bluuebunny/crossref_metadata_2025_split huggingface dataset:
The influence of leaf thickness on the CO2 transfer conductance and leaf stable carbon isotope ratio for some evergreen tree species in Japanese warm‐temperate forests
Authors: Hanba Y. T. , Miyazawa S.‐I. , Terashima I. 
Published: March 2003

1. The influence of leaf thickness on internal conductance for CO2 transfer from substomatal cavity to chloroplast stroma (gi) and carbon isotope ratio (δ13C) of leaf dry matter was investigated for some evergreen tree species from Japanese temperate forests. gi was estimated based on the combined measurements of gas exchange and concurrent carbon isotope discrimination. 2. Leaves with thicker mesophyll tended to have larger leaf dry mass per area (LMA), larger surface area of mesophyll cells exposed to intercellular air spaces per unit leaf area (Smes) and smaller volume ratio of intercellular spaces to the whole mesophyll (mesophyll porosity). 3.
g
i of these leaves was correlated positively to Smes but negatively to mesophyll porosity. The variation in gi among these species would be therefore primarily determined by variation of the conductance in liquid phase rather than that in gas phase. 4.δ13C was positively correlated to mesophyll thickness and leaf nitrogen content on an area basis. However, gi values did not correlate to δ13C. These results suggest that difference in δ13C among the species was not caused by the variation in gi, but mainly by the difference in long‐term photosynthetic capacity. 5. Comparison of our results with those of previous studies showed that the correlation between leaf thickness and gi differed depending on leaf functional types (evergreen, deciduous or annual). Differences in leaf properties among these functional types were discussed.
Effects of herbivory on internal ethylene production and sex expression in Cucurbita texana
Authors: Krupnick G. A. , Avila G. , Brown K. M. , Stephenson A. G. 
Published: March 2003

Abstract1. Field‐grown Cucurbita texana was used in a study to determine if stress ethylene from damaged leaves promotes changes in sex expression.2. Internal ethylene concentrations were experimentally enhanced by inserting an ethylene‐filled syringe into the hollow chamber of an internode seven nodes from the growing tip of a branch. Branches enhanced with ethylene produced significantly more pistillate buds than control branches and experienced greater bud abortion later in floral development.3. The timing and magnitude of Diabrotica beetle leaf damage was simulated using a paper‐hole puncher (15% removed from all leaves). Simulated herbivory was applied to new growth every 3 days throughout the growing season.4. Endogenous ethylene concentrations recovered from the internode adjacent to the growing tip were significantly greater in damaged plants than undamaged plants 1 day after damage to new growth during the second and third week of the experiment, and 2 days after damage during the fourth and fifth week. By the sixth week, no significant differences were evident.5. Damaged plants produced fewer pistillate buds than undamaged plants, indicating that stress ethylene from simulated herbivory does not induce femaleness. A second messenger that suppresses pistillate bud production may be produced during damage.
Long‐range foraging by the honey‐bee, Apis mellifera L.
Authors: Beekman M. , Ratnieks F. L. W. 
Published: March 2003

Abstract1. Waggle dances of honey‐bees (Apis mellifera L.) were decoded to determine where and how far the bees foraged during the blooming of heather (Calluna vulgaris L.) in August 1996 using a hive located in Sheffield, UK, east of the heather moors. The median distance foraged was 6·1 km, and the mean 5·5 km. Only 10% of the bees foraged within 0·5 km of the hive whereas 50% went more than 6 km, 25% more than 7·5 km and 10% more than 9·5 km from the hive.2. These results are in sharp contrast with previous studies in which foraging distances were much closer to the hive. In May 1997 the mean foraging distance was 1 km, showing that long‐range dancing is not the rule in Sheffield.3. The observed foraging distances described in this study may not be exceptional in a patchy environment where differences in patch size and patch quality are large. When travel distances to patches are large, distant patches can probably be utilized only by individuals that live in groups and recruit foragers to the patches found. Only then are the benefits of scouting for distant patches high enough to enable the exploitation of these patches.
Effects of behaviour and ontogeny on the locomotor performance of a West Indian lizard, Anolis lineatopus
Authors: Irschick D. J. 
Published: March 2003

