bluuebunny/crossref_metadata_2025_split huggingface dataset:
Subsurface hydrology and degree of burial affect mass loss and invertebrate colonisation of leaves in a woodland stream
Authors: Tillman Danielle C. , Moerke Ashley H. , Ziehl Carrie L. , Lamberti Gary A. 
Published: March 2003

SUMMARY 1. In deciduous forest streams, fallen leaves form a large component of the total organic matter budget, and many leaves become buried within stream sediments. We examined the processing of buried leaves as compared with those at the surface, and the influence of subsurface hydrology on processing rates.2. Leaf packs were secured on the streambed surface or buried 10 cm deep in upwelling and downwelling reaches of a second‐order stream in Michigan, U.S.A. Mass loss and invertebrate colonisation were measured from October to February.3. Leaves buried in upwelling reaches lost mass more slowly (exponential decay coefficient, k=−0.0097) than did leaves from the other treatments (buried downwelling: −0.017; surface upwelling: −0.022; surface downwelling: −0.021).4. Initially, more invertebrates colonised surface leaf packs than buried packs. During the remainder of the study, however, hydrology had a greater effect on invertebrate abundance than did burial, as more invertebrates were found in packs in downwelling reaches than in upwelling reaches.5. Local subsurface hydrology and degree of burial, factors rarely considered in studies of detritus processing, can significantly influence mass loss and invertebrate colonisation of fallen leaves in streams. Furthermore, because of slower processing, subsurface zones may function as organic matter reservoirs that gradually ‘spiral’ carbon to downstream subsurface and surface habitats.
Allochthonous and autochthonous particulate organic matter in floodplains of the River Danube: the importance of hydrological connectivity
Authors: Hein Thomas , Baranyi Christian , Herndl Gerhard J. , Wanek Wolfgang , Schiemer Fritz 
Published: March 2003

SUMMARY 1. The elemental composition, the proportion of living organic carbon and the carbon stable isotope signatures of particulate organic matter (POM) were determined in a large river floodplain system in order to elucidate the major carbon sources in relation to the hydrological conditions over a 13‐month period.2. Two floodplain segments and the main channel of the River Danube downstream of Vienna (Austria), were compared on the basis of discharge and water age estimations. The more dynamic floodplain was connected to the main channel for 46% of the study period and drained up to 12% of total discharge at high water.3. The mean C : N ratio and δ13C signature of the POM increased from the floodplain site that was more isolated from the river (6.6; −33‰) to the main channel (8.4; −25‰). At the dynamic floodplain site, the C : N ratio and the δ13C signature of the POM increased with hydrological connectivity (expressed as water age).4. Only during flood events (4% frequency of occurrence), a considerable input of riverine POM was observed. This input was indicated by a C : N ratio of the POM pool of more than 10, the amount of detrital carbon (>80% of the total POM pool) and a δ13C signature of POM of more than −25‰ in the dynamic floodplain.5. Plankton derived carbon, indicated by C : N ratios less than eight and δ13C values lower than −25‰, dominated the particulate organic carbon (POC) pool at both floodplain sites, emphasising the importance of local (autochthonous) production. Phytoplankton was the major plankton compartment at the dynamic site, with highest biomasses at medium water ages.6. At the dynamic floodplain site, the Danube Restoration Project has enhanced the duration of upstream surface connection with the main channel from 4 to 46% frequency of occurrence. Therefore, the export of living POC to the main channel is now established during phases of maximum phytoplankton production and doubled the estimated total export of non‐refractory POM compared with prerestoration conditions.
Lignotuber reserves support regrowth following clipping of two Mediterranean shrubs
Authors: Canadell J. , López‐Soria L. 
Published: March 2003

