Climatic influence on a marine fish assemblage

Understanding the fluctuations in marine fish stocks is important for the management of fisheries, and attempts have been made to demonstrate links with oceanographic and climatic variability, including the North Atlantic Oscillation (NAO). The NAO has been correlated with a range of long-term ecological measures, including certain fish stocks. Such environmental influences are most likely to affect susceptible juveniles during estuarine residency, as estuaries are critical juvenile nursery or over-wintering habitats. Here we show that, during a 16-year period, climatic forcing (by means of the NAO) is consistently the most important parameter explaining variation in assemblage composition, abundance and growth of juvenile marine fish during estuarine residency. A possible mechanism for the effect of the NAO is a temperature differential between estuarine and marine waters that allows fish to facultatively exploit optimal thermal habitats. The connection has potentially important implications for the size and numbers of individuals recruited to the fishery, for understanding and predicting the composition of juvenile fish stocks using estuaries, and for the appropriate conservation of estuarine systems in relation to fish stocks.     

Red deer stocks in the Highlands of Scotland

Grazing by hill sheep and red deer prevents the regeneration of woodland in many parts of the Scottish Highlands and has also led to extensive loss of heather cover. Conservation bodies claim that there has been a rapid rise in Highland deer numbers caused by inadequate management and that these need to be drastically reduced. Here we show that the recent increase in red deer stocks has probably been overestimated and suggest that the gradual rise in numbers since 1970 may be a consequence of a reduction in sheep stocks and of changes in winter weather, rather than of a reduction in culling rate. Although there would be environmental benefits in reducing deer numbers, there is an equal need to reduce the numbers of hill sheep in many parts of the Highlands.     

Natural diet and food habitat use of the Tarim red deer,Cervus elaphus yarkandensis

In order to determine the natural diet and food habitat use of Tarim red deer (Cervus elaphus yarkandensis), a study was carried out in Qiemo, Xinjiang , China from October 2000 to June 2001. Direct observation combined with faecal analysis method was used to determine the natural diet of red deer. 15 different species of plant were identified as food items. Among them, 13 species of plants were identified in winter diet and 9 species in summer. Red deer consumed a wider range of species in winter because of their nutrient requirement as well as the shortage of food and the scarcity of high-quality forage in the study area. Phragmites communis, Glycyrrhiza inflata and populus diversifo-lia were frequently present in the deer's diet whenever in winter and summer. Among them, Phragmites communis was the most abundant plant in the area and was included in the deer's diet. Observation on food selection frequency of captive Tarim red deer showed that Populus diversifolia was the first preferred species. However, this food was limited in the study area. Five food habitat types were found in the study area according to plant association: (1) Phragmites communis-Tamarix ramosissima association, (2) Tamarix ramosissima-Halostachys cas-pica association, (3) Tamarix ramosissima-Phragmites communis association, (4) Populus diversifolia-Phragmites communis association, (5) Burned area. Among them, Phragmites communis-Tamarix ramosissima association (reed meadow and reed marsh) was preferred to other types within the study area whenever in summer and winter. Dense reed cover could reduce the chance of detection from predator and obstruct attack from predator. Furthermore, under the cover of the reed, Tarim red deer was protected from direct solar radiation during the hours of hot day in summer. The reed meadow and marsh was preferred, presumably because the red deer could minimize their movements while searching for food, water and cover.     

新疆玛纳斯河径流波动与北大西洋涛动的关系

对新疆玛纳斯河流量资料、北疆地区温度、降水资料进行整理,分析了其变化的特征和规律,并将其与北大西洋涛动指数进行了对比分析.研究发现,冬季北大西洋涛动指数与玛纳斯河冬季流量呈现显著的正向变化关系,夏季两者的关系则相反.利用交叉小波变换,分别发现了冬、夏季北大西洋涛动指数与玛纳斯河流量变化关系最密切的振荡周期.文中还发现冬、夏季北大西洋涛动指数与北疆温度、降水的变化也存在显著的相关关系.     