Abstract1. The speeds of locomotion in nature were quantified for juveniles and adult females of the lizard Anolis lineatopus during escape from a threat, feeding and undisturbed locomotion (juveniles only), and compared these data both with data gathered previously on maximal laboratory performance, and with field data gathered previously for adult males.2. The following questions were addressed: (1) Within a particular intraspecific class, do lizards move at different speeds during different behaviours? (2) Within a particular behaviour, do intraspecific classes differ in speed? (3) Do juveniles differ from adult males in the entire distribution of speeds and distances moved when undisturbed?3. Locomotion was typically fastest during escape, followed by feeding and then undisturbed locomotion. Within escape and undisturbed activity, the intraspecific classes differed significantly in absolute speed, relative speed and percentage maximal speed. For the entire distribution of movements during undisturbed locomotion, juveniles moved shorter distances and at slower speeds (between 0 and 10% of maximal) than adult males.4. The relatively high percentages of maximal speed that juveniles employ when escaping and feeding provide limited support for the hypothesis that juveniles are compensating for their relatively poor sprinting capacities.
Seasonal decline in male‐phase duration in a protandrous plant: a response to increased mating opportunities?
Authors: Sargent R. D. , Roitberg B. D. 
Published: March 2003

Abstract1. We examined the effects of pollinator visitation and time of season on male‐ and female‐phase duration, using experimental manipulation and survey data from naturally occurring populations of Chamerion (= Epilobium) angustifolium (L.) J. Holub (Onagraceae).2. Based on the observation that male mating opportunity (numbers of female flowers/numbers of male flowers) increases seasonally, we predicted that individual flowers should spend more time in the male phase early in the season when mating opportunity is low. We predicted that if seasonal changes in mating opportunity select for phase duration, male‐phase duration should decline when pollinator effects are experimentally controlled.3. A comparison of phase duration in naturally pollinated and pollinator‐excluded plants supported this prediction: male‐phase duration in the pollinator‐exclusion treatment was longer and declined faster than in the naturally pollinated group.4. A population survey revealed that once the effects of temperature were controlled for, male‐phase duration was negatively correlated with date, while female‐phase duration was positively correlated with date.5. These findings suggest that seasonal variation in mating opportunity, and not just pollination rate or temperature, may play a significant role in phase duration in dichogamous plants.
Crown carbon gain and elevated [CO2] responses of understorey saplings with differing allometry and architecture
Authors: E. Naumburg , D. S. Ellsworth , R. W. Pearcy 
Published: March 2003

Abstract1. Attempts at determining the physiological basis of species’ differences, such as the ability to grow in deep shade, have been of limited success. However, this basis is fundamental to predicting species’ responses to rising atmospheric CO2 in the forest understorey. We linked a leaf photosynthesis and a tree architecture model to predict the effects of dynamic and steady state photosynthetic characteristics, crown architecture and elevated atmospheric CO2 concentration ([CO2]) on crown‐level carbon gain (Acrown). Twenty‐four‐h Acrown was modelled for shade‐tolerant Acer rubrum and shade‐intolerant Liriodendron tulipifera saplings growing for three years in a forest understorey under ambient and elevated [CO2] in free‐air CO2 enrichment.2. Two factors best explained Acrown in ambient [CO2]: tree light environment and sapling allometry. Microsite light environment influenced carbon gain via daily photosynthetic photon flux (PFD), average diffuse PFD and sunfleck characteristics. Species differences in specific leaf area (SLA) and size‐related biomass allocation to leaves affected the effective leaf area and hence Acrown.3. At a common above‐ground biomass, small saplings (100 g above‐ground dry mass) of L. tulipifera had higher Acrown than A. rubrum samples due to larger SLA and greater biomass allocation to leaves. Larger saplings of the two species had similar Acrown due to greater carbon allocation to leaves with increasing plant size in A. rubrum vs L. tulipifera. For saplings > 800 g, Acrown was greater in A. rubrum than in L. tulipifera. Enhancement of Acrown by elevated [CO2] on sunny days was similar for both species.4. Overall, though the shade‐tolerant species had lower Acrown than the shade‐intolerant species at a common small size, our results indicate that the relative performance of these species can reverse at larger sizes due to allocational differences. These results suggest that elevated [CO2] may accelerate competition for light between A. rubrum and L. tulipifera as these species grow larger in the understorey.
Root system topology and diameter distribution of species from habitats differing in inundation frequency
Authors: Bouma T. J. , Nielsen K. L. , Van Hal J. , Koutstaal B. 
Published: March 2003

