不同土壤水分对向日葵光合光响应的影响

以食用向日葵为试验材料,大田试验采取人为控制土壤水分在胁迫、适宜和过湿 (土壤田间持水量的40%~54.9%,55%~69.9%和70%~90%) 条件下,研究了向日葵3个生育期 (二对真叶—花序形成期、花序形成—开花期、开花—成熟期) 的光合光响应特性。结果表明:在试验设置光强条件下,各生育期净光合速率随着光合有效辐射的增加而增加,同等的光合有效辐射下净光合速率也随着土壤水分的减少依次降低,尤其是随着光合有效辐射的增大愈加明显。土壤湿度对最大净光合速率和表观量子效率的影响并不是同步的,最大净光合速率随着土壤湿度的增加而增大,而表观量子效率在一定程度的水分胁迫情况下出现最大值。不同的土壤水分含量对光补偿点和光饱和点影响不同,光饱和点随着土壤水分的增加而增加,光补偿点却相反,表明水分胁迫使向日葵可利用光的范围缩小,而适宜水分则扩大了光的利用范围,更有利于干物质积累。暗呼吸速率随着植物的生长进程逐渐降低,不同生育期的水分胁迫均导致暗呼吸速率降低。     

渤海西岸全新世气候演化与海陆变迁

应用第四纪地质学和海相生物等化石数量统计,以天津马棚口海岸带BQ1孔化石鉴定与统计结果,对古气候、古事件进行对比研究。通过岩芯编录,在岩性层中划分出4个海相层、5个过渡层、9个海面波动。结合研究区广泛分布的贝壳堤和牡蛎礁,利用其大量的测年资料,重现了6道海岸线;根据海相化石个体统计数,画出全新世气候演化曲线,与孢粉和物候所画的古气候演化曲线大体一致。研究历代海陆变迁,必然涉及到历史上长期争论不休的西汉大海侵等问题,谭其骧（1965）圈定的大海侵范围、海岸线分布以及考古结果几乎都能联系在一起,因此,大海侵之谜终于尘埃落定。考古界对河北平原自东汉—金的空白也有了初步答案,同时,发现中国朝代兴衰与气候冷暖有明显的对应,从而建立了气候分期。     

黑龙江乌拉嘎金矿成矿热力学参数研究

本文通过对前人工作的总结,在研究矿物共生关系的基础上将乌拉嘎金矿床的成矿作用过程划分为3个成矿阶段,然后利用热力学数据计算出了各个阶段的成矿热力学参数。第1阶段:黄铁矿-早期白色玉髓状石英阶段,Eh范围在-0.5~+0.3 V之间,处于弱还原环境,硫逸度应大于10~(-23);第2阶段:烟灰色玉髓状石英-多金属硫化物阶段,在低温时成矿环境为中酸性(pH=4),弱还原环境(Eh值为-1.0~-0.3 V),硫逸度范围应大于10~(-40),但不会超过10~0。同前一阶段相比,硫逸度下限降低;第3阶段:碳酸盐-石英阶段,碳酸盐矿物的出现预示着成矿已接近尾声,成矿介质的pH值逐步从酸性(pH=3)向中酸性(pH=5)转变,成矿Eh值也从弱还原(-0.5 V)向弱氧化(+0.3 V)过渡,硫逸度下限范围大约在10~(-23)左右,不超过10~0,而氧逸度范围在10~(-20)加左右。这对于深入探讨热液成矿作用过程具有重要参考价值。     

