Home About us Contact
|
Home About us Contact | ||
|
|
||
Allometric Relationships (allometric + relationships)
Selected AbstractsAllometric relationships between lamina area, lamina mass and petiole mass of 93 temperate woody species vary with leaf habit, leaf form and altitudeFUNCTIONAL ECOLOGY, Issue 4 2008Guoyong Li Summary 1The allometric scaling relationship between lamina and lamina support has rarely been examined, such that its significance to plant life-history strategies has not been fully explored and understood so far. We investigated the sizes of leaf lamina and petiole for 93 temperate broad-leaved woody species at two altitudes of a southwestern mountain, and analysed the scaling relationship in relation to leaf habit (evergreen vs. deciduous), leaf form (simple- vs. compound-leaved species), and habitat type (low vs. high altitude). 2Significant allometric scaling relationships were found between petiole mass and lamina mass, and between petiole mass and lamina area, with common slopes of 0·872 and 0·742, respectively, both significantly departed from the value of 1·0. The results of phylogenetic comparative analyses were in accordance with the observed positive scaling relationships. 3The evergreen species were found to have a greater petiole mass than the deciduous at a given lamina area; whilst a contrasting pattern was observed between lamina mass and petiole mass, in which the evergreens had a greater biomass allocation to lamina for the same petiole mass relative to the deciduous. 4The compound-leaved species were observed to be significantly greater in both lamina area and lamina support (including petioles, rachis and petiolules) than the simple-leaved species, whereas the former had a smaller lamina area or lamina mass at a given petiole mass than the latter. 5The plants from the high altitude had less lamina area at a given petiole investment compared to those from the lower altitude, likely due to the large mechanic and transporting requirements of petioles in the species at high altitude. 6Our results indicate that petioles serve as an adverse forcing on the maximization of lamina area and lamina biomass and that the allometric relationship between lamina and lamina support varies with leaf habit, leaf form and habitat. [source] Net changes in regional woody vegetation cover and carbon storage in Texas Drylands, 1937,1999GLOBAL CHANGE BIOLOGY, Issue 3 2003GREGORY P. ASNER Abstract Although local increases in woody plant cover have been documented in arid and semiarid ecosystems worldwide, there have been few long-term, large-scale analyses of changes in woody plant cover and aboveground carbon (C) stocks. We used historical aerial photography, contemporary Landsat satellite data, field observations, and image analysis techniques to assess spatially specific changes in woody vegetation cover and aboveground C stocks between 1937 and 1999 in a 400-km2 region of northern Texas, USA. Changes in land cover were then related to topo-edaphic setting and historical land-use practices. Mechanical or chemical brush management occurred over much of the region in the 1940,1950s. Rangelands not targeted for brush management experienced woody cover increases of up to 500% in 63 years. Areas managed with herbicides, mechanical treatments or fire exhibited a wide range of woody cover changes relative to 1937 (,75% to + 280%), depending on soil type and time since last management action. At the integrated regional scale, there was a net 30% increase in woody plant cover over the 63-year period. Regional increases were greatest in riparian corridors (33%) and shallow clay uplands (26%) and least on upland clay loams (15%). Allometric relationships between canopy cover and aboveground biomass were used to estimate net aboveground C storage changes in upland (nonriparian) portions of regional landscapes. Carbon stocks increased from 380 g C m,2 in 1937 to 500 g C m,2 in 1999, a 32% net increase across the 400 km2 region over the 63-year period. These plant C storage change estimates are highly conservative in that they did not include the substantial increases in woody plant cover observed within riparian landscape elements. Results are discussed in terms of implications for ,carbon accounting' and the global C cycle. [source] Allometric studies on growth and development of the human placenta: growth of tissue compartments and diffusive conductances in relation to placental volume and fetal massJOURNAL OF ANATOMY, Issue 6 2006Terry M. Mayhew Abstract Correlations between placental size and fetal mass during gestation fail to account for changes in composition that accompany placental growth and maturation. This study uses stereological data on the sizes of different tissue compartments in human placentas from 10 weeks of gestation to term