Summary

We compared the root systems of seven halophytic species that occur at different elevations on a salt marsh, in order to (i) test the hypothesis that variations in root system architecture reflect adaptation to inundation frequency or nitrogen limitation, and (ii) verify the theoretically predicted relationships between root diameter, link magnitude and root topology. Diameters and lengths of individual laterals were determined along root axes, and branching patterns were quantified by calculating a topological index (TI).
Chenopodiaceae (annual dicots) showed that with increasing elevation, the branch density and length of individual first‐order laterals tended to increase, so that the relative length of the main axes decreased. Root branching of the Chenopodiaceae at lower elevations was herringbone‐like, whereas species from higher elevations had smaller TIs because their branching patterns were more complex.
The Gramineae, too, showed a tendency to increased length of individual laterals with increasing elevation. However, TI was not related to elevation, did not indicate a herringbone structure for all species, and was within the same range of that of the Chenopodiaceae.
As root topology of the Chenopodiaceae is related to elevation, but that of the grasses is not, topology is not necessarily an important adaptive trait in all plant families that inhabit the salt marsh. Short first‐ and second‐order laterals may represent a more general architectural adaptation to frequent inundation, with longer first‐order laterals being favourable to competition for nutrients.
Diameters at the root base tended to decrease if root branching was herringbone‐like (TI close to 1). Roots of first‐order laterals were approximately one‐third of the diameter of the main axes; second‐order laterals were approximately half the diameter of the first‐order laterals. These ratios illustrate the value of using the developmental segment‐ordering system in describing roots. The theoretically predicted relationship between root diameter and link magnitude was not present within individual orders of roots, whereas diameter did slowly increase with magnitude when combining different root orders.
In the absence of a clear relationship between root diameter and link magnitude, the predicted high carbon costs associated with herringbone root systems disappear, whereas the advantage of minimized inter‐root competition remains. Consequently, herringbone root systems will be most efficient in terms of nutrients gained per carbon invested. However, dichotomous root systems offer a greater potential for exploring the soil, which contributes to the potential competitiveness of plants growing in nutrient limited habitats.
Root life spans of four grass species from habitats differing in nutrient availability
Authors: Van Der Krift T. A. J. , Berendse F. 
Published: March 2003

Summary

In grass species that occur in pastures or hay meadows, life spans of roots determine much of the carbon and nutrient loss from the plant in addition to the amounts that are lost by mowing or grazing. We hypothesized that grass species from nutrient‐poor habitats had longer root life spans and consequently lost smaller quantities of nutrients through root turnover.
In a garden experiment, root life spans and root diameters were measured by repeated observations in minirhizotrons placed in monocultures of Lolium perenne L. and Arrhenatherum elatius L. (characteristic of fertile soils) and Molinia caerulea L. and Nardus stricta L. (preferring nutrient‐poor soils).
Average root life spans were 14 weeks in L. perenne, 40 weeks in A. elatius, 53 weeks in M. caerulea and 58 weeks in N. stricta. Root life spans of species from fertile habitats were significantly shorter than the root life spans of species from low fertility habitats.
In addition, there were significant differences in root diameter among species, root diameter being positively correlated to root life spans. Root diameter decreased during root ageing in all species, while the decline in diameter occurred more slowly in N. stricta than in A. elatius and M. caerulea.
An increase in the abundance of plant species adapted to fertile habitats will, because of the greater C and nutrient returns to the soil in root turnover, increase soil fertility. This effect may constitute a positive feedback between changes in plant species composition and nutrient cycling.
Measuring drag without a force transducer: a terminal velocity assay
Authors: Loudon C. , Zhang J. 
Published: March 2003

