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51.
Multiple exposures and dynamic vulnerability: Evidence from the grape industry in the Okanagan Valley, Canada 总被引:7,自引:1,他引:7
This paper assesses the vulnerability of grape growers and winery operators in the Okanagan Valley, British Columbia to climate variability and change, in the context of other sources of risk. Through interviews and focus groups, producers identified the climatic and non-climatic risks relevant to them and the strategies employed to manage these risks. The results show that the presence of multiple exposures affects the way in which producers are vulnerable to climate change. Producers are vulnerable to conditions that not only affect crop yield, but also affect their ability to compete in or sell to the market. Their sensitivity to these conditions is influenced in part by institutional factors such as trade liberalization and a “markup-free delivery” policy. Producers’ ability to adapt or cope with these risks varies depending on such factors as the availability of resources and technology, and access to government programmes. Producers will likely face challenges associated with the supply of water for irrigation due to a combination of climatic changes and changing demographics in the Okanagan Valley, which in turn affect their ability to adapt to climatic conditions. Finally, adaptations made by producers can change the nature of the operation and its vulnerability, demonstrating the dynamic nature of vulnerability. 相似文献
52.
Ben K. Greenfield Geoffrey S. Siemering Joy C. Andrews Michael Rajan Stephen P. Andrews David F. Spencer 《Estuaries and Coasts》2007,30(4):627-640
Management actions to control invasive aquatic species can have significant ecosystem-scale effects. We evaluated the water
chemistry and nutrient effects of mechanical shredding to control water hyacinth (Eichhornia crassipes) in an agricultural slough and a tidal wetland on the Sacramento-San Joaquin River Delta, California. Shredding was conducted
with two types of shredder boats in fall of 2003 and another boat in spring of 2004. Shredding measurably affected water quality,
but specific effects varied as a function of shredding site and season. Significant increases were observed for total Kjeldahl
nitrogen and total phosphorus for all experiments. Dissolved oxygen effects varied by site, decreasing after shredding at
the agricultural slough but increasing at the tidal wetland. The increase in dissolved oxygen likely resulted from tidal incursions
from the adjacent river. A year-long time series of dissolved oxygen data indicated a negative relationship between hyacinth
abundance and dissolved oxygen concentrations. Hyacinth contained similar tissue concentrations of mercury to underlying sediments,
suggesting that plant harvesting could aid mercury remediation efforts. Simple mass calculations indicated that Delta-wide
shredding operations could cause between 0.1% and 9.6% increases in the overall abundance of carbon, nitrogen, and phosphorus
in the Delta water column. Results suggest that local effects of management actions to control invasive aquatic plants will
vary widely as a function of site-specific hydrology, but that estuary-wide effects would be limited. 相似文献
53.
Ben J. Kefford 《International Journal of Salt Lake Research》1998,7(2):153-170
In order to relate macroinvertebrate fauna to electrical conductivity (EC), a survey of selected orders of macroinvertebrates
was conducted in the Glenelg, Hopkins, Merri and Barwon River Catchments in south-west Victoria, Australia. The survey consisted
of sampling 21 paired sites at confluences of streams. There was little difference between the in-stream habitat but there
was a range of differences in EC between each of the paired sites. The dissimilarity of macroinvertebrate fauna between the
paired sites was compared to the proportional difference in EC and other water quality variables (dissolved oxygen, water
temperature, pH, NO2−N, NO3−N, PO4 and turbidity). This allowed the elimination of EC being confounded with geographical scale parameters and took into account
other water quality parameters that may be confounded with EC. A positive relationship was found between the dissimilarity
of the fauna at each of the two paired sites and the proportional difference in EC. No such relationship was found for any
other measured water quality variable. The results of this survey show that macroinvertebrate community structure is associated
with EC of the river systems investigated after eliminating large scale geographical patterns, in-stream habitat and the measured
water quality parameters. 相似文献
54.
Claude J. Allegre Dalila Ben Othman Mireille Polve Pierre Richard 《Physics of the Earth and Planetary Interiors》1979,19(4):293-306
The neodymium-strontium isotopic correlation observed in most of the Earth mantle materials is evaluated by means of direct modelling. Several geochemical models are quantitatively developed to explain the observations. The main results of this modelling are that such a correlation is not geochemically trivial and that it corresponds to specific conditions in chemical fractionation. These specific conditions seem to be satisfied by solid-liquid partitioning in magmatic conditions. The discussion of the experimental data supports a continuous convecting-magmatic fractionation model for a large proportion of the mantle. 相似文献
55.
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57.
