ungrazed situation was also investigated. Studies in litter decomposition of Mitchell grass are reported. The decline in the above-ground biomass growth rate of both communities over the summer growing period corresponded with a similar trend in the uptake of nitrogen and phosphorus. Moreover, tissue shoot phosphorus concentrations of all perennial grass species were always low. The total amount of nutrient absorbed (nitrogen, phosphorus) was about 35 % greater for the buffel compared with the native grassland community. Both communities could be contrasted with respect to the efficiency of nutrient absorption and nutrient utilization. Continued overgrazing led to a reduction in litter and root yield. As little biomass was produced by the community over the autumn-winter period, the litter production rate could be expressed as a function of herbage yield at the commencement of the period and was found to be relatively independent of grazing pressure. The agronomic and ecological implications of these results are discussed in relation to the management of these grasslands.

Abstract: An imidazoline modified styrene-acrylonitrile polymer composition which is substantially insoluble in aqueous media at about pH 6 or more but swellable or soluble at pH 3 or less is employed as a coating for nutrient or therapeutic substances for administration to ruminants. The substances thus are rendered resistant to attack and breakdown in the rumen yet remain susceptible to release and digestion within the abomasum or small intestine of the animal.

Abstract: The major ion composition and distribution in Lake Myvatn reflects the chemical composition of the cold and warm spring waters which drain into the lake. Spring discharge rates as calculated from chemical balances agree well with direct current measurements. Trace metal concentrations are generally low. The input loading rates of nutrient elements from springs are presently 1.4, 1.5 and 340 g m72 yfC' for N, P and Si respectively. Diatomite mining and refining activities have in recent years increased the N and P loading by 38% and 3% respectively. Dissolved silicate concentrations in the lake remain high throughout the summer but concentrations of inorganic nitrogen compounds are very low. The summer phosphate concentrations are low but biologically significant. In winter after the onset of ice cover an inverse thermocline develops and oxygen may be depleted from the bottom water. Oxygen production by benthic diatoms reestablishes oxic conditions in February-March, with improving light conditions. Chemical balance calculations suggest a net production by diatoms of 380 SiO2 m72 yr' and 222 g C m2 yr-1 and also suggests that the nitrogen fixation by bluegreen algae may amount to 8 g N m2 yr-1. A tephra layer dating from 1477 in a core from the Syorifl6i basin indicates a sedimentation rate of 2.2 mm yr-1 or 500 g m-2 yr1. The annual cycles of plants and nutrients are discussed in the light of results from algal bioassay, the loading and distribution of nutrients and phytoplankton succession.

Abstract: Summary Assuming average values for absorption and steady state conditions for uptake a mathematical model is derived for the uptake of nutrients by root systems growing in uniformly mixed soil Laboratory experiments with young plants grown under these conditions show that the model leads to reasonable predictions of uptake of nitrate and potassium, but not of insoluble nutrients such as phosphate