and relates them to placental volume and to fetal mass by means of allometric analysis. In addition, tissue dimensions are used to calculate a physiological transport measure (diffusive conductance) for the villous membrane. Histological sections randomly sampled from placentas and analysed stereologically provided estimates of structural quantities (volumes, exchange surface areas, lengths, numbers of nuclei, diffusion distances). These data were combined with a physicochemical quantity (Krogh's diffusion coefficient) in order to estimate oxygen diffusive conductances for the villous membrane and its two components (trophoblast and stroma). Allometric relationships between these quantities and placental volume or fetal mass were obtained by linear regression analyses after log-transformation. Placental tissues had different growth trajectories: most grew more rapidly than placental volume and all grew more slowly than fetal mass. Diffusion distances were inversely related to placental and fetal size. Differential growth impacted on diffusive conductances, which, again, did not improve commensurately with placental volume but did match exactly growth of the fetus. Findings show that successful integration between supply and demand can be achieved by differential tissue growth. Allometric analysis of results from recent studies on the murine placenta suggest further that diffusive conductances may also be matched to fetal mass during gestation and to fetal mass at term across species. [source] Egg mass and incubation period allometry in birds and reptiles: effects of phylogenyJOURNAL OF ZOOLOGY, Issue 2 2006D. C. Deeming Abstract Here we test the hypothesis that the relationship between egg mass at oviposition (IEM) and incubation period (Ip) is a function of the taxonomic relatedness of bird and reptile species. Allometric relationships between IEM and Ip were examined for 1525 bird species and 201 reptilian species. Treating species as independent data revealed the allometric exponent linking Ip to IEM to be 0.234 for birds and 0.138 for reptiles. However, ANCOVA revealed that within both birds and reptiles the elevation and slope of the regression lines were dependent on the taxonomic order studied, indicating that the exponents were confounded by the phylogenetic relatedness of species. Thus, allometric exponents were recalculated based on the method of comparative analysis using independent contrasts. This technique revealed that the allometric exponent in both birds and reptiles was confounded by phylogeny. In birds the allometric relationship between Ip and IEM was almost halved to 0.122, whereas in reptiles the exponent increased to 0.185. Importantly, the results demonstrate that some results of allometric analyses can be artefacts of the method of analysis of the dataset. That for bird eggs Ip is not determined in large part by egg mass allows new questions to be posed regarding the ecological and physiological factors affecting the length of incubation, and hence rates of embryonic growth, for different taxa and habitats. [source] Transpiration and stomatal conductance across a steep climate gradient in the southern Rocky MountainsECOHYDROLOGY, Issue 3 2008Nate G. McDowell Abstract Transpiration (E) is regulated over short time periods by stomatal conductance (Gs) and over multi-year periods by tree- and stand-structural factors such as leaf area, height and density, with upper limits ultimately set by climate. We tested the hypothesis that tree structure, stand structure and Gs together regulate E per ground area (Eg) within climatic limits using three sites located across a steep climatic gradient: a low-elevation Juniperus woodland, a mid-elevation Pinus forest and a high-elevation Picea forest. We measured leaf area : sapwood area ratio (Al : As), height and ecosystem sapwood area : ground area ratio (As : Ag) to assess long-term structural adjustments, tree-ring carbon isotope ratios (,13C) to assess seasonal gas exchange, and whole-tree E and Gs to assess short-term regulation. We used a hydraulic model based on Darcy's law to interpret the interactive regulation of Gs and Eg. Common allometric dependencies were found only in the relationship of sapwood area to diameter for pine and spruce; there were strong site differences for allometric relationships of sapwood area to basal area, Al : As and As : Ag. On a sapwood area basis, E decreased with increasing elevation, but this pattern was reversed when E was scaled to the crown using Al : As. Eg was controlled largely by As : Ag, and both Eg and Gs declined from high- to low-elevation sites. Observation-model comparisons of Eg, Gs and ,13C were strongest using the hydraulic model parameterized with precipitation, vapour pressure deficit, Al : As, height, and As : Ag, supporting the concept