bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effects of cadmium stress on periphytic diatom communities in indoor artificial streams
Authors: Gold Caroline , Feurtet‐Mazel Agnès , Coste Michel , Boudou Alain 
Published: March 2003

SUMMARY 1. Two experiments were performed with periphytic diatoms originating from the River Lot (France) and allowed to grow on clean substrata within indoor artificial streams. Three cadmium (Cd) levels (control, low Cd=10 μg L−1 and high Cd=100 μg L−1) were used to test the effects of Cd on (i) the settlement and development of diatom communities (Experiment 1, 4 weeks Cd exposure) and (ii) predeveloped communities grown over a 2‐week period without contamination (Experiment 2, 2 weeks Cd exposure).2. Experiment 1 revealed that growth and taxonomic composition of diatom communities clearly differed with Cd exposure. Biofilms were more adpressed to substrata under low Cd concentration, and were thinner and patchy under high Cd concentration.3. Exposure of developed diatom communities (Experiment 2) to Cd revealed only minor variations in taxonomic composition, possibly linked to the protective role of the developed organic matrix against metal stress.4. These results support the validity of periphytic diatom communities as indicators of metal pollution, although significant structural changes would take longer within developed communities.
The independent and interactive effects of fine sediment and flow on benthic invertebrate communities characteristic of small upland streams
Authors: Bond Nicholas R. , Downes Barbara J. 
Published: March 2003

SUMMARY 1. Floods are an important mechanism of disturbance operating in streams that can markedly influence the abundance and diversity of benthic fauna. In upland streams many studies cite the scouring effects of fine transported sediments as a potential source of disturbance to the biota during spates, but few studies have sought to test this hypothesis critically.2. Here we used a series of eight artificial streams to test whether high suspended‐sediment concentrations influenced the short‐term response of benthic invertebrate fauna to increases in flow. In an experiment designed to simulate a small spate, flow and sediment loads were each manipulated to examine their independent and interactive effects. Benthic invertebrates were sampled before and after the manipulation, and drift samples were taken at regular intervals during the experiment. The experiment was repeated twice, once at the end of winter (June, 1998), and once in summer (February, 1999).3. Flow increases caused large increases in the number and diversity of drifting animals, and significant declines in the numbers and diversity of organisms found in benthic samples, but these declines were apparently not affected by the addition of fine sediment. The addition of sediment alone had little effect on the fauna. These results were consistent across both experiments.4. The results suggest that flow increases alone can disturb benthic fauna, and that neither substrate movement nor suspended sediment increases are necessary for floods and spates to disturb the benthic assemblage. However, as argued elsewhere, the effects of flow increases are likely to be contingent upon the presence or absence of local flow refugia, which can allow animals to escape the shear forces that would otherwise remove them from the surface or interstitial areas of the streambed.
Soil nutrient input effects on seed longevity: a burial experiment with fen‐meadow species
Authors: Bekker R. M. , Knevel I. C. , Tallowin J. B. R. , Troost E. M. L. , Bakker J. P. 
Published: March 2003

1. Effects of high nutrient input on the longevity and viability of buried seed are examined. Seeds of 17 fen‐meadow species were buried in nylon mesh bags at four sites in the Netherlands and one site in Great Britain in plots to which N, P, K fertilizers are applied. Prior to burial germination tests were conducted on the seeds of each species. This paper describes the results of the viability tests on the seeds that were exhumed after one and 2 years of burial. 2. The percentage of seeds that germinated after 1 year of burial was significantly lower than the pre‐burial percentage for the majority of the species. After 2 years of burial the germination percentage further decreased. A few species, such as the Carex species, did, however, show an increase in germination percentage indicating that the burial conditions allowed dormancy controls to be broken. 3. Differences in the edaphic conditions between the sites appeared to affect germination percentages after 1 year of burial. A difference in germination response between sites was observed for Carex acutiformis, Filipendula ulmaria and Lychnis flos‐cuculi. 4. A significantly higher germination percentage was found at the Great Britain site for F. ulmaria in the phosphate treatment compared with the potassium treatment and the control after 1 year of burial. In contrast to many literature assessments no significant effects of fertilizer application was found after 2 years. 5. For all sites, except one in the Netherlands, the total number of seeds that germinated was lower in 1996 than in 1995.
Seasonal and annual changes in leaf δ13C in two co‐occurring Mediterranean oaks: relations to leaf growth and drought progression
Authors: Damesin C. , Rambal S. , Joffre R. 
Published: March 2003

