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301.
Ross C 《Environmental monitoring and assessment》2004,99(1-3):267-274
Loss of vegetation production in arid lands has been difficult to remediate and has signifi- cant economic impacts on human
populations. Restoration efforts based on non-local materials and large-scale mechanization have not been capable of efficiently
reversing the trend of environmental degradation. The use of traditional knowledge and simplified methods of seed harvesting,
storing, marketing and soil preparation have proven that regeneration of native species and efficient land reclamation is
possible in areas that have traditionally been considered degraded beyond redemption. This paper describes a method of land
reclamation that combines tradition and simple mechanics that can be applied in all arid areas that face desertification.
Because the work builds on cultural practices long used in non-industrialized societies, it is particularly adapted to rural
areas. The methods described have the potential to open new low-tech economic opportunities to all segments of local non-urban
populations while combating desertification and creating a more ecologically sound environment. 相似文献
302.
Polycyclic aromatic hydrocarbons in the San Francisco Estuary water column: sources, spatial distributions, and temporal trends (1993-2001) 总被引:3,自引:0,他引:3
The composition of PAH in surface waters was examined over a range of spatial and temporal scales to determine distributions, trends, and possible sources. Water samples were collected from 1993 to 2001. PAH in organic extracts were analyzed by gas chromatography-mass spectrometry (GC-MS) and 25 individual target PAH summed to get the total PAH concentration in each water sample. The distribution of median total PAH concentration by estuary segments was Extreme South Bay (120 ng l(-1)) > South Bay (49 ng l(-1)) > North Estuary (29 ng l(-1)) > Central Bay (12 ng l(-1)) > Delta (7 ng l(-1)). Overall, total PAH concentrations were significantly higher in the Extreme South Bay compared to all other segments, and the Central Bay and Delta were significantly lower than all other segments (Kruskal-Wallis, H = 157.27, df = 4, p < 0.0005). This distribution reflects the large urbanized and industrialized areas that border the southern portions of the estuary and the less populated and rural areas that surround the Delta. Temporal trend analysis showed a statistically significant temporal trend in total PAH concentration at only one of the 18 sampling stations situated throughout the estuary (San Jose, significant decrease, p = 0.031, r(2) = 0.386, n = 12). PAH isomer pair ratio analysis showed that PAH in estuary waters were derived primarily from combustion of fossil fuels/petroleum (possible PAH source contributors include coal, gasoline, kerosene, diesel, No. 2 fuel oil, and crude oil) and biomass (possible contributors include wood and grasses), with lesser amounts of PAH contributed from direct petroleum input. 相似文献
303.
Lead in grain size fractions of road-deposited sediment 总被引:13,自引:0,他引:13
Sutherland RA 《Environmental pollution (Barking, Essex : 1987)》2003,121(2):229-237
Road-deposited sediment (RDS) is an important environmental medium for assessing contaminant levels in urban systems. Their atmospheric resuspension has significant implications for human health, and storm water transport can directly impact aquatic biota. Data from 20 RDS samples from Palolo Valley, Oahu, Hawaii, were fractionated into six grain-size classes and analyzed for Pb using a weak HCl (0.5 M) digestion. Data indicate significant Pb contamination in all samples. Median labile Pb concentration (n = 120) was 170 mg/kg, with a range from 4 to 1750 mg/kg. The five sediment fractions < 1000 microm had statistically similar Pb concentrations, but all were significantly greater than the coarsest fraction examined (1000-2000 microm). Silt plus clay ( < 63 microm) was the single most important mass component with 38% of the total sediment stored in this fraction. Mass of sediment < 63 microm combined with a median labile Pb concentration of 222 mg/kg accounted for 51% of the total Pb load stored in road sediments. These findings are significant from an environmental management perspective, and these issues are discussed in light of street sweeper sediment grain size removal efficiencies. 相似文献
304.
Tatiana Hernandez Mahmood Nachabe Mark Ross Jayantha Obeysekera 《Journal of the American Water Resources Association》2003,39(1):75-85
ABSTRACT: Variable Source Areas (VSAs) are zones with water saturated soils in forested wetlands fringing streams and creeks. Runoff from these areas is generated by saturation excess after a shallow water table rises and inundates the ground surface. In humid regions, like Florida and the Southeast, VSAs are believed to produce most of the runoff in shallow water table environments. Modeling the spatial extent and temporal fluctuation of a VSA is difficult because the formation of a VSA depends on a number of hydrological and morphological factors like rainfall intensity, soil texture, water table depth, and topographic attributes of the terrain. In this paper, we couple a digital elevation model with a two‐dimensional variable saturation model to illustrate the formation of a VSA at the hillside scale. The topography derived from the digital elevation model forms the upper domain geometry for the two‐dimensional finite element simulations of variable saturated flow. The objectives are: (1) to model the spatial and dynamic fluctuation of a VSA, and (2) to understand the roles of rainfall variability and terrain attributes on the formation of a VSA. Results show that hillsides with shallow water table depths, low saturated hydraulic conductivity, mild slopes, and concave slope curvature were more susceptible to runoff from a variable source. Runoff from a variable source showed little sensitivity to rainfall intensity. In general, landscapes with steep slopes generated a small VSA and a seepage face that vanished rapidly with time. In contrast, flat terrains are more amenable to VSA and retain ground surface inundation for longer periods of time. 相似文献
305.
