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Nutrient Status (nutrient + status)
Selected AbstractsA Comparison of the Soil Water, Nutrient Status, and Litterfall Characteristics of Tropical Heath and Mixed-Dipterocarp Forest Sites in Brunei,BIOTROPICA, Issue 1 2000Jonathan A. Moran ABSTRACT Two of the main hypotheses to explain the distribution and special characteristics of tropical heath forest are nutrient and water limitation. A study was undertaken to investigate both factors on two sites under tropical heath forest (Badas Forest Reserve) and mixed-dipterocarp forest (Andulau Forest Reserve) in Brunei. Soil water potentials were monitored at depths of 20, 50, and 90 cm over wet and dry periods for five months at each site. The results showed the mixed-dipterocarp forest site to be drier at 50 cm depth compared to the tropical heath forest site. There was no significant difference in water potentials between sites at 20 or 90 cm. Nutrient concentrations in the soil solution were monitored at the same depths over a seven-month period at the same sites. A 12-month litterfall study was also undertaken to monitor nutrient returns from the canopy at each site. The results of both studies suggest that the tropical heath forest site is poorer in nitrogen, but richer in calcium, than the mixed-dipterocarp forest site. The results for phosphorus are less clear, but do not suggest that its limitation is a significant factor at the tropical heath forest site compared to the mixed-dipterocarp forest site. Phosphorus and magnesium concentrations in the soil solution showed a strong positive correlation with sliding 30-day rainfall totals at both sites. [source] LKB1 and AMP-activated protein kinase control of mTOR signalling and growthACTA PHYSIOLOGICA, Issue 1 2009R. J. Shaw Abstract The AMP-activated serine/threonine protein kinase (AMPK) is a sensor of cellular energy status found in all eukaryotes that is activated under conditions of low intracellular ATP following stresses such as nutrient deprivation or hypoxia. In the past 5 years, work from a large number of laboratories has revealed that one of the major downstream signalling pathways regulated by AMPK is the mammalian target-of-rapamycin [mammalian target of rapamycin (mTOR) pathway]. Interestingly, like AMPK, the mTOR serine/threonine kinase plays key roles not only in growth control and cell proliferation but also in metabolism. Recent work has revealed that across eukaryotes mTOR orthologues are found in two biochemically distinct complexes and only one of those complexes (mTORC1 in mammals) is acutely sensitive to rapamycin and regulated by nutrients and AMPK. Many details of the molecular mechanism by which AMPK inhibits mTORC1 signalling have also been decoded in the past 5 years. AMPK directly phosphorylates at least two proteins to induce rapid suppression of mTORC1 activity, the TSC2 tumour suppressor and the critical mTORC1 binding subunit raptor. Here we explore the molecular connections between AMPK and mTOR signalling pathways and examine the physiological processes in which AMPK regulation of mTOR is critical for growth or metabolic control. The functional conservation of AMPK and TOR in all eukaryotes, and the sequence conservation around the AMPK phosphorylation sites in raptor across all eukaryotes examined suggest that this represents a fundamental cell growth module connecting nutrient status to the cell growth machinery. These findings have broad implications for the control of cell growth by nutrients in a number of cellular and organismal contexts. [source] A cross-system synthesis of consumer and nutrient resource control on producer biomassECOLOGY LETTERS, Issue 7 2008Daniel S. Gruner Abstract Nutrient availability and herbivory control the biomass of primary producer communities to varying degrees across ecosystems. Ecological theory, individual experiments in many different systems, and system-specific quantitative reviews have suggested that (i) bottom,up control is pervasive but top,down control is more influential in aquatic habitats relative to terrestrial systems and (ii) bottom,up and top,down forces are interdependent, with statistical interactions that synergize or dampen relative influences on producer biomass. We used simple dynamic models to review ecological mechanisms that generate independent vs. interactive responses of community-level biomass. We calibrated these mechanistic predictions with the metrics of factorial meta-analysis and tested their prevalence across freshwater, marine and terrestrial ecosystems with a comprehensive meta-analysis of 191 factorial manipulations of herbivores and nutrients. Our analysis showed that producer community biomass increased with fertilization across all systems, although increases were greatest in freshwater habitats. Herbivore removal generally increased producer biomass in both freshwater and marine systems, but effects were inconsistent on land. With the exception of marine temperate rocky reef systems that showed positive synergism of nutrient enrichment and herbivore removal, experimental studies showed limited support for statistical interactions between nutrient and herbivory treatments on producer biomass. Top,down control of herbivores, compensatory behaviour of multiple herbivore guilds, spatial and temporal heterogeneity of interactions, and herbivore-mediated nutrient recycling may lower the probability of consistent interactive effects on producer biomass. Continuing studies should expand the temporal and spatial scales of experiments, particularly in understudied terrestrial systems; broaden factorial designs to manipulate independently multiple producer resources (e.g. nitrogen, phosphorus, light), multiple herbivore taxa or guilds (e.g. vertebrates and invertebrates) and multiple trophic levels; and , in addition to measuring producer biomass , assess the responses of species diversity, community composition and nutrient status. [source] The effects of calcium on stem lesions of silver birch seedlingsFOREST PATHOLOGY, Issue 2 2007A. Lilja Summary In this study, we tested the hypothesis that decreased liming of growth medium has a role in the increase of stem lesions and top dying caused by Phytophthora cactorum in containerized silver birch seedlings (Betula pendula) in Finnish forest nurseries. The effect of limestone dose rates on growth and the nutrient status was also monitored. An index based on severity of symptom expression was used to compare the effect of different liming treatments on P. cactorum infection. Limestone amended into the sphagnum peat growth medium increased the amount of calcium in the seedling stems. Liming did not significantly decrease the disease severity although index values in most cases decreased with the increased limestone dose rates. In general, the lesions were restricted after out-planting and the mortality of seedlings was low. Only inoculated seedlings on which the lesions had spread around the stem in the nursery died. Phytophthora cactorum appears to be a nursery pathogen, as it did not survive under conditions present in the field. Four years after out-planting, the tallest birches were those grown in sphagnum peat amended with the highest limestone dose of 8 kg m,3. [source] Could rising aquatic carbon dioxide concentrations favour the invasion of elodeids in isoetid-dominated softwater lakes?FRESHWATER BIOLOGY, Issue 9 2009P. SPIERENBURG Summary 1. During the past century, isoetid vegetation types in softwater lakes have often been invaded by faster-growing elodeids. In these C-limited systems, this may be related to rising aquatic CO2 levels. 