bluuebunny/crossref_metadata_2025 huggingface dataset:
Riverine landscape dynamics and ecological risk assessment
Authors: LEUVEN ROB S. E. W. , POUDEVIGNE ISABELLE
Published: March 2003

1. The aim of ecological risk assessments is to evaluate the likelihood that ecosystems are adversely affected by human‐induced disturbance that brings the ecosystem into a new dynamic equilibrium with a simpler structure and lower potential energy. The risk probability depends on the threshold capacity of the system (resistance) and on the capacity of the system to return to a state of equilibrium (resilience).

2. There are two complementary approaches to assessing ecological risks of riverine landscape dynamics. The reductionist approach aims at identifying risk to the ecosystem on the basis of accumulated data on simple stressor–effect relationships. The holistic approach aims at taking the whole ecosystem performance into account, which implies meso‐scale analysis.

3. Landscape patterns and their dynamics represent the physical framework of processes determining the ecosystem's equilibrium. Assessing risks of landscape dynamics to riverine ecosystems implies addressing complex interactions of system components (e.g. population dynamics and biogeochemical cycles) occurring at multiple scales of space and time.

4. One of the most important steps in ecological risk assessment is to establish clear assessment endpoints (e.g. vital ecosystem and landscape attributes). Their formulation must recognise that riverine ecosystems are dynamic, structurally complex and composed of both deterministic and stochastic components.

5. Remote sensing (geo)statistics and geographical information systems are primary tools for quantifying spatial and temporal components of riverine ecosystem and landscape attributes.

6. The difficulty to experiment at the riverine landscape level means that ecological risk management is heavily dependent on models. Current models are targeted towards simulating ecological risk at levels ranging from single species to habitats, food webs and meta‐populations to ecosystems and entire riverine landscapes, with some including socio‐economic considerations.
Geomorphic thresholds in riverine landscapes
Authors: CHURCH MICHAEL
Published: March 2003

1. Rivers are subject to thresholds of several types that define significant changes in processes and morphology and delimit distinctive riverine landscapes and habitats. Thresholds are set by the conditions that govern river channel process and form, amongst which the most important are the flow regime, the quantity and calibre of sediment delivered to the channel, and the topographic setting (which determines the gradient of the channel). These factors determine the sediment transport regime and the character of alluvial deposits along the channel.

2. Changes occur systematically along the drainage system as flow, gradient and sediment character change, so a characteristic sequence of morphological and habitat types – hence of riverine landscapes – can be described from uplands to distal channels. The sequence is closely associated with stream competence to move sediment and with bank stability.

3. The paper proposes a first order classification of river channel and landscape types based on these factors. The riverine landscape is affected seasonally by flow thresholds, and further seasonal thresholds in northern rivers are conditioned by the ice regime.

4. It is important to understand geomorphic thresholds in rivers not only for the way they determine morphology and habitat, but because human activity can precipitate threshold crossings which change these features significantly, through either planned or inadvertent actions. Hence, human actions frequently dictate the character of the riverine landscape.
Calcium content of crustacean zooplankton and its potential role in species distribution
Authors: Wærvågen Svein B. , A. Rukke Nina , Hessen Dag O.
Published: March 2003

SUMMARY 1. The occurrence and species composition of crustacean zooplankton in Norwegian lakes was related to ambient Ca concentrations, pH, total phosphorus and chlorophyll a, and to the presence/absence of other zooplankters and a planktivorous fish (roach: Rutilus rutilus).

2. Ambient Ca concentrations appeared to influence the distribution of Daphnia species: Daphnia longispina often occurred in Ca‐rich lakes with low fish‐predation pressure while the smaller Daphnia cristata often occurred in opposite conditions.

3. Body Ca contents were measured in zooplankters from a wide range of localities, to examine Ca requirements and thus the potential for Ca‐limitation of common species.

4. All Daphnia species had relatively high specific Ca contents [ranging from 0.8 to 4.4% Ca dry weight (DW)−1] compared with other cladocerans and also copepods (ranging from 0.1 to 0.4% Ca DW−1). Within the Daphnia genus, the specific Ca content increased with increasing body size of the species, and thus the large‐bodied species had especially high Ca demands.

5. Because of their high Ca demands, species of Daphnia could be competitively disadvantaged in softwater lakes relative to less Ca‐demanding species.
Predation on exotic zebra mussels by native fishes: effects on predator and prey
Authors: Magoulick Daniel D. , Lewis Lindsey C.
Published: March 2003

SUMMARY 1. Exotic zebra mussels, Dreissena polymorpha, occur in southern U.S. waterways in high densities, but little is known about the interaction between native fish predators and zebra mussels. Previous studies have suggested that exotic zebra mussels are low profitability prey items and native vertebrate predators are unlikely to reduce zebra mussel densities. We tested these hypotheses by observing prey use of fishes, determining energy content of primary prey species of fishes, and conducting predator exclusion experiments in Lake Dardanelle, Arkansas.