that climate, Gs, tree- and stand-structure interact to regulate Eg. Copyright © 2008 John Wiley & Sons, Ltd. [source] On the analysis of non-linear allometriesECOLOGICAL ENTOMOLOGY, Issue 1 2009ROBERT J. KNELL Abstract 1.,Non-linear allometries are those where a log,log scatterplot of trait size against body size deviates from simple linearity. These are found in many insects, including the horns of beetles, the forceps of earwigs, and the heads of certain castes of ant. 2.,Non-linear allometries are often associated with polyphenism that is itself related to behaviour: for example, the alternative mating tactics displayed by many species of beetle are widely associated with dimorphisms in horn size. 3.,This paper critically reviews the current techniques used to analyse these datasets. 4.,Recommendations include the use of scatterplots and assessment of the goodness of fit of simple linear models as an initial screen for non-linear allometry. The use of recently developed algorithms for ,segmented' regression to analyse continuous allometric relationships, and a pragmatic approach to the analysis of discontinuous relationships that recognises that there is no simple way to distinguish between morphs in some cases, and that all of the proposed methods for doing so have some drawbacks. 5.,Worked examples of the analysis of two sets of data from animals that have been the subject of controversy regarding the nature of their allometric relationships are given: further worked examples are provided as online Supporting Information. [source] Abnormalities in sexual development of the amphipod Gammarus pulex (L.) found below sewage treatment worksENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 8 2001Melanie Yvette Gross Abstract Increasing numbers of widely used industrial, agricultural, and natural chemicals are known to elicit endocrine-disrupting effects in a wide range of vertebrate and invertebrate species. The objective of this study was to determine whether the sexual development of the freshwater crustacean Gammarus pulex (L.) was affected below sewage treatment works (STW) previously known to contain endocrine-disrupting chemicals in their effluent. The gonadal structure, external sexual characteristics, and size of gammarids from exposed sites were compared to those of gammarids from a reference site. No significant difference was found in the gonadal structure of males collected below two STW. However, a highly significant number of females collected from a site known to elicit high estrogenic responses in vertebrates displayed an abnormal structure of oocytes in vitellogenesis. Body size was significantly shorter and male/female size differential was significantly reduced below one of the STW. Analysis of gnathopod and genital papillae length data suggests that different allometric relationships of these organs to body size exist between sample sites. [source] Pharmacokinetic prediction for intravenous ,-lactam antibiotics in pediatric patientsJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 11 2007Kenji Shimamura Abstract A method for predicting pharmacokinetics in pediatric patients for intravenous ,-lactam antibiotics is proposed. We focused on the allometric relationships of pharmacokinetic parameters with individual body weights (BW) in human including healthy adults and pediatric patients. Drug concentration data for 15 intravenous ,-lactam antibiotics were collected retrospectively from the published articles and the individual pharmacokinetic parameters were re-calculated. A mixed effect modeling (MEM) was applied for the allometric relationship for those ,-lactam antibiotics, and mean and variances of inter-drug variability for the allometric parameters and also variance for intra-drug (residual) variability were estimated. Then drug-specific allometric parameters were estimated by an empirical Bayesian method using the pharmacokinetic parameters for a drug only in healthy adults as observations, and finally the individual pharmacokinetic parameters in pediatric patients were predicted. The predictability of the method was evaluated by the leave-one-out method. We also demonstrated a method for simulating plasma concentration,time profiles in pediatric patients, and the predicted time,course curves generally coincided well with the actual plasma concentration data for the tested drugs. © 2007 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 96: 3125,3139, 2007 [source] Size variation and mating success in the stag beetle, Lucanus cervusPHYSIOLOGICAL ENTOMOLOGY, Issue 3 2006DEBORAH J. HARVEY Abstract The stag beetle, Lucanus cervus, is Britain's largest beetle, with a patchy distribution in southern England. The literature suggests that it displays exceptional size variation, particularly in the males, but no