1.We investigated whether reserves stored in the lignotubers of two Mediterranean shrubs,Arbutus unedoandErica arborea, were significantly mobilized to support the demands of regrowth and respiration after clipping the tops at different frequencies.2.After a single clipping,Arbutusshowed a 29% decrease of phosphorus concentration by the end of the first growing season. Two years after recovery from clipping, the starch levels remained lower than those of unclipped plants. Similarly,Ericashowed depletion of starch, but no nutrient reserves were depleted significantly.3.Regrowth after multiple clippings mobilized a large fraction of the starch and nutrients stored in the lignotuber. Mean starch concentrations were depleted by 87–93% after multiple clippings and concentrations of nitrogen, phosphorus, potassium and magnesium were depleted by 10–45%, 27–41%, 19–39% and 23–31%, respectively.4.An average‐sized lignotuber produced 288 resprouts forArbutusand 1990 resprouts forEricaduring a 27 month period of multiple clippings, at the end of which the first plants died.5.Plant mortality after multiple clipping was 10% forArbutusand 30% forErica, and was primarily attributed to exhaustion of carbon reserves because starch concentrations decreased by 96% in dead plants.
Chemical contents of Macaranga food bodies: adaptations to their role in ant attraction and nutrition
Authors: Heil M. , Fiala B. , Kaiser W. , Linsenmair K. E. 
Published: March 2003

1.
Macaranga (Euphorbiaceae) is a paleotropical tree genus comprising myrmecophytic and non‐myrmecophytic species. All species are presumed to possess food bodies (FBs) to maintain or attract ants as anti‐herbivore defence. 2. The hypothesis was tested that Macaranga species differing in their mode of association with ants would produce FBs differing in their chemical composition. We investigated contents of carbohydrates, proteins and lipids in FBs of four myrmecophytic and one non‐myrmecophytic Macaranga as well as one Parthenocissus (Vitaceae) species. 3. On a dry weight basis, FBs of myrmecophytes contained relatively higher amounts of proteins compared to carbohydrates than those of non‐myrmecophytes. Soluble carbohydrates showed species‐specific patterns and were found in especially high amounts in both non‐myrmecophytes. Furthermore, Parthenocissus FBs contained higher amounts of soluble compared to polymerous substances not only in carbohydrates but also in proteins. 4. FBs seem to be specifically adapted to their respective role in ant attraction and nutrition, with myrmecophytes providing ants with high amounts of lipids and proteins and non‐myrmecophytes mainly offering carbohydrates in the form of common soluble sugars.
Average daily metabolic rate of rodents: habitat and dietary comparisons
Authors: Degen A. A. , Kam M. , Khokhlova I. S. , Krasnov B. R. , Barraclough T. G. 
Published: March 2003

1.Average daily metabolic rate (ADMR) is the metabolizable energy intake required by a caged animal to maintain constant body energy content. Linear regression of standardized, phylogenetically independent contrasts was used to describe the allometric relationship between ADMR and body mass in rodents. It was predicted that desert species would have a lower ADMR than non‐desert species and that granivores would have a lower ADMR than those of herbivores and omnivores. The efficiency of utilization of energy for maintenance was also determined in these species. Here, it was predicted that the efficiency in granivores would be higher than in both herbivores and omnivores and in desert species would be higher than in non‐desert species.2.The regression of the phylogenetic contrasts of ADMR on body mass (mb) for 53 independent data points based on 63 species of rodents was highly significant (P< 0·0001) with an allometric slope of 0·53. Independent comparisons of both basal metabolic rate (BMR) and ADMR showed significantly lower rates in desert than in non‐desert species. There was a trend for granivores to have a lower ADMR per g0.53than either omnivores or herbivores, but this trend is not significant in independent comparisons between the categories. Thus, the predictions in regard to desert and non‐desert habitats were confirmed, and there is a non‐significant trend in the predicted direction with respect to diet. Herbivores and omnivores showed no significant difference in either BMR or ADMR.3.In independent comparisons between categories, there was no evidence for trends in the efficiency of utilization of energy for maintenance (BMR:ADMR ratio orkm) with either habitat or diet categories. Thus, these results are not in agreement with our predictions. Taking simple means,kmequals 0·47±0·21, 0·37±0·12 and 0·56±0·11 for granivores, omnivores and herbivores, respectively, and 0·37±0·12 and 0·55±0·16 for desert and non‐desert mammals, respectively.4.It is recommended that conditions for ADMR measurements be standardized, as is common for basal metabolic rate measurements. This would allow more reliable comparisons among species measured in different laboratories and also provide more accurate estimates of efficiency of utilization of energy.
The effect of plant size on the expression of cleistogamy in Mimulus nasutus
Authors: Diaz A. , Macnair M. R. 
Published: March 2003