2. Zebra mussels were the primary prey eaten by 52.9% of blue catfish, Ictalurus furcatus; 48.2% of freshwater drum, Aplodinotus grunniens; and 100% of adult redear sunfish, Lepomis microlophus. Blue catfish showed distinct seasonal prey shifts, feeding on zebra mussels in summer and shad, Dorosoma spp., during winter. Energy content (joules g−1) of blue catfish prey (threadfin shad, Dorosoma petenense; gizzard shad, D. cepedianum; zebra mussels; and asiatic clams, Corbicula fluminea) showed a significant species by season interaction, but shad were always significantly greater in energy content than bivalves examined as either ash‐free dry mass or whole organism dry mass. Fish predators significantly reduced densities of large zebra mussels (>5 mm length) colonising clay tiles in the summers of 1997 and 1998, but predation effects on small zebra mussels (≤5 mm length) were less clear.

3. Freshwater drum and redear sunfish process bivalve prey by crushing shells and obtain low amounts of higher‐energy food (only the flesh), whereas blue catfish lack a shell‐crushing apparatus and ingest large amounts of low‐energy food per unit time (bivalves with their shells). Blue catfish appeared to select the abundant zebra mussel over the more energetically rich shad during summer, then shifted to shad during winter when shad experienced temperature‐dependent stress and mortality. Native fish predators can suppress adult zebra mussel colonisation, but are ultimately unlikely to limit population density because of zebra mussel reproductive potential.
Growth and survival of Daphnia in epilimnetic and metalimnetic water from oligotrophic lakes: the effects of food and temperature
Authors: Cole Peter C. , Luecke Chris , Wurtsbaugh Wayne A. , Burkart Greta
Published: March 2003

SUMMARY 1. In oligotrophic lakes, phytoplankton and bacteria growing in the deep chlorophyll maximum in the cool metalimnion of lakes often dominate biomass and production, but the importance of this source of food for zooplankton is unknown.

2. During much of the day, Daphnia rosea in two mountain lakes inhabited deep chlorophyll layers where food availability was at least equal to that in the epilimnion.

3. To determine the importance of the two strata (epilimnion and metalimnion) for Daphnia, we used a cross‐classified factorial experiment to measure how epilimnetic and metalimnetic food and temperature (10 and 16 °C) influenced survival, growth and reproduction.

4. Daphnia survived and grew better when fed seston from the epilimnion of one lake, although chlorophyll, particulate nitrogen and particulate carbon were 2–2.5 times greater in the metalimnion.

5. Temperature had no significant influence on Daphnia survival or growth. Similar results were obtained with food from the second lake, with Daphnia surviving and reproducing better when provided with epilimnetic, rather than metalimnetic food, although the quantities of chlorophyll and carbon in the two strata were similar.

6. Food quality, rather than quantity or temperature, appeared to be the most important determinant influencing survival, growth and reproduction, and the greater food quantity in the metalimnia was not used effectively by the Daphnia.
Top‐down control of phytoplankton: the role of time scale, lake depth and trophic state
Authors: Benndorf JÜrgen , Böing Wiebke , Koop Jochen , Neubauer Ivonne
Published: March 2003

SUMMARY 1. One of the most controversial issues in biomanipulation research relates to the conditions required for top‐down control to cascade down from piscivorous fish to phytoplankton. Numerous experiments have demonstrated that Phytoplankton biomass Top‐Down Control (PTDC) occurs under the following conditions: (i) in short‐term experiments, (ii) shallow lakes with macrophytes, and (iii) deep lakes of slightly eutrophic or mesotrophic state. Other experiments indicate that PTDC is unlikely in (iv) eutrophic or hypertrophic deep lakes unless severe light limitation occurs, and (v) all lakes characterised by extreme nutrient limitation (oligo to ultraoligotrophic lakes).

2. Key factors responsible for PTDC under conditions (i) to (iii) are time scales preventing the development of slow‐growing inedible phytoplankton (i), shallow depth allowing macrophytes to become dominant primary producers (ii), and biomanipulation‐induced reduction of phosphorus (P) availability for phytoplankton (iii).

3. Under conditions (iv) and (v), biomanipulation‐induced reduction of P‐availability might also occur but is insufficient to alter the epilimnetic P‐content enough to initiate effective bottom‐up control (P‐limitation) of phytoplankton. In these cases, P‐loading is much too high (iv) or P‐content in the lake much too low (v) to initiate or enhance P‐limitation of phytoplankton by a biomanipulation‐induced reduction of P‐availability. However, PTDC may exceptionally result under condition (iv) if high mixing depth and/or light attenuation cause severe light limitation of phytoplankton.

4. Recognition of the five different conditions reconciles previous seemingly contradictory results from biomanipulation experiments and provides a sound basis for successful application of biomanipulation as a tool for water management.
Thermal patterns in the surface waters of a glacial river corridor (Val Roseg, Switzerland)
Authors: Uehlinger U. , Malard F. , Ward J. V.
Published: March 2003

SUMMARY 1. We examined the thermal patterns of the surface waters in the catchment of the Roseg River, which is fed by the meltwaters of two valley glaciers. One of the glaciers has a lake at its terminus. The river corridor comprised a proglacial stream reach below one glacier, the glacier lake outlet stream, a 2.5‐km long complex floodplain and a constrained reach extending to the end of the catchment.