2. In a laboratory experiment we tested the growth response of two elodeid species, Myriophyllum alterniflorum and Callitriche hamulata, at four different CO2 levels, ranging from 20 to 230 ,mol L,1. In addition, we tested the effect of the nutrient status of the sediment on the growth of C. hamulata at the different CO2 levels. 3. Shoot and root growth increased with rising CO2 availability. Irrespective of sediment type, growth was minimal to negative at the lowest CO2 treatment level, while becoming positive at CO2 levels around 40,50 ,mol L,1. Substantial growth was only obtained when the macrophytes were growing on mesotrophic sediments. The plants reached close to maximal growth at CO2 levels of c. 100 ,mol L,1. 4. Within this experiment, the growth of C. hamulata at CO2 levels above 90 ,mol L,1 may have been limited by N and P availability in both sediment types. The growth rate of M. alterniflorum did not seem to be limited by N and P availability, most likely due to its much higher relative root production. 5. The experimental results show that neither M. alterniflorum nor C. hamulata is able to invade isoetid-dominated softwater lakes at very low aquatic CO2 concentrations. However, if the sediments contain enough nutrients, a rise in aquatic CO2 could allow the invasion of elodeid species leading to the subsequent disappearance of slow-growing isoetids. [source] Plant palatability and disturbance level in aquatic habitats: an experimental approach using the snail Lymnaea stagnalis (L.)FRESHWATER BIOLOGY, Issue 5 2002ARNAUD ELGER 1.,The palatability of aquatic macrophytes to the snail Lymnaea stagnalis was investigated in the laboratory. Eight species of macrophyte were selected from habitats that differed in either flood disturbance regime or nutrient status. 2.,In a non-choice test, single macrophyte species were offered to individual snails. The average amount of plant dry mass consumed per Lymnaea dry mass ranged from 3.6 ± 1.4 (±SE) to 63.6 ± 13.9 mg g,1 day,1 across plant species. In a choice test, all eight plant species were presented simultaneously to sets of five snails. The average total consumption was 66.1 ± 3.8 mg g,1 day,1 and the maximum average consumption for a single plant was 26.2 ± 3.6 mg g,1 day,1. 3.,In both tests, the amount consumed by snails differed significantly between the plant species. The species growing in undisturbed habitats were the least consumed. Habitat nutrient status was unrelated to plant palatability. 4.,These results suggest that macrophyte species growing in habitats that are rarely disturbed by floods allocate a greater proportion of their resources to resisting herbivory. [source] The potential significance of microbial Fe(III) reduction during deposition of Precambrian banded iron formationsGEOBIOLOGY, Issue 3 2005K. O. KONHAUSER ABSTRACT During deposition of late Archean,early Palaeoproterozoic Precambrian banded iron formations (BIFs) the downward flux of ferric hydroxide (Fe(OH)3) and phytoplankton biomass should have facilitated microbial Fe(III) reduction. However, quantifying the significance of such a metabolic pathway in the Precambrian is extremely difficult, considering the post-depositional alteration of the rocks and the lack of ideal modern analogues. Consequently, we have very few constraints on the Fe cycle at that time, namely (i) the concentration of dissolved Fe(II) in the ocean waters; (ii) by what mechanisms Fe(II) was oxidized (chemical, photochemical or biological, the latter using either O2 or light); (iii) where the ferric hydroxide was precipitated (over the shelf vs. open ocean); (iv) the amount of phytoplankton biomass, which relates to the nutrient status of the surface waters; (v) the relative importance of Fe(III) reduction vs. the other types of metabolic pathways utilized by sea floor microbial communities; and (vi) the proportion of primary vs. diagenetic Fe(II) in BIF. Furthermore, although estimates can be made regarding the quantity of reducing equivalents necessary to account for the diagenetic Fe(II) component in Fe-rich BIF layers, those same estimates do not offer any insights into the magnitude of Fe(III) actually generated within the water column, and hence, the efficiency of Fe and C recycling prior to burial. Accordingly, in this study, we have attempted to model the ancient Fe cycle, based simply on conservative experimental rates of photosynthetic Fe(II) oxidation in the euphotic zone. We estimate here that under ideal growth conditions, as much as 70% of the biologically formed Fe(III) could have been recycled back into the water column via fermentation and organic carbon oxidation coupled to microbial Fe(III) reduction. By comparing the potential amount of biomass generated phototrophically with the reducing equivalents required for Fe(III) reduction and magnetite formation, we also hypothesize that another anaerobic metabolic pathway might have been utilized in the surface sediment to oxidize the fermentation by-products. Based on the premise that the deep ocean waters were anoxic, this role could have been fulfilled by methanogens, and maybe even methanotrophs that employed Fe(III) reduction. [source] Toenail selenium and risk of hepatocellular carcinoma mortality in Haimen City, China,INTERNATIONAL JOURNAL OF CANCER, Issue 4 2005Lori C. Sakoda Abstract Selenium (Se) is an essential trace mineral with known anticarcinogenic properties in humans. However, few studies have examined the association between Se nutrient status and risk of liver cancer. We conducted a nested case-control study comparing the Se content in toenail clippings of 166 individuals (154 men, 12 women) with hepatocellular carcinoma (HCC) to 394 healthy controls (360 men, 34 women) in Haimen City, China, where HCC is a leading cause of mortality. Toenail Se concentration was measured by inductively coupled plasma-optical emission spectroscopy. Median toenail Se was lower for HCC cases than controls (p = 0.03). Adjusted odds ratios and 95% confidence intervals for HCC mortality by increasing quartile of toenail Se were 1.00 (reference), 0.58 (0.32,1.03), 0.83 (0.48,1.42) and 0.50 (0.28,0.90), with a marginally significant trend in risk observed (p for trend = 0.06). This inverse association appeared stronger among those