川西坳陷什邡地区蓬莱镇组天然气藏特征及成藏过程分析

川西坳陷什邡地区蓬莱镇组气藏属于浅层常规—致密砂岩次生气藏,其形成机制不同于下伏须家河组储层的致密砂岩气。研究区内主要发育岩性圈闭,天然气来自于下伏须家河组煤系烃源岩及部分受到调整和改造的须家河组原生气藏,经长距离运移后在蓬莱镇组圈闭中聚集成藏。气层集中在蓬莱镇组中上部,天然气干燥系数大,以煤型气为主。流体包裹体分析表明,研究区内蓬莱镇组共经历3期热流体活动,前两期分别为液态烃充注及气液混合烃充注,但并未形成规模油藏;第3期为大规模天然气充注,对应成藏时间为晚白垩世晚期至古近纪早期(78~34Ma)。在此基础上,结合地质构造演化、烃源岩生排烃期、储层致密化窗口及生储盖组合特征,确定了蓬莱镇组天然气藏的形成过程及成藏特征:蓬莱镇组下部储层在晚白垩世中期达到致密化,已不利于天然气聚集成藏;喜山运动时期,下伏须家河组气藏受到调整和改造,早期发育的深大断裂得以扩展,大量深部气源沿断层向上运移至蓬莱镇组中上部,形成了浅层次生气藏。     

Early-season mapping of crops and cultural operations using very high spatial resolution Pléiades images

The aim of this study was to assess the contribution of very high spatial resolution (VHSR) Pléiades images to both early season crop identification and the mapping of bare soil surface characteristics due to cultural operations. The study region covering 21 km² is located west of the peri-urban territory of the Versailles plain and the Alluets plateau (Yvelines, France). About 100 cropped fields were observed on the ground synchronously with two Pléiades images of 3 and 24 April 2013 and one SPOT4 image of 2 April 2013. The GIS structuring of these field data along with vector information about field boundaries was used for delimitating both training and test zones for the support vector machine classifier with polynomial function kernel (pSVM). The pSVM was computed on the spectral bands and NDVI for both single-date Pléiades and the bi-temporal Pléiades pair. For the single-date classifications of crops, the overall per-pixel accuracy reached 87% for the SPOT4 image of 2 April (6 classes), 79% for the Pléiades image of 3 April (6 classes) and 82% for that of 24 April (7 classes). At the earlier date (2–3 April), the Pléiades image very well discriminated cultural operations (>77%, user’s or producer’s accuracies) as well as fallows and grasslands, while winter cereals and rapeseed were better discriminated by the SPOT4 image winter cereals (>70%, user’s or producer’s accuracies). As Pléiades images revealed within-field spatial variations of early phenological stages of winter cereals that could be critical for adjusting management of zones with delayed development during the growing season, they brought information complementary to multispectral images with high spatial resolution. For the bi-temporal Pléiades image, the overall per-pixel accuracy was about 80% (7 classes), winter crops, grasslands and fallows being very well detected while confusions occurred between spring barley at initial stages (2–3 leaves) and bare soils prepared for other spring crops. Using an additional validation field set covering ∼1/3 of the study area croplands, the crop map resulting from the bi-temporal Pléiades pair achieved correct crop prediction for about 89.7% of the validation fields when considering composite classes for winter cereals and for spring crops. Early-season Pléiades images therefore show a considerable potential for anticipating regional crop patterns and detecting soil tillage operations in spring.     

ENSO发展和衰减阶段的陕西夏季降水异常特征

利用1961—2008年陕西78个气象站夏季 (6—8月) 降水资料、NCEP/NCAR位势高度场和风场月平均再分析资料,采用合成及相关分析方法探讨ENSO发展和衰减阶段对陕西夏季降水异常的影响,以期为陕西夏季降水的气候预测提供线索和依据。结果表明:陕西夏季降水异常对ENSO发展和衰减阶段的响应存在显著差异,El Ni?o发展阶段和La Ni?a衰减阶段,陕西夏季降水偏少; El Ni?o衰减阶段和La Ni?a发展阶段,陕西夏季降水偏多; ENSO不同阶段对陕西7月降水影响最为显著。比较而言,El Ni?o事件对陕西夏季降水的影响更加显著。在El Ni?o衰减、La Ni?a发展阶段,西太平洋副热带高压偏强、偏西,东亚夏季风偏弱,而在El Ni?o发展、La Ni?a衰减阶段,西太平洋副热带高压偏弱、偏东,东亚夏季风偏强,El Ni?o过程对东亚夏季风强弱的影响更加显著。ENSO发展和衰减阶段通过影响大气环流变化和东亚夏季风的强弱,进而影响陕西夏季降水。     