2. Temperatures were continuously measured with temperature loggers at 27 sites between 1997 and 1998. Moreover, from 1997 to 1999, spot measurements were taken at 33–165 floodplain sites (depending on water level) at monthly intervals.

3. The temperature regime of glacial streams, including the glacier lake outlet, was characterised by rapidly increasing temperatures in April and May, a moderate decline from June to September (period of glacial melt) and a subsequent fast decline in autumn. During summer, the lake increased temperatures in the outlet stream by 2–4 °C, compared with the adjacent proglacial stream reach.

4. In the main channel (thalweg) of the Roseg River, annual degree‐days (DD) ranged from 176 DD in the upper proglacial reach to 1227 DD at the end of the catchment.

5. Thermal variation among different channels within the floodplain was higher than the variation along the entire main channel. Floodplain channels lacking surface connection to the main channel accumulated up to 1661 annual DDs.

6. Thermal heterogeneity within the floodplain was linked to the glacial flow pulse. With the onset of ice melt, temperatures in the main channel and in channels surface‐connected to the main channel began to decline, whereas in surface‐disconnected channels temperatures continued to increase; as a consequence, thermal heterogeneity at the floodplain scale rose slightly until September.

7. High thermal heterogeneity was not anticipated in the harsh environment of a largely glacierised alpine catchment. The relatively wide range of thermal environments may contribute to the highly diverse zoobenthic community.
Critical thermal limits in Mediterranean ant species: trade‐off between mortality risk and foraging performance
Authors: Cerdá X. , Retana J. , Cros S.
Published: March 2003

1.In Mediterranean ant communities, a close relationship has been found between activity rhythm in the period of maximum activity and position in the dominance hierarchy: subordinate species are active during the day, when conditions are more severe, while dominants are active during the afternoon and the night.

2.Results obtained in this study confirmed that the species foraging at higher temperatures were closer to their critical thermal limits than the species foraging at lower temperatures.

3.This enabled two extreme strategies of foraging in relation to temperature to be distinguished: (1) heat‐intolerant ant species behaved as risk‐averse species, foraging at temperatures very far from their critical thermal limits; and (2) heat‐tolerant ant species behaved as risk‐prone species, foraging very near their critical thermal limits and running a high heat mortality risk.

4.Heat‐tolerant species benefited from this strategy by having better foraging performance at high temperatures.

5.This wide range of thermal niches may be one reason why Mediterranean ant faunas are so diverse in the face of limited diversity in vegetation and habitat structure: the daily range of temperature may be sufficiently great to meet the requirement both of heat‐adapted and cold‐adapted species as well as a spectrum of intermediate forms.
Multiple breeding in the Great Tit, II. The costs of rearing a second clutch
Authors: Verhulst S.
Published: March 2003

1. Multiple breeding (raising more than one batch of young per breeding season) is a common life‐history tactic, but little is known as yet of the accompanying costs and benefits. Second clutches of Great Tits, a facultative multiple breeder, were removed over three years to investigate the costs of rearing a second clutch.

2. Female parents, but not males, survived significantly better than unmanipulated control birds when the second clutch was removed. The difference between the sexes indicates a potential sexual conflict over the decision to start a second clutch. In neither sex were effects found on egg production in the next year. However, birds of both sexes produced more fledglings from first clutches in the following year when the second clutch had been removed.

3. In males, the experimental effect on fledgling production in the next year could be attributed to their mates, because this effect was restricted to males that bred with the same female as in the previous year. In females, this effect was also found among birds that bred with a new mate, which suggests that rearing a second clutch had a long‐term effect. Females, but not males, found roosting in the following winter had lower mass when the second clutch had been removed, which supports the conclusion that rearing a second clutch has long‐term effects.

4. The experimental effect on female survival was found in two winters with low food availability, but not in a winter with high food availability. This is in agreement with the results of a non‐experimental analysis of data collected in the same population. The effect on fledgling production in the next year was also restricted to years with low food availability in the intervening winter. This suggests that the costs of rearing a second clutch depend on food availability in winter. The possibility that the costs of reproduction generally depend on environmental quality and possible mechanisms are discussed.

5. Food availability in winter is probably unpredictable at the time second clutches are started, and therefore Great Tits should ‘bet‐hedge’ with regard to the decision to start a second clutch.
The contribution of fungus to the diets of three mycophagous marsupials in Eucalyptus forests, revealed by stable isotope analysis
Authors: Mcilwee A. P. , Johnson C. N.
Published: March 2003

1. Many field studies have shown that small herbivorous mammals include fungus (usually hypogeous sporocarps of ectomycorrhizal fungi) in their diets. However, the dietary importance of fungus relative to other foods is generally unclear because of limitations on the power of conventional techniques of diet analysis. Stable isotope analysis in conjunction with faecal analysis was used in an attempt to overcome these limitations.

