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Low N (low + n)
Selected AbstractsResponse of beech (Fagus sylvatica) to elevated CO2 and N: Influence on larval performance of the gypsy moth Lymantria dispar (Lep., Lymantriidae)JOURNAL OF APPLIED ENTOMOLOGY, Issue 9-10 2001M. W. Henn Two-year-old beech seedlings were kept from germination to bioassays with Lymantriadispar under the following conditions: ambient CO2/low N, elevated CO2/low N, ambient CO2/elevated N, and elevated CO2/elevated N. The effect of these growing conditions of the trees on the performance of the defoliator L. dispar was studied 2 years after initiating the tree cultivation. The developmental success of third-instar larvae of L. dispar was characterized by the weight gained, percentage of weight gain, relative growth rate (RGR), relative consumption rate (RCR), and efficiency of conversion of ingested food into body substance (ECI). Contrary to our expectations, additional N-fertilization did not increase and elevated CO2 did not delay larval growth rate. However, the environmental treatments of the beech seedlings were found to affect the larval performance. Larvae consumed significantly higher amounts of foliage (RCR) on beech trees under controlled conditions (ambient CO2 and low N) compared to those under elevated CO2 and enhanced N. The opposite was true for ECI. The lowest efficacy to convert consumed food to body substance was observed under control conditions and the highest when the larvae were kept on beech trees grown under elevated CO2 and additional N-fertilization. These opposite effects resulted in the weight gain-based parameters (absolute growth, percentage of growth, and RGR) of the gypsy moth larvae remaining unaffected. The results indicate that the gypsy moth larvae are able to change their ECI and RCR to obtain a specific growth rate. This is discussed as an adaptation to specific food qualities. [source] Personality traits and parenting: neuroticism, extraversion, and openness to experience as discriminative factorsEUROPEAN JOURNAL OF PERSONALITY, Issue 1 2003Riitta-Leena Metsäpelto This study used variable- and person-oriented approaches to examine the relationship between personality traits (at age 33) and parenting (at age 36) among 94 mothers and 78 fathers. The SEM revealed that Openness to Experience (O), low Neuroticism (N), and Extraversion (E) were related to parental nurturance; low O to parental restrictiveness; and low N to parental knowledge about the child's activities. Cluster analysis based on the three parenting factors yielded six gender-related parenting types with distinguishable personality profiles. Authoritative parents (mostly mothers) and emotionally involved parents (mostly fathers), who were high in nurturance and high to moderate in parental knowledge, were high in E and high to moderate in O. Authoritarian parents (mostly fathers) and emotionally detached parents (mostly mothers), who were low in nurturance, high to moderate in restrictiveness, and moderate to low in parental knowledge, were low in O and E. Permissive parents, who were low in restrictiveness and parental knowledge and moderate in nurturance, were high in N, E, and O. Engaged parents, who were high in nurturance, restrictiveness, and parental knowledge, were moderate in all personality traits. Agreeableness and Conscientiousness did not differ between the parenting types. Copyright © 2002 John Wiley & Sons, Ltd. [source] Assessing the effect of elevated carbon dioxide on soil carbon: a comparison of four meta-analysesGLOBAL CHANGE BIOLOGY, Issue 8 2009BRUCE A. HUNGATE Abstract Soil is the largest reservoir of organic carbon (C) in the terrestrial biosphere and soil C has a relatively long mean residence time. Rising atmospheric carbon dioxide (CO2) concentrations generally increase plant growth and C input to soil, suggesting that soil might help mitigate atmospheric CO2 rise and global warming. But to what extent mitigation will occur is unclear. The large size of the soil C pool not only makes it a potential buffer against rising atmospheric CO2, but also makes it difficult to measure changes amid the existing background. Meta-analysis is one tool that can overcome the limited power of single studies. Four recent meta-analyses addressed this issue but reached somewhat different conclusions about the effect of elevated CO2 on soil C accumulation, especially regarding the role of nitrogen (N) inputs. Here, we assess the extent of differences between these conclusions and propose a new analysis of the data. The four meta-analyses included different studies, derived different effect size estimates from common studies, used different weighting functions and metrics of effect size, and used different approaches