who did not consume alcohol and among women. Future studies are needed to examine the interrelationship between Se, viral hepatitis infection and HCC in order to better understand the etiologic mechanisms involved and evaluate the true chemopreventive potential of Se compounds for liver diseases. © 2005 Wiley-Liss, Inc. [source] Cell Lysis of Cyanobacteria and Its Implications for Nutrient DynamicsINTERNATIONAL REVIEW OF HYDROBIOLOGY, Issue 3 2010Linlin Ye Abstract The dynamics of nutrients, such as phosphorus, nitrogen, and carbohydrates, during cyanobacteria cell lysis was investigated under darkness incubation in the laboratory. The cell lysis rate of cyanobacteria sampled from Lake Taihu was measured using an esterase assay. Based on particulate esterase activity, the calculated cyanobacteria lysis rate was 0.094 d,1. During 30 days of darkness incubation, Chlorophyll a concentration decreased from 56 ,g L,1 to 2.0 ,g L,1. Parallel to this, total particulate carbohydrate concentration decreased rapidly. The fluctuation of dissolved organic carbon concentration was a function of the production of non-carbohydrate by cyanobacteria and the decomposition of carbohydrate by bacteria. Total dissolved carbohydrates and dissolved polysaccharides concentrations showed a similar pattern, declining at the beginning of the experiment and keeping relatively stable, thereafter. In contrast, the concentration of dissolved monosaccharides remained constant during the entire process. The concentrations of NH4+ and PO43, increased at the early stage, and then decreased afterwards. A gradual decrease in NO3, concentration after day 8 indicated that anaerobic conditions might be produced during the cell lysis process. The present results demonstrated cyanobacteria cell lysis has a big influence on the nutrient status of the surrounding water. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Interactions between nutrient status and weevil herbivory in the biological control of water hyacinthJOURNAL OF APPLIED ECOLOGY, Issue 1 2000Tim A. Heard Summary 1.,Despite the widespread release of effective biocontrol agents, water hyacinth remains the world's most problematic aquatic weed, particularly in eutrophic waterbodies. However, understanding of the interaction between control and trophic status is still incomplete. 2.,Growth of water hyacinth plants was measured at two water nutrient concentrations (high and medium) and in the presence and absence of two insect biocontrol agents in a large circulating hydroponic system in a glasshouse. 3.,At the high nutrient concentration (1·6 mg l,1 N and 1·0 mg l,1 P), plants multiplied more quickly, attaining greater biomass. Both insect species reduced plant growth at both nutrient concentrations. Neochetina bruchi, however, performed better than N. eichhorniae at the high nutrient concentration by inflicting more damage on the plants and reducing biomass by a greater extent. 4.,Insect damage reduced the concentrations of nitrogen and phosphorus found in plants growing in high nutrient water but not in medium nutrient water (0·4 mg l,1 N and 0·025 mg l,1 P). 5.,The developmental and reproductive performance of N. bruchi was determined at both nutrient concentrations. Water hyacinth plants grown at higher nutrient concentration were superior hosts to N. bruchi than plants grown at medium concentrations. Net reproductive rate and intrinsic rate of increase were significantly greater at the high concentrations. Greater damage by N. bruchi to water hyacinth at the high nutrient concentration was due to the greater production of offspring, and hence greater larval damage. 6.,We predict that water hyacinth problems will be greater in eutrophic waterbodies, where N. bruchi will be a superior biocontrol agent to N. eichhorniae. In low-nutrient waterbodies, local nutrient enrichment of water may assist the establishment of control agents. These results illustrate the importance of wider ecological factors on the success of biological control. [source] Erythroneura lawsoni abundance and feeding injury levels are influenced by foliar nutrient status in intensively managed American sycamoreAGRICULTURAL AND FOREST ENTOMOLOGY, Issue 1 2010David Robert Coyle 1Abundance and feeding injury of the leafhopper Erythroneura lawsoni Robinson was measured in an intensively-managed American sycamore Platanus occidentalis L. plantation. Trees were planted in spring 2000 in a randomized complete block design, and received one of three annual treatments: (i) fertilization (120 kg N/ha/year); (ii) irrigation (3.0 cm/week); (iii) fertilization + irrigation; or (iv) control (no treatment). 2Foliar nutrient concentrations were significantly influenced by the treatments because only sulphur and manganese levels were not statistically greater in trees receiving fertilization. 3Over 116 000 E. lawsoni were captured on sticky traps during the study. Leafhopper abundance was highest on nonfertilized trees for the majority of the season, and was positively correlated with foliar nutrient concentrations. Significant temporal variation in E. lawsoni abundance occurred, suggesting five discrete generations in South Carolina. 4Significant temporal variation occurred in E. lawsoni foliar injury levels, with the highest injury ratings occurring in late June and August. Foliar injury was negatively correlated with foliar nutrient content, and higher levels of injury occurred more frequently on nonfertilized trees. 5The results obtained in the present study indicated that increased E. lawsoni abundance occurred on trees that did not receive fertilization. Nonfertilized trees experienced greater foliar injury, suggesting that lower foliar nutrient status may have led to increased levels of compensatory feeding. [source] Dietary intakes and nutrient status of vegetarian preschool children from a British national surveyJOURNAL OF HUMAN NUTRITION & DIETETICS, Issue 3 2000C.W. Thane Background Dietary intakes and nutrient status were compared in meat-eaters and non-meat-eaters from the National Diet and Nutrition Survey of children aged 1.5,4.5 years. Methods Children (n = 1351) were categorized as ,omnivores' or ,vegetarians', according to whether they consumed meat or meat products during a 4-day dietary record. Blood samples were also obtained for analysis of haematological and biochemical nutrient status. Results Three per cent of children were ,vegetarian'. They consumed higher proportions of milk and milk products, although this was significant only in older children (P = 0.007), owing to high consumption by the high proportion of Asian children. In vegetarians, energy intakes tended to be lower in both age groups. Percentage energy from protein and fat were lower, while that from carbohydrate was higher compared with omnivores. Cholesterol intakes were lower, significantly so for younger children (P < 0.001). Intakes of micronutrients were either higher (vitamins C and E, potassium) or