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831.
We studied a guild of desert winter annual plants that differ in long-term variation in per capita reproductive success (lb, the product of per capita survival from germination to reproduction, l, times per capita reproduction of survivors, b) to relate individual function to population and community dynamics. We hypothesized that variation in lb should be related to species' positions along a trade-off between relative growth rate (RGR) and photosynthetic water-use efficiency (WUE) because lb is a species-specific function of growing-season precipitation. We found that demographically variable species have greater RGR and greater leaf carbon isotope discrimination (Delta, a proxy inversely related to WUE). We examined leaf nitrogen and photosynthetic characteristics and found that, in this system, variation in Delta is a function of photosynthetic demand rather than stomatal regulation of water loss. The physiological characteristics that result in low Delta in some species may confer greater photosynthetic performance during the reliably moist but low temperature periods that immediately follow winter rainfall in the Sonoran Desert or alternatively during cool periods of the day or early growing season. Conversely, while species with high Delta and high RGR exhibit low leaf N, they have high biomass allocation to canopy leaf area display. Such trait associations may allow for greater performance during the infrequent conditions where high soil moisture persists into warmer conditions, resulting in high demographic variance. Alternatively, high variance could arise from specialization to warm periods of the day or season. Population dynamic buffering via stress tolerance (low RGR and Delta) correlates negatively with buffering via seed banks, as predicted by bet-hedging theory. By merging analyses of population dynamics with functional trait relationships, we develop a deeper understanding of the physiological, ecological, and evolutionary mechanisms involved in population and community dynamics. 相似文献
832.
Kate F. Lankin Myron A. Peck Lawrence J. Buckley David A. Bengtson 《Marine Biology》2008,155(5):461-472
Rates of routine respiration (R
R, μl O2 fish−1 h−1) and total ammonia nitrogen excretion (E
R, μg NH4–N + NH3–N fish−1 h−1) were measured on larval and juvenile haddock (Melanogrammus aeglefinus) to ascertain how energy losses due to metabolism were influenced by temperature (T), dry body mass (M
D, mg) and specific growth rate (SGR, % per day). R
R and E
R increased with M
D according to y = a · M
D
b
with b-values of 0.96, 0.98, 1.14, and 0.89, 0.78, 0.74, respectively, at 10, 7, and 4°C, respectively. Multiple regressions explained
98% of the variability in the combined effects of M
D and T on R
R and E
R in larval haddock: R
R = 0.97 · M
D
0.98 · e0.092 · T
; E
R = 0.06 · M
D
0.79 · e0.092 · T
. In young juvenile (24–30 mm standard length) haddock, R
R tended to decline (P = 0.06) and E
R significantly declined (P = 0.02) with increasing SGR. O:N ratios significantly increased with increasing SGR suggesting that N was spared in relatively
fast-growing individuals. Our results for young larval and juvenile haddock suggest: (1) nearly isometric scaling of R
R with increasing body size, (2) allometric scaling of E
R with increasing body size, (3) Q
10 values of 2.5 for both R
R and E
R, (4) metabolic differences in substrate utilization between relatively fast- and slow-growing individuals, and (5) that rates
of routine energy loss and growth were not positively related. The measurements in this study will provide robust parameter
estimates for individual-based models that are currently being utilized to investigate how variability in climatic forcing
influences the vital rates of early life stages of haddock. Our results also stress that inter-individual differences in rates
of energy loss should not be overlooked as a factor influencing growth variability among individuals. 相似文献
833.
This paper has studied the environmental deterioration due to copper mining in Malanjkhand at Central-east India. No data
is available on environmental degradation at the studied site although geological aspects are well studied. Mine drainage
from the mines is definitively toxic. The site is also undergoing various stages of acid mine drainage (AMD) particularly
from the heap leaching sites and the tailing area. AMD impacted water steam and sediment were also analysed. Results show
substantial level of contamination of almost all segments of environment. Presence of elevated level of other heavy metal
viz. Au, Ag, Pb, Cr, Cd, Fe, Cu and base metals like Na, K in AMD impacted water and sediments is due to metal leaching effect
of AMD. Bio monitoring with the help of benthic macro invertebrates and metal accumulation in plants was also carried to know
the impact of the toxic drainage. Results prove a very significant impact on the environmental health. 相似文献
834.
835.
836.
Russell E. Keenan James W. Knight Elizabeth R. Rand Mary M. Sauer Bruce W. Found Frank H. Lawrence 《Chemosphere》1990,20(10-12)
Potential human and wildlife exposures to TCDD in landspread pulp and paper mill sludge in the State of Maine were evaluated by means of a human health and an ecological risk assessment methodology. The highest historical concentrations of TCDD reported for these sludges do not present a risk to American woodcock, selected as an indicator species for this analysis. Concentrations of TCDD as high as 50 ppt in soil are not likely to produce adverse effects in the embryonic/hatchling stage of the woodcock. This soil concentration of TCDD does not present a significant risk to sportsmen and their families that may consume birds which inhabit these sites. 相似文献
837.