Estuarine retention of larvae of the crab Rhithropanopeus harrisii

Larvae of estuarine organisms continually face possible export from the parent estuary. Retention of larvae of the estuarine crab Rhithropanopeus harrisii was investigated in the upper Newport River estuary, North Carolina. All of the developmental stages occurred in the same area of the estuary with similar horizontal distributions, and the concentrations of intermediate and late stages were not greatly reduced from those of the first larval stage. This was strong evidence for the continuous retention of larvae in the upper estuary.To determine mechanisms by which retention might be effected, field studies of the vertical distributions and migrations of these larvae were made. The four zoeal stages had similar but complex vertical migration patterns, which varied from study to study. These migrations centered on the depth of no net flow, reducing longitudinal transport during development. Cross-spectral analysis of the larval migrations and the environmental cycles of light, salinity and current speed revealed that each of these external cycles affected larval depth. Megalopae of R. harrisii also migrated vertically, but they were present in much lower concentrations than the zoeal stages, an indication of a change to benthic existence in this final larval form.     

Floribec: The life and death of a tourism-based transnational community

The authors outline how a tourist destination can morph into a tourism-based transnational community. A three-phase model is designed to explore the touristification process of a transnational community. The phases are the adoption of a tourist destination, the transformation of the destination into a tourism-based transnational community, and decline under real estate and ageing population pressures.     

Early and Middle Pleistocene landscapes of eastern England

This paper reviews the pattern of climate and environmental change in eastern England over the period of the Early and Middle Pleistocene, focussing especially upon northern East Anglia. Particular attention is given to the climate and tectonics that have brought about these changes and the distinctive geology, topography and biology that has developed. Throughout, an attempt is made to describe the new models that have been proposed for the Early and Middle Pleistocene of eastern England, and explain the reasons for these changes. The Early Pleistocene experienced relatively high insulation and relatively low magnitude climatic change and is represented primarily by non-climatically forced processes in the form of tidal current- and wave-activity which formed shallow marine deposits. It is possible to recognise a tectonic control in the distribution of deposits of this age because the surface processes do not have the power to remove this signature. The early Middle Pleistocene was dominated by higher magnitude climatic change involving, occasionally, climatic extremes that ranged from permafrost to mediterranean. The landscape at this time was dominated by the behaviour of major rivers (Thames, Bytham, Ancaster) and extensive coastal activity. In the latter part of the early Middle Pleistocene and the Late Middle Pleistocene the climate experienced major changes which resulted in periods of lowland glaciation and short intervals when the climate was warmer than the present. Details of tectonic activity are difficult to identify because they are removed by powerful surface processes, but it is possible to infer uplift focussed on the major interfluves of central England and subsidence in the North Seas basin. In the areas of glaciation the landscape changed radically from an organised terrain dominated by large rivers and extensive shallow coastal zones to complex, with small valleys, disrupted drainage and often discontinuous river, slope and coastal deposits. Likewise the switching off of the North Sea Delta and the opening of the Strait of Dover, separating Britain from continental Europe can be attributed to the onset of lowland glaciation. The case is made that eastern England was glaciated four times during the Middle Pleistocene: during MIS 16, 12, 10 and 6, and attention is given to recent evidence contradicting this model. Over the period of the Middle Pleistocene there is evidence for high biomass production occurring over short intervals coinciding with the climatic optima of MIS 19, 17, 15, 13, 11, and 7c, 7a and during most of these warmer periods, extending back to c. 750 ka (MIS 19/17), there is evidence in the region for the brief appearance of humans.