to address nonindependence of effect sizes. Although all factors influenced the mean effect size estimates and subsequent inferences, the approach to independence had the largest influence. We recommend that meta-analysts critically assess and report choices about effect size metrics and weighting functions, and criteria for study selection and independence. Such decisions need to be justified carefully because they affect the basis for inference. Our new analysis, with a combined data set, confirms that the effect of elevated CO2 on net soil C accumulation increases with the addition of N fertilizers. Although the effect at low N inputs was not significant, statistical power to detect biogeochemically important effect sizes at low N is limited, even with meta-analysis, suggesting the continued need for long-term experiments. [source] Ten years of free-air CO2 enrichment altered the mobilization of N from soil in Lolium perenne L. swardsGLOBAL CHANGE BIOLOGY, Issue 8 2004Manuel K. Schneider Abstract Effects of free-air carbon dioxide enrichment (FACE, 60 Pa pCO2) on plant growth as compared with ambient pCO2 (36 Pa) were studied in swards of Lolium perenne L. (perennial ryegrass) at two levels of N fertilization (14 and 56 g m,2 a,1) from 1993 to 2002. The objectives were to determine how plant growth responded to the availability of C and N in the long term and how the supply of N to the plant from the two sources of N in the soil, soil organic matter (SOM) and mineral fertilizer, varied over time. In three field experiments, 15N-labelled fertilizer was used to distinguish the sources of available N. In 1993, harvestable biomass under elevated pCO2 was 7% higher than under ambient pCO2. This relative pCO2 response increased to 32% in 2002 at high N, but remained low at low N. Between 1993 and 2002, the proportions and amounts of N in harvestable biomass derived from SOM (excluding remobilized fertilizer) were, at high N, increasingly higher at elevated pCO2 than at ambient pCO2. Two factorial experiments confirmed that at high N, but not at low N, a higher proportion of N in harvestable biomass was derived from soil (including remobilized fertilizer) following 7 and 9 years of elevated pCO2, when compared with ambient pCO2. It is suggested that N availability in the soil initially limited the pCO2 response of harvestable biomass. At high N, the limitation of plant growth decreased over time as a result of the stimulated mobilization of N from soil, especially from SOM. Consequently, harvestable biomass increasingly responded to elevated pCO2. The underlying mechanisms which contributed to the increased mobilization of N from SOM under elevated pCO2 are discussed. This study demonstrated that there are feedback mechanisms in the soil which are only revealed during long-term field experiments. Such investigations are thus, a prerequisite for understanding the responses of ecosystems to elevated pCO2 and N supply. [source] Response of beech (Fagus sylvatica) to elevated CO2 and N: Influence on larval performance of the gypsy moth Lymantria dispar (Lep., Lymantriidae)JOURNAL OF APPLIED ENTOMOLOGY, Issue 9-10 2001M. W. Henn Two-year-old beech seedlings were kept from germination to bioassays with Lymantriadispar under the following conditions: ambient CO2/low N, elevated CO2/low N, ambient CO2/elevated N, and elevated CO2/elevated N. The effect of these growing conditions of the trees on the performance of the defoliator L. dispar was studied 2 years after initiating the tree cultivation. The developmental success of third-instar larvae of L. dispar was characterized by the weight gained, percentage of weight gain, relative growth rate (RGR), relative consumption rate (RCR), and efficiency of conversion of ingested food into body substance (ECI). Contrary to our expectations, additional N-fertilization did not increase and elevated CO2 did not delay larval growth rate. However, the environmental treatments of the beech seedlings were found to affect the larval performance. Larvae consumed significantly higher amounts of foliage (RCR) on beech trees under controlled conditions (ambient CO2 and low N) compared to those under elevated CO2 and enhanced N. The opposite was true for ECI. The lowest efficacy to convert consumed food to body substance was observed under control conditions and the highest when the larvae were kept on beech trees grown under elevated CO2 and additional N-fertilization. These opposite effects resulted in the weight gain-based parameters (absolute growth, percentage of growth, and RGR) of the gypsy moth larvae remaining unaffected. The results indicate that the gypsy moth larvae are able to change their ECI and RCR to obtain a specific growth rate. This is discussed as an adaptation