1. Changes of δ13C and its relation to leaf development, biochemical content and water stress were monitored over a 2 year period in two co‐occurring Mediterranean oak species: the deciduous Quercus pubescens and the evergreen Quercus ilex. 2. The time course of leaf δ13C showed different patterns in the two species. Young Q. pubescens leaves had a high δ13C and a marked decrease occurred during leaf growth. In contrast, leaves at budburst and maturity did not differ significantly in the case of Q. ilex. We suggest that the difference between δ13C of young leaves was linked to differential use of reserves of carbon compounds in the two species. 3.δ13C values of mature leaves were negatively correlated with minimum seasonal values of predawn water potential, suggesting that a functional adjustment to water resources occurred. 4. There was a significant correlation between individual δ13C values for two successive years. This interannual dependence showed that δ13C rankings between trees were constant through time.
In situ responses to elevated CO2 in tropical forest understorey plants
Authors: WÜrth M. K. R. , Winter K. , KÖrner CH. 
Published: March 2003

1. Plants growing in deep shade and high temperature, such as in the understorey of humid tropical forests, have been predicted to be particularly sensitive to rising atmospheric CO2. We tested this hypothesis in five species whose microhabitat quantum flux density (QFD) was documented as a covariable. After 7 (tree seedlings of Tachigalia versicolor and Beilschmiedia pendula) and 18 months (shrubs Piper cordulatum and Psychotria limonensis, and grass Pharus latifolius) of elevated CO2 treatment (c. 700 μl litre–1) under mean QFD of less than 11 μmol m–2 s–1, all species produced more biomass (25–76%) under elevated CO2. 2. Total plant biomass tended to increase with microhabitat QFD (daytime means varying from 5 to 11μmol m–2 s–1) but the relative stimulation by elevated CO2 was higher at low QFD except in Pharus. 3. Non‐structural carbohydrate concentrations in leaves increased significantly in Pharus (+ 27%) and Tachigalia (+ 40%). 4. The data support the hypothesis that tropical plants growing near the photosynthetic light compensation point are responsive to elevated CO2. An improved plant carbon balance in deep shade is likely to influence understorey plant recruitment and competition as atmospheric CO2 continues to rise.
Maternal effects and their consequences for offspring fitness in the Yellow Dung Fly
Authors: Jann P. , Ward P. I. 
Published: March 2003

1. Maternal adult diet and body size influence the fecundity of a female and possibly the quality and the performance of her offspring via egg size or egg quality. In laboratory experiments, negative effects in the offspring generation have often been obscured by optimal rearing conditions. 2. To estimate these effects in the Yellow Dung Fly, Scathophaga stercoraria, how maternal body size and adult nutritional status affected her fecundity, longevity and egg size were first investigated. 3. Second, it was investigated how female age and adult nutritional experience, mediated through the effects of egg size or egg quality, influenced the performance of offspring at different larval densities. 4. Maternal size was less important than maternal adult feeding in increasing reproductive output. Without food restriction, large females had larger clutch sizes and higher oviposition rates, whereas under food restriction this advantage was reversed in favour of small females. 5. Offspring from mothers reared under nutritional stress experienced reduced fitness in terms of egg mortality and survival to adult emergence. If the offspring from low‐quality eggs survived, the transmitted maternal food deficiency only affected adult male body size under stressful larval environments. 6. Smaller egg sizes due to maternal age only slightly affected the performance of the offspring under all larval conditions.
Reverse flow of sap in tree roots and downward siphoning of water by Grevillea robusta
Authors: SMITH D. M. , JACKSON N. A. , ROBERTS J. M. , ONG C. K. 
Published: March 2003