Interannual and interdecadal variations in the North Atlantic Oscillation spatial shift

The spatial shift of the North Atlantic Oscillation (NAO) is analyzed by using the Twentieth Century Reanalysis version 2 dataset and identifying NAO action centers directly on winter mean sealevel pressure (SLP) anomaly maps. The spatial shift of the NAO is characterized by four NAO spatial shift indices: the zonal and meridional shifts of the NAO southern and northern action centers. It is found that the zonal and meridional shift trends of the NAO action centers move along a path of southwest-northwest direction. Spectral analysis shows that the four NAO spatial shift indices have periodicity of 2-6 years and the NAO index has periodicity of 2-3 years in terms of high-frequency variations. On a decadal time scale, the NAO spatial shift indices are closely (positively) related to the NAO index, which is in agreement with previous studies of the relationship between the NAO index and the spatial shift of the NAO pattern. However, there is no relationship between the NAO index and the meridional shift of the northern action center on an interannual time scale. The significant relationship between the NAO index and the interannual variability of NAO spatial shift indices is very likely to be associated with synopticscale Rossby wave breaking, which generates surface pressure anomalies and thus affects the phase and pattern of the NAO. The correlations of winter westerly winds over 90°W-0° and the NAO index and the NAO spatial shift indices have a ’+ - + -’ structure from the Equator to the North Pole. Although there is close correlation between the NAO spatial shift indices and the strength of the zonal winds in the North Atlantic region, the effect of the zonal winds on the NAO spatial shift differs at different latitudes. Hence, the role of the zonal winds is probably a result of the NAO spatial shifts.     

Population density affects sex ratio variation in red deer.

Many mammal populations show significant deviations from an equal sex ratio at birth, but these effects are notoriously inconsistent. This may be because more than one mechanism affects the sex ratio and the action of these mechanisms depends on environmental conditions. Here we show that the adaptive relationship between maternal dominance and offspring sex ratio previously demonstrated in red deer (Cervus elaphus), where dominant females produced more males, disappeared at high population density. The proportion of males born each year declined with increasing population density and with winter rainfall, both of which are environmental variables associated with nutritional stress during pregnancy. These changes in the sex ratio corresponded to reductions in fecundity, suggesting that they were caused by differential fetal loss. In contrast, the earlier association with maternal dominance is presumed to have been generated pre-implantation. The effects of one source of variation superseded the other within about two generations. Comparison with other ungulate studies indicates that positive associations between maternal quality and the proportion of male offspring born have only been documented in populations below carrying capacity.     

Roaring by red deer stags advances the date of oestrus in hinds

Some male mammals call loudly and repeatedly during the breeding season. Although the song of male birds is known to have effects on male-male competition, mate selection and ovulation, until now the loud calls of male mammals have been shown to affect only competition between males. Although it has been suggested that loud calling could also serve to attract females, the possibility that it has a direct effect on reproduction in females has not previously been investigated for any mammal. Here I report that roaring in red deer (Cervus elaphus) advances ovulation and that harem-holding males can improve their mating success by regular calling.     

Phytohaemagglutinin activation of T cells through the sheep red blood cell receptor

Expression of receptors for sheep red blood cells and the ability to proliferate in response to phytohaemagglutinin (PHA) are the traditional properties of human T cells, but the function of the sheep red cell receptor (the T11 antigen) is controversial and the mechanism of PHA-induced mitogenesis unclear. Mitogenesis involves a complex series of cell-mediated and factor-dependent interactions, but a rise in intracellular free calcium concentration, [Ca2+]i, seems to be an important primary event in T-cell activation. We have now investigated the effects of three monoclonal antibodies, previously shown to inhibit mitogen-induced proliferation, on T-cell [Ca2+]i. We find that anti-LFA-2 and OKT11, which react with the sheep red cell receptor, have no effect on [Ca2+]i, nor do they inhibit the rise in [Ca2+]i induced by concanavalin A (Con A) or the mitogenic anti-T3 monoclonal antibody UCHT1 (ref. 11). They do, however, block PHA-induced Ca2+ mobilization. Anti-LFA-1, which reacts with the lymphocyte function-associated antigen, has no effect on intracellular Ca2+. These studies suggest that the sheep red blood cell receptor is an activation pathway for T cells and that the effects of PHA are mediated through this pathway.     

Millennial-scale climate change since the last glaciation recorded by grain sizes of loess deposits on the northeastern Tibetan Plateau

Whether climatic changes in high latitudes of the Northern Hemisphere since the last glaciation have effects on the Tibetan Plateau monsoon, and the variation characteristics of the Plateau monsoon itself are still not solved but of great significance. The 22-m high-resolution Ioess-paleosol sequence in the Hezuo Basin on the northeastern Tibetan Plateau demonstrates that the Plateau winter monsoon experienced a millennial variation similar to high latitude Northern Hemisphere, with cold events clearly correlated with Heinrich events but less for the warm events (Dansgarrd-Oeschger events). It may indicate that the climate system at high latitudes in the Northern Hemisphere had played an important role in both the Plateau monsoon and the high-level westerlies. On 10^4 year scale, there are two distinct anomalous changes, which are not found in the records from high latitude northern hemisphere, revealed by the loess grain size in the Hezuo Basin. One is that there was a considerable grain size increase at -36 kaBP, suggesting an abrupt enhancement of the Plateau winter monsoon at that time; the other is that, during 43--36 kaBP, the grain size decreased distinctly, indicating a notable weakening of the Plateau winter monsoon around that period. Both of the two anomalies suggest that the Tibetan climate may have been controlled by some other factors, besides the high latitude climatic changes in the Northern Hemisphere.     