to specific food qualities. [source] Greater capacity for division of labour in clones of Fragaria chiloensis from patchier habitatsJOURNAL OF ECOLOGY, Issue 3 2007SERGIO R. ROILOA Summary 1Unlike non-clonal plants, clonal plants can develop a division of labour in which connected ramets specialize to acquire different, locally abundant resources. This occurs as a plastic response to a patchy environment where two resources tend not to occur together and different ramets experience high availabilities of different resources. We hypothesized that if division of labour is an important advantage of clonal growth in such environments in nature, then clones from habitats where resource availabilities are negatively associated should show a greater capacity for division of labour than clones from habitats where resource availabilities are more uniform. 2To test this, we collected clones of Fragaria chiloensis from sand dune and grassland sites in each of three regions of the central coast of California, grew pairs of connected or severed ramets under low light and high N or under high light and low N, and measured leaf area, chlorophyll content and final dry mass. Given that previous work has indicated that high availabilities of light and N show a stronger tendency not to occur together in the dune than in the grassland sites, we expected that clones from dunes would show greater capacity for division of labour than clones from grasslands. 3Clones from dunes showed a greater capacity than clones from grasslands to specialize for acquisition of abundant N via high proportional mass of roots. Clones from the two types of habitats showed similar capacity to specialize for acquisition of abundant light via high leaf area and chlorophyll content of leaves. Specialization via leaf area and chlorophyll content took place mainly within the first half of the 60-day experiment. 4These results provide evidence that division of labour in a clonal plant has been selected for in natural habitats where high levels of different resources tend to be spatially separated. Results also show that division of labour can occur, not just via allocation of mass, but also via physiological traits, and that both morphological and physiological specialization can take place within a few weeks. 5Clonal plants dominate many habitats and include many highly invasive species. Division of labour is one of the most striking potential advantages of clonal growth, and is a remarkable instance of phenotypic plasticity in plants. This study further suggests that division of labour in clonal plants is an instance of adaptive plasticity and could therefore play a part in their widespread ecological success. [source] Analgesic Effects of Ethanol Are Influenced by Family History of Alcoholism and NeuroticismALCOHOLISM, Issue 8 2010Elizabeth Ralevski Background:, Although personality factors and family history of substance abuse influence how individuals experience pain and respond to analgesics, the combined effects of those factors have not been extensively studied. The objective of this study was to consider the possible role of personality trait of neuroticism and family history of alcoholism on the experience of pain and their role in the analgesic response to an ethanol challenge. Methods:, Forty-eight healthy subjects participated in this study; thirty-one had a positive family history of alcoholism (FHP), seventeen had a negative family history of alcoholism (FHN). They were also categorized based on their neuroticism (N) scores (low N = 28, and high N = 20). This was a double-blind, placebo-controlled, randomized, within-subject design study of intravenous administration of three doses of ethanol. The testing consisted of 3 separate test days scheduled at least 3 days apart. Test days included a placebo day (saline solution), low-exposure ethanol day (targeted breathalyzer = 0.040 g/dl), and high-exposure ethanol day (targeted breathalyzer = 0.100 g/dl). Noxious electrical stimulation and pain assessments were performed prior to start of infusion and at the 60-minute infusion mark. Results:, The analgesic effect of ethanol was mediated by an interaction between the personality trait of neuroticism and family history. Individuals with family history of alcoholism and high N scores reported significantly more analgesia on low dose of ethanol than those with low N scores. There was no difference in the analgesic response to ethanol among FHNs with low and high N scores. Conclusion:, These findings support the conclusion that neuroticism and family history of alcoholism both influence the analgesic response of alcohol. Individuals with high N scores and FHP have the strongest response to ethanol analgesia particularly on the low exposure to