bluuebunny/crossref_metadata_2025_split huggingface dataset:
Pattern of defoliation and its effect on photosynthesis and growth of Goldenrod
Authors: Meyer G. A. 
Published: March 2003

1. Leaf area was removed from Solidago altissima in either a dispersed pattern (half of every leaf removed) or a concentrated pattern (every other leaf removed) and effects on leaf gas exchange, vegetative growth and flowering were examined relative to undefoliated controls. Gas exchange was measured for leaves remaining after defoliation and for regrowth leaves that developed post‐damage (at 7, 16 and 26 days post‐defoliation). 2. Area‐based photosynthetic rates of leaves remaining after defoliation were not affected by either dispersed or concentrated damage, but damage of both types enhanced area‐based photosynthesis of regrowth leaves at 16 days post‐defoliation and to a lesser extent at 26 days post‐defoliation. 3. Dispersed damage, but not concentrated damage, stimulated mass‐based photosynthesis of undamaged leaves remaining after defoliation. Undamaged leaves remaining after defoliation and regrowth leaves on damaged plants had higher specific leaf area (leaf area/leaf mass) than comparable leaves on control plants. Mass‐based photosynthesis was more strongly elevated by defoliation than area‐based photosynthesis because of this increase in specific leaf area. 4. Plants with dispersed damage recovered more quickly from defoliation; they had higher relative growth rates in the first week post‐defoliation than plants with concentrated damage. Both types of defoliation caused similar reductions in flower production. 5. These results add to accumulating evidence that dispersed damage is generally less detrimental to plants than concentrated damage and suggest that physiological changes in leaves may be part of the reason.
Carbon transfer between plants and its control in networks of arbuscular mycorrhizas
Authors: Fitter A. H. , Graves J. D. , Watkins N. K. , Robinson D. , Scrimgeour C. 
Published: March 2003

1. Two studies using the stable‐isotope 13C have shown that large amounts of carbon can move between plants linked by arbuscular mycorrhizal fungi. Quantities comparable to the carbon cost of the symbiosis for an individual plant may be transferred. 2. We measured C transfer between linked plants of the grass Cynodon dactylon (C4, δ13C ≈– 14‰) and the herb Plantago lanceolata (C3, δ13C ~ – 28‰). To test the hypothesis that the carbon transferred between plants remained in fungal structures at all times, plants were grown for two harvests; at the first harvest they were clipped to ground level, so that shoot re‐growth required the transport of carbon from the roots. We also tested the influence of the direction of growth of the fungus, to determine whether C was transported out of or into a newly colonized root, and of growing plants in elevated CO2, to increase the availability of carbon compounds in the roots. 3. Large amounts of C were transferred between linked plants, more so into Plantago than into Cynodon roots. Transfer occurred whether root systems were separated by a 20 μm mesh, that excluded roots but not hyphae, or a 0·45 μm mesh, intended to act as a barrier to hyphae as well. We believe that the high root densities achieved in the experiment allowed hyphae to cross the finer mesh between the two dense root mats. 4. Clipping the plants did not result in any movement of C from roots to shoots, thus confirming the prediction that all C transferred remains in fungal structures. 5. The direction of growth of the fungus did not affect the direction of transfer, nor did the CO2 concentration in which the plants were grown. 6. The amount of C transferred was a positive correlate of the frequency of vesicles in the roots but a negative correlate of the frequency of hyphae. If C were moving into developing colonization units, thus effectively giving the plant a ‘free’ symbiosis, the correlation with internal hyphae should be positive. The positive correlation with vesicles suggests that C is moving into fungal storage structures. 7. We propose a mycocentric view of the phenomenon of interplant C transfer, in which the fungal colonies within roots are seen as parts of an extended mycelium between which the fungus moves resources depending on the dynamics of its own growth. We do not believe that the transfer has an impact on plant C budgets or fitness, but that it may be a major element in the understanding of fungal C budgets.
Photosynthesis and respiration rates depend on leaf and root morphology and nitrogen concentration in nine boreal tree species differing in relative growth rate
Authors: Reich P. B. , Walters M. B. , Tjoelker M. G. , Vanderklein D. , Buschena C. 
Published: March 2003