东北梅花鹿种群活动节律和集群行为研究?

活动节律和集群行为是评价野生动物种群状态的重要参数.本研究自2012年11月至2013年12月在吉林珲春国家级自然保护区利用红外相机陷阱法对东北梅花鹿(Cervus nippon mantchuricus)种群的活动节律和集群行为进行了研究.结果表明东北梅花鹿全年日活动节律具有明显的双峰趋势,主要在晨昏前后活动,且日活动节律存在明显的季节性变化,春夏两季的活动强度较大,秋季次之,冬季的活动强度最小且持续时间最短;监测期内梅花鹿的平均集群大小为(1.42±0.03)只,集群大小和集群类型出现的频次在全年及各个季节间存在极显著差异,其中,1~2个个体出现的频次最高,主要集群类型为雌性单个个体和雄性单个个体,其次为雌性群和母子群.梅花鹿的行为表现差异受生活史特征、气温、日照长度和人类活动的季节性变化等环境条件的综合影响.     

近40年大尺度气候因子对中国洪涝灾害的可能影响

基于中国1980—2018年0.5°×0.5°逐日降水数据、紧急灾害数据库数据（EM-DAT）,分析了厄尔尼诺-南方涛动（ENSO）和北大西洋涛动（NAO）对中国极端降水频次及强度、洪水发生率及损失的可能影响．结论如下:1)当冬季厄尔尼诺发生后,次年我国东部沿海及黄河、长江下游地区秋季极端降水强度增加26%;当冬季拉尼娜发生后,次年我国东部地区春、夏季极端降水强度分别增加8.8%、5.1%．2)当NAO为正位相时,我国大部分地区春、夏、秋季极端降水频次较高,华东地区夏季极端降水强度增加8.5%．3)与正常年份相比,冬季厄尔尼诺或拉尼娜发生后,次年我国春季洪水损失偏多14.5%,秋季洪水发生率偏低30%;NAO为正位相时,我国春季洪水损失偏少20%,秋季洪水发生率偏高14%．4)当拉尼娜发生后及NAO正位相、负位相时,我国长江、黄河和珠江流域极端降水与洪涝灾害的变化具有一致性．      

Intraseasonal interaction between the Madden-Julian Oscillation and the North Atlantic Oscillation

Bridging the traditional gap between the spatio-temporal scales of weather and climate is a significant challenge facing the atmospheric community. In particular, progress in both medium-range and seasonal-to-interannual climate prediction relies on our understanding of recurrent weather patterns and the identification of specific causes responsible for their favoured occurrence, persistence or transition. Within this framework, I here present evidence that the main climate intra-seasonal oscillation in the tropics-the Madden-Julian Oscillation (MJO)-controls part of the distribution and sequences of the four daily weather regimes defined over the North Atlantic-European region in winter. North Atlantic Oscillation (NAO) regimes are the most affected, allowing for medium-range predictability of their phase far exceeding the limit of around one week that is usually quoted. The tropical-extratropical lagged relationship is asymmetrical. Positive NAO events mostly respond to a mid-latitude low-frequency wave train initiated by the MJO in the western-central tropical Pacific and propagating eastwards. Precursors for negative NAO events are found in the eastern tropical Pacific-western Atlantic, leading to changes along the North Atlantic storm track. Wave-breaking diagnostics tend to support the MJO preconditioning and the role of transient eddies in setting the phase of the NAO. I present a simple statistical model to quantitatively assess the potential predictability of the daily NAO index or the sign of the NAO regimes when they occur. Forecasts are successful in approximately 70 per cent of the cases based on the knowledge of the previous approximately 12-day MJO phase used as a predictor. This promising skill could be of importance considering the tight link between weather regimes and both mean conditions and the chances of extreme events occurring over Europe. These findings are useful for further stressing the need to better simulate and forecast the tropical coupled ocean-atmosphere dynamics, which is a source of medium-to-long range predictability and is the Achilles' heel of the current seamless prediction suites.     

