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Nutrient Addition (nutrient + addition)
Selected AbstractsEffects of Interactions of Moisture Regime and Nutrient Addition on Nodulation and Carbon Partitioning in Two Cultivars of Bean (Phaseolus vulgaris L.)JOURNAL OF AGRONOMY AND CROP SCIENCE, Issue 4 2001T. Boutraa Major limitations of bean (Phaseolus vulgaris L.) production in arid and semiarid regions are lack of moisture and low soil fertility. An experiment was conducted to determine the effects of soil moisture and N : P : K (20 : 10 : 10) fertilizer on root and shoot growth of two cultivars of bean: cv. Carioca, an indeterminate Brazilian landrace, and cv. Prince, a determinate cultivar grown in Europe. Carioca appears generally stress-tolerant while Prince is intolerant. Seedlings were grown in pots of non-sterile soil at 30, 60 or 90 % field capacity (FC), and given 0, 0.1 or 1 g (kg soil),1 of compound fertilizer. The soil contained a population of effective Rhizobium. Growth of both cultivars was greatest in the high moisture and high nutrient treatments. Root fractions were highest at low nutrient supply; the effect of water was not significant. Leaf fraction decreased as root fraction increased. Numbers of nodules were highest at high and intermediate moisture when no fertilizer was applied. Numbers were lowest at 30 % FC and at the highest fertilizer rate. Masses of nodules and fractions followed the same pattern. Decreasing water regime reduced the relative growth rate (RGR) of Prince, while Carioca maintained high RGR at unfavourable conditions of water and nutrients. Net assimilation rates (NAR) were unaffected by nutrient addition, and reduced by low moisture regime. Water use efficiencies (WUEs) were reduced by water stress but increased by nutrient deficiency. The water utilization for dry matter production was optimal at 60 % FC. Einflüsse der Interaktionen von Bodendenfeuchte und Düngung auf die Knöllchenbildung und Kohlenstoff verteilung bei zwei Bohnenkultivaren (Phaseolus vulgaris L.) Der begrenzende Hauptfaktor der Bohnenproduktion in ariden und semiariden Regionen sind der Feuchtigkeitsmangel und die Bodenfruchbarkeit. Es wurde ein Experiment durchgeführt, um die Wirkungen des Bodenwassers und von N : P : K (20 : 10 : 10) Dünger auf das Wurzel- und Sproßwachstum an zwei Kultivaren von Bohnen (Phaseolus vulgaris L. cv. Carioca, eine brasilianischen, indeterminierte Landsorte und cv. Prince, eine determinierter in Europa angebauter Kultivar) zu untersuchen. Carioca erscheint grundsätzlich streßtoleranter im Vergleich zu Prince. Die Sämlinge wurden in Gefäßen mit nichtsterilisiertem Boden unter Feldkapazitäten von 30,60 oder 90 % mit 0, 0,1 oder 1 g eines Volldüngers angezogen. Der Boden enthielt eine Population von wirksamem Rhizobium. Das stärkste Wachstum wurde bei beiden Kultivaren unter dem Einfluß des höchsten Feuchtigkeitsgehaltes und der höchsten Düngermenge gefunden. Der Wurzelanteil war bei der geringen Düngermenge am niedrigsten. Der Einfluß der Bodenfeuchtigkeit war nicht signifikant. Der Blattanteil nahm mit zunehmendem Wurzelanteil ab. Die Anzahl der Knötchen war bei hoher und mittlerer Bodenfeuchte und ohne Düngeranwendung am höchsten. Die Anzahl war am geringsten bei 30 % FC und der höchsten Düngermenge. Die Knötchenmasse und ihr Anteil reagierte entsprechend. Abnehmende Bodenfeuchte reduzierte die relative Wachtumsrate (RGR) von Prince, während Carioca einen hohen RGR auch bei ungünstigen Bedingungen bezüglich Wasser und Düngung behielt. Die Nettoassimilationsraten wurden durch die Düngung nicht beeinflußt; sie gingen bei geringer Bodenfeuchte zurück. Die Wassernutzungseffiziens (WUE) wurde bei Wasserstreß reduziert, nahm aber bei Düngermangel zu. Die Wassernutzung für die Trockenmasseproduktion war bei 60 % Feldkapazität am höchsten. [source] Effects of environmental perturbations on abundance of subarctic plants after three, seven and ten years of treatmentsECOGRAPHY, Issue 1 2001Enrico Graglia Analyses of changes in vegetation were carried out after three, seven and ten years of fertilizer addition, warming and light attenuation in two subarctic, alpine dwarf shrub heaths. One site was just above the tree line, at ca 450 m a.s.l., and the other at a much colder fell-field at ca 1150 m altitude. The aim was to investigate how the treatments affected the abundance of different species and growth forms over time, including examinations of transient changes. Grasses, which increased in abundance by fertilizer addition, and cryptogams, which, by contrast, decreased by fertilizer addition and warming, were the most sensitive functional groups to the treatments at both sites. Nutrient addition exerted a stronger and more consistent effect than both shading and warming. Warming at the fell-field had slightly greater effect than at the warmer tree line with an increase in deciduous shrubs. The decreased abundance of mosses and lichens to fertilizer addition and/or warming was most likely an indirect treatment effect, caused by competition through increased abundance and overgrowth of grasses. Such changes in species composition are likely to alter decomposition rates and the water and energy exchange at the soil surface. We observed few, if any, transient effects of declining responses during the 10 yr of treatments. Instead, there were many cumulative effects of the treatments for all functional groups and many interactions between time and treatment, suggesting that once a change in community composition is triggered, it will continue with unchanged or accelerated rate for a long period of time. [source] A comparison of invasive and non-invasive dayflowers (Commelinaceae) across experimental nutrient and water gradientsDIVERSITY AND DISTRIBUTIONS, Issue 5-6 2004Jean H. Burns ABSTRACT Little is known about the traits and mechanisms that determine whether or not a species will be invasive. Invasive species are those that establish and spread after being introduced to a novel habitat. A number of previous studies have attempted to correlate specific plant traits with invasiveness. However, many such studies may be flawed because they fail to account for shared evolutionary history or fail to measure performance directly. It is also clear that performance is context dependent. Thus, an approach that corrects for relatedness and incorporates multiple experimental conditions will provide additional information on performance traits of invasive species. I use this approach with two or three pairs of invasive