1. To test several hypotheses about acclimation and adaptation of photosynthesis and respiration to differing light conditions, we investigated the interspecific relationships between leaf and root metabolism, chemistry and morphology in high and low light conditions for young seedlings of nine boreal tree species that differ in relative growth rate (RGR). 2. Light‐saturated net photosynthesis (Asat), whole‐plant nitrogen (N) uptake rates, leaf and root respiration and morphology, and RGR all varied in parallel among the nine species when grown in both 5% and 25% of full sunlight. RGR, Asat, leaf and root respiration (Rd), and N uptake rate per unit root mass or length differed significantly among species, ranking (from high to low): Populus, Betula and Larix spp. (all deciduous) and then to five evergreen conifers (Pinus, Picea and Thuja spp.), which were generally comparable in these measures. 3.
A
sat, leaf and root Rd and N uptake rates were all correlated (r≈ 0·8 to 0·9) with species traits, such as seed mass, leaf life span and shade‐tolerance rankings. Mass‐based Asat was greater in conifer seedlings raised in low than high light. In contrast, area‐based Asat was higher for plants grown in high than low light, especially in the deciduous species. Once adjusted for differences in plant mass, leaf or root respiration rates did not differ for plants grown in low vs high light. 4. Interspecific variation in RGR was positively correlated (r≈ 0·9) with rates of photosynthesis, respiration and N uptake. Leaf photosynthesis and respiration rates were correlated to specific leaf area and leaf N concentrations (r≈ 0·9). Root respiration rates, N uptake rates, specific root length (root length per root dry mass) and root N concentrations were all highly correlated with each other (r≈ 0·8 to 0·9). These data suggest a close coupling of tissue‐level metabolism, chemistry and structure with whole‐plant performance and species ecophysiological and life‐history traits.
The responses of Briza media and Koeleria macrantha to drought and re‐watering
Authors: Milnes K. J. , Davies W. J. , Rodwell J. S. , Francis B. J. 
Published: March 2003

1. To test whether differences in response to drought can help to explain the differing distributions of Briza media and Koeleria macrantha, changes in their leaf growth and water relations during soil drying were measured. After droughting, plants were re‐watered and recovery recorded. 2. Leaf growth of the two species showed a similar sensitivity to drought with respect to duration of soil drying and soil moisture content. 3. In both species tiller base relative water content (RWC) was maintained at similar levels to controls until soil moisture content had fallen to less than 9%. This may aid survival in habitats subject to periodic droughting by preventing damage to the meristems. 4.
Briza media did not respond to re‐watering. However, plants of K. macrantha re‐grew after periods of over 20 days of drought, when tiller base RWCs had fallen as low as 13%. This ability to resurrect may explain the occurrence of K. macrantha in xeric calcicolous grasslands subject to episodes of severe droughting, from which B. media is absent.
Effects of elevated temperature and carbon dioxide on the nutritional quality of leaves of oak (Quercus robur L.) as food for the Winter Moth (Operophtera brumata L.)
Authors: Buse A. , Good J. E. G. , Dury S. , Perrins C. M. 
Published: March 2003

1. Pedunculate Oak trees were grown in ambient and elevated temperatures and CO2. Leaves were fed to Winter Moth caterpillars reared either in constant conditions or with the trees (caged or on‐tree). 2. Caterpillars in constant conditions ate the same mass and produced the same mass of faeces whether fed elevated or ambient temperature leaves. However, less was assimilated from elevated leaves, resulting in lighter pupae and fewer, lighter eggs. 3. Caterpillars in constant conditions ate more and produced more faeces when fed elevated CO2 leaves than when fed ambient CO2 leaves, but the mass assimilated and pupal mass were unchanged. 4. Caged caterpillars reared with the trees from which they were fed had constant pupal mass in all treatments, but pupated earlier at elevated temperature. Pupal mass was also unaffected when caterpillars fed on the trees. 5. Nitrogen was reduced in both elevated temperature and elevated CO2 leaves. Increased fibre in the former prevented increased consumption and resulted in reduced pupal mass and fecundity. Reduced fibre in the latter allowed increased consumption, resulting in pupae of normal mass. 6. Despite the clear effect of nutrient quality, experiments rearing caterpillars and trees together suggest that anticipated climatic change will have no nutritional effect on Winter Moth development.
Effects of tail loss on the movement patterns of the lizard, Psammodromus algirus
Authors: Martin J. , Avery R. A. 
Published: March 2003