2. Two foregut‐fermenting marsupials (the Northern Bettong Bettongia tropica and Rufous Bettong Aepyprymnus rufescens) and a hindgut fermenter (the Northern Brown Bandicoot Isoodon macrourus) were studied. The Northern Bettong and Northern Brown Bandicoot are of similar body size (around 1 kg); the Rufous Bettong is significantly larger at 3 kg. Faecal analysis showed that the two bettongs ate a variety of grasses, lilies and fungi; the bandicoot ate these foods and also invertebrates.

3. Ratios of 15N/14N and 13C/12C differed in major food types collected in the field (fungus, grass, lily and invertebrates). Grass was clearly separated from the other food types by its low 13C/12C ratio, while fungus was separated from the other types by its high 15N/14N ratio. Invertebrates and lilies differed slightly in 13C/12C ratios.

4. Isotope ratios in body tissue (sampled in hair) of the three mammals were also discrete, showing that the species differed in the predominant sources of their C and N. Estimates of the proportion of C assimilated in body tissue that was derived from grass were 80% for the Rufous Bettong, 40% for the Northern Bettong and 45% for the Northern Brown Bandicoot. Analysis of 15N/14N ratios suggested that the Northern Bettong derived almost all its N from fungus, the Northern Brown Bandicoot derived practically no N from fungus, and the Rufous Bettong was intermediate.

5. The results confirm that for the Northern Bettong, fungus is a predominant source of N and C assimilated into body tissue. Differences between the use of fungi by the Northern Bettong and the Northern Brown Bandicoot strengthen conclusions from other studies that foregut fermentation confers on small mammals a greater ability to utilize fungus than does hindgut fermentation. It is hypothesized that the limited use of fungus by the Rufous Bettong is due to the patchy distribution of hypogeous sporocarps, which would result in a high energy cost of foraging for this larger‐bodied species with a higher absolute food requirement.
A simple graphical technique for displaying individual fertility data and cohort survival: case study of 1000 Mediterranean Fruit Fly females
Authors: Carey J. R. , Liedo P. , MÜller H.‐G. , Wang J.‐L. , Vaupel J. W.
Published: March 2003

1.A graphic technique is presented in which data on age‐specific reproduction of individuals are portrayed using: (i) a horizontal life line, the length of which is proportional to individual longevity; (ii) colour‐coded segments depicting the level of reproduction at each age; and (iii) a cohort survival schedule created by rank‐ordering individual life lines from shortest‐ to longest‐lived.

2.The resulting graphic, referred to as an event history diagram, portrays data at the individual level and thus allows visual comparisons of detailed life‐history patterns such as age of first reproduction, longevity, ages of high, medium, low and zero reproduction, and post‐reproductive period.

3.Example graphs are shown for reproductive and longevity data gathered on 1000 medfly females. The average female lived 35·6 days and laid 759·3 eggs and therefore the graphs display information for 35 600 fly days and the age‐distribution of laying for 759 300 eggs.

4.Because the graphics provide a means for visualizing large amounts of data precisely and efficiently, they reveal details and nuances in the data that are not apparent from conventional graphic methods.

5.The advantages of longitudinal data gathered on individuals and reasons why visualizing individual‐level data is important are discussed.
Echolocation, olfaction and fruit display: how bats find fruit of flagellichorous cucurbits
Authors: Kalko E. K. V. , Condon M. A.
Published: March 2003

1. The relationship between plant morphology and the senses used by dispersal agents to find fruit was examined. ‘Flagellichory’ (fruit borne on pendulous structures), a costly morphology associated with dispersal by bats, is focused on.

2. Using Gurania spinulosa, a flagellichorous vine, and its major dispersal agent, Phyllostomus hastatus, the hypothesis was tested that flagellichory increases the conspicuousness of fruit to bats that use echolocation to find fruit.

3. The responses of wild‐caught P. hastatus to various fruiting branch morphologies and fruit odour were recorded. Phyllostomus hastatus used echolocation rather than olfaction to detect fruit, and consistently chose fruit displayed on pendulous leafless branches, ignoring fruit held among leaves on horizontal branches.

4. By comparing echolocation signals with the distance between fruiting branches of G. spinulosa and surrounding vegetation, it was shown that pendulous fruiting branches present clear, clutter‐free targets that can be detected by echolocating bats. This is the first demonstration of neotropical frugivorous bats using echolocation to find fruit.
Growth and physiology of Picea abies populations from elevational transects: common garden evidence for altitudinal ecotypes and cold adaptation
Authors: Oleksyn J. , Modrzýnski J. , Tjoelker M. G. , Z·ytkowiak R. , Reich P. B. , Karolewski P.
Published: March 2003

1. There are conflicting reports concerning the adaptive features of tree populations originating from cold, high‐altitude environments. We hypothesize that such trees will possess adaptive features that will be demonstrated in a common environment, such as elevated rates of net CO2 exchange, elevated needle nitrogen concentration and high proportional biomass allocation to roots. To test this hypothesis we measured tree and seed properties of 54 populations of Norway spruce [Picea abies (L.) Karst.] located along eight altitudinal transects (from c.600 to 1500m) in southern Poland. We also measured growth, biomass partitioning, net photosynthetic capacity (Amax), needle dark respiration (RS) and carbohydrate, nitrogen (N) and chlorophyll concentration of seedlings originating from these populations grown for 2 to 7 years in a common garden at 150m elevation. Measured in situ along the elevational transects, there were linear declines in seed mass, average d.b.h. and height growth increment of seed trees with increased altitude or lower mean annual temperature.

