Remote sensing of spider mite damage in California peach orchards     

Eike Luedeling  Adam Hale  Minghua Zhang  Walter J. Bentley  L. Cecil Dharmasri 《International Journal of Applied Earth Observation and Geoinformation》2009

Remote sensing techniques can decrease pest monitoring costs in orchards. To evaluate the feasibility of detecting spider mite damage in orchards, we measured visible and near infrared reflectance of 1153 leaves and 392 canopies in 11 peach orchards in California. Pairs of significant wavelengths, identified by Partial Least Squares regression, were combined into normalized difference indices. These and 9 previously published indices were evaluated for correlation with mite damage.  相似文献   

Comparative biomass structure and estimated carbon flow in food webs in the deep Gulf of Mexico     

Gilbert T. Rowe  Chihlin Wei  Clifton Nunnally  Richard Haedrich  Paul Montagna  Jeffrey G. Baguley  Joan M. Bernhard  Mary Wicksten  Archie Ammons  Elva Escobar Briones  Yousra Soliman  Jody W. Deming 《Deep Sea Research Part II: Topical Studies in Oceanography》2008,55(24-26):2699

A budget of the standing stocks and cycling of organic carbon associated with the sea floor has been generated for seven sites across a 3-km depth gradient in the NE Gulf of Mexico, based on a series of reports by co-authors on specific biotic groups or processes. The standing stocks measured at each site were bacteria, Foraminifera, metazoan meiofauna, macrofauna, invertebrate megafauna, and demersal fishes. Sediment community oxygen consumption (SCOC) by the sediment-dwelling organisms was measured at each site using a remotely deployed benthic lander, profiles of oxygen concentration in the sediment pore water of recovered cores and ship-board core incubations. The long-term incorporation and burial of organic carbon into the sediments has been estimated using profiles of a combination of stable and radiocarbon isotopes. The total stock estimates, carbon burial, and the SCOC allowed estimates of living and detrital carbon residence time within the sediments, illustrating that the total biota turns over on time scales of months on the upper continental slope but this is extended to years on the abyssal plain at 3.6 km depth. The detrital carbon turnover is many times longer, however, over the same depths. A composite carbon budget illustrates that total carbon biomass and associated fluxes declined precipitously with increasing depth. Imbalances in the carbon budgets suggest that organic detritus is exported from the upper continental slope to greater depths offshore.The respiration of each individual “size” or functional group within the community has been estimated from allometric models, supplemented by direct measurements in the laboratory. The respiration and standing stocks were incorporated into budgets of carbon flow through and between the different size groups in hypothetical food webs. The decline in stocks and respiration with depth were more abrupt in the larger forms (fishes and megafauna), resulting in an increase in the relative predominance of smaller sizes (bacteria and meiofauna) at depth. Rates and stocks in the deep northern GoM appeared to be comparable to other continental margins where similar comparisons have been made.  相似文献   

About the Symmetry of the Upscaled Equivalent Transmissivity Tensor   总被引：1，自引：0，他引：1  

Mauro Giudici  Chiara Vassena 《Mathematical Geology》2007,39(4):399-408

This paper provides a proof of the symmetry of the equivalent transmissivity tensor computed with a method based on the solution of the balance equation at the fine scale with integrated finite differences. The basic hypotheses are that the balance equation is solved on a block assigning Dirichlet boundary conditions that vary linearly with the space coordinates and the equivalent transmissivity tensor is computed as the linear tensor relating average flux and hydraulic gradient.  相似文献   

Moving beyond Component Research in Mountain Regions： Operationalizing Systems Integration .at Farm and Landscape Scales     

Laura German 《山地科学学报》2006,3(4):287-304

Introduction Agricultural research continues to face criticism for its shortcomings in reversing current trends toward increased poverty and natural resource degradation. While some of these criticisms would be better attributed to broader structural constraints, shortcomings of the conventional agricultural research paradigm are nevertheless apparent. Researchers continue to frame research objectives, questions and methods with limited consultation of farmers and limited consideration of othe…  相似文献   

Sub‐fossil Chironomidae as indicators of palaeoflow regimes: integration into the PalaeoLIFE flow index     

Lynda C. Howard  Paul J. Wood  Malcolm T. Greenwood  Helen M. Rendell  Stephen J. Brooks  Patrick D. Armitage  Chris A. Extence 《第四纪科学杂志》2010,25(8):1270-1283