and closely related non-invasive species of Commelinaceae grown over experimental gradients of nutrient and water availability. Invasive species have been introduced, established, and spread outside their native range; non-invasive species have been introduced, possibly (but not necessarily) established, but are not known to have spread outside their native range. The invasive species had higher relative growth rates (RGR) than non-invasive congeners at high nutrient availabilities, but did not differ from non-invasive species at low nutrient availabilities. This is consistent with a strategy where these particular invasive species are able to rapidly use available resources. Relative growth rates were also higher for two out of three invasive species across a water availability gradient, but RGR did not differ in plasticity between the invasive and non-invasive species. This suggests that nutrient addition, but not changes in water availability, might favour invasion of dayflowers. This approach is novel in comparing multiple pairs of invasive and non-invasive congeners across multiple experimental conditions and allows evaluation of the robustness of performance differences. It also controls for some of the effects of relatedness that might confound multispecies comparisons. [source] Are UV-induced nonculturable Escherichia coli K-12 cells alive or dead?FEBS JOURNAL, Issue 12 2003Andrea Villarino Cells that have lost the ability to grow in culture could be defined operationally as either alive or dead depending on the method used to determine cell viability. As a consequence, the interpretation of the state of ,nonculturable' cells is often ambiguous. Escherichia coli K12 cells inactivated by UV-irradiation with a low (UV1) and a high (UV2) dose were used as a model of nonculturable cells. Cells inactivated by the UV1 dose lost ,culturability' but they were not lysed and maintained the capacity to respond to nutrient addition by protein synthesis and cell wall synthesis. The cells also retained both a high level of glucose transport and the capacity for metabolizing glucose. Moreover, during glucose incorporation, UV1-treated cells showed the capacity to respond to aeration conditions modifying their metabolic flux through the Embden,Meyerhof and pentose-phosphate pathways. However, nonculturable cells obtained by irradiation with the high UV2 dose showed several levels of metabolic imbalance and retained only residual metabolic activities. Nonculturable cells obtained by irradiation with UV1 and UV2 doses were diagnosed as active and inactive (dying) cells, respectively. [source] Species-level effects more important than functional group-level responses to elevated CO2: evidence from simulated turvesFUNCTIONAL ECOLOGY, Issue 3 2004M. E. HANLEY Summary 1Using mixtures of 14 calcareous grassland plant species drawn from three functional groups, we looked at the effects of elevated atmospheric CO2 on contrasting levels of ecosystem performance (species, functional group and community). Experimental communities were subjected to ambient (,350 µmol mol,1) or elevated CO2 (,600 µmol mol,1) in controlled environments, with grazing simulated by clipping at monthly intervals for 546 days. 2We assessed the effect of elevated CO2 on plant performance by quantifying the productivity (biomass) and cover of component species. We also examined the effect of elevated CO2 on the vertical structure of the plant canopy. Elevated CO2 resulted in a significant increase in total community biomass only following nutrient addition. Within functional groups, non-leguminous forb species had significantly greater biomass and cover in elevated CO2 both before and after nutrient addition, although the effect was mainly due to the influence of one species (Centaurea nigra). Grasses, in contrast, responded negatively to elevated CO2, although again significant reductions in biomass and cover could mainly be ascribed to a single species (Brachypodium pinnatum). Legumes exhibited increased biomass and cover in elevated CO2 (the effects being particularly marked for Anthyllis vulneraria and Lotus corniculatus), but this response disappeared following nutrient addition. Vertical structure was little affected by CO2 treatment. 3We conclude that due to the idiosyncratic responses of individual species, the categorization of plants into broad functional groups is of limited use in guiding our understanding of the impacts of elevated atmospheric CO2 on plant communities. [source] Effects of nutrient additions on ecosystem carbon cycle in a Puerto Rican tropical wet forestGLOBAL CHANGE BIOLOGY, Issue 2 2006YIQING LI Abstract Wet tropical forests play a critical role in global ecosystem carbon (C) cycle, but C allocation and the response of different C pools to nutrient addition in these forests remain poorly understood. We measured soil organic carbon (SOC), litterfall, root biomass, microbial biomass and soil physical and chemical properties in a wet tropical forest from May 1996 to July 1997 following a 7-year continuous fertilization. We found that although there was no significant difference in total SOC in the top 0,10 cm of the soils between the fertilization plots (5.42±0.18 kg m,2) and the control plots (5.27±0.22 kg m,2), the proportion of the heavy-fraction organic C in the total SOC was significantly higher in the fertilized plots (59%) than in the control plots (46%) (P<0.05). The annual decomposition rate of fertilized leaf litter was 13% higher than that of the control leaf litter. We also found that fertilization significantly increased microbial biomass (fungi+bacteria) with 952±48 mg kg,1soil in the fertilized plots and 755±37 mg kg,1soil in the control plots. Our results suggest that fertilization in tropical forests may enhance long-term C sequestration in the soils of tropical wet forests. [source] Effects of Interactions of Moisture Regime and Nutrient Addition on Nodulation and Carbon Partitioning in Two Cultivars of Bean (Phaseolus vulgaris L.)JOURNAL OF AGRONOMY AND CROP SCIENCE, Issue 4 2001T. Boutraa Major limitations of bean (Phaseolus vulgaris L.) production in arid and semiarid regions are lack of moisture and low soil fertility. An experiment was conducted to determine the effects of soil moisture and N : P : K (20 : 10 : 10) fertilizer on root and shoot growth of two cultivars of bean: cv. Carioca, an indeterminate Brazilian landrace, and cv. Prince, a determinate cultivar grown in Europe. Carioca appears generally stress-tolerant while Prince