2. In the common garden, the Norway spruce populations from colder, high‐altitude habitats had higher N concentration in needles than those from low altitudes. Both Amax and needle RS increased with altitude of seed origin and were significantly related to needle N concentration. High‐altitude populations also had higher concentrations of chlorophyll and carotene than those from low elevations. Despite higher photosynthetic rates in high‐altitude populations, seedling height and dry mass in the common garden declined with altitude of seed origin. Proportional dry mass partitioning to roots nearly doubled with increasing altitude of origin, while the length of the shoot‐growth period was reduced. The high respiration rates, high allocation to roots and reduced shoot‐growth period are probably responsible for the low growth rate potential of high‐altitude populations, more than offsetting their higher photosynthetic rates.

3. The results of this study showed that Norway spruce populations from cold mountain environments are characterized by several potentially adaptive features. Because these were similar to conifer population responses along a latitudinal gradient of origin, they are probably driven by climate. These climate‐driven differences were common to all transects: for a given altitude or mean annual temperature, plant traits were independent of mountain range of origin. However, populations originating from cold high‐elevation sites often differed per unit change in altitude or mean annual temperature more than did low elevation populations. The scaling of nitrogen, CO2 exchange and biomass and allocation patterns may be useful in modelling Norway spruce response on montane forest ecosystems under changing environments.
Seed size, shape and vertical distribution in the soil: indicators of seed longevity
Authors: Bekker R. M. , Bakker J. P. , Grandin U. , Kalamees R. , Milberg P. , Poschlod P. , Thompson K. , Willems J. H.
Published: March 2003

1. We investigated the vertical distribution of seeds in the soil, using data from nine studies in five European countries. We discovered significant correlations between seed shape and distribution in the soil.

2. The classification of the longevity of seeds of plant species has been improved by the introduction of a ‘longevity index’, expressing on a continuous scale the most recent information on seed longevity represented as the proportion of non‐transient seed bank records in the database of Thompson et al. (1997). Remarkably, no difference in seed longevity was found if the index was based on direct observations only when compared with the index based on the complete data set where indirect, ‘depth‐derived’ observations were included.

3. Seed longevity was best estimated using a multiple regression model with an integrated measure of seed size and shape and depth distribution of seeds.

4. The shape of seeds, known to be a consistent character of species, was shown to be constant within species, whereas depth distribution of seeds was highly variable among sites. This is consistent with the variability of seed longevity found in published seed bank data.
Energetically costly behaviour and the evolution of resting metabolic rate in insects
Authors: REINHOLD K.
Published: March 2003

1. A general hypothesis is presented to explain interspecific differences in size‐independent resting metabolic rate. This hypothesis is based on a presumed trade‐off between a low resting metabolism and adaptations of metabolism during activity.

2. With such a trade‐off, selection to reduce resting metabolism is less intense in active species than in species where resting metabolism constitutes a large proportion of the daily metabolic costs. Those animals that spend more energy on activity should therefore have a higher resting metabolic rate than animals that spend less energy on activity.

3. A literature review reveals that flying insects have higher resting metabolic rates than species that use energetically less demanding types of locomotion.

4. Insects producing acoustic advertisement signals can be shown to have higher mass‐independent resting metabolic rates than closely related species without this energetically demanding behaviour.

5. Literature data on vertebrate resting metabolic rates are also consistent with the presented hypothesis: the more energy animals spend on activity, the higher the mass‐independent resting metabolic rate.
Relationships between body composition, body size and alternative reproductive tactics in a lekking sandpiper, the Ruff (Philomachus pugnax)
Authors: Bachman G. , Widemo F.
Published: March 2003

1. The Ruff is a lekking sandpiper in which males have two genetically determined alternative mating strategies: ‘satellite’ or ‘independent’. Satellite males are non‐territorial, following groups of females on and off leks. Independent males attempt to establish territories on leks and can be either ‘resident’ territory holders, or non‐territorial ‘marginals’. The time budgets of the three behavioural tactics (resident, marginal and satellite) differ notably in time allocated to foraging, aggression and display activity. These differences have led to the suggestion that the benefits of size and energy stores may vary with mating tactic.

2. In this paper in vivo estimates of body composition (fat, fat‐free mass) for breeding male Ruffs using total body electrical conductivity (TOBEC) are presented.

3. Satellite males have significantly shorter tarsi and wings than independent males.

4. After correcting for size, independent males are significantly heavier and fatter than satellites, and marginals in particular are heavier and fatter than both residents and satellites.