1. Constant‐power heat‐balance sap flow gauges were used to compare sap flow in vertical and lateral roots of Grevillea robusta trees growing without access to ground water at a semiarid site in Kenya. 2. Reversal of sap flow occurred when root systems crossed gradients in soil water potential. Measurement of changes in the direction of flow was possible because of the symmetrical construction of the sap flow gauges; gradients in temperature across the gauges, and thus computed rates of sap flow, changed sign when reverse flow occurred. 3. Reverse flow in roots descending vertically from the base of the tree occurred, while uptake by lateral roots continued, when the top of the soil profile was wetter than the subsoil. The transfer of water downwards by root systems, from high to low soil water potential, was termed ‘downward siphoning’; this is the reverse of hydraulic lift. 4. Downward siphoning was induced by the first rain at the end of the dry season and by irrigation of the soil surface during a dry period. 5. Downward siphoning may be an important component of the soil water balance where there are large gradients in water potential across root systems, from a wet soil surface downwards. By transferring water beyond the reach of shallow‐rooted neighbours, downward siphoning may enhance the competitiveness of deep‐rooted perennials.
Energy budgets of lactating and non‐reproductive Brown Long‐Eared Bats (Plecotus auritus) suggest females use compensation in lactation
Authors: Mclean J. A. , Speakman J. R. 
Published: March 2003

1. The energy budgets of lactating and non‐reproductive female Brown Long‐Eared Bats fed primarily on noctuid moths (≈ 27·2 kJ g–1) were constructed and compared in flight enclosures in captivity. 2. The average dry food consumption of non‐reproductive individuals was 1·8 g bat–1 day–1 (gross energy intake = 48 kJ day–1). The average food consumption throughout days 10–35 of lactation was 2·0 g bat–1 day–1 (gross energy intake = 53 kJ day–1). Lactating females obtained six times more energy from increased food consumption than from mobilization of fat stores, compared with non‐reproductive bats. 3. Milk export, calculated using the difference in water turnover between lactating and non‐reproductive bats (measured using 2H turnover) averaged 2·6 ml bat–1 day–1 (22·9 kJ day–1). This was similar to the average milk intake of sucklings estimated from 3H turnover (22·9 kJ day–1). 4. Energy available for respiration from food and mobilization of fat stores was 18·2 kJ day–1 for lactating females compared with 36·8 kJ day–1 for non‐reproductive females. In comparison, respiratory daily energy expenditure (DEE) of lactating and non‐reproductive bats, measured by doubly labelled water (DLW), was 21·3 kJ day–1 and 23·6 kJ day–1, respectively. Hence, there was a discrepancy between respiratory DEE (measured by DLW) and net available energy estimates for non‐reproductive bats but not for lactating bats. 5. Respiratory DEE for lactating bats was equal to or less than that of non‐reproductive females, suggesting they used compensatory mechanisms in their energy budgets in lactation.
The CO2dependence of photosynthesis, plant growth responses to elevated CO2concentrations and their interaction with soil nutrient status, II. Temperate and boreal forest productivity and the combined effects of increasing CO2concentrations and increased nitrogen deposition at a global scale
Authors: Lloyd J. 
Published: March 2003

