华北平原参考作物蒸散量变化特征及气候影响因素

参考作物蒸散量是估算作物需水量的关键因子,对指导农田灌溉是有十分重要的现实意义。在气候变化的背景下,利用Penman-Monteith方法,计算华北平原典型站点1961 2007年逐日参考作物蒸散量,并从能量平衡和动力学角度对其分解,分析年际变化和季节变化特征;结合数理统计方法,研究影响参考作物蒸散量及其构成项变化的主次气候因子,为该区农田水分管理提供更有效的科学指导。研究结果表明:在华北平原全区温度显著上升、日照时数,相对湿度,平均风速呈显著下降的背景下,绝大部分站点参考作物蒸散量及构成项呈显著下降趋势。夏季的参考作物蒸散量和辐射项值相对最高,冬季值最低;春季的空气动力学项值相对比例最高。辐射项与空气动力学项年际间呈负相关关系,春夏两季之间呈不显著正相关趋势,秋冬两季呈不显著负相关趋势。辐射项的变化主要受日照时数、风速及温度的影响,其中风速的贡献是负效应;空气动力学项的变化主要受风速、相对湿度及平均温度的影响,相对湿度的贡献是负效应。参考作物蒸散量的变化主要受日照时数、相对湿度、温度日较差和风速的综合影响。此外,降水与其呈显著负相关关系,下降幅度略高于参考作物蒸散量的变化幅度。     

1940—2002年长江中下游平原乡村景观区域中土地利用覆被及其土壤有机碳储量变化

过去60a来,长江中下游平原的乡村地区发展迅速,引起土地利用覆被及其土壤有机碳储量明显地变化。通过选取区域代表性样方、基于1942年航片和2002年IKONOS影像研究小尺度土地利用覆被变化、土壤取样和收集1965年前土壤有机碳历史数据,用尺度推绎和蒙特卡洛不确定性分析方法,评价了19402002年长江中下游平原人口密集的乡村景观区域中土地利用覆被的面积及其030cm土壤(或底泥)有机碳储量的变化。结果表明:近60a来,在86×103km2的区域中有47%的面积发生土地利用覆被转化,其中耕地转化为非耕地的面积为21%(18×103km2)。土地利用覆被类型转化及其有机碳密度的变化导致该区域土壤有机碳储量的净增加。该区域稻田和闲置水域面积分别减少了21.5%(18.5×103km2)和6.7%(5.7×103km2),导致其土壤(或底泥)有机碳储量分别减少41.8TgC和12.9TgC;而水产养殖、非渗漏表面为主的建筑用地、种植木本作物和种植1年生作物的水浇地面积分别增加了14.2%(12.2×103km2)、7.7%(6.7×103km2)、3.5%(3.0×103km2)和2.0%(1.7×103km2),使其土壤(或底泥)有机碳储量分别增加32.2TgC、22.2TgC、12.2TgC和6.5TgC。近60a来,整个区域030cm土壤有机碳的储量增加了18.2TgC,其净增加的可能性为75%,形成了弱碳汇。这主要是由于区域稻田土壤有机碳密度增加了17%,使区域土壤有机碳储量增加了22.2TgC(其净增加的可能性为92%);而且,稻田转化为种植木本作物和种植1年生作物的水浇地也使区域土壤有机碳储量分别增加了1.3TgC(净增加的可能性为86%)和0.3TgC(净增加的可能性为70%);此外,闲置水域转化为水产养殖也使区域土壤有机碳储量增加1.3TgC(净增加的可能性为77%)。但是,稻田转化为水产养殖和非渗漏表面为主的建筑用地导致区域土壤有机碳储量损失6.3TgC和0.6TgC。因稻田土壤有机碳密度增加及稻田转化类型的土壤有机碳储量变化的影响,使整个区域形成弱碳汇,但如果稻田继续减少的话,很可能变成碳源。通过选取区域代表性样方、研究小尺度土地利用覆被变化、土壤取样和收集土壤历史数据,采用尺度推绎方法,研究揭示了19402002年长江中下游平原人口密集的乡村景观区域中土地利用覆被的面积及其土壤有机碳储量的变化。     