5. Estimates of energy expenditure during flight suggest that satellites may maintain reduced energy reserves to minimize flight costs, while the larger fat stores of independent males are consistent with the benefits of endurance as a territory holder.
The role of mycorrhizal fungi in growth enhancement of dune plants following burial in sand
Authors: Perumal J. V. , Maun M. A.
Published: March 2003

1. Burial in sand of Agropyron psammophilum and Panicum virgatum plants had a stimulating effect on carbon dioxide exchange rate, leaf area and biomass, irrespective of whether sand used for burial did or did not contain mycorrhizal fungi.

2. Plants of both A. psammophilum and P. virgatum species grown in mycorrhiza‐containing sand and then buried with mycorrhiza‐containing sand had the highest CO2 exchange rate, leaf area and biomass.

3. The growth stimulation following a burial episode is probably a composite response of several factors. The major contribution of mycorrhizal fungi will possibly be the exploitation of resources in the burial deposit.
Biomarkers and fluctuating asymmetry as indicators of pollution‐induced stress in two hole‐nesting passerines
Authors: Eeva T. , Tanhuanpää S. , Råbergh C. , Airaksinen S. , Nikinmaa M. , Lehikoinen E.
Published: March 2003

1. The stress caused by air pollutants was studied at biochemical, morphological and ecological levels in the Pied Flycatcher, Ficedula hypoleuca, and Great Tit, Parus major, nestlings in 10 study sites along the pollution gradient of a copper smelter.

2. First, stress was measured using four biomarkers from blood and liver: ethoxyresorufin O‐deethylase (EROD) enzyme, haemoglobin, stress protein Hsp70 and delta‐aminolevulinic acid dehydratase (ALA‐d) enzyme. Second, the amount of fluctuating asymmetry (FA) in the length of the 3rd primary and the outermost rectrix (in P. major) and the length and thickness of the tarsus were measured. These stress indicators were further examined in relation to the breeding performance of birds, i.e. the ecological response.

3. EROD activity was increased in F. hypoleuca nestlings near the pollution source. In P. major, it was not related to the pollution gradient but correlated well with the proportion of starved nestlings, i.e. the nutritional stress during the nestling period. The variations in haemoglobin, Hsp70 and ALA‐d enzyme activity were not significantly related to pollution gradient.

4. The tarsus length of F. hypoleuca nestlings and primary length of P. major nestlings showed increased asymmetry in the vicinity of the pollution source. Breeding success decreased towards the pollution source in both species.

5. In F. hypoleuca, the pollution‐related stress was verified at all three target levels. In P. major, pollution‐related effects were found at morphological and ecological levels but not at the biochemical level, which suggests that direct toxic effect of heavy metals was not the main mechanism in this species.
Growth and physiological acclimation to temperature and inorganic carbon availability by two submerged aquatic macrophyte species, Callitriche cophocarpa and Elodea canadensis
Authors: Olesen B. , Madsen T. V.
Published: March 2003

1. Interactive effects of temperature and inorganic carbon availability on photosynthetic acclimation and growth of two submerged macrophyte species, Elodea canadensis and Callitriche cophocarpa, were examined to test the hypotheses that: (1) effects of temperature on growth rate and photosynthetic acclimation are suppressed under low inorganic carbon availability; (2) the plants compensate for the reduction in activity of individual enzymes at lower temperatures by increasing the activity per unit plant mass, here exemplified by Rubisco. The experiments were performed in the laboratory where plants were grown in a factorial combination of three temperatures (7–25 °C) and three inorganic carbon regimes.

2. The relative growth rate of both species was strongly affected by growth conditions and increased by up to 4·5 times with increased temperature and inorganic carbon availability. The sensitivity to inorganic carbon was greatest at high temperature and the sensitivity to temperature greatest at high carbon concentrations.

3. Photosynthetic acclimation occurred in response to growth conditions for both species. The affinity for inorganic carbon and the photosynthetic capacity, both measured at 15 °C, increased with reduced inorganic carbon availability during growth and were greater at warmer than at cooler growth temperature. The acclimative change in photosynthesis was related to the extent of temperature and inorganic carbon stress. Using data for Elodea, a negative relationship between degree of temperature stress and photosynthetic performance was found. In relation to inorganic carbon, a linear increase in CO2 affinity and photosynthetic capacity was found with increased inorganic carbon stress during growth.

4. The total Rubisco activity declined with increased inorganic carbon availability during growth and with enhanced growth temperature. In addition, the activation state of Rubisco was higher at cooler than at warmer temperatures for Callitriche. This suggests that low‐temperature grown plants compensate for the temperature‐dependent reduction in activity of the individual Rubisco molecules by enhancing resource allocations towards Rubisco.
Spatial and temporal variations in hectare‐scale net CO2 flux, respiration and gross primary production of Arctic tundra ecosystems
Authors: Vourlitis G. L. , Harazono Y. , Oechel W. C. , Yoshimoto M. , Mano M.
Published: March 2003

1. Eddy covariance was used to measure the net CO2 flux of Alaskan moist‐tussock and wet‐sedge tundra ecosystems between 1 June and 31 August 1995. The sites were located within 2·5 km of each other and, depending on wind speed and thermal stability, the eddy‐covariance measurements integrated surface fluxes over 0·8–26·5 ha (mean 3·8 ha) at the moist‐tussock site and 0·1–4·2 ha (mean 0·6) at the wet‐sedge site.