1.Appropriate rates of carbon acquisition by temperate and boreal forests are re‐evaluated. Based on continental‐scale forestry data it is suggested that the productivity of temperate and boreal forests has been overestimated previously.2.Using these values, a model of the integrated response of ecosystems to carbon dioxide concentration and soil nitrogen availability is presented. The model does not assume constant C/N ratios in plant or soil and considers effects of increases in atmospheric CO2concentrations and nitrogen deposition separately or together.3.For temperate‐zone forests a co‐occurrence of a CO2increase and nitrogen deposition doubles the increase in net primary productivity and carbon sequestration that would be the case for nitrogen deposition occurring on its own. Considered separately, the effect of the atmospheric CO2increase is less than even moderate rates of anthropogenic N deposition for temperate or boreal forests. By contrast, for tropical forests, the atmospheric CO2increase is sufficient to induce large rates of carbon accumulation in plants and soil.4.Application of the model at the global scale suggests large localized sinks for CO2in either tropical rain forests or in forested or grassland areas of Europe and North America where appreciable N deposition occurs. Overall, the model suggests a terrestrial sink owing to CO2fertilization and N deposition of about 0·2 Pmol C per year. About half of this is in the mid‐latitudes of the northern hemisphere and about half in the tropics.
On the relationship between the composition, morphology and function of leaves
Authors: Roderick M. L. , Berry S. L. , Saunders A. R. , Noble I. R. 
Published: March 2003

1. It is common practice to express measurements of leaf composition and morphology using dry mass as a basis. Relationships established using those measurements are difficult to interpret because the leaves may have different liquid contents or fractional air space. 2. In a previous theoretical investigation, we showed that the liquid content of leaves was important and the following hypotheses were proposed: (1) the mass of nitrogen per unit mass of liquid is relatively constant within leaves and (2) the surface area to volume ratio of leaves is proportional to leaf liquid content. That investigation also proposed that fractional air spaces were important, because they confer plasticity in construction, with apparently minimal cost in terms of CO2 uptake. In this paper we use a set of comprehensive measurements to address the above hypotheses and to assess whether the fractional air space does vary in a consistent manner. 3. We found that the specific gravity of the non‐gaseous fraction in the leaves we measured was within the range ≈ 0·9–3·0 and increased with the fractional air space in a regular manner. Consequently, the specific gravity varied over a much smaller range (≈ 0·9–1·4). The specific gravity at high liquid contents approached unity but at low liquid contents it was variable. 4. The mass of nitrogen (N) per unit mass of liquid was found to be relatively constant (0·01 ± 0·003, n = 76). 5. The surface area to volume ratio was positively correlated with the liquid content (R2 = 0·87, n = 27). 6. The mass of carbon (C) per unit dry mass was relatively constant (0·49 ± 0·04, n = 76). Because N was a constant fraction of the liquid mass but C was a constant fraction of the dry mass, the N:C ratio was positively correlated with the liquid content (R2 = 0·76, n = 27). 7. A comparison with leaf measurements from several external databases confirm that the relationships described above are widely applicable. 8. It is concluded that the composition and morphology of leaves are linked and that leaf function is a consequence of that linkage. Both the liquids and air spaces are integral to leaf function and need to be considered in analysis of experimental results.
Comparing population response to contaminants between laboratory and field: an approach using Daphnia magna ephippial egg banks
Authors: Barata C. , Baird D. J. , Amat F. , Soares A. M. V. M. 
Published: March 2003

Abstract1. The life‐history responses of one field and two laboratory populations of Daphnia magna were studied under exposure to cadmium and ethyl parathion to assess by how much the response to toxic chemicals of laboratory populations with low genetic diversity differs from the response of genetically diverse field populations.2. The field population was represented by at least 50 unique clones hatched from resting eggs (ephippia) collected at the beginning of the growing season from a temporary water‐body located in the north‐east Mediterranean Spanish coast. The laboratory populations were clonal lines established from two geographically and genetically distinct genotypes, which differed in their tolerance to cadmium and ethyl parathion. Toxicant effects on the mean and the variance of life‐history responses of the laboratory and the field populations were determined. For the field population, toxicant effects on the components of variance of primary fitness traits were also studied.3. In addition to lethal effects, exposure to cadmium had strong sub‐lethal effects on clutch size and age at first reproduction whereas ethyl parathion only affected juvenile survival. The results reported for life‐history responses showed that the field population had a similar or greater mean tolerance to cadmium and ethyl parathion than the laboratory populations, but the breadth of its tolerance distribution (measured as the coefficient of variation, CV) was higher. Furthermore in contrast with the field population, laboratory populations did not show increased phenotypic plasticity (measured as CV) under increasing toxicant exposure. A further analysis of the components of variability for life‐history responses of the field population showed that increases in phenotypic plasticity with exposure levels were explained by increased levels of genetic variability.4. These results support the conclusion that as the tolerance of a field population is strongly influenced by genetic factors, the use of genetically homogeneous laboratory populations has limited relevance in predicting long‐term responses of field populations to toxic chemicals. However, this conclusion must remain tentative until further supporting evidence is obtained from this and other species.
Developmental plasticity in Painted Turtles, Chrysemys picta
Authors: Packard G. C. , Packard M. J. 
Published: March 2003