is intolerant. Seedlings were grown in pots of non-sterile soil at 30, 60 or 90 % field capacity (FC), and given 0, 0.1 or 1 g (kg soil),1 of compound fertilizer. The soil contained a population of effective Rhizobium. Growth of both cultivars was greatest in the high moisture and high nutrient treatments. Root fractions were highest at low nutrient supply; the effect of water was not significant. Leaf fraction decreased as root fraction increased. Numbers of nodules were highest at high and intermediate moisture when no fertilizer was applied. Numbers were lowest at 30 % FC and at the highest fertilizer rate. Masses of nodules and fractions followed the same pattern. Decreasing water regime reduced the relative growth rate (RGR) of Prince, while Carioca maintained high RGR at unfavourable conditions of water and nutrients. Net assimilation rates (NAR) were unaffected by nutrient addition, and reduced by low moisture regime. Water use efficiencies (WUEs) were reduced by water stress but increased by nutrient deficiency. The water utilization for dry matter production was optimal at 60 % FC. Einflüsse der Interaktionen von Bodendenfeuchte und Düngung auf die Knöllchenbildung und Kohlenstoff verteilung bei zwei Bohnenkultivaren (Phaseolus vulgaris L.) Der begrenzende Hauptfaktor der Bohnenproduktion in ariden und semiariden Regionen sind der Feuchtigkeitsmangel und die Bodenfruchbarkeit. Es wurde ein Experiment durchgeführt, um die Wirkungen des Bodenwassers und von N : P : K (20 : 10 : 10) Dünger auf das Wurzel- und Sproßwachstum an zwei Kultivaren von Bohnen (Phaseolus vulgaris L. cv. Carioca, eine brasilianischen, indeterminierte Landsorte und cv. Prince, eine determinierter in Europa angebauter Kultivar) zu untersuchen. Carioca erscheint grundsätzlich streßtoleranter im Vergleich zu Prince. Die Sämlinge wurden in Gefäßen mit nichtsterilisiertem Boden unter Feldkapazitäten von 30,60 oder 90 % mit 0, 0,1 oder 1 g eines Volldüngers angezogen. Der Boden enthielt eine Population von wirksamem Rhizobium. Das stärkste Wachstum wurde bei beiden Kultivaren unter dem Einfluß des höchsten Feuchtigkeitsgehaltes und der höchsten Düngermenge gefunden. Der Wurzelanteil war bei der geringen Düngermenge am niedrigsten. Der Einfluß der Bodenfeuchtigkeit war nicht signifikant. Der Blattanteil nahm mit zunehmendem Wurzelanteil ab. Die Anzahl der Knötchen war bei hoher und mittlerer Bodenfeuchte und ohne Düngeranwendung am höchsten. Die Anzahl war am geringsten bei 30 % FC und der höchsten Düngermenge. Die Knötchenmasse und ihr Anteil reagierte entsprechend. Abnehmende Bodenfeuchte reduzierte die relative Wachtumsrate (RGR) von Prince, während Carioca einen hohen RGR auch bei ungünstigen Bedingungen bezüglich Wasser und Düngung behielt. Die Nettoassimilationsraten wurden durch die Düngung nicht beeinflußt; sie gingen bei geringer Bodenfeuchte zurück. Die Wassernutzungseffiziens (WUE) wurde bei Wasserstreß reduziert, nahm aber bei Düngermangel zu. Die Wassernutzung für die Trockenmasseproduktion war bei 60 % Feldkapazität am höchsten. [source] How important is climate?JOURNAL OF APPLIED ECOLOGY, Issue 5 2003Effects of warming, fish on phytoplankton in shallow lake microcosms, nutrient addition Summary 1Climate is changing. Predictions are for at least a 3 °C rise in mean temperature in northern Europe over the next century. Existing severe impacts of nutrients and inappropriate fish stocking in freshwater systems remain. 2Effects of warming by 3 °C above ambient, nutrient addition and the presence or absence of sticklebacks Gasterosteus aculeatus were studied in experimental microcosms dominated by submerged plants, mimicking shallow lake ecosystems. 3Warming had considerably smaller effects on the phytoplankton community than did fish and nutrients. It had very minor effects on chlorophyll a and total phytoplankton biovolume. However, it significantly decreased the biovolumes of Cryptophyceae (a major component in the controls) and Dinophyceae. Contrary to expectation, warming did not increase the abundance of blue-green algae (cyanophytes). Warming decreased the abundances of Cryptomonas erosa (Cryptophyceae) and Oocystis pusilla (Chlorophycota) and increased those of two other green algae, Tetraedron minimum and Micractinium pusillum. It had no effect on a further 17 species that were predominant in a community of about 90 species. 4Fish and nutrients, either together or separately, generally increased the crops of most of the 21 abundant species and of the algal groups. Exceptions were for diatoms and chrysophytes, which were very minor components of the communities. Fish, but neither nutrients nor warming, increased the number of species of phytoplankton detected. This was probably through removal of zooplankton grazers, and parallels terrestrial studies where the presence of top predators, by controlling herbivores, leads to increased plant diversity. 5There was no particular pattern in the taxonomy or biological characteristics of those species affected by the treatments. In particular, there was no link between organism size (a surrogate for many important biological features of phytoplankton species) and the effects of warming, nutrient addition or presence or absence of fish. However, all species were relatively small and potentially vulnerable to grazing. 6Synthesis and applications. The results suggest that fears of an increasing abundance of cyanophytes with current projections of global warming may be unrealized, at least in shallow unstratified lakes still dominated by macrophytes. However, they emphasize that eutrophication and fish manipulations remain very important impact factors that determine the abundance of phytoplankton and subsequent problems caused by large growths. [source] Formation of nonculturable Escherichia coli in drinking waterJOURNAL OF APPLIED MICROBIOLOGY, Issue 5 2005L.A. Bjergbæk Abstract Aims:, To examine whether incubation of Escherichia coli in nondisinfected drinking water result in development of cells that are not detectable using standard procedures but maintain a potential for metabolic activity and cell division. Methods and Results:, Survival and detectability of four different E. coli strains were studied using drinking water microcosms and samples from contaminated drinking water wells. Recovery of E. coli was compared using different cultivation-dependent methods, fluorescence in situ hybridization (FISH) using specific oligonucleotide probes, direct viable counts (DVC), and by enumeration of gfp -tagged E. coli (green fluorescent protein, GFP). Two levels of stress responses were observed after incubation of E. coli in nondisinfected drinking water: (i) the presence of cells that were not detected using standard cultivation methods but could be cultivated after gentle resuscitation on nonselective nutrient-rich media, and (ii) the presence of cells that responded to nutrient addition but could only be detected by cultivation-independent methods (DVC, FISH and GFP). Collectively, the experiments demonstrated that incubation for 20,60 days in nondisinfected drinking water resulted in detection of only 0·7,5% of the initial E. coli population using standard cultivation methods, whereas 1,20% could be resuscitated to a culturable state, and 17,49% could be clearly detected using cultivation-independent methods. Conclusions:, Resuscitation of stressed E. coli on nonselective nutrient-rich media increased cell counts in drinking water using both traditional (CFU), and cultivation-independent methods (DVC, FISH and GFP). The cultivation-independent methods resulted in detection of 10,20 times more E. coli than the traditional methods. The results indicate that a subpopulation of substrate-responsive but apparent nonculturable E. coli may develop in drinking water during long-term starvation survival. Significance and Impact of the Study:, The existence of substrate-responsive but nonculturable cells should be considered when evaluating the survival potential of E. coli in nondisinfected drinking water. [source] EFFECT OF NUTRIENT DEPRIVATION AND RESUPPLY ON METABOLITES AND ENZYMES RELATED TO CARBON ALLOCATION IN GRACILARIA TENUISTIPITATA (RHODOPHYTA),JOURNAL OF PHYCOLOGY, Issue 2 2004Pi Nyvall Collén The starch content of red algae normally increases during nitrogen limitation. Based on this we hypothesized that nutrient deprivation would result in an increased activity of starch-synthesizing enzymes and a decrease in the activity of starch-degrading enzymes, with the opposite scenario when nutrients were sufficient. We therefore examined the effect of the nutrient status of Gracilaria tenuistipitata Chang et Xia on the content of starch and floridoside and on the activity of enzymes involved in the allocation of carbon into starch, floridoside, and agar; floridoside phosphate synthase and ,-galactosidase involved in synthesis and degradation of floridoside; starch synthase and starch phosphorylase involved in the metabolism of starch; uridine 5,-diphosphate (UDP)-glucose pyrophosphorylase; adenosine 5,-diphosphate-glucose pyrophosphorylase; UDP-glucose 4-epimerase; and phosphoglucomutase. During the period of nutrient limitation the starch and floridoside content increased, as did dry weight and C/N ratio, whereas growth rate and protein content decreased. A general decrease in the enzyme activities during nutrient limitation was also observed, indicating a decrease in overall cellular metabolism. The addition of nutrients caused an increase in enzyme activities and a decrease in the contents of starch and floridoside. Of the enzymes examined, only the activity of UDP-glucose pyrophosphorylase increased during nutrient limitation and decreased abruptly after nutrient addition. This implies a regulatory role for this enzyme in the supply of UDP-glucose for starch synthesis. It also supports our suggestion that UDP-glucose is the substrate for starch synthesis in red algae. This assertion is further strengthened by the observation that of the potential starch synthases only the UDP-glucose starch synthase could support the observed rate of starch synthesis. [source] Responses of subalpine dwarf-shrub heath to irrigation and fertilizationJOURNAL OF VEGETATION SCIENCE, Issue 3 2007Lisa Brancaleoni Aeschimann et al. (2004) for vascular plants with the exceptions of Vaccinium uliginosum ssp. microphyl-lum, henceforth called V. uliginosum (instead of Vaccinium gaultherioides Bigelow) and Festuca rubra L. ssp. commu-tata Gaudin, henceforth called F. rubra (instead of Festuca nigrescens Lam.); Frahm & Frey (1987) for bryophytes with the exception of Polytrichastrum alpinum (Hedw.) G.L. Smith instead of Polytrichum alpinum Hedw Abstract Question: Our study aimed at testing to what extent water and/or nutrients affect community composition in sub-alpine heath. We hypothesized that nutrient addition will have an overall positive effect on heath vegetation but water addition will have greater effects and will probably reinforce the effects of fertilization in drier habitat conditions. Location: Monte Rondinaio, northern Apennines, Italy (44°08' N; 10°35' E, ca. 1850-1930 m a.s.l.). Methods: Nutrients and water were added during five growing seasons in two communities (HV community, moister; EV community, drier) and the biomass of all species was estimated non-destructively by the point-quadrat method. Results: Total above-ground biomass increased in both communities with fertilization due to increased graminoid biomass and decreased moss biomass, but was unaffected by irrigation. In the HV community species richness decreased as an effect of fertilization while in the EV community species richness was raised by irrigation. Conclusions: Our study partly supported our hypothesis since water addition had a stronger effect in the drier community. However, this effect was not revealed by changes in above-ground biomass but rather by differing responses of individual species in the two communities. [source] Stress tolerance abilities and competitive responses in a watering and fertilization field experimentJOURNAL OF VEGETATION SCIENCE, Issue 6 2005P. Liancourt Abstract Question: Do water gradients produce patterns of responses to stress and competition similar to those induced by nutrient gradients? Location: French Alps. Methods: We established a split-plot design in a calcareous grassland, with watering and fertilization as main plot treatments and competition as subplot treatment. We followed individual and competitive responses of transplants of the three potential dominant grass species: Bromus erectus, Brachypodium rupestre and Arrhenatherum elatius, in all plots during two growing seasons. Changes in natural relative abundances of the three grass species were also monitored. Results: The growth and the relative abundance of A. elatius were primarily stimulated by nutrient addition and those of B. rupestre by water addition, whereas B. erectus decreased in abundance and had a very low flexibility with enhanced resource supply. Competition intensity increased for