基于CVM的三江平原湿地非使用价值评价

基于条件价值评估法(CVM)这一当前国际上流行的生态系统经济价值评价方法,对三江平原湿地的非使用价值进行了研究。研究中采用实地调研的方式,进行支付意愿问卷调查,共发放支付卡式CVM问卷552份,回收有效问卷513份。分别采用非参数估计和参数估计方法对调查数据进行分析处理,评价了三江平原湿地的非使用价值,得出三江平原湿地2007年人均支付意愿为71.66元/a,并进一步计算出三江平原湿地的非使用价值为24.638亿元/a。该值仅为三江平原湿地部分,如果扩大到三江平原涵盖的所有自然资源,其值还将大幅上扬。三江平原蕴含的自然资源价值是巨大的,保护三江平原的生态环境也将创造巨大的价值,研究结论使得湿地环境保护和开发的价值对比成为可能,为政府相关政策的制定提供理论基础。     

长江中游地区野生百合资源调查及利用前景

通过对长江中游地区野生百合资源进行调查,发现长江中游地区有野生百合资源14个种和3个变种即野百合(Lilium brownii F. E. Brown ex Miellez var. brownii)、百合(L. brownii F. E. Brown ex Miellez var. viridulum Baker)、宜昌百合(L. leucanthum (Baker) Baker)、渥丹(L. concolor Salisb. var. concolor)、有斑百合(L. concolor Sali sb. var. pulchellum (Fisch.)Regel)、滇百合(L. baberianum Coll.et Hemsl)、大理百合(L.taliense Franch.)、药百合(L.speciosum Thunb. var. gloriosoides Baker)、湖北百合(L.henryi Baker)、南川百合(L. rosthornii Diels)、宝兴百合(L. duchartrei Franch.)、山丹(L. pumilum DC.)、川百合(L. davidii Duchartre)、条叶百合(L. callosum Sieb. et Zucc.)、乳头百合(L. papilliferum Franch.)、绿花百合(L. fargesii Franch.)和卷丹(L. tigrinum Ker Gawler)。对野生百合在长江中游地区分布现状、观赏特性及开发利用价值进行了分析,为百合新品种培育奠定基础。同时对长江中游地区野生百合资源的保护和合理开发利用提出建议。     

Palynofacies Analysis of Inner Continental Shelf and Middle Slope Sediments offshore Egypt, South-eastern Mediterranean

Marine palynological studies of Quaternary sediments usually focus on dinoflagellate and pollen assemblages for paleoceanographic and paleohydrographic interpretations of past events. This paper focuses on the use of palynofacies analysis for paleohydrological reconstructions of deltaic and deep sea environments to evaluate transport of organic matter to the ocean. These palynodebris data are used to interpret palaeoenvironmental and paleohydrographic changes in two marine cores from the continental shelf (core-1, 27 m water depth) and middle slope (core-2, 1030 m) offshore Egypt, south-eastern Mediterranean Sea, during the latest Pleistocene and the Holocene. The relative abundances of various types of sedimentary organic matter such as phytoclasts, zooclasts, amorphous organic matter and palynomorphs are related to paleohydrographic changes of the overlying water column. Based on the total palynodebris and organic carbon content, sediments of the inner continental shelf core are characteristic of a prodelta environment proximal to a fluvio-deltaic source and moderately distal oxic environments with enhanced structured organic matter preservation potential. In contrast, the palynodebris of the middle slope core show that the basal sediments (105-140 cm depth) indicate suboxic to dysoxic bottom water conditions, followed by anoxic-suboxic bottom water conditions for the interval from 30-85 cm, which represents the S1 Sapropel. The top sediments of core-2 (0-25 cm) were deposited under oxic bottom water conditions, suggesting good ventilation in the water column. A quantitative approach was also used for interpreting the Holocene sea-level changes, based on the correlation between phytoclast and organic matter abundances. Sedimentation rate in the continental shelf is varied, being relatively very low (6.7 cm/kyr) in the basal part and increased upward to be 20 cm/kyr (depth 115-120 cm). In the upper Gray clayey silt layer the sedimentation rate was high (about 40-45 cm/kyr) due to the high discharge from El Manzala Lagoon and Damietta Nile branch. In the middle slope depth the sedimentation rate was relatively low and uniform, around 14 cm/kyr.     

