Nutrient Limitation on Phytoplankton Growth in the Upper Barataria Basin,Louisiana: Microcosm Bioassays     

Ling Ren  Nancy N. Rabalais  R. Eugene Turner  Wendy Morrison  Warren Mendenhall 《Estuaries and Coasts》2009,32(5):958-974

The Davis Pond Diversion (DPD) was constructed to divert Mississippi River (MR) water into the Barataria Basin to reduce the salinity in support of wetland restoration on the Louisiana coast. To assess the phytoplankton nutrient limitation in adjacent water systems and potential impacts of DPD, 12 seasonal nutrient-phytoplankton bioassay experiments were conducted from October 2003 to July 2004 using the natural phytoplankton assemblages from freshwater and brackish-water lakes, Cataouatche and Salvador, LA (USA), which receive Mississippi River water from the DPD, and from a nearby freshwater lake, Lac des Allemands, that does not. Dissolved inorganic nitrogen (N), phosphorus (P), and silicate (Si) were added with different combinations at Redfield ratios in 10-l microcosms. Nitrogen was found to be the sole or primary limiting nutrient in all 12 experiments. N and P colimitations were found in seven of 12 experiments, but N was always the stronger limiting factor. P limitation was never observed to be the sole limiting nutrient. The results showed that a low concentration of P and a relatively high concentration of N do not necessarily indicate only P limitation in these lakes. Lake Cataouatche and Lake Salvador were dominated by centric diatoms, and Anabaena spp. were detected at high levels, particularly in summer. Lac des Allemands was generally dominated by N-fixing Anabaena spp. and other cyanobacteria, and their biomass responded significantly to N addition but not to P addition, indicating that nitrogen fixation in Lac des Allemands may be inhibited by other factors such as iron. Our bioassay results demonstrate that whether a water body is N- or P-limited is the consequence of the nutrient status and not the salinity regime. The results suggest that the addition of nutrient-rich waters via diversions of Mississippi River water into these lakes might increase the frequency of algal blooms, including noxious and toxic freshwater cyanobacteria.  相似文献   

From economic globalisation to globalising economic processes: towards post-structural political economies     

Wendy LarnerRichard Le Heron 《Geoforum》2002,33(4):415-419

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Biodiversity conservation and land rights in South Africa: Whither the farm dwellers?     

Wendy Crane   《Geoforum》2006,37(6):1035-1045

South Africa is unique in that its globally significant biodiversity, which is under significant threat, coexists with an apartheid history of dispossession that produced a starkly unequal land ownership pattern and widespread rural poverty. It is in this context that the post-apartheid government must fulfil constitutional and international obligations to safeguard environmental assets as well as undertake land reform benefiting the previously dispossessed. Consequently, there is a continuous challenge of reconciling complex and often conflicting relationships between poverty, inequitable access to resources, and the protection of biodiversity. Current efforts to conserve the Cape Floral Kingdom emphasize partnerships between private landowners and existing nature reserves to promote sustainable utilisation of biodiversity. This paper presents a case study exploring how this approach might be reconciled with land rights and opportunities for land-based livelihoods among farm dwellers in the Baviaanskloof area of the Eastern Cape. The paper identifies systemic and structural tensions in current attempts to reconcile biodiversity conservation and farm dwellers’ interests, and documents issues of process and principle that could become important in the future. In doing so, it highlights the influence of on-farm power relations and overly complex institutional arrangements in determining the real extent of participation by affected farm dwellers and the efficacy of social safeguard policies. Findings also caution against an over-reliance on ecotourism as the major occupation and the paper argues instead for support for multiple livelihood strategies.  相似文献   

Consumption preferences and environmental externalities: A hedonic analysis of the housing market in Guangzhou   总被引：2，自引：0，他引：2  

C.Y. Jim  Wendy Y. Chen 《Geoforum》2007,38(2):414-431

The urban housing market of China has been transformed since the 1980s from a centrally-planned to a free-market system. This study aimed to (1) investigate the position of outdoor environmental quality in house-buyers’ preferences; (2) assess monetary values attributed to environmental externalities by the hedonic pricing method (HPM); and (3) test the applicability of HPM in China. The study area was Guangzhou, the major city of south China with a booming real-estate market. A questionnaire survey was conducted with households in new residences sold in 2004. The main buying motives were improving living quarters and floor area. Security concerns and a preference for high-rise buildings were somewhat unexpected. Good outdoor environment, including green space provision, proximity to parks, and views of green space and water, carried significant hedonic values. Differences between the submarkets of old and new towns were found; new town households expected apartments in high-rise blocks, exclusive residential land use, and views of green space, while old town households preferred proximity to shopping areas and workplaces, green space within the development and proximity to nearby parks. The findings could help to fine tune the developing housing market to match supply with demand in quality terms. Values accorded to environmental attributes could justify funding for urban green spaces and nature conservation. The study verified the applicability of HPM to the housing context in China.  相似文献   

The future of climate modeling     

Joel Katzav  Wendy S. Parker 《Climatic change》2015,132(4):475-487

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Water quality assessment for sustainable agriculture in the Wet Tropics--a community-assisted approach     