alcohol. [source] Land use history and site location are more important for grassland species richness than local soil propertiesNORDIC JOURNAL OF BOTANY, Issue 6 2009Sara A. O. Cousins Lately there has been a shift in Sweden from grazing species-rich semi-natural grasslands towards grazing ex-arable fields in the modern agricultural landscape. Grazing ex-arable fields contain a fraction of the plant species richness confined to semi-natural grasslands. Still, they have been suggested as potential target sites for re-creation of semi-natural grasslands. We asked to what extent does fine-scale variation in soil conditions, management history and site location effect local plant diversity in grazed ex-arable fields. We examined local soil conditions such as texture, pH, organic carbon, nitrogen (N) and extractable phosphate (P) and effects on plant richness in ten pairs of grazed ex-fields and neighbouring semi-natural grasslands in different rural landscapes. Each grassland pair where in the same paddock. A multivariate test showed that site location and land use history explained more of differences in species richness than local soil property variables. Plant species richness was positively associated to grazed ex-fields with low pH, low N and P levels. Sites with high plant richness in semi-natural grasslands also had more species in the adjacent grazed ex-fields, compared to sites neighbouring less species-rich semi-natural grasslands. Although both soil properties and species richness were different in grazed ex-fields compared to semi-natural grassland, the site location within a landscape, and vicinity to species-rich grasslands, can override effects of soil properties. In conclusion, if properly located, ex-arable fields may be an important habitat to maintain plant diversity at larger spatio-temporal scales and should considered as potential sites for grassland restoration. [source] The application of ethephon (an ethylene releaser) increases growth, photosynthesis and nitrogen accumulation in mustard (Brassica juncea L.) under high nitrogen levelsPLANT BIOLOGY, Issue 5 2008N. A. Khan Abstract Ethephon (2-chloroethyl phosphonic acid), an ethylene-releasing compound, influences growth and photosynthesis of mustard (Brassica juncea L. Czern & Coss.). We show the effect of nitrogen availability on ethylene evolution and how this affects growth, photosynthesis and nitrogen accumulation. Ethylene evolution in the control with low N (100 mg N kg,1 soil) was two-times higher than with high N (200 mg N kg,1 soil). The application of 100,400 ,l·l,1 ethephon post-flowering, i.e. 60 days after sowing, on plants receiving low or high N further increased ethylene evolution. Leaf area, relative growth rate (RGR), photosynthesis, leaf nitrate reductase (NR) activity and leaf N reached a maximum with application of 200 ,l·l,1 ethephon and high N. The results suggest that the application of ethephon influences growth, photosynthesis and N accumulation, depending on the amount of nitrogen in the soil. [source] Mitochondrial respiratory pathways modulate nitrate sensing and nitrogen-dependent regulation of plant architecture in Nicotiana sylvestrisTHE PLANT JOURNAL, Issue 6 2008Till K. Pellny Summary Mitochondrial electron transport pathways exert effects on carbon,nitrogen (C/N) relationships. To examine whether mitochondria,N interactions also influence plant growth and development, we explored the responses of roots and shoots to external N supply in wild-type (WT) Nicotiana sylvestris and the cytoplasmic male sterile II (CMSII) mutant, which has a N-rich phenotype. Root architecture in N. sylvestris seedlings showed classic responses to nitrate and sucrose availability. In contrast, CMSII showed an altered ,nitrate-sensing' phenotype with decreased sensitivity to C and N metabolites. The WT growth phenotype was restored in CMSII seedling roots by high nitrate plus sugars and in shoots by gibberellic acid (GA). Genome-wide cDNA-amplified fragment length polymorphism (AFLP) analysis of leaves from mature plants revealed that only a small subset of transcripts was altered in CMSII. Tissue abscisic acid content was similar in CMSII and WT roots and shoots, and growth responses to zeatin were comparable. However, the abundance of key transcripts associated with GA synthesis was modified both by the availability of N and by the CMSII mutation. The CMSII mutant maintained a much higher shoot/root ratio at low N than WT, whereas no difference was observed at high N. Shoot/root ratios were strikingly correlated with root amines/nitrate ratios, values of <1 being characteristic of high N status. We propose a model in which the amine/nitrate ratio interacts with GA signalling and respiratory pathways to regulate the partitioning