Temporal and spatial zonation of macroepiphytes on Posidonia oceanica (L.) Delile leaves in a meadow off Tunisia 下载免费PDF全文
The aim of this survey was to study the cover and the composition of macroepiphytic species on the leaves of Posidonia oceanica in the east of Tunisia. Surveys were conducted in December 2009 (winter period), March (spring period) and August 2010 (summer period) in a fringing reef located in Chebba. At each sampling date, 15 adult leaves were randomly collected and divided into basal and apical parts. The inner face of each part was examined with ocular glasses and microscope to estimate species cover by orthogonal projection. PERMANOVA and ANOSIM were used to test for differences of cover between sampling dates and leaf parts. SIMPER, cluster analysis, and PCA were used to ordinate species assemblages. Comparison of epiphytic cover along leaf blades showed significant differences for all groups, except cyanophycea, with high cover of hydrozoans and bryozoans in the basal part and high cover of algae in the apical part. The species composition and cover also vary with sampling date; minimum values were detected in December and the epiphytic community was composed of a few pioneer species, whereas maximum epiphytic cover values were registered in August, with the epiphytic community being composed of a more mature and more diverse community, termed ‘climax’. The main regulatory factors for this distribution are discussed. 相似文献
58.
拉伸纪作为承接中元古代蓝菌时代以及成冰纪生物锐减的关键地质历史时期,是探索早期生命与环境演化最重要的时期之一。吉林南部地区地处华北板块东北缘,拉伸系发育完整、出露全,在燧石条带、燧石结核和泥页岩中富含微生物化石,是开展拉伸纪古生物学、生物地层学和古环境研究的理想地区。本次工作利用岩石切片法在吉林南部二道江地区万隆组顶部燧石中发现微生物化石6属9种,其中丝状蓝菌1属4种Siphonophycus robustum,S.typicum,S.kestron,S.solidum;球状蓝菌3属3种Eoentophysalis belcherensis,Gloeodiniopsis lamellosa,Scissilisphaera bistratosa;分类位置未定2属2种Glenobotrydion majorinum,Globophycus rugosum。这些微体化石的发现为开展万隆组古环境分析及生物地层对比研究提供了新的素材。研究显示,万隆组燧石相微生物组合以发育管鞘藻席(Siphonophycus mat)为主要特征,丝状蓝菌呈横向展布,长可达400μm以上,显示原地或近原地埋藏的特点... 相似文献
59.
Ben Buse John C. Schumacher R. Stephen J. Sparks Matthew Field 《Contributions to Mineralogy and Petrology》2010,160(4):533-550
Metamorphic assemblages within Karoo basalt xenoliths, found within volcaniclastic kimberlite of the B/K9 pipe, Damtshaa,
Botswana, constrain conditions of kimberlite alteration. Bultfonteinite and chlorite partially replace the original augite-plagioclase
assemblage, driven by the serpentinisation of the kimberlite creating strong chemical potential gradients for Si and Mg. Hydrogarnet
and serpentine replace these earlier metamorphic assemblages as the deposits cool. The bultfonteinite (ideally Ca2SiO2[OH,F]4) and hydrogarnet assemblages require a water-rich fluid containing F−, and imply hydrothermal alteration dominated by external fluids rather than autometamorphism from deuteric fluids. Bultfonteinite
and hydrogarnet are estimated to form at temperatures of ca. 350–250°C, which are similar to those for serpentinisation. Alteration
within the B/K9 kimberlite predominantly occurs between 250 and 400°C. We attribute these conditions to increased efficiency
of mass transfer and chemical reactions below the critical point of water and a consequence of volume-increasing serpentinisation
and metasomatic reactions that take place over this temperature range. A comparison of the B/K9 kimberlite with kimberlites
from Venetia, South Africa suggests that the composition and mineralogy of included xenoliths affects the alteration assemblages
within kimberlite deposits. 相似文献
60.
Gregory F. de Souza Ben C. Reynolds Bernard Bourdon 《Geochimica et cosmochimica acta》2010,74(9):2596-5573
The stable isotope composition of strontium (expressed as δ88/86Sr) may provide important constraints on the global exogenic strontium cycle. Here, we present δ88/86Sr values and 87Sr/86Sr ratios for granitoid rocks, a 150 yr soil chronosequence formed from these rocks, surface waters and plants in a small glaciated watershed in the central Swiss Alps. Incipient chemical weathering in this young system, whether of inorganic or biological origin, has no resolvable effect on the 87Sr/86Sr ratios and δ88/86Sr values of bulk soils, which remain indistinguishable from bedrock in terms of Sr isotopic composition. Although due in part to the chemical heterogeneity of the forefield, the lack of a resolvable difference between soil and bedrock isotopic composition indicates that these soils have thus far witnessed minimal net loss of Sr; a low degree of chemical weathering is also implied by bulk soil chemistry. The isotopic composition of Sr in streamwater is more radiogenic than median soil, reflecting the preferential weathering of biotite in the catchment; streamwater δ88/86Sr values, however, are indistinguishable from bulk soil δ88/86Sr values, implying that no resolvable fractionation of Sr isotopes takes place during release to the weathering flux in the Damma forefield. Analyses of plant tissue reveal that plants (Rhododendron and Vaccinium) preferentially assimilate the lighter isotopes of Sr such that their δ88/86Sr values are significantly lower than those of the soils in which they grow. Additionally, δ88/86Sr values of foliar and floral tissues are lower than those of roots, contrary to observations for Ca, for which Sr is often used as an analogue in weathering studies. We suggest that processes that discriminate against Sr in favour of Ca, due to the different nutritional requirement of plants for these two elements, are responsible for the observed contrast. 相似文献