Faithful J  Finlayson W 《Marine pollution bulletin》2005,51(1-4):99-112

A number of studies in north Queensland over the past two decades have concluded that large amounts of nutrients and sediments are exported from agricultural watersheds, particularly during wet season rainfall events. With the co-operation of a number of growers, runoff from Queensland Wet Tropics banana and cane farm paddocks in two distinct tropical river catchments was examined to provide an estimate of nutrient and sediment concentrations and export, with comparison to water quality of flow through a small urban lakes system. Median total nitrogen concentrations in cane drainage runoff (3110 microg N/L) were higher than for banana paddock drainage (2580 microg N/L), although the maximum concentration was recorded from a banana paddock (20,900 microg N/L). Nitrogen losses during post-event drainage flow were supplemented by high proportions of NO(X) (nitrate + nitrite) sourced from groundwater inputs. Banana paddocks had the highest maximum and median total phosphorus and TSS concentrations (5120 and 286 microg P/L, and 7250 and 75 mg/L respectively) compared to the cane farms (1430 and 50 microg P/L, and 1840 and 14 mg/L respectively). The higher phosphorus and TSS concentrations in the banana runoff were attributed to higher paddock slopes and a greater proportion of exposed ground surface during the wet season. Highest nutrient and TSS concentrations corresponded with samples collected near the peak discharge periods; however, the rising stage of the drainage flows, where the highest nutrient and TSS concentrations are often reported, were difficult to target because of the manual sampling strategy used. This study shows that high concentrations of nutrients and TSS occur in the runoff from cane and banana paddocks. Median total nitrogen, total phosphorus and TSS concentrations in flow through the urban lakes were 369 microg N/L, 16 microg P/L and 11 mg/L, respectively. Flux estimates of 9.2 kg N, 0.8 kg P and 126 kg TSS/ha were determined for drainage runoff from a banana paddock during a single intensive storm event.  相似文献   

Preparing Preservice Teachers to Incorporate Geospatial Technologies in Geography Teaching     

Wendy Harte 《The Journal of geography》2017,116(5):226-236

This study evaluated the efficacy of geospatial technology (GT) learning experiences in two geography curriculum courses to determine their effectiveness for developing preservice teacher confidence and preparing preservice teachers to incorporate GT in their teaching practices. Surveys were used to collect data from preservice teachers at three intervals over one semester. Results indicate preservice teachers' confidence and competencies to successfully integrate GT in their teaching increased over the duration of the study. The findings highlight the value of providing GT learning experiences in geography curriculum courses and contribute to the literature on preparing preservice teachers to incorporate GT in teaching geography.  相似文献   

Latitudinal Distribution of O₂on Ganymede: Observations with the Hubble Space Telescope     

Wendy M. Calvin  John R. Spencer 《Icarus》1997,130(2):505-516

To help constrain the spatial variation of oxygen on Jupiter's satellite Ganymede, and hence have more clues to its mode of production and stability, we have obtained spectral data from the Faint Object Spectrograph (FOS) for a single pole-to-pole latitudinal strip, along with several Wide Field Planetary Camera 2 (WFPC2) images in three narrow band visible filters. All observations were made of the trailing hemisphere. In the FOS data we observe both visible absorptions at 0.577 and 0.627 μm, associated with dense-phase oxygen (compressed gases, liquids, or solids). Filter options limited the WFPC2 observations to wavelengths near the weaker oxygen absorption at 0.627 μm. These observations suggest that the dense-phase or dimer oxygen form is predominantly found in equatorial and mid-latitudes. The spectroscopic absorption feature appears in both bright and dark terrains but may be somewhat weaker in dark regions, which is consistent with the smaller mean photon path length in the surface in darker areas. Therefore, the abundance of oxygen appears more dependent on latitude and longitude constraints than surface albedo. At the highest latitudes, where the ratio spectra have a strong upturn toward the blue, the oxygen bands do not appear. This relation suggests that dimer oxygen and ozone (as seen by Galileo) have opposite trends with latitude. Possible causes include competition or variation in the preferred stable form, which depends on temperature, solar ultraviolet flux, and/or surface age; enhancement of O₃at the poles due to plasma interactions; or viewing geometry effects that reduce the oxygen features at the poles when observed from Earth. The predominantly equatorial feature supports the production of O₂through plasma bombardment and favors defect trapping over physical adsorption of the dimer molecules in the surface. We briefly consider the implications of Ganymede's magnetosphere for our understanding of O₂and O₃distribution on Ganymede.  相似文献   

“Doing Geography”: Evaluating an Independent Geographic Inquiry Assessment Task in an Initial Teacher Education Program     

Wendy Harte  Paul Reitano 《The Journal of geography》2016,115(6):233-243

The assessment task of the final course in a bachelor of secondary education program is examined for opportunities for preservice geography teachers to achieve the course aims of integrating, consolidating, applying, and reflecting on the knowledge and skills they have learned during their initial teacher education program. The results show that the preservice teachers did better in some areas (integrating, consolidating, and reflecting) than in others (applying). This has implications for curriculum renewal in geography methods courses—specifically to provide more opportunities for preservice teachers to practice applying the knowledge and skills they have gained during the program, essential for their future roles as senior geography teachers.  相似文献   

Country-Specific Market Impacts of Climate Change   总被引：3，自引：3，他引：0  

Robert Mendelsohn  Wendy Morrison  Michael E. Schlesinger  Natalia G. Andronova 《Climatic change》2000,45(3-4):553-569

We develop a new climate-impact model, theGlobal Impact Model (GIM), which combines futurescenarios, detailed spatial simulations by generalcirculation models (GCMs), sectoral features,climate-response functions, and adaptation to generatecountry-specific impacts by market sector. Estimatesare made for three future scenarios, two GCMs, andtwo climate-response functions – a reduced-form modeland a cross-sectional model. Combining empiricallybased response functions, sectoral data by country,and careful climate forecasts gives analysts a morepowerful tool for estimating market impacts. GIMpredicts that country specific results vary, implyingthat research in this area is likely to bepolicy-relevant.  相似文献