lower (niacin and sodium) in younger vegetarians compared with omnivores. Energy-adjusted intakes of iron and zinc did not differ significantly from those of omnivores, although both intakes were low in many children (6,20% < LRNI), particularly in the younger group. Haematological and biochemical nutrient status indices showed few differences. Serum ferritin was lower in vegetarians, significantly so in younger children (P = 0.002). Antioxidant vitamin (A, C and E) status tended to be higher in vegetarians, while vitamin B12 intakes and status were more than adequate. Apart from poorer vitamin D intake and status in older Asian vegetarians, very few ethnic differences were observed. Conclusions Nutrient intakes and status were generally adequate in preschool children who did not eat meat. Although serum ferritin levels were inferior (particularly in vegetarians under 3 years old), the lower intakes of fat, cholesterol and sodium, and higher antioxidant vitamin intakes and status indices were potentially beneficial. Given a balanced diet, adequate nutrient intakes and status can be maintained without consuming meat. [source] INTERCOLONIAL VARIABILITY IN MACROMOLECULAR COMPOSITION IN P-STARVED AND P-REPLETE SCENEDESMUS POPULATIONS REVEALED BY INFRARED MICROSPECTROSCOPY,JOURNAL OF PHYCOLOGY, Issue 5 2008Philip Heraud Macromolecular variability in microalgal populations subject to different nutrient environments was investigated, using the chlorophyte alga Scenedesmus quadricauda (Turpin) Bréb. as a model organism. The large size of the four-cell coenobia in the strain used in this study (,35 ,m diameter) conveniently allowed high quality spectra to be obtained from individual coenobia using a laboratory-based Fourier transform infrared (FTIR) microscope with a conventional globar source of IR. By drawing sizable subpopulations of coenobia from two Scenedesmus cultures grown under either nutrient-replete or P-starved conditions, the population variability in macromolecular composition, and the effects of nutrient change upon this, could be estimated. On average, P-starved coenobia had higher carbohydrate and lower protein absorbance compared with P-replete coenobia. These parameters varied between coenobia with histograms of the ratio of absorbance of the largest protein and carbohydrate bands being Gaussian distributed. Distributions for the P-replete and P-starved subpopulations were nonoverlapping, with the difference in mean ratios for the two populations being statistically significant. Greater variance was observed in the P-starved subpopulation. In addition, multivariate models were developed using the spectral data, which could accurately predict the nutrient status of an independent individual coenobium, based on its FTIR spectrum. Partial least squares discriminant analysis (PLS-DA) was a better prediction method compared with soft independent modeling by class analogy (SIMCA). [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] Montezuma pine nutrient status as affected by alder densities nitrogen fertilizationJOURNAL OF PLANT NUTRITION AND SOIL SCIENCE, Issue 6 2006Miguel Abstract Literature reports both positive and negative effects of N-fixing alders on conifer growth in alder-conifer stands. Such divergent effects probably result from poorly understood species interactions. The aim of this work was to examine how varying alder-to-pine ratios (APRs) and N fertilization affect pine nutrient status. A pseudo-experiment was installed in each of two areas of regeneration (AR) with different amounts of radiation reaching alder. The experimental approach consisted of a series of pseudoreplicated plots with five APRs within each AR. Half of each plot received 200,kg N ha,1. Data were interpreted by vector analysis. Alders in the AR 1987 induced needle-biomass reductions, K deficiency, and P accumulation in pine needles. However, nutrient availability increased with the proportion of alders in the AR 1989, where alders received high sunlight due to a less dense pine stand. Nitrogen fertilization increased needle biomass and N in three out of five alder proportions where alders were sunlight-limited. In the other stand, with the exception of the no-alder and A4 plots, positive effects of N fertilization increased with decreasing alder density. We conclude that sunlight-limited alders may not positively affect associated-species growth even in N-limited sites. [source] Microbial biomass and activity under oxic and anoxic conditions as affected by nitrate additionsJOURNAL OF PLANT NUTRITION AND SOIL SCIENCE, Issue 1 2006Jens Dyckmans Abstract Soil microbial activity, biomass, and community structure were examined during the transition from oxic to anoxic conditions after the addition of glucose and with or without nitrate addition. In two sets of treatments, samples were incubated for up to 35 d in closed ampoules either aerobically until oxygen was depleted or anoxically throughout the experiment. Heat-flow rate was monitored to indicate microbial activity. Microbial biomass and community structure were measured by adenylate and phospholipid fatty acid (PFLA) content, and adenylate energy charge (AEC) was used to monitor the physiological status of the microbial biomass. Microbial activity was highest under oxic conditions and abruptly decreased under anoxic conditions. Activity peaks were observed after about 9 d of anoxic conditions probably triggered by increased nutrient availability from dying microbial biomass, but these peaks were smaller after initial oxic incubation or nitrate addition. Microbial biomass was unchanged under oxic conditions but decreased under anoxic conditions. Most surviving microbes switched into dormancy. Changes in the microbial-population structure were small and occurred only after 9 d of anoxic incubation. The results show that the nutrient status and the availability of electron acceptors such as nitrate were important factors ruling the direction and the extent of shifts in the microbial activity and community structures due to anoxic conditions. Mikrobielle Biomasse und Aktivität unter oxischen und anoxischen Bedingungen in Abhängigkeit von Nitratzugabe Untersucht wurden Aktivität, Menge und Zusammensetzung der mikrobiellen Biomasse im Übergang von oxischen zu anoxischen Bedingungen in Bodenproben nach Zugabe von Glucose sowie mit und ohne Nitratzugabe. Bodenproben wurden bis zu 35 Tage in geschlossenen Gefäßen entweder oxisch bis zum Verbrauch des Sauerstoffs oder von Beginn an anoxisch inkubiert. Dabei wurde der Wärmefluss als Indikator für die mikrobielle Aktivität gemessen. Menge und Zusammensetzung der mikrobiellen Biomasse wurden über die Gehalte an Adenylaten und Phospholipidfettsäuren bestimmt. Der ,Adenylate Energy Charge" (AEC) wurde genutzt, um den physiologischen Status der mikrobiellen Biomasse zu bestimmen. Die mikrobielle Aktivität war unter oxischen Bedingungen am höchsten und ging unter anoxischen Bedingungen