Summary

Organisms live surrounded by air or water, which exert drag on an organism when moving. These forces are significant ecologically because they can affect organisms’ distribution, behaviour or dispersal.
Appropriate techniques for measuring or estimating these forces vary greatly depending on the magnitude of the forces and the flow pattern of the moving fluid (air or water; both gases and liquids are fluids). A simple method for estimating the drag in uniform steady flow is described. This technique is particularly well suited for forces of small magnitude (micronewtons) and slow flows (1 < Re < 100), and provides very uniform and well‐characterized ambient flow relative to the object.
This method capitalizes on the force balance that exists when a falling object reaches terminal velocity. At terminal velocity, all of the forces sum to zero, and therefore the drag may be estimated from the other (known) forces (buoyancy and gravitational force). Orientation during falling may be controlled if necessary.
Repeatability estimates do not always set an upper limit to heritability
Authors: M. R. Dohm 
Published: March 2003

Summary The concept of repeatability, the measurement of consistent individual differences, has become an increasingly important tool in evolutionary and ecological physiology. Significant repeatability facilitates the study of selection acting on natural populations and the concept has several practical implications for identifying traits. When properly defined and measured, repeatability can set the upper limit to heritability. This is potentially a very useful interpretation of the repeatability of traits measured on natural populations because often, estimates of heritability cannot be obtained. Many recent reports of repeatability of individual differences for traits have made this interpretation. However, repeatability estimates may not set an upper limit to heritability if: (a) measured traits are not genetically identical, (b) common environmental effects work in opposition to direct genetic effects, (c) the temporary environments for each trait are negatively correlated, (d) significant genotype–environment interaction is present, or (e) the traits are influenced by maternal effects. The quantitative genetic theory that defines the concept of repeatability is reviewed and implications of violations of the five assumptions are discussed in the context of interpreting repeatability as an upper estimate to heritability.
High leaf mass per area of related species assemblages may reflect low rainfall and carbon isotope discrimination rather than low phosphorus and nitrogen concentrations
Authors: Lamont Byron B. , Groom Philip K. , Cowling R. M. 
Published: March 2003

Summary 1. Leaf morphology at the site/species level should reflect environmental constraints on plant growth. One of the oldest controversies in ecology is the environmental basis for sclerophylly. The dominant view (Beadle’s theory) is that it has a nutritional, rather than a drought, basis, especially low phosphorus. 2. Using leaf mass per area (LMA) as an index of sclerophylly, we assessed its relationship with leaf phosphorus (P) and nitrogen (N) along extensive rainfall gradients in southwestern Australia and the Cape of South Africa. Leaf 13C/12C discrimination (Δ13C), as an index of intrinsic water‐use efficiency, was also examined in the Cape. All Hakea species (Proteaceae) were sampled at 10 sites in Australia (96 species), and all Proteaceae at 14 sites in the Cape (82 species). All were evergreen shrubs with iso(bi)‐lateral leaves. 3. In each region there was a strong (inverse) curvilinear relationship between mean LMA per site and mean annual rainfall and Δ13C, but none with mean P or N on a mass basis (although P and N on an area basis declined with rainfall). The Cape study was a particularly good test of Beadle’s theory, as P varied as much between sites as rainfall, and more between sites than within sites. 4. Leaf thickness and dry density were not as well correlated with rainfall as LMA, and leaf area and mass showed no relationship with rainfall. Area and mass had much greater variation within sites than between sites, limiting their value in plant–environment studies, while LMA was the most site‐stable of the eight leaf attributes measured, except for Δ13C. 5. For all species considered individually in each region, there was a similar pattern as the site level, with LMA most strongly correlated (negatively) with rainfall and Δ13C and (positively) with leaf thickness, but no consistent relationship with P, N or density. 6. We conclude that when water and nutrient supply vary independently in the field, rainfall (as an index of water status) and Δ13C may be more closely correlated (inversely) with level of sclerophylly than nutrient status among evergreens, so that the role of sclerophylly as a drought adaptation warrants further consideration.
Interspecific and spatial differences in nitrogen uptake in monocultures and two‐species mixtures in north European grasslands
Authors: Jumpponen A. , Högberg P. , Huss‐Danell K. , Mulder C. P. H. 
Published: March 2003