1. Many lizards use caudal autotomy as a defensive strategy. However, subsequent costs related to the alteration of locomotor abilities might decrease the fitness of individuals. In this paper, the movement patterns of spontaneously moving Psammodromus algirus lizards and their escape performance running at high speed were compared before and after tail loss. A control tailed group was also studied to assess the repeatability of locomotor patterns between trials. 2. Tail loss had a significant effect on spontaneous movement patterns. Tailless individuals moved at significantly slower speeds during bursts of locomotion, and distances moved within bursts were significantly reduced. The overall time spent pausing increased, and, as a result, overall speeds decreased to an even greater extent than burst speeds. However, mean durations of individual locomotor bursts and mean pause durations did not change significantly after tail loss. 3. Loss of the tail decreased mean stride length, although the positive relation between stride length and speed was retained. 4. Escape performance was also greatly affected; loss of the tail resulted in substantially reduced attained, maximal and overall escape speeds. These changes resulted in shorter escape distances (the time of the first pause after the initiation of the escape response) because the mean duration of escape responses did not change. 5. The relevance of these alterations for the ecology of this species, and how individuals may compensate for the costs of tail loss, favouring autotomy as an escape strategy, are discussed.
Leaf photosynthetic light response: a mechanistic model for scaling photosynthesis to leaves and canopies
Authors: Kull O. , Kruijt B. 
Published: March 2003

1. The response of photosynthesis to radiation is an often‐studied but poorly understood process, represented empirically in most photosynthesis models. However, in scaling photosynthesis from leaf to canopy, predictions of canopy photosynthesis are very sensitive to parameters describing the response of leaves to Photosynthetic Photon Flux Density (PPFD). 2. In this study, a mechanistic, yet still simple, approach is presented that models the degree of light saturation in leaves explicitly, assuming a heterogeneous environment of PPFD and chlorophyll. 3. Possible mechanisms determining the ratio of chlorophyll to nitrogen are considered, including a direct dependence on PPFD, a mechanism involving the red/far‐red ratio of light in the canopy, and an approach based upon maximizing photosynthesis. 4. Comparison of model predictions with two data sets of light, nitrogen and chlorophyll from canopies of Populus and Corylus suggests that the red/far‐red mechanism is the most realistic. The data also show that the trees studied do not always optimize their nitrogen partitioning to maximize photosynthetic yield. 5. We then apply the model to the data sets, to predict the shape of light response curves of leaves within canopies and assess the applicability of simple scaling schemes, in which full acclimation of photosynthesis to PPFD justifies the use of big‐leaf models. We conclude that, at least for the data used, basic assumptions of such schemes do not hold.
Leaf structure (specific leaf area) modulates photosynthesis–nitrogen relations: evidence from within and across species and functional groups
Authors: Reich P. B. , Ellsworth D. S. , Walters M. B. 
Published: March 2003