Abstract1. The contents of newly constructed nests of Painted Turtles, Chrysemys picta, were manipulated by reciprocal transplant, so that each of several nests received a complement of eggs from each of several females. The eggs were recovered from nests after 8 weeks and allowed to complete incubation under standard conditions in the laboratory.2. Live mass, dry mass and water content of carcasses, and dry mass of unused yolk, varied significantly among hatchlings from eggs that incubated in different nests. Indeed, hatchlings from different nests sometimes differed as much in size or physiological condition as animals from different clutches.3. Stepwise linear regression indicated that size of hatchlings and water content of their carcasses were positively correlated with water exchanges by eggs whereas mass of the unused yolk was negatively correlated with water exchanges. Although the statistical procedure is only correlative, the findings accord well with results of laboratory studies documenting a relationship between uptake of water by eggs, metabolism and growth by embryos, and size and condition of hatchlings.4. Developmental plasticity, coupled with variation in the physical environment within and among nests, probably accounts (minimally) for 19% of the variation in live mass of hatchlings in the field; 24% of the variation in dry mass of carcasses; 11% of the variation in hydration of carcasses; and 26% of the variation in dry mass of unused yolk. Such variation may impact survival by neonatal animals, and needs to be addressed explicitly by models for the evolution of life history in Painted Turtles.
Mortality risk of rapid growth in the spider Nephila clavipes
Authors: L. E. Higgins , M. A. Rankin 
Published: March 2003

Summary

Female Nephila clavipes from univoltine populations have greatly reduced reproductive success if they grow slowly and reach maturity late in the growing season. Although such fitness costs are expected to select for rapid increases in mass, several authors have presented models and data describing physiological costs of rapidly increasing mass.
In order to test the hypothesis that there are inherent costs of rapid growth (increasing mass), laboratory‐reared juveniles of the orb‐weaving spider Nephila clavipes were randomly assigned to receive daily feedings ranging from 2·5% to 23% of their initial mass.
Spiders receiving higher amounts of food were more likely to die at or immediately before the next moulting cycle.
These results indicate that there may be inherent physiological costs of rapidly increasing mass. In opportunistic feeders such as spiders that tend to gorge when prey are abundant, this could present a real cost to a common foraging strategy.
Phenotypic plasticity in reproductive traits: geographical variation in plasticity in a viviparous snake
Authors: R. A. Seigel , N. B. Ford 
Published: March 2003

Summary

Previous experiments showed that Checkered Garter Snakes (Thamnophis marcianus) from south Texas, USA (an environment subject to high seasonal and annual variation in environmental conditions), demonstrated marked phenotypic plasticity in clutch size and clutch mass in response to experimental changes in prey availability.
In this study, the extent of phenotypic plasticity in life‐history traits in Checkered Garter Snakes from south Texas was experimentally compared with a population of the same species from south‐eastern Arizona, where the environment may be more constant.
Unlike results from south Texas, Checkered Garter Snakes from Arizona showed no significant phenotypic plasticity in clutch size, clutch mass or any other life‐history trait in response to changes in food availability, at least within the boundaries of our experimental conditions.
The data indicate that the degree of phenotypic plasticity in life‐history traits differs among populations within the same species. However, these differences are subject to both adaptive and non‐adaptive explanations.