The sub‐fossil head capsules of larval Chironomidae have been widely exploited as palaeoecological indicators of lentic ecosystems but their value in the interpretation of the evolution of lotic systems has been underutilised by comparison. Recent research has demonstrated that the remains of Chironomidae are abundant within fluvial sequences and that they offer a valuable record of channel change and floodplain evolution that may complement that derived from existing biological and sedimentological techniques. This paper demonstrates the use of Chironomidae in characterising the palaeoflow regime of a large mid–late Holocene floodplain palaeochannel (5470–4960 to 1530–1350 cal. a BP) of the River Trent (Derbyshire, UK). Using expert knowledge and published information regarding flow preferences, larval Chironomidae were incorporated into the PalaeoLIFE (Lotic‐invertebrate Index for Flow Evaluation) methodology. The results clearly demonstrate that the sub‐fossil record provided by Chironomidae can be used to characterise changes in the flow regime within palaeochannel sections. At the scale of the channel section, species‐ and generic‐level ecological associations can provide useful information regarding habitat characteristics, including the presence of instream vegetation, mineral substrates and woody debris. The ability to undertake environmental reconstruction and channel evolution history was significantly enhanced through the application of a multi‐proxy approach, by incorporating other aquatic insect groups (Trichoptera and Coleoptera) into the PalaeoLIFE metric, together with sedimentological data. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

基于主成分分析法的泉州湾表层沉积物中重金属污染可能来源分析   总被引：3，自引：0，他引：3  

蔡龙炎 《台湾海峡》2010,29(3):325-331

通过测定泉州湾潮间带表层沉积物中重金属含量,并用地质累积指数（Igeo）对各重金属元素的污染状况进行了评价,发现泉州湾表层沉积物中各重金属元素污染状况可分为4类：无污染（Igeo〈0）的元素为Co（Igeo=-0.67）;轻-中度污染（0〈Igeo〈1）的元素为Cr（Igeo=0.65）、As（Igeo=0.52）、Zn（Igeo=0.75）、Pb（Igeo=0.11）;中度污染（1〈Igeo〈2）的元素为Cu（Igeo=1.58）、Ni（Igeo=1.32）、Mn（Igeo=1.08）;极严重污染（Igeo〉5）的元素为Cd（Igeo=8.70）.通过主成分分析法（PCA）进一步研究了沉积物中重金属的来源,发现前3个主成分的贡献率分别为32.884%、31.676%、21.988%.这表明重金属污染主要有3个来源：即工业点源排污;矿物开采及农业化肥农药使用的非点源污染;岩石的自然风化侵蚀过程和有机质降解产生的内源释放.同时聚类分析结果表明,调查的9个站位根据其在重金属污染程度上的差异,可分为3个大类：2～7号站位为第1类;1号站位为第2类;8、9号站位为第3类.这反映了泉州湾潮间带表层沉积物中的重金属污染物空间分布特点即重金属污染物含量由湾内向湾外逐渐降低,同时也支持了晋江和洛阳江的工业点源排污、矿物开采和化肥农药残留的非点源污染是沉积物中重金属主要污染源的分析.  相似文献   

The many faces of ecosystem-based management: Making the process work today in real places     

Heather Tallis  Phillip S. Levin  Mary Ruckelshaus  Sarah E. Lester  Karen L. McLeod  David L. Fluharty  Benjamin S. Halpern 《Marine Policy》2010,34(2):340-348

Despite the widely accepted need for ecosystem-based management of coastal and marine systems, many managers struggle with how to put these principles into practice. Commonly voiced concerns include complicated and expensive implementation, prohibitive data requirements, and lack of testing with long-term applications. We address some of these perceived barriers by providing guidance on strategies and approaches that can be used for the steps of one ecosystem-based management process, the integrated ecosystem assessment framework, including scoping, defining indicators, setting thresholds, risk analysis, management strategy evaluation, monitoring and evaluation. Importantly, we demonstrate how an ecosystem-based management approach can be utilized in a variety of contexts which vary widely in data quality and availability, governance structure, and time frame. We then illustrate the suggested steps in the process by exploring two case studies that represent realistic ends of the data/governance/time frame spectrum: Puget Sound, Washington, USA and Raja Ampat, Indonesia. By providing concrete suggestions for how to move forward with key steps in an integrated management process, we show that ecosystem-based management is feasible from a range of starting points and that for any given starting point there are numerous productive paths forward.  相似文献   

Benthic mucilaginous aggregates in the Mediterranean Sea: Origin, chemical composition and polysaccharide characterization     