drastisch zurück. Aktivitätspeaks wurden nach etwa 10 Tagen anoxischer Inkubation beobachtet und waren vermutlich verursacht durch ein erhöhtes Nährstoffangebot aus der abgestorbenen Biomasse. Diese Peaks waren geringer nach vorhergehender oxischer Inkubation bzw. nach Nitratzugabe. Die mikrobielle Biomasse war unter oxischen Bedingungen unverändert, nahm aber unter anoxischen Bedingungen ab, die meisten überlebenden Mikroben waren dabei dormant. Änderungen in der mikrobiellen Gesellschaft traten nur in geringem Umfang und erst nach 9 Tagen anoxischer Inkubation auf. Unsere Ergebnisse zeigen, dass das Nährstoffangebot und die Verfügbarkeit von Elektronenakzeptoren wie z.,B. Nitrat wichtige Steuergrößen für Richtung und Ausmaß von Veränderungen in der mikrobiellen Aktivität und Zusammensetzung unter anoxischen Bedingungen sind. [source] Stratified resampling of phytosociological databases: some strategies for obtaining more representative data sets for classification studiesJOURNAL OF VEGETATION SCIENCE, Issue 4 2005Ilona Knollová Abstract Question: The heterogeneous origin of the data in large phytosociological databases may seriously influence the results of their analysis. Therefore we propose some strategies for stratified resampling of such databases, which may improve the representativeness of the data. We also explore the effects of different resampling options on vegetation classification. Methods: We used 6050 plot samples (relevés) of mesic grasslands from the Czech Republic. We stratified this database using (1) geographical stratification in a grid; (2) habitat stratification created by an overlay of digital maps in GIS; (3) habitat stratification with strata defined by traditional phytosociological associations; (4) habitat stratification by numerical classification and (5) habitat stratification by Ellenberg indicator values. Each time we resampled the database, taking equal numbers of relevés per stratum. We then carried out cluster analyses for the resampled data sets and compared the resulting classifications using a newly developed procedure. Results: Random resampling of the initial data set and geographically stratified resampling resulted in similar classifications. By contrast, classifications of the resampled data sets that were based on habitat stratifications (2,5) differed from each other and from the initial data set. Stratification 2 resulted in classifications that strongly reflected environmental factors with a coarse grain of spatial heterogeneity (e.g. macroclimate), whereas stratification 5 resulted in classifications emphasizing fine-grained factors (e.g. soil nutrient status). Stratification 3 led to the most deviating results, possibly due to the subjective nature of the traditional phytosociological classifications. Conclusions: Stratified resampling may increase the representativeness of phytosociological data sets, but different types of stratification may result in different classifications. No single resampling strategy is optimal or superior: the appropriate stratification method must be selected according to the objectives of specific studies. [source] Is sustainable development based on agriculture attainable in Kenya?LAND DEGRADATION AND DEVELOPMENT, Issue 5 2001A multidisciplinary case study of Murang'a district Abstract Kenya's development seems trapped in a vicious circle caused by soil erosion, declining soil fertility, land fragmentation, fluctuating agricultural production, widespread poverty, corruption, ethnic tension, rapid population, urban growth and a declining economy. The development challenge is to reverse the negative effects of these processes and promote sustainable development. This paper, based on multidisciplinary work discusses whether sustainable development based on agriculture is attainable in Murang'a district in Kenya's Central Highlands. Firstly, it investigates some biophysical aspects of sustainable agriculture such as land use across time, soil nutrient status and yield, cultivated crops and soil productivity by analysing aerial photographs and soil samples and conducting interviews. It suggests that the area has gone through major biophysical changes. Second, it relates the farmers' attitude to promotion of sustainable development as carried out by the National Soil and Water Conservation Programme. It suggests that farmers carry ideas of corruption, often following ethnic lines that hampers efficient implementation of the extension advise. Finally, it identifies links behind rural-urban migration by estimating households' probability of generating incomes outside the farm, typically in urban areas. Opportunistic farming, manifested by temporary reduction of farming on own land to satisfy immediate income needs, is very common among farmers. More needs to be done to promote agro-based, small-scale rural industries, improve agricultural management practices, facilitate appropriate credits, enhance marketing opportunities, ensure timely crop payments, and increase participation in decision making. It is important to realize that for farmers to embrace policies which promote agriculturely-based sustainable development the policies ought to biophysically possible, socio-politically acceptable and economically feasible. Copyright © 2001 John Wiley & Sons, Ltd. [source] Chlorophyll content and fluorescence responses cannot be used to gauge reliably phytoplankton biomass, nutrient status or growth rateNEW PHYTOLOGIST, Issue 3 2006Mikaela Kruskopf Summary ,,To consider the relationship between chlorophyll a (Chl a) content and phytoplankton growth and nutrient status, four phytoplankton species were grown in nitrogen (N)-limited [and, for one species, phosphorus (P)-limited] culture and measurements were made of CNP biomass, in vivo and in vitro Chl a content, the ratio of variable to maximum fluorescence (FV/FM) and the performance index for photosynthesis, PIABS (a derivative of the O-J-I-P analysis of photosystem II functionality). ,,Interspecies differences plus the development of intraspecies differences during nutrient stress produced c. 10-fold variations in Chl : C. Estimates of C from in vivo Chl content were better than those from extracted Chl content, as the decline in Chl : C during nutrient stress was offset in part by increased Chl fluorescence. ,,FV/FM was not a robust indicator of nutrient status or relative growth rate. Responses of FV/FM in cells re-fed the limiting nutrient showed no consistent pattern with which to gauge nutrient status. PIABS showed some promise as an indicator of nutrient status and relative growth rate. ,,Chl a content and fluorescence parameters do not deserve the unquestioned status they usually enjoy as indicators of biomass and physiological status. [source] Calluna vulgaris root cells show increased capacity for amino acid uptake when colonized with the mycorrhizal fungus Hymenoscyphus ericaeNEW PHYTOLOGIST, Issue 3 2002Sergei G. Sokolovski Summary ,,Ericoid