1. Most dimorphic angiosperm species produce chasmogamous flowers adapted for allogamy and cleistogamous flowers adapted for autogamy. Plant size is an important internal environmental factor and several studies have suggested an adaptive strategy whereby cleistogamous flowering ensures a basic seed output while larger plants can spare resources to make additional investment in the more expensive but presumably more fit outcrossed seed produced by chasmogamous flowering. This study tests the effect of plant size on the percentage of chasmogamy in a species, Mimulus nasutus, where both the cleistogamous and chasmogamous flowers are autogamous and so seed from chasmogamous flowers has no genetic advantage. 2. We measured change in expression of cleistogamy/chasmogamy in glasshouse‐grown plants of different sizes and architecture. Size was manipulated by varying the length of time for which the plants were grown under short days. Architecture was manipulated by removing stems. 3. We found that increased size led to an increase in the percentage of chasmogamy in M. nasutus. This is unexpected given the lack of genetic advantage of outcrossing and suggests that this effect can occur as a direct result of increased resource availability without the necessity of selection for progeny fitness. 4. An increase in plant size was also found to lead to an increase in resource sinks (developing flowers and seed capsules on other parts of the plant). As increased plant size can therefore produce both increased total resources and increased number of resource sinks, the net resources available to a developing flower will be a balance of these two effects. Resource re‐allocation is shown to occur between flowers on a stem, between stems and between flowers and seed set. In each case, this results in a net decrease in resources to new flowers and so results in there being only sufficient resources for cleistogamous flowering. 5. We discuss the difficulties of using species with varying growth forms to test the hypothesis that expression of allogamous chasmogamy increases with plant size because of the genetic advantage of outcrossing.
Life‐history responses of British grasshoppers (Orthoptera: Acrididae) to temperature change
Authors: Willott S. J. , Hassall M. 
Published: March 2003

1.Ectotherms may be thermal generalists, or high‐ or low‐temperature thermal specialists. The thermal strategy of four species of grasshoppers occurring in Britain is determined, where unpredictable variation in the generally cool climate should preclude the low‐temperature thermal specialist strategy. It is predicted that temperature sensitivity will determine geographical distribution, with generalist species widespread, and thermally specialized species restricted to warmer habitats.2.The developmental and reproductive responses to different rearing temperatures of the grasshoppers are examined in a laboratory experiment. Life‐history traits are integrated into a fitness model to determine the sensitivity of each species to temperature change.3.Growth and development rates increased with temperature for each species. The frequency with which an additional instar was inserted during nymphal development increased with temperature inChorthippus brunneus. Adult mass and size increased with temperature.4.Egg pod production rate increased with temperature. InOmocestus viridulus, Myrmeleotettix maculatusandStenobothrus lineatus, temperature had no effect on egg mass, eggs per pod or number of pods per female. Number of pods per female increased with temperature inC. brunneus.5.Fitness ofS. lineatusdecreased by 88% for a 5 °C fall in temperature compared with 58% and 56% forC. brunneusandM. maculatus, respectively.Omocestus viridulusis least sensitive to temperature change with only a 27% reduction in fitness at the lower rearing temperature.6.It is concluded that all the species are high‐temperature thermal specialists, and variation in their sensitivity to temperature is a good predictor of their distribution. The most generalist species,O. viridulus, is the most widespread, while the more specialist speciesS. lineatusandM. maculatusare restricted to warmer habitats.Chorthippus brunneusis also a high‐temperature specialist, but is more widespread as a consequence of developmental and reproductive plasticity and efficient behavioural thermoregulation.
Distribution of leaf photosynthetic properties in tree canopies: comparison of species with different shade tolerance
Authors: Kull O. , Niinemets Ü. 
Published: March 2003

