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941.
Predicting Opportunities for Greening and Patterns of Vegetation on Private Urban Lands 总被引:1,自引:1,他引:1
Troy AR Grove JM O'Neil-Dunne JP Pickett ST Cadenasso ML 《Environmental management》2007,40(3):394-412
This paper examines predictors of vegetative cover on private lands in Baltimore, Maryland. Using high-resolution spatial
data, we generated two measures: “possible stewardship,” which is the proportion of private land that does not have built
structures on it and hence has the possibility of supporting vegetation, and “realized stewardship,” which is the proportion
of possible stewardship land upon which vegetation is growing. These measures were calculated at the parcel level and averaged
by US Census block group. Realized stewardship was further defined by proportion of tree canopy and grass. Expenditures on
yard supplies and services, available by block group, were used to help understand where vegetation condition appears to be
the result of current activity, past legacies, or abandonment. PRIZM™ market segmentation data were tested as categorical
predictors of possible and realized stewardship and yard expenditures. PRIZM™ segmentations are hierarchically clustered into
5, 15, and 62 categories, which correspond to population density, social stratification (income and education), and lifestyle
clusters, respectively. We found that PRIZM 15 best predicted variation in possible stewardship and PRIZM 62 best predicted
variation in realized stewardship. These results were further analyzed by regressing each dependent variable against a set
of continuous variables reflective of each of the three PRIZM groupings. Housing age, vacancy, and population density were
found to be critical determinants of both stewardship metrics. A number of lifestyle factors, such as average family size,
marriage rates, and percentage of single-family detached homes, were strongly related to realized stewardship. The percentage
of African Americans by block group was positively related to realized stewardship but negatively related to yard expenditures. 相似文献
942.
Using GIS to Generate Spatially Balanced Random Survey Designs for Natural Resource Applications 总被引:2,自引:0,他引:2
Theobald DM Stevens DL White D Urquhart NS Olsen AR Norman JB 《Environmental management》2007,40(1):134-146
Sampling of a population is frequently required to understand trends and patterns in natural resource management because financial
and time constraints preclude a complete census. A rigorous probability-based survey design specifies where to sample so that
inferences from the sample apply to the entire population. Probability survey designs should be used in natural resource and
environmental management situations because they provide the mathematical foundation for statistical inference. Development
of long-term monitoring designs demand survey designs that achieve statistical rigor and are efficient but remain flexible
to inevitable logistical or practical constraints during field data collection. Here we describe an approach to probability-based
survey design, called the Reversed Randomized Quadrant-Recursive Raster, based on the concept of spatially balanced sampling
and implemented in a geographic information system. This provides environmental managers a practical tool to generate flexible
and efficient survey designs for natural resource applications. Factors commonly used to modify sampling intensity, such as
categories, gradients, or accessibility, can be readily incorporated into the spatially balanced sample design. 相似文献
943.
Heide Spiegel Manfred Sager Michael Oberforster Klemens Mechtler Hans Peter Stüger Andreas Baumgarten 《Environmental geochemistry and health》2009,31(5):549-560
Eighteen representative sites for the Austrian grain-growing and eight for the potato-growing zones (soils and crops) were
investigated. On each site, total element contents (B, Ba, Ca, Cd, Co, Cu, Fe, K, Li, Mg, Mn, Mo, Na, P, Sr and Zn) were determined
in 4–12 varieties of winter wheat (n = 136), 6 varieties of spring durum wheat (n = 30), 5 varieties of winter durum wheat (n = 15), 7 varieties of rye (n = 49), 5 varieties of spring barley (n = 30) and 5 varieties of potatoes (n = 40). Element accumulations in grain species and potato tubers varied significantly with site conditions, with the main
exceptions for B in potatoes and wheat as well as for Zn, Cu and Co in durum wheat. On average, across all investigated sites,
differences in varieties occurred concerning the elements Ca, Cd, Ba, Sr and Zn (except Zn in potatoes and winter durum).
