Multiple Regression Equations (multiple + regression_equation)

Distribution by Scientific Domains

Selected Abstracts

Growth and reproduction of three cladoceran species from a small wetland in the south-eastern U.S.A.

A. M. Lemke
SUMMARY 1.,Growth, reproduction and life-history parameters were measured for three cladoceran species from a small south-eastern wetland, U.S.A. Simocephalus serrulatus, Diaphanosoma brachyurum and Scapholeberis mucronata juveniles were reared at temperatures between 10 and 25 °C on natural food resources. 2.,Growth rate increased with temperature and decreased with individual size for all three species. Maximum somatic growth rate was higher for Simocephalus (49,72% day,1) and Diaphanosoma (21,91% day,1) than for Scapholeberis (11,45% day,1). Multiple regression equations were developed which predict temperature- and mass-specific growth rates for each species. 3.,Scapholeberis egg production was positively related to temperature; however, maximum egg production occurred at intermediate temperatures for Simocephalus and Diaphanosoma. Mean cumulative egg production was higher for Scapholeberis (28,92 eggs per female) than for Simocephalus (18,25 eggs per female) and Diaphanosoma (1,41 eggs per female), and was related to differences in reproductive strategy and survival. 4.,Survival was inversely related to temperature in most cases. For all three cladocerans, the intrinsic rate of increase (r) and net reproductive rate (R0) increased with temperature, whereas generation time (G) decreased. Greater egg production by Scapholeberis compared with the other two cladocerans was consistent with higher R0 values for Scapholeberis at any given temperature. Although r was very similar among species, G was typically longer for Scapholeberis than for Simocephalus and Diaphanosoma. 5.,This analysis provides basic information about the population parameters of these coexisting wetland species, and the growth rate models can be applied to field data to determine production dynamics. [source]

Determination of essential oil quality index by using energy summation indices in an elite strain of Cymbopogon citratus (DC) Stapf [RRL(J)CCA12]

Ashok Kumar Shahi
Abstract Out of the several accessions of Cymbopogon citratus (DC) Stapf introduced from Central and West India, one accession coded as RRL(J)CCA12, selected through a mass selection technique, was found to have citral (,80%) as the major constituent in its essential oil. Citral has tremendous application in the ,avour and perfume industries. Plant adaptation was judged by quantifying the regression coef,cient (b) value, which was 1.0 using essential oil growth indices. For prediction of essential oil quality index (EOQI), a multiple regression equation was developed for the ,rst time by using essential oil yield/plant and energy summation indices as EOQI (citral %) = 61.6 + 1.09 × essential oil yield/plant (g) - 0.005 × heat use ef,ciency + 0.675 × phenothermal index. For obtaining a better quality of essential oil (citral ,78%), the optimal value of independent variable would be: X1 = 2.49; X2 = 0.018 and X3 = 20.47, where X1, X2 and X3 denote essential oil yield/plant, heat use ef,ciency and phenothermal index, respectively. The validation of the EOQI model is done by correlating the predicted and calculated values of citral (%) which exhibited signi,cant r value = 0.955 at 5% probability level. The thermal requirement of the selectant was ,5500 degree days to exhibit plant maturity in terms of qualitative and quantitative characteristics of its essential oil at 6.0 vegetative lea,ng stage, with attainment of plant height ,1.0 m from previous date of harvest (December 2001). Prediction of essential oil quality by using the mathematical model is helpful for integrating the growth processes and evaluating crop management strategies. Copyright © 2004 John Wiley & Sons, Ltd. [source]

Productivity of Bahiagrass Pastures in South-western Japan: Synthesis of Data from Grazing Trials

M. Hirata
Abstract This study examined the rate of herbage production and herbage quality of bahiagrass (Paspalum notatum Flügge) using data from five grazing trials in the low-altitude region of Kyushu, south-western Japan, in an effort to (a) evaluate productivity of bahiagrass pastures, (b) analyse its relationship to meteorological, vegetational and managerial variables, and (c) obtain implications for better management of bahiagrass pastures. The rate of herbage production, ranging from ,56 to 213 kg DM ha,1 day,1, tended to increase from spring (April,May) to mid-summer (July) and decrease thereafter. The rate was expressed by a multiple regression equation where nitrogen fertilizer rate, air temperature, rainfall and herbage mass had positive effects. Dry matter digestibility (DMD) and crude protein (CP) concentration of herbage were in the range of 471,727 and 84,161 g kg,1 DM respectively. DMD was expressed by a regression equation where the day number from 1 April and herbage mass had negative effects, and the sampling height and nitrogen rate had positive effects. CP concentration was expressed by an equation showing a positive effect of nitrogen rate and a negative effect of herbage mass. The results indicate that management of bahiagrass pastures should aim at maintaining herbage mass closely above the critical level below which intake by grazing animals is restricted, in order to increase quality and ensure quantity. This is particularly important when nitrogen fertilizer is applied. [source]

Concentrations of Ag, In, Sn, Sb and Bi, and their chemical fractionation in typical soils in Japan