2. Both sites were net sinks for atmospheric CO2 during the 92‐day measurement period but wet‐sedge tundra accumulated 1·5 times more CO2 than moist‐tussock tundra. Wet‐sedge tundra was a net CO2 sink of −6·4 mol m−2 and moist‐tussock tundra was a net sink of −4·6 mol m−2 over the June–August measurement period.

3. Estimates of whole‐ecosystem respiration (R) were made using multiple non‐linear regression by quantifying the response of measured nocturnal CO2 efflux (Fn) to fluctuations in air temperature and water‐table depth (r2 = 0·68). Partial regression analysis revealed that water‐table depth explained relatively more of the variance in Fn (45%) than temperature (11%). R was estimated to be 14·9 mol m−2 for moist‐tussock tundra and 5·4 mol m−2 for wet‐sedge tundra over the 92‐day measurement period. The large difference in R was apparently owing to a substantially higher water table in wet‐sedge tundra.

4. Estimated rates of gross primary production (GPP), calculated from measured net CO2 flux and estimated R, were 40% lower for wet‐sedge tundra over the 92‐day measurement period. Rates of GPP integrated over diel (24 h) periods were substantially larger for moist‐tussock tundra ecosystems throughout June and July but during the month of August, total diel rates of GPP for moist‐tussock and wet‐sedge tundra were comparable.

5. Our results demonstrate that R and GPP of moist‐tussock and wet‐sedge tundra ecosystems can be reliably estimated from eddy‐covariance measurements using functional relationships developed from plot‐scale studies. Given the large spatial differences in hydrology, the larger sink observed for wet‐sedge tundra was probably the result of relatively lower rates of R.
Geographical variation in the size of body organs in seabirds
Authors: Hilton G. M. , Lilliendahl K. , Solmundsson J. , Houston D. C. , Furness R. W.
Published: March 2003

1. The size of body organs shows adaptive temporal variation in many animal species. The variation in the size of body organs was examined to see if it is also a component of local adaptation to geographical variation in ecological conditions.

2. Major body organs were measured in five species of Icelandic seabirds, sampled from two areas where birds experience slightly different ecological conditions. Between‐area differences in ecological conditions were consistent among the study species, allowing tests of the generality of ecological effects on organ size.

3. All major body organs showed geographical size variation. Livers and kidneys were larger in locations where daily energy expenditure was expected to be higher; small intestines were heavier where food was of lower energy density; stomachs were heavier where food was less digestible; heart and flight muscle were larger where flight costs were greater.

4. It is concluded that adaptive variation in organ size may be an important means by which animals optimize exploitation of their local environment, and may be a proximate factor in intraspecific life‐history and metabolic variations between geographically separate populations.
Patterns and consequences of stigma height variation in a natural population of a distylous plant, Primula sieboldii
Authors: Nishihiro J. , Washitani I. , Thomson J. D. , Thomson B. A.
Published: March 2003

1. In order to reveal the direction and magnitude of phenotypic selection on the stigma height of heterostylous morphs in a natural population of Primula sieboldii E. Morren (Primulaceae), morphological traits including stigma and anther heights, flowering phenology, local density of potential mating partners, size of ramet, number of pollen grains deposited from the opposite morph and seed set were measured in two flowering seasons.

2. Both components of female reproductive success, pollen receipt and seed set, were significantly larger in the long‐styled than in the short‐styled morph in both years.

3. Selection analyses based on bivariate correlation and path‐analysis models revealed positive relationships between stigma height and pollination or seed set in the short‐styled morph only, although the effect was statistically significant only in one year. In contrast, seed set in the long‐styled morph was correlated with ramet size.

4. Morph difference in reproductive success and the natural selection revealed for higher stigmas in the short‐styled morph should be ascribed to the narrow corolla tube of the species that strictly restrict the path of the proboscis of the pollinators.
Metabolic cold adaptation in insects: a large‐scale perspective
Authors: Addo‐Bediako A. , Chown S. L. , Gaston K. J.
Published: March 2003

1. Despite its significance from both life‐history and physiological perspectives, metabolic cold adaptation (MCA) in insects remains controversial. Although several small‐scale studies have provided support for such adaptation, many others have not.

2. Using a global‐scale analysis of the standard metabolic rates of 346 species, it is shown that after removing the effects of trial temperature and body mass, environmental temperature significantly influences interspecific variation in metabolic rate, such that insects from colder environments tend to have higher, whole‐organism, metabolic rates. Although this effect is weak, it does provide evidence in favour of MCA in this important terrestrial group.

3. Although data from the Southern Hemisphere are limited, we show that this adaptation also takes the form of an increase in the slope of the metabolic rate–temperature relationship in Northern, but not in Southern, Hemisphere species.

4. Metabolic cold adaptation and its variation among the hemispheres should be counted among the causes of interspecific variation in metabolic rate.
Leaf size and foraging for light in a sclerophyll woodland
Authors: Bragg J. G. , Westoby M.
Published: March 2003

It has been suggested that leaf size may represent a foraging scale, with smaller‐leaved species exploiting and requiring higher resource concentrations that are available in smaller patches.