A rough estimation revealed that an average Austrian consumer of wheat, rye and potatoes meets more than 50% of the needs
of daily element intake for K, P and Mg, between 36 and 72% for Fe, Zn and Cu, and more than 100% for Co, Mo and Mn. In particular,
the elements Ca and Na have to be added from other sources. 相似文献
944.
Great scallop, Pecten maximus, and blue mussel, Mytilus edulis, clearance rate (CR) responses to low natural seston concentrations were investigated in the laboratory to study (1) short-term
CR variations in individual bivalves exposed to a single low seston diet, and (2) seasonal variations in average CR responses
of bivalve cohorts to natural environmental variations. On a short temporal scale, mean CR response of both species to 0.06 μg L−1 chlorophyll a (Chl a) and 0.23 mg L−1 suspended particulate matter (SPM) remained constant despite large intra-individual fluctuations in CR. In the seasonal study,
cohorts of each species were exposed to four seston treatments consisting of ambient and diluted natural seston that ranged
in mean concentration from 0.15 to 0.43 mg L−1 SPM, 0.01 to 0.88 μg L−1 Chl a, 36 to 131 μg L−1 particulate organic carbon and 0.019 to 0.330 mm3 L−1 particle volume. Although food abundance in all treatments was low, the nutritional quality of the seston was relatively
high (e.g., mean particulate organic content ranged from 68 to 75%). Under these low seston conditions, a high percentage
of P. maximus (81–98%) and M. edulis (67–97%) actively cleared particles at mean rates between 9 and 12 and between 4 and 6 L g−1 h−1, respectively. For both species, minimum mean CR values were obtained for animals exposed to the lowest seston concentrations.
Within treatments, P. maximus showed a greater degree of seasonality in CR than M. edulis, which fed at a relatively constant rate despite seasonal changes in food and temperature. P. maximus showed a non-linear CR response to increasing Chl a levels, with rates increasing to a maximum at approximately 0.4 μg L−1 Chl a and then decreasing as food quantity continued to increase. Mean CR of M. edulis also peaked at a similar concentration, but remained high and stable as the food supply continued to increase and as temperatures
varied between 4.6 and 19.6°C. The results show that P. maximus and M. edulis from a low seston environment, do not stop suspension-feeding at very low seston quantities; a result that contradicts previous
conclusions on the suspension-feeding behavior of bivalve mollusks and which is pertinent to interpreting the biogeographic
distribution of bivalve mollusks and site suitability for aquaculture. 相似文献
945.
Claudia Ursprung Michelle den Hollander Darryl T. Gwynne 《Behavioral ecology and sociobiology》2009,63(6):781-788
Female seed beetles, Callosobruchus maculatus, mate multiply even though association with males and copulations carry costs, such as injury to the genital tract. Multiple
mating (polyandry) may, however, offset these costs through the acquisition of food and water, two material benefits hypothesized
to be obtained from the large ejaculates produced by males. The material benefits hypothesis can be tested by increasing female
access to nutrients and water, with the prediction that female mating frequency will decrease as copulation is no longer required
to derive these materials. Females were given water, 5% sugar–water or baker’s yeast, and were compared with females deprived
of these. We presented females with virgin males daily for 8 days and recorded female mating frequency, survivorship, and
fecundity. Females provided with water and sugar–water decreased mating frequency. Thus, water, rather than nutrients in the
ejaculate, appears to be important to females of this species. In addition, both life span and fecundity were extended for
females in the sugar–water and water treatments. Since water is scarce in the arid environment in which this species is found,
we conclude that polyandry provides material benefits to females that may offset some of the costs of associating with males. 相似文献
946.