H. Hou
Summary We determined concentrations of Ag, In, Sn, Sb and Bi, and fractionated them by sequential extraction procedures, in five Japanese soils: Andosol-1 (grassland), Andosol-2 (forest), Cambisol (forest), Fluvisol (vegetable garden) and Regosol (forest). Average concentrations of Ag, In, Sn, Sb and Bi were 0.17 ± 0.08, 0.081 ± 0.019, 2.2 ± 0.5, 0.83 ± 0.32 and 0.32 ± 0.12 mg kg,1, respectively. Average distributions of the chemical fractions (omitting those with an abundance < 5%) were: Ag, residual (60%) > H2O2 -extractable, organically bound (H2O2 -Org) (18%) > metal,organic complex-bound (Me-Org) (10%) > amorphous metal oxide-bound (am-MeOx) (8.3%); In, residual (61%) > H2O2 -Org (12%) > Me-Org (8.7%) , crystalline Fe oxide-bound (cr-FeOx) (8.2%) > am-MeOx (7.4%); Sn, residual (40%) > Me-Org (19%) > carbonate-bound (12%) > cr-FeOx (9.0%) > H2O2 -Org (7.8%) > am-MeOx (6.9%); Sb, residual (34%) > Me-Org (18%) > am-MeOx (16%) > cr-FeOx (8.9%) , H2O2 -Org (8.7%) > easily reducible metal oxide-bound (re-MeOx) (6.8%) > carbonate-bound (6.1%); Bi, am-MeOx (26%) , H2O2 -Org (26%) > Me-Org (19%) > residual (17%) > cr-FeOx (12%). Proportions of the mobilizable (exchangeable + carbonate-bound + Me-Org + re-MeOx) metal fractions were in the order Sn , Sb > Bi > Ag ? In, and Cambisol > Andosol-2 > Regosol > Andosol-1 > Fluvisol. The proportions were predicted by multiple regression equations including pH, surface area, C contents, cation exchange capacity and clay content of the soils as independent variables (R2 > 0.96, P < 0.02). [source]

Leaf litter nitrogen concentration as related to climatic factors in Eurasian forests

GLOBAL ECOLOGY, Issue 5 2006
Chunjiang Liu
ABSTRACT Aim, The aim of this study is to determine the patterns of nitrogen (N) concentrations in leaf litter of forest trees as functions of climatic factors, annual average temperature (Temp, °C) and annual precipitation (Precip, dm) and of forest type (coniferous vs. broadleaf, deciduous vs. evergreen, Pinus, etc.). Location, The review was conducted using data from studies across the Eurasian continent. Methods, Leaf litter N concentration was compiled from 204 sets of published data (81 sets from coniferous and 123 from broadleaf forests in Eurasia). We explored the relationships between leaf litter N concentration and Temp and Precip by means of regression analysis. Leaf litter data from N2 -fixing species were excluded from the analysis. Results, Over the Eurasian continent, leaf litter N concentration increased with increasing Temp and Precip within functional groups such as conifers, broadleaf, deciduous, evergreen and the genus Pinus. There were highly significant linear relationships between ln(N) and Temp and Precip (P < 0.001) for all available data combined, as well as for coniferous trees, broadleaf trees, deciduous trees, evergreen trees and Pinus separately. With both Temp and Precip as independent variables in multiple regression equations, the adjusted coefficient of determination () was evidently higher than in simple regressions with either Temp or Precip as independent variable. Standardized regression coefficients showed that Temp had a larger impact than Precip on litter N concentration for all groups except evergreens. The impact of temperature was particularly strong for Pinus. Conclusions, The relationship between leaf litter N concentration and temperature and precipitation can be well described with simple or multiple linear regression equations for forests over Eurasia. In the context of global warming, these regression equations are useful for a better understanding and modelling of the effects of geographical and climatic factors on leaf litter N at a regional and continental scale. [source]

Explanatory Variables for per Capita Stocks and Flows of Copper and Zinc

Claudia R. Binder
A number of potential explanatory variables for the stocks and flows of copper and zinc in contemporary technological societies are co-analyzed with the tools of exploratory data analysis. A one-year analysis (circa 1994) is performed for 50 countries that comprise essentially all anthropogenic stocks and flows of the two metals. The results show that (1) The key explanatory variable for metal use is gross domestic product (GDP) per capita (purchasing power parity, PPP). By itself, GDP explains between one-third and one-half of the variance of per capita copper and zinc use. Other variables that were significantly correlated with copper and zinc use included stock of passenger cars and television sets (per 1, 000 people); two infrastructure variables, wired telephone connections, urban population, and value added inmanufacturing. The results do not provide evidence supporting the Kuznets curve hypothesis for these metals. (2) Metal use per capita can be estimated using multiple regression equations. For copper, the natural logarithm of use is related to the explanatory variables GDP (PPP), value added in manufacturing, and urban population. This model explains 80% of the variance among the different countries (r2= 0.79). The natural logarithm of zinc use is related to GDP (PPP) and value added in manufacturing with an r2 of 0.75; (3) For both metals, rates of metal fabrication, use, net addition to stock, and discard in low-and high-income countries differ significantly from each other. Our statistical analyses thus provide a basis for estimating the potential development of metal use, net addition to stock, and discard, using data on explanatory variables that are available at the international level. [source]

Optimum dietary soybean meal level for maximizing growth and nutrient utilization of on-growing gilthead sea bream (Sparus aurata)

Abstract Six isonitrogenous [450 g kg,1 crude protein (CP)] and isoenergetic diets (23 kJ g,1) with six levels of defatted soybean meal inclusion (0, 132, 263, 395, 526 and 658 g kg,1) in substitution of fish meal were evaluated in gilthead sea bream of 242 g initial weight for 134 days. Fish fed diets S0, S13, S26 and S39 had a similar live weight (422, 422, 438 and 422 g, respectively) but fish fed diets S53 and S66 obtained the lowest final weight (385 and 333g, respectively), and similar results were presented in specific growth rate (SGR). Fish fed diets S53 and S66 also obtained the highest feed conversion ratio (FCR). Quadratic multiple regression equations were developed for SGR and FCR which were closely related to dietary soybean level. The optimum dietary soybean levels were 205 g kg,1 for maximum SGR and 10 g kg,1 for minimum FCR. Sensorial differences were appreciated by judges between fish fed S0 and S39 soybean level, but after a re-feeding period of 28 days with diet S0, these differences disappeared. [source]