of biomass between shoots and roots. [source] Importance of sediment deposition and denitrification for nutrient retention in floodplain wetlandsAPPLIED VEGETATION SCIENCE, Issue 2 2006Harry Olde Venterink Abstract Questions: Various floodplain communities may differ in their relative abilities to influence water quality through nutrient retention and denitrification. Our main questions were: (1) what is the importance of sediment deposition and denitrification for plant productivity and nutrient retention in floodplains; (2) will rehabilitation of natural floodplain communities (semi-natural grassland, reedbed, woodland, pond) from agricultural grassland affect nutrient retention? Location: Floodplains of two Rhine distributaries (rivers Ussel and Waal), The Netherlands. Methods: Net sedimentation was measured using mats, denitrification in soil cores by acetylene inhibition and bio-mass production by clipping above-ground vegetation in winter and summer. Results: Sediment deposition was a major source of N and P in all floodplain communities. Highest deposition rates were found where water velocity was reduced by vegetation structure (reedbeds) or by a drop in surface elevation (pond). Sediment deposition was not higher in woodlands than in grassland types. Denitrification rates were low in winter but significantly higher in summer. Highest denitrification rates were found in an agricultural grassland (winter and summer) and in the ponds (summer). Plant productivity and nutrient uptake were high in reedbeds, intermediate in agricultural grasslands, ponds and semi-natural grasslands and very low in woodlands (only understorey). All wetlands were N-limited, which could be explained by low N:P ratios in sediment. Conclusions: Considering Rhine water quality: only substantial P-retention is expected because, relative to the annual nutrient loads in the river, the floodplains are important sinks for P, but much less for N. Rehabilitation of agricultural grasslands into ponds or reedbeds will probably be more beneficial for downstream water quality (lower P-concentrations) than into woodlands or semi-natural grasslands. [source] Nitrogen Fixation in Bryophytes, Lichens, and Decaying Wood along a Soil-age Gradient in Hawaiian Montane Rain ForestBIOTROPICA, Issue 1 2003Virginia Matzek ABSTRACT We determined rates of acetylene reduction and estimated total nitrogen fixation associated with bryophytes, lichens, and decaying wood in Hawaiian montane rain forest sites with underlying substrate ranging in age from 300 to 4.1 million years. Potential N fixation ranged from ca 0.2 kg/ha annually in the 300-year-old site to ca 1 kg/ha annually in the 150,000-year-old site. Rates of acetylene reduction were surprisingly uniform along the soil-age gradient, except for high rates in symbiotic/associative fixers at the 150,000-year-old site and in heterotrophic fixers at the 2100-year-old site. Low fixation at the youngest site, where plant production is known to be N-limited, suggests that demand for N alone does not govern N fixation. Total N fixation was highest in sites with low N:P ratios in leaves and stem wood, perhaps because epiphytic bryophytes and lichens depend on canopy leachate for mineral nutrients and because heterotrophic fixation is partly controlled by nutrient supply in the decomposing substrate; however, differences in substrate cover, rather than in fixation rates, had the largest effect on the total N input from fixation at these sites. [source] Polyunsaturated fatty acid status in attention deficit hyperactivity disorder, depression, and Alzheimer's disease: towards an omega-3 index for mental health?NUTRITION REVIEWS, Issue 10 2009Catherine M Milte Interest in the role of polyunsaturated fatty acids (PUFAs), particularly long-chain (LC) omega-3 (n -3) PUFAs, in mental health is increasing. This review investigates whether n -3 PUFA levels are abnormal in people with three prevalent mental health problems , attention deficit hyperactivity disorder, depression, and dementia. Data sources included PubMed, Web of Science, and bibliographies of papers published in English that describe PUFA levels in the circulation of individuals who have these mental health conditions. Although abnormal blood PUFA levels were reported in a number of studies, weighted comparisons of PUFA status showed no significant differences overall between people with mental health problems and controls. Whether those with low n -3 PUFA status are likely to be more responsive to n -3 PUFA supplementation is not yet resolved. Further studies assessing PUFA levels and mental status with greater uniformity are required in order to clarify the relationship between LC n -3 PUFA status and mental health. [source] | |||||||||||||