The cardinalfish Siphamia versicolor (Perciformes: Apogonidae) forms a bioluminescent symbiosis with the marine luminous bacterium Photobacterium mandapamensis, harboring the bacteria in a ventral, disc-shaped light organ and using the bacterial light apparently for counterillumination
and attracting prey. Little definitive information has been available on the developmental and microbiological events surrounding
the initiation of symbiosis, a critical stage in the life history of the fish, in S. versicolor or any of the many other species of bacterially luminous fish. To identify the stage at which light organ formation begins,
to determine the origin of cells forming the light organ, and to characterize its bacterial colonization status during development,
early developmental stages of S. versicolor obtained and reared from wild-caught mouth-brooding males were examined with histological and microbiological methods. A
light organ primordium was not evident in embryos, post-embryos, or pre-release larvae, whereas the light organ began to form
within 1 day of release of full-term pre-flexion larvae from the mouths of male fish. Analysis of post-release larvae revealed
that the light organ arises from a proliferation and differentiation of intestinal epithelial cells, and that it quickly develops
structural complexity, including the formation of chambers and gaps contiguous with the intestinal epithelium. However, the
nascent light organ remained uncolonized by the symbiotic bacteria through several days of post-release development, even
in the presence of high numbers of the symbiotic bacteria. These results demonstrate that the inception of light organ formation
in S. versicolor occurs independently of its symbiotic bacteria and that receptivity to bacterial colonization apparently requires substantial
post-release development of the light organ. Larvae therefore most likely acquire their symbiotic bacteria from seawater,
during or shortly after the transition from the pre-flexion to the flexion developmental stage. 相似文献
947.
María del Mar Delgado Vincenzo Penteriani Vilis O. Nams Letizia Campioni 《Behavioral ecology and sociobiology》2009,64(1):35-43
Moving and spatial learning are two intertwined processes: (a) changes in movement behavior determine the learning of the
spatial environment, and (b) information plays a crucial role in several animal decision-making processes like movement decisions.
A useful way to explore the interactions between movement decisions and learning of the spatial environment is by comparing
individual behaviors during the different phases of natal dispersal (when individuals move across more or less unknown habitats)
with movements and choices of breeders (who repeatedly move within fixed home ranges), that is, by comparing behaviors between
individuals who are still acquiring information vs. individuals with a more complete knowledge of their surroundings. When
analyzing movement patterns of eagle owls, Bubo bubo, belonging to three status classes (floaters wandering across unknown environments, floaters already settled in temporary
settlement areas, and territory owners with a well-established home range), we found that: (1) wandering individuals move
faster than when established in a more stable or fixed settlement area, traveling larger and straighter paths with longer
move steps; and (2) when floaters settle in a permanent area, then they show movement behavior similar to territory owners.
Thus, movement patterns show a transition from exploratory strategies, when animals have incomplete environmental information,
to a more familiar way to exploit their activity areas as they get to know the environment better. 相似文献
948.
One of the major consequences of global warming is a rise in sea surface temperature which may affect the survival of marine
organisms including phytoplankton. Here, we provide experimental evidence for heat-induced cell death in a symbiotic microalga.
Shifting Symbiodinium microadriaticum from 27 to 32°C resulted in an increase in mortality, an increase in caspase 3-like activity, and an increase in nitric oxide
(NO) production. The caspase-like activity was strongly correlated with the production of NO in thermally challenged microalgae.
For this experiment, the application of Ac-DEVD-CHO, a mammalian caspase 3-specific inhibitor, partly prevented (by 65%) the
increase in caspase-like activity. To verify the relationship between NO and the caspase-like activity, S. microadriaticum were subsequently incubated with 1.0 mM of the following chemical NO donors: sodium nitroprusside (SNP), S-nitrosoglutathione (GSNO), S-nitroso-N-acetylpenicillamine (SNAP) and 3,3bis(Aminoethyl)-1-hydroxy-2-oxo-1-triazene (NOC-18). The supplementation of both SNP and
NOC-18 caused a significant increase in caspase-like activity compared to the control treatment. Pre-treatment of the microalgae
with the inhibitor Ac-DEVD-CHO before the supplementation of the different NO donors completely prevented the increase in
caspase-like activity. These results suggest that NO could play a role in the induction of cell death in heat-stressed S. microadriaticum by mediating an increase in caspase-like activity. 相似文献
949.
Teresa Moreno Marco Pandolfi Xavier Querol Javier Lavín Andrés Alastuey Mar Viana Wes Gibbons 《Environmental science and pollution research international》2011,18(2):173-183
Purpose
Industrial emissions can raise urban background levels of inhalable Mn particles in an order of magnitude above normal, eclipsing the contribution made by natural sources and traffic. 相似文献950.