Gianfranco Sartoni  Ranieri Urbani  Paola Sist  Daniela Berto  Caterina Nuccio  Michele Giani   《Marine Chemistry》2008,111(3-4):184-198

Benthic mucilaginous aggregates are frequently formed in various parts of the Mediterranean basin, as in the Tyrrhenian and Adriatic Seas. Notwithstanding their wide spatial distribution, the role played by these aggregates in the biogeochemical cycling of organic matter is still largely unknown.The characteristics of the benthic aggregates examined in the present study showed that they are different from other mucilaginous aggregates, such as the “pelagic” ones that can form in the same areas in the water column and subsequently sediment to the seafloor. The aggregates are usually formed of structures of the filamentous macroalgae Acinetospora crinita, Chrysonephos lewisii and Nematochrysopsis marina. The elemental composition of the aggregates showed a marine macrophyte origin on the basis of the bulk organic matter content of the aggregates. Carbohydrates and proteins account for 26.6 to 55.9% of the organic carbon in the mucilage, respectively. Monosaccharide composition of exopolysaccharides in the mucilage aggregates revealed a characteristic pattern, with galactose, xylose or mannose and fucose as the major components. The relatively high content of deoxysugars is another distinctive feature. The abundant sulphate and uronic groups present in the polysaccharides in addition to their macromolecular dimensions and elongation contribute to inter-chain aggregation. Electron microscopic observations suggest that the polysaccharide fraction is the main macromolecular component in the formation of the persistent gel network in the aggregates.  相似文献   

Seasonal variability of living benthic foraminifera from the outer continental shelf of the Bay of Biscay   总被引：1，自引：0，他引：1  

Grald Duchemin  Frans J. Jorissen  Franois Le Loc'h  Franoise Andrieux-Loyer  Christian Hily  Grard Thouzeau 《Journal of Sea Research》2008,59(4):297-319

Living benthic foraminiferal faunas of six stations from the continental shelf of the Bay of Biscay have been investigated during three successive seasons (spring, summer and autumn 2002). For the three investigated stations, bottom water oxygen concentration, oxygen penetration into the sediment and sediment organic carbon contents are all relatively similar. Therefore, we think that the density and the composition of the foraminiferal faunas is mainly controlled by the quantity and quality of organic input resulting from a succession of phytoplankton bloom events, occurring from late February to early September. The earliest blooms are positioned at the shelf break, late spring and early summer blooms occur off Brittany, whereas in late summer and early autumn, only coastal blooms appear, often in the vicinity of river outlets. In spring, the benthic foraminiferal faunas of central (B, C and D) and outer (E) continental shelf stations are characterised by strong dominance in the first area and strong presence in the second area of Nonionella iridea. In fact, station E does not serve as a major depocenter for the remains of phytoplankton blooms. If station E is not considered, the densities of this taxon show a clear gradient from the shelf-break, where the species dominates the assemblages, to the coast, where it attains very low densities. We explain this gradient as a response to the presence, in early spring, of an important phytoplankton bloom, mainly composed of coccolithophorids, over the shelf break. This observation is supported by the maximum particles flux values at stations close to the shelf break (18.5 g m^− 2 h^− 1) and lower values in a station closer to the coast (6.8 g m^− 2 h^− 1). In summer, the faunal density is maximum at station A, relatively close to more varied phytoplancton blooms that occur off Brittany until early June. We suggest that the dominant species, Nonion fabum, Cassidulina carinata and Bolivina ex. gr. dilatata respond to phytodetritus input from these blooms. In autumn, the rich faunas of inner shelf station G are dominated by N. fabum, B. ex. gr. dilatata, Hyalinea balthica and Nonionella turgida. These taxa seem to be correlated with the presence of coastal blooms phenomena, in front of river outlets. They may be favoured by an organic input with a significant contribution of terrestrial, rather low quality organic matter.  相似文献   

ENSO事件指数与指标研究   总被引：101，自引：4，他引：97  

李晓燕  翟盘茂 《气象学报》2000,58(1):102-109

根据 1 951～ 1 996年完整可靠的海面温度 ( SST)和南方涛动指数 ( SOI)资料 ,以中、东太平洋 SST异常变化为指标 ,定义了 ENSO事件 ,并在此基础上提出了以 ENSO事件过程海温距平累积值为指标的强度指数。此外 ,还定义了 ENSO事件的海 -气综合强度指数 ,并对 ENSO事件的长度、强度及爆发类型等进行了分类。  相似文献