Delta-Notch signaling is involved in the segregation of the three germ layers in Xenopus laevis

In vertebrates, the induction of the three germ layers (ectoderm, mesoderm and endoderm) has been extensively studied, but less is known about how they segregate. Here, we investigated whether Delta-Notch signaling is involved in this process. Activating the pathway in the marginal zone with Notch^ICD resulted in an expansion of endodermal and neural ectoderm precursors, leaving a thinner mesodermal ring around the blastopore at gastrula stage, when germ layers are segregated. On the other hand, when the pathway was blocked with Delta-1^STU or with an antisense morpholino oligonucleotide against Notch, the pan-mesodermal brachyury (bra) domain was expanded and the neural border was moved animalwards. Strikingly, the suprablastoporal endoderm was either expanded when Delta-1 signaling was blocked, or reduced after the general knock-down of Notch. In addition, either activating or blocking the pathway delays the blastopore closure. We conclude that the process of delimiting the three germ layers requires Notch signaling, which may be finely regulated by ligands and/or involve non-canonical components of the pathway. Moreover, Notch activity must be modulated at appropriate levels during this process in order to keep normal morphogenetic movements during gastrulation.     

Comparison of confidence intervals for adjusted attributable risk estimates under multinomial sampling

The epidemiologic concept of the adjusted attributable risk is a useful approach to quantitatively describe the importance of risk factors on the population level. It measures the proportional reduction in disease probability when a risk factor is eliminated from the population, accounting for effects of confounding and effect-modification by nuisance variables. The computation of asymptotic variance estimates for estimates of the adjusted attributable risk is often done by applying the delta method. Investigations on the delta method have shown, however, that the delta method generally tends to underestimate the standard error, leading to biased confidence intervals. We compare confidence intervals for the adjusted attributable risk derived by applying computer intensive methods like the bootstrap or jackknife to confidence intervals based on asymptotic variance estimates using an extensive Monte Carlo simulation and within a real data example from a cohort study in cardiovascular disease epidemiology. Our results show that confidence intervals based on bootstrap and jackknife methods outperform intervals based on asymptotic theory. Best variants of computer intensive confidence intervals are indicated for different situations.     

Use of wetlands at the mouth of the Yangtze River by shorebirds during spring and fall migration

ABSTRACT.   The mouth of the Yangtze River is an important stopover site for migratory shorebirds using the East Asian-Australasian Flyway. From 1984 to 2004, we censused and banded shorebirds and monitored hunting activities at the mouth of the Yangtze River to understand how shorebirds used the study area. Counts and banding data revealed greater numbers of shorebirds at the mouth of the Yangtze River during northward migration (spring) than during southward migration (fall), with ratios varying from 1.5:1 to 7.2:1 at different sites from 1984 to 2005. The most common species observed during spring (northward) migration were Great Knots ( Calidris tenuirostris ), Red Knots ( Calidris canutus ), Bar-tailed Godwits ( Limosa lapponica ), Sharp-tailed Sandpipers ( Calidris acuminata ), and Red-necked Stints ( Calidris ruficollis ). During spring 2003–2004, 96.98% of the shorebirds observed were adults (ASY or older) and 3% were after hatching-year and second-year birds (AHY or SY). In contrast, almost all (94.73%) birds counted during the fall were hatching-year (HY) birds. These results indicate that adult shorebirds either use a different migration route during fall migration or use the same route, but do not stop at the mouth of the Yangtze River. HY birds, however, may depend on the coastal stopover sites for feeding during their first southward passage.     

Respiratory pattern of captive Yangtze finless porpoises (Neophocaena phocaenoides asiaeorientalis)

Cetacean respiration usually happen in bouts. The most widely applied quantitative method used to analyze the structure of these bouts is the log_e-survivorship analysis, based on the assumption that the respiratory intervals are distributed as negative exponentials. However, for the data collected from three captive Yangtze finless porpoises (Neophocaena phocaenoides asiaeorientalis), we failed to obtain a convergent result with the application of log_e-survivorship analysis. However, the two-Gaussian model, which was recently proposed to analyze the feeding behavior of cows, was successfully fitted to the data. According to the fitting results, the overall respiratory pattern of the captive Yangtze finless porpoises can be described as a dive with a mean duration of around 30–40 s, followed by two or three ventilations with a mean interval of approximately 9 s. The average intra-bout intervals during both active and inactive periods are constant at 7.7–9.9 s for all individuals. However, when shifting from active to inactive states, the adult male and female decrease their mean numbers of respirations per bout and average length of inter-bout respiratory intervals, while the estimates of both parameters increase for the juvenile female. It was pointed out that the two-Gaussian model might be more adequate for cetacean respiratory-bout structure analyses than the log_e-survivorship technique.