Among 26 shrub species from a sclerophyll woodland community in New South Wales, Australia, species with smaller leaves tended to occur in better light environments, after controlling for height. The dark respiration rates of small‐leaved species tended to exceed those of larger‐leaved species.

However, the higher‐light environments where smaller‐leaved species tended to occur had a patch scale larger than whole plants. There would not have been any foraging‐scale impediment to large‐leaved species occupying these higher‐light patches. An alternative explanation for small‐leaved species being more successful in higher‐light patches, in this vegetation with moderate shading, might be that they were less prone to leaf overheating.

Such relationships of leaf size to light across species at a given height may be important contributors to the wide spread of leaf sizes among species within a vegetation type, along with patterns down the light profile of the canopy, and effects associated with architecture and ramification strategy.
Trade‐offs between net assimilation rate and specific leaf area in determining relative growth rate: relationship with daily irradiance
Authors: Shipley B.
Published: March 2003

Three separate experiments were conducted, involving 27 herbaceous species and 14 woody species aged 15–30 days, in order to determine the relative importance of net assimilation rate (NAR), specific leaf area (SLA) and leaf weight ratio (LWR) in explaining interspecific variations in relative growth rate.

Daily quantum inputs were 31·12 mol m−2 day−1 in the first experiment and 33·17 mol m−2 day−1 in the second and third experiments. This is about twice the typical irradiance of most other experiments in this area, but only about 85% of the daily photon flux in nature. Plants were cultivated in hydroponic sand culture in a solution containing 5·8 mm nitrogen.

RGR was strongly and positively correlated with NAR in all three experiments. RGR was weakly and negatively correlated with SLA, while the correlation between RGR and LWR was weak and variable.

These results are compared to those already published in the literature: the commonly reported result that interspecific variation in RGR is determined primarily by SLA is partly due to the low irradiance used in most experiments, and the relative importance of SLA and NAR changes depending on irradiance.

A hypothesis is proposed in which direct and indirect effects of SLA on each of NAR and RGR are decomposed, and which leads to a trade‐off between SLA and NAR as a function of daily irradiance.
Leaf dry matter content as an integrative expression of plant palatability: the case of freshwater macrophytes
Authors: Elger A. , Willby N. J.
Published: March 2003

We examined the possibility of using the dry matter content (DMC) of macrophytes (the ratio of dry mass to wet mass) as an integrative variable to predict their palatability to generalist invertebrate grazers.

We assessed the palatability of 20 macrophyte species, using the snail Lymnaea stagnalis (L.) in non‐choice feeding experiments. Three of the species were studied at two different dates in the year, at two or four sites.

The average dry mass consumed by L. stagnalis ranged widely between species, and was negatively correlated to plant DMC. At the intraspecific level, the dry mass consumed varied over time but was not related to site location. Again, the dry mass consumed was negatively correlated to plant DMC.

The DMC of the macrophytes studied explained about 30% of interspecific variability, and >80% of seasonal variability, in snail consumption rate. Therefore this trait could be used as a shortcut to predict variations in macrophyte palatability, especially at the intraspecific level. At the interspecific level, the relationship between DMC and palatability might be weakened by the presence in some plants of low molecular weight chemical deterrents.
Scaling foliar respiration in two contrasting forest canopies
Authors: Turnbull M. H. , Whitehead D. , Tissue D. T. , Schuster W. S. F. , Brown K. J. , Griffin K. L.
Published: March 2003

The responses of night‐time dark respiration (Rd) to temperature and leaf characteristics were measured through the canopies of tree species from two distinct forests – an oak‐dominated deciduous forest in north‐eastern USA, and a conifer‐dominated temperate rainforest in New Zealand. These were chosen to examine the extent to which canopy level changes in dark respiration can be applied across forest biomes, and the appropriateness of scaling rules to calculations of whole‐canopy carbon efflux.

The response of respiration to temperature differed significantly between species and with height in the canopy. This involved changes in both Rd at a reference temperature, and the extent to which Rd increased with temperature (described by the energy of activation, Eo, or the change in Rd over a 10 °C range, Q10). Eo ranged from 25 (lower‐canopy leaves) to 53·8 kJ mol−1 K−1 (upper‐canopy leaves) in the deciduous forest, and from 24–37 kJ mol−1 K−1 in the temperate rainforest site.

Relationships between respiratory and leaf characteristics indicated that the instantaneous rate of respiration covaries with soluble sugar concentration and leaf nitrogen, but the temperature response of respiration (Eo or Q10) appears to be driven by leaf N.

Scaling leaf respiratory carbon loss to the whole‐canopy level indicated that simplifying assumptions regarding the variation in respiration and its temperature response with canopy height tend to underestimate carbon loss if the assumptions are based on lower‐canopy leaf physiology, but overestimate carbon loss if the assumptions are based on upper‐canopy physiology. Thus, canopy‐level differences in leaf respiratory characteristics should be considered in modelling efforts attempting to estimate whole‐canopy respiration.