analysis of size inequality has ever been conducted. In the present study, stag beetle adults are measured and allometric relationships derived between various parameters and total body length. Most of the specimens found each year are fragments and head width can be used as a good predictor of total body length in each sex. Body size differs between years and between localities and male beetles show a greater degree of size inequality than females. However, L. cervus does not show greater inequality in size than many other beetle species and populations of males are composed of a relatively large number of small individuals. These males are not at a disadvantage in mating because it is the ratio of male : female size that determines mating success. Very large males are less successful in mating and it is suggested that lack of mating success may act as an additional constraint on mandible size in this species. Size variation is most likely caused by variation in larval food resources, coupled with variation in local climatic conditions. [source] Allometric growth relationships of East Africa highland bananas (Musa AAA-EAHB) cv. Kisansa and MbwazirumeANNALS OF APPLIED BIOLOGY, Issue 3 2009K. Nyombi Abstract Highland bananas are an important staple food in East Africa, but there is little information on their physiology and growth patterns. This makes it difficult to identify opportunities for yield improvement. We studied allometric relationships by evaluating different phenological stages of highland banana growth for use in growth assessment, understanding banana crop physiology and yield prediction. Pared corms of uniform size (cv. Kisansa) were planted in a pest-free field in Kawanda (central Uganda), supplied with fertilizers and irrigated during dry periods. In addition, tissue-cultured plants (cv. Kisansa) were planted in an adjacent field and in Ntungamo (southwest Uganda), with various nutrient addition treatments (of N, P, K, Mg, S, Zn, B and Mo). Plant height, girth at base, number of functional leaves and phenological stages were monitored monthly. Destructive sampling allowed derivation of allometric relationships to describe leaf area and biomass distribution in plants throughout the growth cycle. Individual leaf area was estimated as LA (m2) = length (m) × maximum lamina width (m) × 0.68. Total plant leaf area (TLA) was estimated as the product of the measured middle leaf area (MLA) and the number of functional leaves. MLA was estimated as MLA (m2) = ,0.404 + 0.381 height (m) + 0.411 girth (m). A light extinction coefficient (k = 0.7) was estimated from photosynthetically active radiation measurements in a 1.0 m grid over the entire day. The dominant dry matter (DM) sinks changed from leaves at 1118 °C days (47% of DM) and 1518 °C days (46% of DM), to the stem at 2125 °C days (43% of DM) and 3383 °C days (58% of DM), and finally to the bunch at harvest (4326 °C days) with 53% of DM. The allometric relationship between above-ground biomass (AGB in kg DM) and girth (cm) during the vegetative phase followed a power function, AGB = 0.0001 (girth)2.35 (R2 = 0.99), but followed exponential functions at flowering, AGB = 0.325 e0.036(girth) (R2 = 0.79) and at harvest, AGB = 0.069 e0.068(girth) (R2 = 0.96). Girth at flowering was a good parameter for predicting yields with R2 = 0.7 (cv. Mbwazirume) and R2 = 0.57 (cv. Kisansa) obtained between actual and predicted bunch weights. This article shows that allometric relationship can be derived and used to assess biomass production and for developing banana growth models, which can help breeders and agronomists to further exploit the crop's potential. [source] A test of Rensch's rule in varanid lizardsBIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 2 2010PETRA FRÝDLOVÁ In a model group of giant reptiles, we explored the allometric relationships between male and female body size and compared the effects of sexual and fecundity selection, as well as some proximate causes, on macroevolutionary patterns of sexual size dimorphism (SSD). Monitor lizards are a morphologically homogeneous group that has been affected by extreme changes in body size during their evolutionary history, resulting in 14-fold differences among the body sizes of recent species. Here, we analysed data concerning the maximum and/or mean male and female snout,vent lengths in 42 species of monitor lizard from literary sources and supplemented these data with measurements made in zoos. There was a wide scale of SSD from nearly monomorphic species belonging mostly to the subgenus Odatria and Prasinus group of the Euprepriosaurus to apparently male-larger taxa. The variable best explaining SSD was the body size itself; the larger the species, the higher the SSD. This pattern agrees with the currently discussed Rensch's rule, claiming