1.
Parameters of the photosynthesis vs CO2 response curve, nitrogen and chlorophyll contents were studied in Populus tremula, Tilia cordata and Corylus avellana leaves along a natural light gradient in the canopy. 2. In all species, leaf nitrogen content per unit area (Ns) declined with decreasing fractional transmission of photon flux density (Ksum), measured by a hemispheric photographic technique. However, the shape of the relationship between Ns and Ksum depended on species. Ns was almost linearly related to Ksum in the most light‐demanding species P. tremula but this relationship was curved in two other species. Populus tremula possessed the largest values of Ns at given Ksum, while C. avellana, the most shade‐tolerant species, had the lowest values of Ns. 3. Both the initial slope, characterizing the maximum carboxylation efficiency, and the plateau value, providing an estimate of the photosynthetic electron transport capacity, of the photosynthesis vs CO2 response curves, were linearly related to Ns and only minor differences were observed among the studied species. Leaf chlorophyll content per area was also related to Ns but the ratio of Chl/N increased substantially at low Ksum in the lower canopy. It was concluded that the partitioning of nitrogen between light harvesting, electron transport and carboxylation components of the photosynthetic apparatus may change with depth in the canopy as a result of a relative increase in the light‐harvesting complexes in relation to the rest of the photosynthetic apparatus. 4. The interspecific differences in species’ photosynthetic potentials are mainly associated with different nitrogen distribution patterns along the canopy and in minor part with differences in nitrogen partitioning among photosynthetic machinery.
Air pollution fades the plumage of the Great Tit
Authors: Eeva T. , Lehikoinen E. , RÖnkÄ M. 
Published: March 2003

1. Great Tits (Parus major) derive the carotenoid pigments for their yellow plumage via the prey items in their diet. Air pollution is known to affect the abundance of many forest insects, e.g. green caterpillars, which are an important source of food and pigments for tits. This study investigates whether air pollutants indirectly affected the intensity of the yellow colour in P. major plumage via the reduced access to carotenoid sources. 2. The intensity of the yellow colour in the plumage of P. major nestlings was scored and the relative abundance of green herbivorous larvae in territories around a polluting copper smelter in SW Finland was simultaneously measured. 3. Both the intensity of yellow colour in nestling plumage and caterpillar abundance increased with increasing distance from the pollution source. The colour intensity correlated significantly with the density of green herbivorous larvae in a territory. 4.
Parus major nestlings were significantly heavier at distant sites than close to the pollution source which suggests that the future survival probability of pale nestlings may be lowered. 5. Young birds, after their first moult, were studied for the relationships between condition, size and plumage colour by the means of ptilochronology. The plumage colour intensity did not correlate with the size corrected width of the growth bars in fifth rectrix (condition at moult) but was correlated positively with the length of the rectrix (size). 6. The implications of colour change for survival and mate choice are discussed.
δ13C of wood in growth‐rings indicates cambial activity of drought‐stressed trees of Eucalyptus globulus
Authors: Macfarlane C. , Adams M. A. 
Published: March 2003

1. Growth, density and δ13C of wood and leaf area were measured in two adjacent stands of 6 year‐old Eucalyptus globulus growing in the 600–700 mm year–1 rainfall region of south‐western Australia. Study sites were identical except for differences in the availability of water owing to physical properties of soil profiles and location of sites within the landscape. 2. Abundance of 13C (expressed as δ13C) in wood of trees growing on the drought‐prone site (– 24·8‰±1·4) was greater than in other trees (– 25·8‰±1·2, P<0·001) throughout the 6 years and, with further development, the δ13C signatures of wood may become useful indices of drought‐susceptibility in plantations within a few years of establishment. The seasonal pattern of δ13C of wood appeared to reflect seasonal variation in water availability and duration of cambial activity. 3. Basic density of wood of trees growing on the more drought‐prone site (496±14·0 kg m–3) was reduced compared to other trees (554±5·3 kg m–3, P<0·001). δ13C of wood across boundaries of growth‐rings suggested that drought stopped cambial activity resulting in less production of late wood and less dense wood. 4. The stand growing on the drought‐prone site had reduced growth, wood yield and leaf area but identical specific leaf area. Annual growth was correlated with the previous season’s rainfall. Together, these results suggested that within the same evaporative climate, drought reduces growth primarily by reducing leaf area and that there is a lag between onset of drought and reduced productivity.
The effect of variation in light and nitrogen on growth and defence in young Sitka Spruce
Authors: Wainhouse D. , Ashburner R. , Ward E. , Rose J. 
Published: March 2003