mycorrhizas are believed to improve N nutrition of many ericaceous plant species that typically occur in habitats with impoverished nutrient status, by releasing amino acids from organic N forms. Despite the ubiquity of mycorrhizal formation the mechanisms and regulation of nutrient transport in mycorrhizal associations are poorly understood. ,,We used an electrophysiological approach to study how amino acid transport characteristics of Calluna vulgaris were affected by colonization with the ericoid mycorrhiza fungus Hymenoscyphus ericae . ,,Both the Vmax and Km parameters of amino acid uptake were affected by fungal colonization in a manner consistent with an increased availability of amino acid to the plant. ,,The ecophysiological significance of altered amino acid transport in colonized root cells of C. vulgaris is discussed. [source] Impact of Solar Ultraviolet Radiation on Marine Phytoplankton of Patagonia, Argentina,PHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 4 2005E. Walter Helbling ABSTRACT Patagonia area is located in close proximity to the Antarctic ozone "hole" and thus receives enhanced ultraviolet B (UV-B) radiation (280,315 nm) in addition to the normal levels of ultraviolet A (UV-A; 315,400 nm) and photosynthetically available radiation (PAR; 400-700 nm). In marine ecosystems of Patagonia, normal ultraviolet radiation (UVR) levels affect phytoplankton assemblages during the three phases of the annual succession: (1) prebloom season (late summer-fall), (2) bloom season (winter-early spring) and (3) postbloom season (late spring-summer). Small-size cells characterize the pre-and postbloom communities, which have a relatively high photosynthetic inhibition because of high UVR levels during those seasons. During the bloom, characterized by micro-plankton diatoms, photosynthetic inhibition is low because of the low UVR levels reaching the earth's surface during winter; this community, however, is more sensitive to UV-B when inhibition is normalized by irradiance (i.e. biological weighting functions). In situ studies have shown that UVR significantly affects not only photosynthesis but also the DNA molecule, but these negative effects are rapidly reduced in the water column because of the differential attenuation of solar radiation. UVR also affects photosynthesis versus irradiance (P vs E) parameters of some natural phytoplankton assemblages (i.e. during the pre- but not during the postbloom season). However, there is a significant temporal variability of P vs E parameters, which are influenced by the nutrient status of cells and taxonomic composition; taxonomic composition is in turn associated with the stratification conditions (e.g. wind speed and duration). In Patagonia, wind speed is one of the most important variables that conditions the development of the winter bloom by regulating the depth of the upper mixed layer (UML) and hence the mean irradiance received by cells. Studies on the interactive effects of UVR and mixing show that responses of phytoplankton vary according to the taxonomic composition and cell structure of assemblages; therefore cells use UVR if >90% of the euphotic zone is being mixed. In fact, cell size plays a very important role when estimating the impact of UVR on phytoplankton, with large cells being more sensitive when determining photosynthesis inhibition, whereas small cells are more sensitive to DNA damage. Finally, in long-term experiments, it was determined that UVR can shape the diatom community structure in some assemblages of coastal waters, but it is virtually unknown how these changes affect the trophody-namics of marine systems. Future studies should consider the combined effects of UVR on both phytoplankton and grazers to establish potential changes in biodiversity of the area. [source] Endocrine mechanisms of primate life history trade-offs: Growth and reproductive maturation in vervet monkeysAMERICAN JOURNAL OF HUMAN BIOLOGY, Issue 6 2009Patricia L. Whitten Life history theory predicts that the timing of maturation will result from a trade-off between growth and the age of first reproduction. This trade-off and its mechanisms of action are still poorly understood in many species and have not been well studied at the individual level. This study examined hypothesized trade-offs between growth and reproductive maturation in wild populations of vervet monkeys (Cercopithecus aethiops) from Kenya, East Africa. Individuals were sampled from four populations in widely separated sites differing in temperature, altitude, and rainfall. Biological samples and morphometric measures were collected from 50 adult males, 83 adult females, and 225 juveniles. Gonadal steroids and leptin levels were analyzed by radioimmunoassay of sera from 136 juvenile males and 90 juvenile females. Cross-sectional profiles of morphometric and endocrine data were used to assess the onset and cessation of growth in relation to sexual maturation. Gonadal steroids were used to assess sexual maturation and breeding onset. Leptin was used as an index of nutritional state. Estimates of mortality were derived from population age-structure. Across populations, higher resource productivity and nutrient status were associated with more rapid growth. Shorter growth duration was associated with earlier reproductive onset. These findings provide support for models of trade-offs between the timing of growth completion and reproductive onset, but they are contradicted by the evidence that reproduction precedes the cessation of growth in these populations. The biphasic actions of estradiol provide an alternative model and mechanism for the growth-reproduction trade-off. Am. J. Hum. Biol., 2009. © 2009 Wiley-Liss, Inc. [source] Magnitude of nighttime transpiration does not affect plant growth or nutrition in well-watered ArabidopsisPHYSIOLOGIA PLANTARUM, Issue 3 2009Mairgareth A. Christman Significant water loss occurs throughout the night via partially open stomata in many C3 and C4 plant species. Although apparently wasteful in terms of water use, nighttime transpiration (Enight) is hypothesized to benefit plants by enhancing nutrient supply. We tested the hypothesis that plants with greater Enight would have improved plant nutrient status and greater fitness, estimated as pre-bolting biomass, for Arabidopsis thaliana. Two very different levels of Enight were generated in plants by exposing them to high vs low nighttime leaf-to-air vapor pressure deficits (VPDleaf) in controlled environment chambers. An assessment of responses of nighttime leaf conductance (gnight) to VPDleaf indicated that Enight differed by at least 80% between the treatments. This large difference in Enight, imposed over the entire vegetative growth phase of Arabidopsis, had no effect on leaf nutrient content (N, Ca, K) or pre-bolting rosette biomass. The lack of response to differences in Enight held true for both a high and a low nitrogen (N) treatment, even though the low N treatment