Summary 1. To study the potential for complementarity in nitrogen acquisition from different soil depths, we injected an isotope tracer (15NH4Cl) at 5 and 20 cm depths in plant communities containing Achillea millefolium L. and Festuca ovina L. or Phleum pratense L. and Trifolium pratense L. in monocultures and two‐species mixtures. 2. In monoculture, Festuca and Phleum took up tracer at 5 and 20 cm depths. In contrast, Achillea and Trifolium monocultures acquired the tracer mainly from 5 cm depth. In two‐species mixtures, all four species took up tracer at 5 cm depth. 3. Achillea N acquisition from 20 cm depth increased in mixture with Festuca in comparison to that in monoculture; Festuca N acquisition from 20 cm depth decreased, although not significantly. Trifolium N acquisition remained unchanged when grown in mixture with Phleum. Phleum behaved like Festuca: its N acquisition from 20 cm depth in mixture was reduced in comparison to monoculture. 4. Our data on Festuca and Achillea support spatial partitioning in resource acquisition. This was not evident in Phleum and Trifolium mixture, potentially because Trifolium relied on N2 fixation as N source. 5. These results demonstrate spatial variation among plant species and plant communities in their N acquisition in the field.
Blood concentration of organochlorine pollutants and wing feather asymmetry in Glaucous Gulls
Authors: Bustnes J. O. , Folstad I. , Erikstad K. E. , Fjeld M. , Miland Ø. O. , Skaare J. U. 
Published: March 2003

SummaryNon‐directional asymmetries (fluctuating asymmetry, FA) from bilateral symmetry in morphological traits have been used as an indicator of environmental stress and may become an important diagnostic tool in environmental sciences, such as ecotoxicology.In this study the relationship was examined between wing feather asymmetry, measured as the difference between the length of the third primary on the left and right wing, and blood concentration of selected persistent organochlorines (OCs) in Arctic breeding Glaucous Gulls (Larus hyperboreus, Gunnerus).There was a positive relationship between primary asymmetry and blood concentrations of two PCB (polychlorinated biphenyl) congeners (P < 0·05), oxychlordane (P < 0·05), DDE (p′p′‐dichlorodiphenyldichloroethylene) (P < 0·05), and especially HCB (hexachlorbenzene) (P < 0·001). At HCB levels above 30 ng g−1(wet mass) there was a 60% probability that the birds had asymmetric wing feathers.This study indicated that the present levels of organochlorines in the European Arctic are stressors for Glaucous Gulls, and that asymmetry measurements of wing feathers may be used as an indicator of both exposure and effects of such contaminants. FA may also be a promising measurement for monitoring the early effects of organochlorine pollution on bird populations.
Effects of temperature and food quality on anuran larval growth and metamorphosis
Authors: Álvarez D. , Nicieza A. G. 
Published: March 2003

Summary

Anurans exhibit high levels of growth‐mediated phenotypic plasticity in age and size at metamorphosis. Although temperature and food quality exert a strong influence on larval growth, little is known about the interacting effects of these factors on age and size at metamorphosis.
Plasticity in growth rates, maximum larval mass, mass loss, larval period and size at metamorphosis was examined in Iberian Painted Frogs (Discoglossus galganoi Capula, Nascetti, Lanza, Bullini & Crespo 1985) under different combinations of temperature and diet quality.
Temperature and diet had strong effects on the maximum size reached by tadpoles throughout the premetamorphic stages. Larval body mass varied inversely with temperature. The effect of diet depended on temperature; larvae fed on a ‘carnivorous’ diet (rich in protein and lipids) achieved a larger size than larvae offered an ‘herbivorous’ diet (rich in carbohydrates) at 17 °C but not at 12 or 22 °C.
Larval period was insensitive to diet composition, and varied only with temperature. Primarily the interacting effects of food quality and temperature affected size at metamorphosis. Size at metamorphosis varied inversely with temperature under the plant‐ and the animal‐based diets. However, the carnivorous diet resulted in bigger metamorphs at 17 and 22 °C, but did not influence final mass at 12 °C. Maximum size over the larval period explained most of the variation in mass loss after the premetamorphic growing phase.