1.Young plants of a northern (Alaska) and southern (Oregon) provenance of Sitka Spruce,Picea sitchensis, were subject to high and low light and high and low nitrogen treatments in a polyhouse experiment. The effect of treatments on growth, needle and resin duct size, water content and concentration of quantitative defences (resin and polyphenols), sugars and nitrogen in needles, stems and roots was determined.2.Concentrations of resin, polyphenols and carbohydrates were higher in low nitrogen treatments as predicted by resource‐availability models of defence and the changes were similar in all parts of the trees including roots and in tissues formed prior to experimental treatments. Variation in the relative concentration of resin and polyphenols between tissues may indicate a defensive trade‐off. The size of needle resin ducts was positively correlated with tree growth but no evidence for ‘structural’ limitation of resin concentration in needles was found.3.Changes in concentration of quantitative defences did not appear to be the result of a direct trade‐off with growth but reflected treatment‐induced variation in the root/shoot ratio. Production of quantitative secondary chemicals may therefore be part of an integrated response of the trees to environmental stress.4.Bioassays withElatobium abietinum, Gilpinia hercyniaeand the fungusPhacidium coniferarumshowed that changes in needle size, the nutritional and water content of tissues and the balance between nutrients and secondary chemicals influenced performance of one or more of the organisms. Changes in the concentration of carbon‐based secondary chemicals alone were, therefore, of only limited value in predicting susceptibility of Spruce to insects and fungi.
Measurement of prestrain in trees: implications for the determination of safety factors
Authors: Bonser R. H. C. , Ennos A. R. 
Published: March 2003

1. It has long been known that wood in trees is under internally generated tensile or compressive forces, known as ‘prestrains’. These prestrains are thought to limit compressive loading at points of high strain within the tree to counteract the mechanical anisotropy of wood. Prestrains can be relieved by making cuts in wood, allowing it to recover to an unstrained state. 2. Recently, electrical resistance strain gauges have been used to measure surface strains on the trunk, roots and branches of trees. We have found that, by making a shallow cut above and below gauges, the prestrain can be measured as an apparent residual negative strain. This negative strain, after prestrain relief, is indicative of a tensile prestrain having been present in the wood before cutting. 3. It is a simple procedure to determine prestrain magnitude at the site of gauge attachment. By knowing the prestrain state of wood at the measurement site of strain determination, a more reliable estimate of surface stress and safety factors in tree design can be made.
Intraspecific variation in habitat availability among ectothermic animals near their climatic limits and their centres of range
Authors: Thomas J. A. , Rose R. J. , Clarke R. T. , Thomas C. D. , Webb N. R. 
Published: March 2003

1. In a modelling exercise, the quantity and distribution of habitat patches within a heathland biotope for four ectothermic heathland animals (silver‐studded blue butterfly [Plebejus argus], a red ant [Myrmica sabuleti], heath grasshopper [Chorthippus vagans] and sand lizard [Lacerta agilis]) were compared in space and time assuming two climates: that experienced at the northern edge of the species’ ranges and that 300–400 km further south, where mean summer temperatures are 2–3 °C warmer. 2. Habitats both at the northern edge of their ranges and 300–400 km further south for the four species were defined qualitatively from existing sources and then expressed quantitatively in terms of the attributes recorded in the Dorset Heathland Survey. The Survey was then used as a GIS to map the occurrence of the habitats of the four species under two climates and a decade apart. 3. The model predicts that an increase of 2–3 °C can result in a large increase in the area of habitat available to these north temperate species, that the length of time that individual patches of successional habitat may be occupied increases and that the distance between habitat patches within the biotope decreases. 4. The warmer conditions should result in a more stable metapopulation structure for P. argus, with fewer metapopulations existing in the landscape but each, on average, containing a greater number of larger and more stable constituent populations. 5. These predictions are of significance to ectothermic species which currently live at the northern limits of their ranges in the British Isles. The reverse effect is likely for species at the southern limits of their ranges. Conservationists who wish to maintain the status quo may be able to reduce some effects of these changes by appropriate habitat management.