R. M. Ross 《Marine Biology》1982,68(1):1-13
Laboratory production during the life span of Euphausia pacifica was measured directly (as the sum of growth, molting and reproduction) and indirectly (as assimilation minus metabolism and leakage) to test the hypothesis that weight-specific production is a constant for all sizes. Euphausiids were collected in Puget Sound, Washington State, USA, from September 1973 to March 1978. Equations were determined (in terms of carbon and nitrogen at 8° and 12° C) expressing the relationships between body weight and the daily rates of growth, molting, reproduction, ingestion and metabolism. The allometric equation (R=aW
b
) best related body weight (W) to the rate (R) for growth, molting, ingestion, respiration and excretion for life stages from late larvae through adults. As predicted by the original above hypothesis, the weight-specific coefficient (b) was close to 1.0 for ingestion and excretion; in contrast, b was 0.62 for growth, and 0.77 to 0.85 for molting and respiration. The Q10 s also varied: 3.5 for growth, 2.4 for molting, about 3.0 for ingestion, and 2.0 for respiration and excretion. Assimilation efficiencies, for all weights and at both temperatures, were 81.3% of carbon and 85.9% of nitrogen ingested. The relationships between rate and body weight of early larvae for growth and molting were linear, as was the relationship for reproduction in adults. Weight-specific production was higher by I to 2% at 12° than 8° C for all life stages, and was 2 to 4% for carbon and 2 to 6% for nitrogen in adults, but 13 to 17% for carbon and 14 to 15% for nitrogen in early furcilia larvae. The null hypothesis was rejected for production measured directly, but would have been accepted if only an indirect measurement of nitrogen production had been considered. Clearly, indirect measurement incorporates all errors of measurement and assumption and makes interpretation difficult. 相似文献
306.
B. P. Oldroyd Morag J. Clifton Siriwat Wongsiri Thomas E. Rinderer H. Allen Sylvester Ross H. Crozier 《Behavioral ecology and sociobiology》1997,40(1):17-26
Using four polymorphic microsatellite loci, we found that four Apis andreniformis queens collected in Thailand each mated at least 10–20 times, producing an average relatedness, g
ww, of workers of 0.30 ± 0.007, and an average effective number of matings of 9.1 ± 2.2. The degrees of polyandry and intra-colonial
genetic relatedness in A. andreniformis are similar to those in A. mellifera, slightly more than in A. florea, and up to 6 times less than in A. dorsata. We argue that while presently favoured hypotheses for the evolution of polyandry in monogynous social insects may adequately
explain the evolution of up to five or six matings, they are inadequate to explain the extreme polyandry (10–60 matings) observed
in Apis. One alternative possibility is that colony fitness is a non-additive function of the fitness of individual subfamilies.
Such behavioral over-dominance may mean that queen fitness is increased by high levels of polyandry, which increase the probability
of desirable combinations of worker genotypes occurring in one colony. The special attributes of honey bees which may lead
to behavioral over-dominance include colony aggregation (which may increase the incidence of disease), and frequent long-distance
migration.
Received: 8 May 1996/Accepted after revision: 9 August 1996 相似文献
307.
Depth distribution of developing Euphausia superba embryos,predicted from sinking rates 总被引:1,自引:0,他引:1
Sinking rates of the embryos of Euphausia superba were measured during development in the laboratory at Palmer Station. Antarctic Peninsula, during austral summer 1982. Two densities of seawater were used in these experiments; the lower density (1.027 g cm-3) is characteristic of the upper 300 m of the water column, the higher (1.029 g cm-3) is characteristic of the deeper circumpolar deep water. During development, the eggs sank at an initial average rate of 175 m d-1, declining to 51 m d-1 during the gastrula to early limb bud stages and increasing before hatching to near initial rates. The larvae hatched within 6 d. We predict that the majority of the embryos of E. superba should hatch at a depth of about 850 m. 相似文献
308.