1. Net photosynthetic capacity (Amax, defined as light‐saturated net photosynthesis under near optimal ambient environmental conditions) of mature leaves often depends on the level of leaf nitrogen (N), but an assortment of relationships between these variables has been observed in studies of diverse plant species. Variation in leaf structure has been identified as an important factor associated with differences between the area‐ and mass‐based expressions of the Amax–N relationship. In this paper we test the hypothesis that leaf structure, quantified using a measure of leaf area displayed per unit dry mass invested [specific leaf area (SLA)], is more than just a conversion factor, but itself can influence Amax–N relationships. We test this using several kinds of comparisons, based on field data for 107 species from sites representing six biomes and on literature data for 162 species from an equally diverse set of biomes. 2. Species and genera with thicker and/or denser leaves (lower SLA) consistently have flatter slopes of the Amax–N (mass‐based) relationship than those with higher SLA. These and all other contrasts usually applied as well using area‐based expressions, although such relationships were less consistent and weaker overall. A steeper slope indicates greater incremental change in Amax per unit variation in N. 3. Functional groups (e.g. needle‐leafed evergreen trees, broad‐leafed trees or shrubs, forbs) show the same patterns: groups with lower SLA have lower Amax–N slopes. Functional groups differ in mean leaf traits as well as in Amax–N relationships. Forbs have the highest SLA and mass‐based N and Amax, followed by deciduous species (whether needle‐leafed or broad‐leafed, shrub or tree), with lowest values in evergreen species (again regardless of leaf type or functional group). 4. Interspecific variation in mass‐based Amax is highly significantly related to the combination of leaf N and SLA (r2 = 0·86). At any value of leaf N, Amax increases with increasing SLA and at any value of SLA, Amax increases with increasing leaf N. Because this relationship, between Amax and the combination of N and SLA, is similar in two independent data sets, and as well, across broad taxonomic and geographic gradients, we hypothesize that it is universal in nature. Therefore, for broad interspecific contrasts among dicotyledons in any biome, we can reasonably well predict Amax based on the combination of SLA and leaf N. These findings have important implications for convergent evolution of leaf adaptation and great potential utility in models of global vegetation functioning.
The influence of year‐to‐year variations in winter weather on the dynamics of Daphnia and Eudiaptomus in Esthwaite Water, Cumbria
Authors: George D. G. , Hewitt D. P. 
Published: March 2003

1. Micro‐crustacea of the genus Daphnia and Eudiaptomus have evolved different physiological mechanisms for coping with life in a rapidly changing environment. In this paper, we analyse some of the physical and biological factors influencing the winter abundance of the two species in a small lake (Esthwaite Water in Cumbria). 2. The results demonstrate that much of the year‐to‐year variation in their relative abundance can be related to long‐term changes in the weather. The highest numbers of Daphnia were typically found in cold, calm winters when small flagellates were relatively abundant. In contrast, the highest numbers of Eudiaptomus were found in mild, windy winters when the phytoplankton community was dominated by colonial diatoms. 3. Year‐to‐year variations in the winter abundance of Eudiaptomus had no effect on their subsequent development but the numbers of overwintering Daphnia had a significant effect on the size of their first spring ‘cohort’. The most important factor influencing the overwintering performance of the two species was the water temperature. 4. Winter air temperatures over much of Europe are influenced by the atmospheric pressure variation known as the North Atlantic Oscillation (NAO). Winter water temperatures in Esthwaite Water were strongly correlated with this empirical index and there was a significant positive correlation between the NAO and the number of overwintering Eudiaptomus.
Thermal and fitness‐related consequences of nest location in Painted Turtles (Chrysemys picta)
Authors: Weisrock D. W. , Janzen F. J. 
Published: March 2003

1. Laboratory experiments have documented substantial temperature effects on the physiological ecology of reptilian eggs, embryos and offspring. However, functional links between important habitat characteristics, nest microenvironments and fitness‐related traits of neonates in natural nests have rarely been studied. 2. A field study of 11 Painted Turtle (Chrysemys picta) nests was conducted to quantify the relationships between a habitat characteristic (i.e. vegetational cover around nests at oviposition) and (1) developmental temperature and its effect on offspring sex ratio and (2) hibernation temperature and its effect on offspring survivorship. 3. Vegetational cover was negatively correlated with nest temperatures in July, the period when offspring sex is determined. However, neither vegetational cover nor mean nest temperature predicted nest sex ratios, although correlations among these variables were consistent with causal relationships derived from laboratory studies. 4. Summer vegetational cover was also negatively correlated with measures of winter nest temperatures. Of the three nests exhibiting overwinter mortality, two were surrounded by thick vegetation and all experienced temperatures below – 8 °C. The remaining nests reached temperatures as low as – 6 °C without mortality, indicating that hatchlings in these nests exhibited remarkable supercooling ability. 5. The results suggest that habitat characteristics and nest microenvironments are functionally linked and have fitness consequences for both embryos and offspring, implying that nest‐site choice by female turtles could have considerable utility.
Interactive effects of elevated CO2, P availability and legume presence on calcareous grassland: results of a glasshouse experiment
Authors: STÖCKLIN J. , KÖRNER CH. 
Published: March 2003