decreased leaf N and biomass by 40,60%. The N treatment had no effect on gnight. Thus, higher Enight did not provide a nutrient or growth benefit to Arabidopsis, even when the plants were N-limited. [source] Restoration of a Mediterranean Postfire Shrubland: Plant Functional Responses to Organic Soil AmendmentRESTORATION ECOLOGY, Issue 5 2010Marie Larchevêque We investigated the potential of plant functional responses to speed up restoration in a postfire ecosystem. The patterns of change in plant nutrient uptake and water potential after compost amendment were monitored for 2 years in a 7-year-old postfire shrubland in southeastern France. We studied four different stress-tolerant species with contrasting life traits: three shrub species and a perennial herb. Three treatments were applied: control, 50 and 100 Mg/ha of fresh cocomposted sewage sludge and green waste. In both compost treatments, concentrations of all the macronutrients increased. The amendment improved N and cation nutrition, but the positive effect of compost on plant nutrient status was most apparent on leaf P concentrations, indicating that P was a limiting nutrient in this shrubland. Compost had no significant short-term effect on trace metal concentrations in plants. The plant nutrition response of different species to the compost varied; the nutritional status of Brachypodium retusum and Cistus albidus improved the most, whereas that of Quercus coccifera and Ulex parviflorus improved the least. Woody species exhibited no increase in N stocks. Phosphorus accumulation was also about three times higher in plots amended at 50 Mg/ha than in control plots for B. retusum and C. albidus. The severe summer drought of 2003 altered the compost effect. Contrary to our expectations, plants on amended plots did not exhibit a better water status in summer: the effect of the summer drought had a greater effect on water status than did the compost treatment. [source] Dynamics of species-rich upland hay meadows over 15 years and their relation with agricultural management practicesAPPLIED VEGETATION SCIENCE, Issue 3 2007C.N.R. Critchley Stace (1997) Abstract Questions: Has the species-rich vegetation of upland hay meadows been maintained under low intensity management imposed by an agri-environment scheme? Is the target plant community re-establishing where it has been modified previously by intensive agricultural practices? What combinations of management practices and soil properties are associated with changes towards or away from the target community? Location: The Pennines, northern England, UK. Methods: A survey of 116 hay meadows in 1987 was repeated in 2002 by recording plant species in permanent quadrats. Changes in community variables (species richness, Ellenberg values, upland hay meadow community coefficients) were analysed in species-rich, modified species-rich and degraded grassland types. Redundancy Analysis and Generalised Linear Models were used to show the relationship between management practices and soil properties and change in species composition and community variables. Results: Few sites contained the species-rich grassland type, and here forb richness declined. In the modified species-rich type, total and grass species richness increased but Ellenberg N-values also increased. Total and grass species richness increased in the degraded type and the community coefficient increased. Management was weakly related to change in species composition but showed clear relationships with the community variables. Re-establishment of the target species-rich community was more likely with late cutting, in the absence of cattle or prolonged spring grazing, and at lower soil nutrient status. Conclusion: The species-rich community was not maintained but some reversion occurred in degraded grassland. Inorganic fertiliser application and intensive spring grazing should be avoided and cutting delayed until late July. [source] Distinctiveness of macroinvertebrate communities in turloughs (temporary ponds) and their response to environmental variablesAQUATIC CONSERVATION: MARINE AND FRESHWATER ECOSYSTEMS, Issue 4 2009Gwendolin Porst Abstract 1.Turloughs are a prime example of a water body type that interfaces with both the European Habitats Directive (92/43/EEC) and Water Framework Directive (2000/60/EC) (WFD), highlighting the need for an integrated strategy to protect and manage surface waters and groundwaters. To date, research on turloughs, including their invertebrate communities is limited. 2.Eight turloughs were sampled for their macroinvertebrate communities and water chemistry in April 2007. Faunal samples were collected by means of a simple box sampler. 3.Replicate samples within each turlough clustered together, indicating that a single sample can provide a meaningful description of the turlough invertebrate community. Variation of invertebrate communities within turloughs was nested among turloughs. 4.Hydroperiod influenced mean abundance and taxon richness of macroinvertebrates, but no correlation was found between nutrient status and either mean abundance or taxon richness. 5.Turloughs are priority habitats under the EC Habitats Directive, requiring maintenance of ,favourable conservation status', which needs to be assessed through monitoring, and effected through appropriate management plans. While the distinctiveness of macroinvertebrate communities across turloughs is conducive to simple and cost-effective monitoring, this also challenges the applicability of the concept of type-specific communities across these highly dynamic ecosystems. Copyright © 2009 John Wiley & Sons Ltd. [source] Magnetic ghosts: mineral magnetic measurements on Roman and Anglo-Saxon graves,,ARCHAEOLOGICAL PROSPECTION, Issue 3 2004N. T. Linford Abstract The location of inhumations, in the absence of ferrous grave goods, often presents a considerable challenge to archaeological geophysics, given the small size of the features and the slight physical contrast between the fill of the grave and the surrounding subsoil. Even during excavation, the identification of graves may be complicated where site conditions do not favour the preservation of human skeletal remains and only a subtle soil stain is likely to survive. A recent initiative in the UK has seen the formation of the Buried Organic-matter,Decomposition Integrated with Elemental Status (BODIES) research group, to examine the decomposition of organic artefacts in ancient graves with respect to localized changes in pH, redox potential and nutrient status. This paper presents initial results from a limited mineral magnetic study of two grave sites in an attempt to ascertain whether the decomposition of organic remains may lead to a detectable magnetic signature within the soil. Results from a series of isothermal, hysteresis and magneto-thermal experiments will be presented together with surface magnetometer and topsoil susceptibility surveys. Copyright © Crown Copyright 