Mikaela?A.?J.?BergeniusEmail author Mark?I.?McCormick Mark?G.?Meekan D.?Ross?Robertson 《Marine Biology》2005,147(2):291-300
The influence of environmental variables on the planktonic growth, pelagic larval duration and settlement magnitude was examined for the coral reef surgeonfish Acanthurus chirurgus. Newly settled fish were collected daily from patch reefs in the San Blas Archipelago, Caribbean Panama for 3.5 years. Environmental influences on growth were examined at three different life history stages: from 0 to 6 days, 7 to 25 days and from 26 to 50 days after hatching. Larval growth was correlated, using multiple regression techniques, with a combination of factors including solar radiation, rainfall, and along-shore winds. Depending on the life history stage, these accounted for 13–38% of the variation in growth rates when all the months were included in the analyses. Correlations between environmental variables and growth also varied among seasons and were stronger in the dry than in the wet season. During the dry season solar radiation, rainfall and along-shore winds described 57%, 86% and 74% of the variability in growth between 0 and 6 days, 7 and 25 days and 26 and 50 days, respectively. During the wet season rainfall, along-shore winds and temperature only described 38% of the variability in early growth and 27% of growth just before settlement. No significant model was found to describe growth 7–25 days after hatching during the wet season. Rainfall, solar radiation and along-shore winds were negatively correlated with growth up to 25 days after hatching but positively correlated as larvae approached settlement at a mean age of 52 days. Over 65% of the variability in pelagic larval duration was accounted for by a regression model that included solar radiation and along-shore winds. When data sets from wet and dry seasons were analysed separately, along-shore winds accounted for 67% of the change in larval duration in the dry season, and solar radiation accounted for 23% of the variation in larval duration in the wet season. Only 22% of the variability in settlement intensity could be described by solar radiation and temperature, when all months of the year were included in the analysis. Solar radiation and rainfall were included in a regression model that accounted for 40% of the variation in numbers of fish settling during the dry season. This study suggests that the levels of solar radiation, along-shore winds and rainfall during the early larval life can have important effects on the growth, larval duration and consequently, the settlement magnitude of marine fishes. Results also highlight the need to account for seasonality and ontogeny in studies of environmental influences.Communicated by G.F. Humphrey, Sydney 相似文献
309.
Michael A. Goodisman Robert W. Matthews Ross H. Crozier 《Behavioral ecology and sociobiology》2002,51(6):497-502
We used polymorphic microsatellite markers to study patterns of queen and worker reproduction in annual nests of the wasp Vespula germanica in its introduced range in Australia. We found that queens were typically polyandrous (at least 85.4% mated multiply), with the minimum number of male mates ranging from 1 to 7. Calculations based on nestmate worker relatedness (r=0.46) yielded an estimate of effective queen mating frequency of 2.35. Queens were unrelated to their mates (r=-0.01), indicating that mating occurred at random within Australian V. germanica populations. In addition, the distribution of the minimum number of male mates of queens followed a Poisson distribution. This result suggested that the probability of a queen remating was not affected by previous copulations. We also discovered that mates of polyandrous queens contributed unequally to progeny production leading to significant male reproductive skew within nests. Analyses of nestmate male genotypes revealed that queens usually produced most or all males. However, workers were responsible for the production of many males in a few nests, and, in contrast to theoretical expectations, two of these nests were apparently queenright. 相似文献
310.
Reptile and arboreal marsupial response to replanted vegetation in agricultural landscapes. 总被引:1,自引:0,他引:1
Ross B Cunningham David B Lindenmayer Mason Crane Damian Michael Christopher MacGregor 《Ecological applications》2007,17(2):609-619
We report reptile and arboreal marsupial responses to vegetation planting and remnant native vegetation in agricultural landscapes in southeastern Australia. We used a hierarchical survey to select 23 landscapes that varied in the amounts of remnant native vegetation and planted native vegetation. We selected two farms within each landscape. In landscapes with plantings, we selected one farm with and one farm without plantings. We surveyed arboreal marsupials and reptiles on four sites on each farm that encompassed four vegetation types (plantings 7-20 years old, old-growth woodland, naturally occurring seedling regrowth woodland, and coppice [i.e., multistemmed] regrowth woodland). Reptiles and arboreal marsupials were less likely to occur on farms and in landscapes with comparatively large areas of plantings. Such farms and landscapes had less native vegetation, fewer paddock trees, and less woody debris within those areas of natural vegetation. The relatively large area of planting on these farms was insufficient to overcome the lack of these key structural attributes. Old-growth woodland, coppice regrowth, seedling regrowth, and planted areas had different habitat values for different reptiles and arboreal marsupials. We conclude that, although plantings may improve habitat conditions for some taxa, they may not effectively offset the negative effects of native vegetation clearing for all species, especially those reliant on old-growth woodland. Restoring suitable habitat for such species may take decades to centuries. 相似文献