all species with both watering and fertilization and the ranking in competitive responses did not change with treatments: A. elatius > B. rupestre > B. erectus. Conclusions: Patterns of dominance were efficiently explained by stress tolerance abilities and competitive responses for dry and poor sites, and wet and rich sites for B. erectus and A. elatius respectively, whereas competitive responses were poor predictors of dominance for B. rupestre in wet and nutrient-poor sites. Further studies are needed to assess the potential role of other processes, such as increasing competitive effect on light with increasing age as well as interference, to explain the dominance of this conservative competitor type of species in wet and nutrient-poor sites. [source] Nutrient limitation and morphological plasticity of the carnivorous pitcher plant Sarracenia purpurea in contrasting wetland environmentsNEW PHYTOLOGIST, Issue 3 2008Terry Bott Summary ,,Plasticity of leaf nutrient content and morphology, and macronutrient limitation were examined in the northern pitcher plant, Sarracenia purpurea subsp. purpurea, in relation to soil nutrient availability in an open, neutral pH fen and a shady, acidic ombrotrophic bog, over 2 yr following reciprocal transplantation of S. purpurea between the wetlands. ,,In both wetlands, plants were limited by nitrogen (N) but not phosphorus (P) (N content < 2% DW,1, N : P < 14) but photosynthetic quantum yields were high (FV/FM > 0.79). Despite carnivory, leaf N content correlated with dissolved N availability to plant roots (leaf N vs , r2 = 0.344, P < 0.0001); carnivorous N acquisition did not apparently overcome N limitation. ,,Following transplantation, N content and leaf morphological traits changed in new leaves to become more similar to plants in the new environment, reflecting wetland nutrient availability. Changes in leaf morphology were faster when plants were transplanted from fen to bog than from bog to fen, possibly reflecting a more stressful environment in the bog. ,,Morphological plasticity observed in response to changes in nutrient supply to the roots in natural habitats complements previous observations of morphological changes with experimental nutrient addition to pitchers. [source] Remedial options for chlorinated volatile organics in a partially anaerobic aquiferREMEDIATION, Issue 4 2004Xiujin Qiu A laboratory study was conducted for the selection of appropriate remedial technologies for a partially anaerobic aquifer contaminated with chlorinated volatile organics (VOCs). Evaluation of in situ bioremediation demonstrated that the addition of electron donors to anaerobic microcosms enhanced biological reductive dechlorination of tetrachloroethene (PCE), trichloroethene (TCE), and 1,1,1-trichloroethane (1,1,1-TCA) with half-lives of 20, 22, and 41 days, respectively. Nearly complete reductions of PCE, TCE, 1,1,1-TCA, and the derivative cis-dichloroethene were accompanied by a corresponding increase in chloride concentrations. Accumulation of vinyl chloride, ethene, and ethane was not observed; however, elevated levels of 14CO2 (from 14C-TCE spiked) were recovered, indicating the occurrence of anaerobic oxidation. In contrast, very little degradation of 1,2-dichloropropane (1,2-DCP) and 1,1-dichlorethane (1,1-DCA) was observed in the anaerobic microcosms, but nutrient addition enhanced their degradation in the aerobic biotic microcosms. The aerobic degradation half-lives for 1,2-DCP and 1,1-DCA were 63 and 56 days, respectively. Evaluation of in situ chemical oxidation (ISCO) demonstrated that chelate-modified Fenton's reagent was effective in degrading aqueous-phase PCE, TCE, 1,1,1-TCA, 1,2-DCP, etc.; however, this approach had minimal effects on solid-phase contaminants. The observed oxidant demand was 16 g-H2O2/L-groundwater. The oxidation reaction rates were not highly sensitive to the molar ratio of H2O2:Fe2+:citrate. A ratio of 60:1:1 resulted in slightly faster removal of chemicals of concern (COCs) than those of 12:1:1 and 300:1:1. This treatment resulted in increases in dissolved metals (Ca, Cr, Mg, K, and Mn) and a minor increase of vinyl chloride. Treatment with zero-valent iron (ZVI) resulted in complete dechlorination of PCE, and TCE to ethene and ethane. ZVI treatment reduced 1,1,1-TCA only to 1,1-DCA and chloroethane (CA) but had little effect on reducing the levels of 1,2-DCP, 1,1-DCA, and CA. The longevity test showed that one gram of 325-mesh iron powder was exhausted in reaction with > 22 mL of groundwater. The short life of ZVI may be a barrier to implementation. The ZVI surface reaction rates (ksa) were 1.2 × 10,2 Lm,2h,1, 2 × 10,3 Lm,2h,1, and 1.2 × 10,3 Lm,2h,1 for 1,1,1-TCA, TCE, and PCE, respectively. Based upon the results of this study, in situ bioremediation appeared to be more suitable than ISCO and ZVI for effectively treating the groundwater contamination at the site. © 2004 Wiley Periodicals, Inc. [source] Bottom-up effects on a plant-endophage-parasitoid system: The role of flower-head size and chemistryAUSTRAL ECOLOGY, Issue 1 2010ANDRÉ T. C. DIAS Abstract The effects of water and nutrient addition on a trophic chain were studied in a plant-endophage-parasitoid system comprised of insects associated with flower heads of Chromolaena squalida (Asteraceae). Nine species of endophages associated with C. squalida flower heads were found, belonging to two families of Diptera , Tephritidae (Cecidochares sp1, Cecidochares sp2, Xanthaciura biocellata, X. chrysura, X. sp. and Neomyopites sp.) and Agromyzidae (Melanagromyza sp.), and two families of Coleoptera , Apionidae (Apion sp.) and Anthicidae (Anthicidae sp.). A factorial field experiment with water and nutrient addition showed that resource availability can affect the developmental process of flower heads. Fertilization increased flower-head diameter and nitrogen and alkaloid concentrations. Although nutrient availability affected the size and chemistry of flower heads, endophage species did not respond consistently to the experimental treatments. This is contrary to other studies where endophages showed preference for larger flower heads. Thus, the plant vigour hypothesis was not corroborated for our study system. Our results also showed that coupled responses of plants to resource availability (i.e. tissue nutritional quality and investment in growth of the structure that serves as shelter for endophages) can represent distinct kinds of indirect interactions with opposing effects on the herbivore-parasitoid interaction. [source] Why