1. We investigated the interactive effects of elevated CO2, supply of phosphorus (P) and legume presence in model communities of calcareous grassland. Half of the communities contained six graminoids and eight non‐legume forb species. In the other half, four non‐legume forbs were replaced by legumes. 2.
Ecosystem responses. Above‐ground phytomass (>5 cm) hardly responded to elevated CO2 alone. However, when P and legumes were combined, the CO2 effect on above‐ground community phytomass in year two was a stimulation of 45% (P<0·001). Below‐ground community dry matter was stimulated by elevated CO2 alone by + 36% (P<0·01), but was only + 20% (P<0·05) when legumes were present and P was added. At the final (late season) harvest the mean effect of elevated CO2 on total above‐ and below‐ground phytomass was + 23% (P<0·001) and revealed no significant interactions among treatment combinations, because above‐ and below‐ground effects of CO2 enrichment had opposite directions. 3.
Functional group responses. When legumes were absent, graminoids increased their total above‐ and below‐ground phytomass in elevated CO2 by 60% (P<0·001) but there was no increase when legumes were present. The response of forbs to CO2 was not significant, irrespective of co‐treatment. Legumes, however, were significantly stimulated by P supply and their CO2 response was much larger when P was added (+ 55%, P<0·01 vs + 25%, NS). 4.
Species responses. CO2 effects on species ranged from highly positive (+ 143%) to moderately negative (– 43%). 5. Our results demonstrate that the effect of CO2 enrichment in such natural grassland communities will be low on above‐ground phytomass and largely below‐ground if no additional nutrients are provided. N2‐fixing legumes appear to be crucial for the community response to elevated CO2 but legume responsiveness is largely controlled by P availability.
Atmospheric and hydraulic limitations on transpiration in Brazilian cerrado woody species
Authors: MEINZER F. C. , GOLDSTEIN G. , FRANCO A. C. , BUSTAMANTE M. , IGLER E. , JACKSON P. , CALDAS L. , RUNDEL P. W. 
Published: March 2003

1. Seasonal regulation of transpiration was studied in four evergreen woody species growing in a Brazilian cerrado (savanna) site with a 5 month dry season. 2. Both seasonal and interspecifc variation in leaf water potential (ΨL) were relatively small. Predawn ΨL was about 0·1–0·25 MPa more negative in the dry season than in the wet season. 3. The dependence of maximum whole‐plant sap flow rates on sapwood area was similar among all four species during both the wet and dry seasons. When total daily sap flow on a leaf area basis was normalized by the daily average air saturation deficit (ASD), only one of the four species showed significantly greater water use during the wet season. 4. Although seasonal differences in regulation of transpiration were not pronounced, strong stomatal limitation of both maximum daily transpiration rates and total daily transpiration was evident during both the wet and dry seasons. Sap flow typically increased sharply in the morning, briefly attained a maximum value by about 09.30–10.30 h, then decreased sharply, despite steadily increasing solar radiation and atmospheric evaporative demand. 5. The total leaf area‐specific apparent hydraulic conductance of the soil/leaf pathway (Gt) varied among plants and diurnally. The identical linear dependence of transpiration and stomatal conductance (gs) on Gt among the four study species suggested that stomatal adjustment to variation in Gt limited transpiration over the entire range of Gt observed. 6. When gs was normalized for daily variation in Gt, about 80% of the remaining variation in gs was associated with variation in ASD. The results suggested that transpiration in these species was not limited by soil water availability per se, but by high atmospheric evaporative demand and hydraulic constraints possibly arising from their deep rooting habit.