2004. Recorded with the permission of Her Majesty's Stationery Office. Published by John Wiley & Sons, Ltd. [source] Comparison of the nutrient ecology of coastal Banksia grandis elfinwood (windswept shrub-like form) and low trees, Cape Leeuwin-Naturaliste National Park, Western AustraliaAUSTRAL ECOLOGY, Issue 3 2003KENNETH A. BARRICK Abstract Trees growing along windy coasts often have canopies that are greatly reduced in size by the sculpting effects of wind and salt spray. Trees with environmentally reduced stature are called elfinwood (windswept shrub-form or krummholz) and are ecologically important because they represent outposts growing at the limit of tree success. The purpose of this study was to assess if Banksia grandis elfinwood growing at Cape Leeuwin had a different nutrient status than normal low-form (LF) trees growing nearby, and if nutrient deficiencies, toxicities and/or imbalances were among the limiting factors imposed on elfinwood. The concentrations of N, P, K, Ca, Mg, Na, Cl,, Fe, Mn, Zn, Cu, Mo and B were analysed for mature green foliage, immature foliage, foliage litter, flowers and soil. When the elfinwood and LF trees were compared, the foliar nutrient status was generally similar, except that elfinwood foliage had significantly higher mean concentrations of N, Zn and Cu, while LF trees had higher Fe and Mn contents. Many nutrients were conserved before leaves were shed in both elfinwood and LF trees, including N, P, K, Na, Cl,, Mn and Cu (LF trees also conserved Ca and Mg). However, elfinwood and LF tree-litter contained significantly higher Fe concentrations than green foliage (elfinwood litter also had higher levels of Mg and B). It is tempting to suggest that the translocation of Fe into leaves before they were shed is a regulation mechanism to prevent Fe toxicity, or imbalance in the Fe : Mn ratio. Proteoid roots strongly acidify the soil to mobilize P, which also chemically reduces Fe+3 to plant-available Fe+2. The increased supply of Fe+2 in the rhizosphere, caused by the action of proteoid roots, might tend to defeat self-regulation of Fe uptake. It is possible that excess Fe accumulation in the plant might be regulated, in part, by exporting Fe into the leaves before they are shed. The nutrient status of B. grandis elfinwood is compared with mountain elfinwood of North America. The extreme habitat of coastal elfinwood provides many theoretical pathways for nutrient limitation, but B. grandis elfinwood at Cape Leeuwin does not appear to be nutrient deficient. [source] Effects of timing and rate of N supply on leaf nitrogen status, grape yield and juice composition from Shiraz grapevines grafted to one of three different rootstocksAUSTRALIAN JOURNAL OF GRAPE AND WINE RESEARCH, Issue 1 2007B.P. HOLZAPFEL Abstract Yeast cells have a minimum N requirement to ferment a must through to dryness, so that grape N content (hence must N) becomes critical in meeting that prerequisite. Viticultural practices aimed at meeting that N requirement are of special relevance because interactions between rootstock and vineyard nitrogen supply strongly influence scion mineral nutrient status as well as shoot vigour, and via those processes, fruit composition. Such outcomes were investigated in a field trial involving Shiraz on three rootstocks viz. Teleki 5C, Schwarzmann and Ramsey. Five N supply regimes, varying from 0 to 80 kg/(haseason), were imposed through a drip-irrigation system during two periods (either flowering to veraison, or post-harvest to leaf-fall, or both) over three successive growing seasons. Post-harvest N supply increased scion leaf N and nitrate N concentrations at flowering for vines on Teleki 5C and Schwarzmann. By veraison, N recently applied in the flowering to veraison period elevated these indicators of N status in all vines on all rootstocks. Grape yields from vines on Teleki 5C and Schwarzmann were elevated by N supply after harvest, whereas juice soluble solids levels were lowered. Free amino acids in Shiraz juice were dominated by non-assimilable N, amounting to about 50% or more of the total free amino-N in the juice. Increasing N supply increased free amino acid concentrations in the juice of berries from vines on all rootstocks, but only vines on Schwarzmann derived any benefit from N supplied after harvest. The highest concentrations of free amino acids were measured in the berries from vines on Schwarzmann receiving 80 kg N/(ha.season). Of immediate practical relevance for N management of Shiraz grapevines on either Teleki 5C or Ramsey rootstocks, the minimum value for assimilable free amino-N concentration required to ferment a must through to dryness was not achieved if vineyard N application was limited to the post-harvest period. [source] Nutrition and allergic diseaseCLINICAL & EXPERIMENTAL ALLERGY REVIEWS, Issue 5 2006S. Tricon Summary The prevalence of asthma and allergic diseases has increased dramatically over the past few decades with the highest incidence occurring in children. Most asthma and related atopic disorders have their origins in early life. Thus, it is imperative to understand the early life origins of the disease in order to identify targets for prevention and early intervention. Although atopic diseases have genetic determinants, the increased incidence of these diseases has occurred far too rapidly for genetic changes to explain the increase. This, most likely, results from changes in environmental influences acting on a pre-existent genetic susceptibility. One of the environmental changes over the last 20,40 years that could have contributed to the recent increase in atopic diseases is diet. Food allergy is often one of the earliest manifestations of atopy, and sensitization to food is a risk factor for the subsequent appearance of respiratory allergy and asthma. However, studies investigating the effects of dietary restrictions on the prevention of allergy have been disappointing. On the other hand, current data suggests that exclusive breastfeeding should be encouraged for at least 4,6 months in infants at both high and low risk of atopy. Increased risk of asthma has also been observed in low birth weight infants, suggesting that under-nutrition can detrimentally alter foetal development. Epidemiological and immunological studies also suggest that dietary modification or supplementation in the foetal and early life could reduce the development of atopic diseases. The current dietary hypotheses relate to antioxidants, lipids, electrolytes and probiotics. The aims of this report are: (i) to assess the best methods to analyse nutrient intake and nutrient status; (ii) to review the existing epidemiological evidence for an association between dietary intake (nutrients and food) and allergic diseases; and (iii) to define the windows of opportunity for nutritional supplementation to be used as a preventative strategy for asthma and allergy. 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