do some species in arid lands increase under grazing?AUSTRAL ECOLOGY, Issue 5 2009Mechanisms that favour increased abundance of Maireana pyramidata in overgrazed chenopod shrublands of South Australia Abstract While the abundance of some plant species decreases under high grazing intensity, others become more abundant. Release from competition by decreaser species contributes to this pattern in mesic systems, but this may not be the case in xeric systems where competition may be less intense. Here we examine three mechanisms that may be involved: (i) increased recruitment and growth because of soil changes produced by grazing, for example, increased soil nutrient availability through dung accumulation; (ii) increased recruitment favoured by the breaking up of the lichen crust; and (iii) reduced competition because of the decline of decreaser species. We used field and glasshouse experiments to determine the possible contribution of these mechanisms to the increase of the chenopod Maireana pyramidata around a watering point in a chenopod shrubland of South Australia. There was no evidence of nutrient accumulation close to the watering point, and while seedlings of M. pyramidata responded to nutrient addition, their growth was the same in soil collected from areas with different grazing intensity. While a broken lichen crust increased the emergence of both M. pyramidata and the decreaser Atriplex vesicaria, the effect was larger for the former. We found no competition between seedlings of the two species or between juveniles of A. vesicaria and seedlings of M. pyramidata in glasshouse experiments. Adult plants of both A. vesicaria and M. pyramidata produced similar growth reduction in seedlings of M. pyramidata. Furthermore, a field removal experiment failed to detect any competitive effect of A. vesicaria on M. pyramidata. Our data indicate that the disintegration of the soil crust by grazer activities can be a major factor controlling floristic changes in overgrazed rangelands. These results imply that factors that control establishment may be more important than competition in shaping shrub population dynamics in these systems. Ground surface itself can affect establishment opportunities, and this should be taken into account in management and restoration efforts in arid lands. [source] Potential of agroindustrial waste from olive oil industry for fuel ethanol productionBIOTECHNOLOGY JOURNAL, Issue 12 2007Tania I. Georgieva Abstract Olive pulp (OP) is a highly polluting semi-solid residue generated from the two-stage extraction processing of olives and is a major environmental issue in Southern Europe, where 80% of the world olive oil is produced. At present, OP is either discarded to the environment or combusted with low calorific value. In this work, utilization of OP as a potential substrate for production of bioethanol was studied. Enzymatic hydrolysis and subsequent glucose fermentation by baker's yeast were evaluated for OP from 10% to 30% dry matter (i.e., undiluted). Enzymatic hydrolysis resulted in an increase in glucose concentration by 75%, giving final glucose yields near 70%. Fermentation of undiluted OP hydrolysate (OPH) resulted in the maximum ethanol produced (11.2 g/L) with productivity of 2.1 g/L/h. Ethanol yields were similar for all tested OPH concentrations and were in the range of 0.49-0.51 g/g. Results showed that yeast could effectively ferment OPH even without nutrient addition, revealing the tolerance of yeast to OP toxicity. Because of low xylan (12.4%) and glucan (16%) content in OP, this specific type of OP is not a suitable material for producing only ethanol and thus, bioethanol production should be integrated with production of other value-added products. [source] Efficacy of intervention strategies for bioremediation of crude oil in marine systems and effects on indigenous hydrocarbonoclastic bacteriaENVIRONMENTAL MICROBIOLOGY, Issue 6 2007Boyd A. McKew Summary There is little information on how different strategies for the bioremediation of marine oil spills influence the key indigenous hydrocarbon-degrading bacteria (hydrocarbonoclastic bacteria, HCB), and hence their remediation efficacy. Therefore, we have used quantitative polymerase chain reaction to analyse changes in concentrations of HCB in response to intervention strategies applied to experimental microcosms. Biostimulation with nutrients (N and P) produced no measurable increase in either biodegradation or concentration of HCB within the first 5 days, but after 15 days there was a significant increase (29%; P < 0.05) in degradation of n -alkanes, and an increase of one order of magnitude in concentration of Thalassolituus (to 107 cells ml,1). Rhamnolipid bioemulsifier additions alone had little effect on biodegradation, but, in combination with nutrient additions, provoked a significant increase: 59% (P < 0.05) more n -alkane degradation by 5 days than was achieved with nutrient additions alone. The very low Alcanivorax cell concentrations in the microcosms were hardly influenced by addition of nutrients or bioemulsifier, but strongly increased after their combined addition, reflecting the synergistic action of the two types of biostimulatory agents. Bioaugmentation with Thalassolituus positively influenced hydrocarbon degradation only during the initial 5 days and only of the n -alkane fraction. Bioaugmentation with Alcanivorax was clearly much more effective, resulting in 73% greater degradation of n -alkanes, 59% of branched alkanes, and 28% of polynuclear aromatic hydrocarbons, in the first 5 days than that obtained through nutrient addition alone (P < 0.01). Enhanced degradation due to augmentation with Alcanivorax continued throughout the 30-day period of the experiment. In addition to providing insight into the factors limiting oil biodegradation over time, and the competition and synergism between HCB, these results add weight to the use of bioaugmentation in oil pollution mitigation strategies. [source] Effects of upstream lakes and nutrient limitation on periphytic biomass and nitrogen fixation in oligotrophic, subalpine streamsFRESHWATER BIOLOGY, Issue 11 2007AMY M. MARCARELLI Summary 1. We conducted bioassays of nutrient limitation to understand how macronutrients and the position of streams relative to lakes control nitrogen (N2) fixation and periphytic biomass in three oligotrophic Rocky Mountain catchments. We measured periphytic chlorophyll- a (chl- a) and nitrogen-fixation responses to nitrogen (N) and phosphorus (P) additions using nutrient-diffusing substrata at 19 stream study sites, located above and below lakes within the study catchments. 