Lam LT 《Journal of Safety Research》2005,36(2):181-187
INTRODUCTION: This cross-sectional community-based randomized telephone survey, aimed to compare the parental risk perceptions on childhood pedestrian road safety among three different major community language speaking groups and the mainstream English speaking Australians in Sydney, Australia. METHOD: This was a community-based telephone survey with subjects randomly selected from the population of specific cultural languages in Sydney. RESULTS: Results indicated that Chinese and Arabic speaking parents or caregivers perceived the road environments as significantly less hazardous for their 4-12 year old children as pedestrians when compared with Vietnamese and English speaking parents. This was true even after adjusting for the age of child, socioeconomic status, and the living environments of respondents. CONCLUSION: The implication of the results was discussed in light of possible application to childhood safety behavior across different cultures. IMPACT TO THE INDUSTRY: The results obtained have highlighted the importance of cultural factors in risk perceptions, and safety behaviors. Cultural differences in risk perceptions should be taken into consideration in the design of safety education programs. 相似文献
838.
Sikora LJ 《Waste management (New York, N.Y.)》2004,24(2):139-142
A by-product of the construction aggregate industry is fines or dust that contain trace elements such as zinc and copper and significant amounts of iron, aluminum, silica and potassium. Beneficial uses for these materials have been proposed such as replenishing depleted soils and amendment in mixtures of organic byproducts prior to composting. To evaluate the beneficial uses in composting, outdoor bin studies were conducted using a beef cattle manure, straw and wood chip mixture amended with and without basaltic mineral fines. Temperature differences in composting mixtures of equal volumes, equal moisture and relatively equal material content are considered an indication of differing biological activities [Haug, Compost Engineering Principles and Practice. Ann Arbor Science, Ann Arbor, MI. (1980)]. Temperatures were lower in the mineral fine-treated manure mixture initially. After turning the piles at six weeks, temperatures tended to be higher in the mineral fine amended mixture. Overall, temperatures were not significantly different suggesting that mineral fines amendment does not significantly increase temperature and activity in composting mixtures. 相似文献
839.
Acid-neutralizing capacity (ANC) and pH were measured weekly from October 1991 through September 2001 in three streams in the western Adirondack Mountain region of New York to identify trends in stream chemistry that might be related to changes in acidic deposition. A decreasing trend in atmospheric deposition of SO4/2- was observed within the region over the 10-yr period, although most of the decrease occurred between 1991 and 1995. Both ANC and pH were inversely related to flow in all streams; therefore, a trend analysis was conducted on (i) the measured values of ANC and pH and (ii) the residuals of the concentration-discharge relations. In Buck Creek, ANC increased significantly (p < 0.05) over the 10 yr, but the residuals of ANC showed no trend (p > 0.10). In Bald Mountain Brook, ANC and residuals of ANC increased significantly (p < 0.01), although the trend was diatonic-a distinct decrease from 1991 to 1996 was followed by a distinct increase from 1996 to 2001. In Fly Pond outlet, ANC and residuals of ANC increased over the study period (p < 0.01), although the trend of the residuals resulted largely from an abrupt increase in 1997. In general, the trends observed in the three streams are similar to results presented for Adirondack lakes in a previous study, and are consistent with the declining trend in atmospheric deposition for this region, although the observed trends in ANC and pH in streams could not be directly attributed to the trends in acidic deposition. 相似文献
840.
Biobased Epoxy/Layered Silicate Nanocomposites: Thermophysical Properties and Fracture Behavior Evaluation 总被引:1,自引:0,他引:1
Hiroaki?Miyagawa Manjusri?Misra Lawrence?T.?Drzal Amar?K.?MohantyEmail author 《Journal of Polymers and the Environment》2005,13(2):87-96
The biobased epoxy containing epoxidized linseed oil (ELO) and its clay nanocomposites were processed with an anhydride curing agent. The certain amount of diglycidyl ether of bisphenol F (DGEBF) was replaced by ELO. The selection of the DGEBF, ELO, an anhydride curing agent, and organo-montmorillonite clay resulted in an excellent combination, to provide new biobased epoxy/clay nanocomposites showing high elastic modulus, high glass transition temperature, and high fracture toughness with larger amount of ELO. Izod impact strength was almost constant while changing the amount of ELO. This is a promising result for future applications in different engineering industries. 相似文献