that the relationship between male and female body size is hyperallometric, i.e. the allometric exponent of this relationship exceeds unity and thus SSD increases with body size in the case of male-larger taxa. All our estimates of the reduced major axis regression slopes of this relationship ranged from 1.132 to 1.155. These estimates are significantly higher than unity, and thus unequivocally corroborate the validity of Rensch's rule in this reptilian group. In spite of our expectation that the variation in SSD can be alternatively explained by variables reflecting the strength of sexual selection (presence of male combat), fecundity selection (e.g. clutch size and mass) and/or proximate ecological factors (habitat type), none of these variables had consistent effects on SSD, especially when the data were adjusted to phylogenetic dependence and/or body size. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 100, 293,306. [source] Structure and Biomass of Four Lowland Neotropical ForestsBIOTROPICA, Issue 1 2004Saara J. DeWalt ABSTRACT We contrasted the structure and biomass of four lowland Neotropical forests (La Selva, Costa Rica; Barro Colorado Island, Panama; Cocha Cashu, Peru; and KM41, Brazil) to determine if commonalities exist within and among forests differing in latitude, rainfall, seasonality, and soil fertility. We examined the effect of soil fertility specifically by measuring the density and basal area of trees, lianas, and palms on two soil types differing in fertility at each site. We used allometric relationships to estimate the contribution of the various life-forms to total aboveground biomass (AGB) and compared two relationships for trees 30 cm diameter or greater. Estimated liana density and AGB were similar among sites, but the density and AGB of trees and palms, estimated using diameter alone, differed significantly. Basal area and AGB of trees 10 cm diameter at breast height (DBH) or greater differed among forests and averaged 30.2 m2/ha and 250 Mg/ha, respectively. Cocha Cashu and KM41 had higher tree basal area and AGB than La Selva or Barro Colorado Island. Across forests, lianas and small trees (1,10 cm DBH) each contributed between 4 and 5 percent of the total AGB and small palms contributed ca 1 percent. Many forest inventories ignore lianas, as well as trees and palms less than 10 cm DBH, and therefore underestimate AGB by ca 10 percent. Soil type had little influence on the forest structure within sites, except at Cocha Cashu where total AGB was much higher and liana density much lower on the more fertile old floodplain Entisols than the serra firme Oxisols. Although total stem density, basal area, and some biomass components differed significantly among forests, they seemed less variable than other quantitative measures (e.g., species richness). RESUMEN Contrastamos la estructura y la biomasa de cuatro bosques de bajura Neotropicales (La Selva, Costa Rica; Isla Barro Colorado, Panamá; Cocha Cashu, Perú; y KM41, Brasil) para determinar si existen patrones comunes entre bosques que difieren en la latitud, en la lluvia total, en la estacionalidad, y en la fertilidad de suelo. Examinamos el efecto de la fertilidad de suelo en cada sitio específicamente midiendo el área basal y densidad de árboles, lianas, y palmas en dos tipos de suelo que difieren en fertilidad. Usamos ecuaciones alométricas para estimar la contributión relativa de las varias formas de vida a la biomasa aérea (AGB) y comparamos dos ecuaciones para estimar biomasa con base en árboles , 30 cm diámetro. La densidad y AGB estimada de lianas fueron similares entre sitios, pero la densidad y AGB de árboles y palmas estimada en base solamente a diámetros fueron significativamente distintas. El área basal y la AGB de árboles , 10 cm diámetro a la altura de pecho (DAP) difirieron entre bosques y promediaron 30.2 m2/ ha y 250 Mg/ha. En Cocha Cashu y KM41 observamos mayor área basal y AGB para árboles que en La Selva o la Isla Barro Colorado. En general lianas y árboles pequeños (1,10 cm DAP) contribuyeron entre 4,5 porciento del AGB total cada uno y palmas pequeñas contribuyeron alrededor de 1 porciento. Muchos inventarios del bosque ignoran tanto las lianas como los árboles y palmas <10 cm DAP y por lo tanto subestiman AGB en alrededor de un 10 porciento. El tipo del suelo mostró una influencia pequena en la estructura del bosque dentro de sitios, menos en Cocha Cashu donde AGB total fue mucho más alto y densidad de lianas y palmas fue más bajo en los Entisols de mayor fertilidad que los Ultisols de menor fertilidad. Aunque la densidad de tallos, área basal, y algunos componentes de la biomasa difirieron significativamente entre bosques, estos parecieron menos variables que otras medidas cuanti-tativas (por ejemplo, riqueza de especies). [source] | ||||||||||