2. We found that periphytic chl- a was significantly co-limited by N and P at 13 of the 19 sites, with sole limitation by P observed at another four sites, and no nutrient response at the final two sites. On average, the addition of N, P and N + P stimulated chl- a 35%, 114% and 700% above control values respectively. The addition of P alone stimulated nitrogen fixation by 2500% at five of the 19 sites. The addition of N, either with or without simultaneous P addition, suppressed nitrogen fixation by 73% at nine of the 19 sites. 3. Lake outlet streams were warmer and had higher dissolved organic carbon concentrations than inlet streams and those further upstream, but position relative to lakes did not affect chl- a and nitrogen fixation in the absence of nutrient additions. Chl- a response to nutrient additions did not change along the length of the study streams, but nitrogen fixation was suppressed more strongly by N, and stimulated more strongly by P, at lower altitude sites. The responses of chl- a and nitrogen fixation to nutrients were not affected by location relative to lakes. Some variation in responses to nutrients could be explained by nitrate and/or total N concentration. 4. Periphytic chl- a and nitrogen fixation were affected by nutrient supply, but responses to nutrients were independent of stream position in the landscape relative to lakes. Understanding interactions between nutrient supply, nitrogen fixation and chl- a may help predict periphytic responses to future perturbations of oligotrophic streams, such as the deposition of atmospheric N. [source] Effects of experimentally induced cyanobacterial blooms on crustacean zooplankton communitiesFRESHWATER BIOLOGY, Issue 2 2003Anas Ghadouani SUMMARY 1.,Large in situ enclosures were used to study the effects of experimentally induced cyanobacterial blooms on zooplankton communities. A combination of N and P was added to shallow (2 m) and deep enclosures (5 m) with the goal of reducing the TN : TP ratio to a low level (,5 : 1) to promote cyanobacterial growth. After nutrient additions, high biomass of cyanobacteria developed rapidly in shallow enclosures reaching levels only observed during bloom events in eutrophic lakes. 2.,In the shallow enclosures, particulate phosphorus (PP) was on average 35% higher in comparison with deep enclosures, suggesting that depth plays a key role in P uptake by algae. Phytoplankton communities in both deep and shallow enclosures were dominated by three cyanobacteria species ,Aphanizomenon flos-aquae, Anabaena flos-aquae and Microcystis aeruginosa, which accounted for up to 70% of total phytoplankton biomass. However, the absolute biomass of the three species was much higher in shallow enclosures, especially Aphanizomenon flos-aquae. The three cyanobacteria species responded in contrasting ways to nutrient manipulation because of their different physiology. 3.,Standardised concentrations of the hepatotoxic microcystin-LR increased as a result of nutrient manipulations by a factor of four in the treated enclosures. Increased biomass of inedible and toxin producing cyanobacteria was associated with a decline in Daphnia pulicaria biomass caused by a reduction in the number of individuals with a body length of >1 mm. Zooplankton biomass did not decline at moderate cyanobacteria biomass, but when cyanobacteria reached high biomass large cladocerans were reduced. 4.,Our results demonstrate that zooplankton communities can be negatively affected by cyanobacterial blooms and therefore the potential to use herbivory to reduce algal blooms in such eutrophic lakes appears limited. [source] Effects of nutrient additions on ecosystem carbon cycle in a Puerto Rican tropical wet forestGLOBAL CHANGE BIOLOGY, Issue 2 2006YIQING LI Abstract Wet tropical forests play a critical role in global ecosystem carbon (C) cycle, but C allocation and the response of different C pools to nutrient addition in these forests remain poorly understood. We measured soil organic carbon (SOC), litterfall, root biomass, microbial biomass and soil physical and chemical properties in a wet tropical forest from May 1996 to July 1997 following a 7-year continuous fertilization. We found that although there was no significant difference in total SOC in the top 0,10 cm of the soils between the fertilization plots (5.42±0.18 kg m,2) and the control plots (5.27±0.22 kg m,2), the proportion of the heavy-fraction organic C in the total SOC was significantly higher in the fertilized plots (59%) than in the control plots (46%) (P<0.05). The annual decomposition rate of fertilized leaf litter was 13% higher than that of the control leaf litter. We also found that fertilization significantly increased microbial biomass (fungi+bacteria) with 952±48 mg kg,1soil in the fertilized plots and 755±37 mg kg,1soil in the control plots. Our results suggest that fertilization in tropical forests may enhance long-term C sequestration in the soils of tropical wet forests. [source] The impact of tourism on dune lakes on Fraser Island, AustraliaLAKES & RESERVOIRS: RESEARCH AND MANAGEMENT, Issue 1 2003Wade L. Hadwen Abstract In view of the increasing tourism to Fraser Island, Queensland, a tourist pressure index (TPI) was developed to assess the potential threat of tourism to 15 of the most accessible dune lakes on the island. Tourist pressure index scores indicated that the two clear lakes on the island, Lake McKenzie and Lake Birrabeen, are most threatened by tourist activities owing to their accessibility, facilities and prominence in advertising campaigns. In addition, limnological investigations of the same 15 lakes were conducted in February 1999 to determine their current trophic status and potential susceptibility to adverse impacts from tourism, particularly with reference to eutrophication. On the basis of nutrient and chlorophyll a concentrations, the two water table window lakes, Ocean Lake and Lake Wabby, were classed as mesotrophic and oligo-mesotrophic, while all of the perched dune lakes were oligotrophic. Lake McKenzie and Lake Birrabeen, the two most threatened lakes according to TPI scores, had the lowest nutrient concentrations of all of the lakes examined and, consequently, we suggest that nutrient additions might elicit rapid algal growth responses in these systems. Comparisons between current data and historical data from Arthington et al. (1990) indicate that increases in planktonic chlorophyll a concentrations were not always directly mirrored by increases in total phosphorus concentrations. We found that while chlorophyll a concentrations were significantly higher in the 1999 samples than in the 1990 samples for all lakes, total phosphorus concentrations were higher in Ocean Lake, lower in Lake Jennings and similar in lakes McKenzie, Birrabeen and Wabby. [source] Do nutrient additions alter carbon sink strength of ectomycorrhizal fungi?NEW PHYTOLOGIST, Issue 2 2001M. I. Bidartondo Summary ,,Carbon sink strength differences are examined here between ectomycorrhizal fungi in interaction with additions of ammonium and apatite (a phosphorus- and calcium-containing mineral). ,,Pinus muricata associated with Paxillus involutus and four suilloid isolates (Suillus pungens and members of three Rhizopogon section Amylopogon species groups) were used in microcosm nutrient addition experiments. ,,The associations differed in ectomycorrhizal biomass, mycelial growth rate, biomass and respiration. P. involutus produced the lowest biomass of ectomycorrhizal connections to P. muricata, but it consumed proportionally more carbon per connection and transferred more than twice as much ammonium to the host per unit mycorrhizal biomass. Paxillus also colonized the soil more rapidly and intensely than the other fungi, but its mycelial respiration was lowest. Ammonium and apatite addition resulted in a marked increase in respiration and mycelial biomass, respectively, by the suilloid fungi. ,,The high carbon cost of ammonium uptake is suggested as one explanation for reduced sporocarp production and mycelial growth by ectomycorrhizal fungi commonly found after high levels of nitrogen addition. [source] Nutrient Limitation to Primary Productivity in a Secondary Savanna in Venezuela1BIOTROPICA, Issue 4 2002Nichole N. Barger ABSTRACT We examined nutrient limitation to primary productivity in a secondary savanna in the interior branch of the Coastal Range of Venezuela, which was converted from forest to savanna more than 100 years ago. We manipulated soil nutrients by adding nitrogen (+N), phosphorus and potassium (+PK), and nitrogen, phosphorus, and potassium (+NPK) to intact savanna. Eleven months after fertilization, we measured aboveground biomass and belowground biomass as live fine roots in the top 20 cm of soil, and species and functional group composition in response to nutrient additions. Aboveground biomass was highest in the NPK treatment ([mean g/m2]; control = 402, +N = 718, +PK = 490, +NPK = 949). Aboveground production, however, appeared to be limited primarily by N. Aboveground biomass increased 78 percent when N was added alone but did not significantly respond to PK additions when compared to controls. In contrast to aboveground biomass, belowground biomass increased with PK additions but showed no significant increase with N (depth 0,20 cm; [mean g/m2]; control = 685, +N = 443, +PK = 827, +NPK = 832). There was also a 36 percent increase in root length with PK additions when compared to controls. Whole savanna shoot:root ratios were similar for control and +PK (0.6), while those for +N or +NPK fertilization were significantly higher (1.7 and 1.2, respectively). Total biomass response (above + belowground) to nutrient additions showed a strong N and PK co-limitation ([mean g/m2]; control = 1073, +N = 1111, +PK = 1258, +NPK = 1713). Aboveground biomass of all monocots increased with N additions, whereas dicots showed no response to nutrient additions. Trachypogon spp. (T. plumosus+T. vestitus) and Axonopus canescens, the two dominant grasses, made up more than 89 percent of the total aboveground biomass in these sites. Trachypogon spp. responded to NPK, whereas A. canescens, sedges, and the remaining monocots only responded to N. Even though nutrient additions resulted in higher aboveground biomass in N and NPK fertilized plots, this had little effect on plant community composition. With the exception of sedges, which responded positively to N additions and increased from 4 to 8 percent of die plant community, no changes were observed in plant community composition after 11 months. RESUMEN En este estudio se examinaron las limitaciones nutricionales en la productividad primatia de una sabana secundaria de más de 100 años localizada en el brazo interior de la Cordillera de la Costa de Venezuela. Se manipularon los nutrientes del suelo mediante la adición de nitrógeno (+N), fósforo y potasio (+PK), y nitrógeno, fósforo, y potasio (+NPK) al suelo de la sabana. Después de once meses de iniciarse los experimentos se midió la respuesta a la adición de nutrientes en términos de producción de biomasa aérea, biomasa de raíces finas vivas en los primeros 20 cm de suelo, y cambios en la composición de especies y grupos funcionales. La biomasa aérea fue mayor en las parcelas fertilizadas con N o en combinación de NPK ([promedio g/m2]; control = 402, +N = 718, +PK = 490, +NPK = 949) indicando que la producción aéiea está limitada principalmente por N. No hubo respuesta estadísticamente significativa a la adición de PK con respecto a los controles. La biomasa de raíces finas aumentó con la adición de PK y NPK mientras que no hubo aumento significativo con N (Profundidad 0,20 cm; [promedio g/m2]; control=685, +N=443, +PK=827, +NPK=832). La adición de PK modificó la arquitectura radical con un anmento de 36 por ciento en la longitud de las raíces con respecto al control. La relación vástago/raíz fue similar en los tratmientos controly + PK (0.6), pero significativamente mayor en +N (1.7)y +NPK(1.2) indicando nuevamente una limitación principal por N. La respuesta de la biomasa total (vástago +raíces vivas) a la adición de nutrientes refleja una colimitación de N y PK ([promedio g/m2]; control=1073, +N=1111, +PK+1258,+NPK=1713). La biomasa aérea de las monocotiledóneas aumentó de N, mientras que no hubo respuesta significativa a la adición de nutrientes en las dicotiledóneas. Trachypogon spp (T. Plumosus+T. vestitus) and Axonopus canescens, las dos gramíneas dominantes, representaron más del 89 por ciento de la biomasa total en las parcelas. Trachypogon spp respondieron a NPK, mientras que A. canescens, cuoeráceas, y las otras monocotiledóneas sólo respondieron a N. No hubo cambios significativos en la composición de especies como respuesta a la adición de nutrientes, con la excepción de las ciperáceas que respondieron significativamente a la adición de N con un aumento de 4 a 8 por ciento. [source] | |||||||||||||||||||||||||