应用E_2P_4浓度比判断雌性多浪绵羊和塔里木马鹿血浆P_4含量的波动

为了找出能够准确反映雌性哺乳动物体内血浆孕酮(P4)波动的检测方法,实验以多浪绵羊和塔里木马鹿为实验动物,分别对其发情周期各阶段的血液样本外周血雌二醇(E2),P4与促黄体生成素(LH)含量进行了放射免疫分析(RIA)测定。发现,应用E2 P4比值比传统的方法更能准确反映雌性哺乳动物体内血浆孕酮含量的波动情况。     

Pleistocene to Holocene extinction dynamics in giant deer and woolly mammoth

The extinction of the many well-known large mammals (megafauna) of the Late Pleistocene epoch has usually been attributed to 'overkill' by human hunters, climatic/vegetational changes or to a combination of both. An accurate knowledge of the geography and chronology of these extinctions is crucial for testing these hypotheses. Previous assumptions that the megafauna of northern Eurasia had disappeared by the Pleistocene/Holocene transition were first challenged a decade ago by the discovery that the latest woolly mammoths on Wrangel Island, northeastern Siberia, were contemporaneous with ancient Egyptian civilization. Here we show that another spectacular megafaunal species, the giant deer or 'Irish elk', survived to around 6,900 radiocarbon yr bp (about 7,700 yr ago) in western Siberia-more than three millennia later than its previously accepted terminal date-and therefore, that the reasons for its ultimate demise are to be sought in Holocene not Pleistocene events. Before their extinction, both giant deer and woolly mammoth underwent dramatic shifts in distribution, driven largely by climatic/vegetational changes. Their differing responses reflect major differences in ecology.     

Interannual precipitation variations in the mid-latitude Asia and their association with large-scale atmospheric circulation

This study analyzed the spatial differences of the precipitation variations in the mid-latitude Asia and their possible physical mechanisms during 1960–2009. The annual precipitation showed an opposite variations between the westerlies-dominated arid Central Asia (ACA) and monsoon-dominated North China (NC) during the study period. Given the different contributions of seasonal precipitation to annual total precipitation in ACA and NC, the atmospheric circulation anomalies during the major precipitation seasons (winter in ACA/summer in NC) were analyzed. In winter, negative North Atlantic Oscillation may cause negative height anomalies over the north side and positive anomalies over the south side of the ACA. Together, the enhanced pressure gradient and anomalous westerly wind brings more water vapor to ACA, and leaves less precipitation in NC. In summer, the low-pressure anomalies in Northeast China, along with a weaker summer monsoon and negative height anomalies in Eastern Europe together contribute to reduced (excessive) summer precipitation in NC (ACA). The interactions between ENSO and NAO may result in the opposite precipitation variations between ACA and NC. A significant 2–3-year cycle is identified in ACA, which is linked to the variations of westerly circulation in the middle troposphere.     

沙地放牧系统反刍家畜选择性采食行为的研究

分别在春、夏、秋、冬四季对蒙古牛和蒙古羊24小时放牧周期内的选择性采食行为进行了观测研究.研究结果表明:蒙古牛和蒙古羊均表现出一定强度的选择性采食行为,但蒙古牛和蒙古羊的食物构成具有明显不同.蒙古牛和蒙古羊的食物生态位宽度分别为0.64和0.67,二者无明显差异(P>0.05).蒙古牛春季的生态位宽度显著低于夏季,而与秋季和冬季类似;蒙古羊则以春季的生态位宽度最大,秋季最小.蒙古牛和蒙古羊的食物生态位重叠度为60%.     

Forced response of atmospheric oscillations during the last millennium simulated by a climate system model

Variations in global atmospheric oscillations during the last millennium are simulated using the climate system model FGOALS_gl. The model was driven by reconstructions of both natural forcing (solar variability and volcanic aerosol) and anthropogenic forcing (greenhouse gases and sulfate aerosol). The model results are compared against proxy reconstruction data. The reconstructed North Atlantic Oscillation (NAO) was out of phase with the Pacific Decadal Oscillation (PDO) in the last millennium. During the Medieval Warm Period (MWP), the NAO was strong while the PDO was weak. During the Little Ice Age (LIA), the NAO was weak while the PDO was strong. A La Niña-like state prevailed in the MWP, while an El Niño-like state dominated in the LIA. This phenomenon is particularly obvious in the 15th, 17th and 19th centuries. Analysis of the model output indicates that the NAO was generally positive during 1000?C1400 AD and negative during 1650?C1900 AD. There is a discrepancy between the simulation and reconstruction during 1400?C1650 AD. The simulated PDO generally varies in parallel with the reconstruction, which has a negative phase during the MWP and a positive phase during the LIA. The correlation coefficient between the reconstruction and simulation is 0.61, and the correlation is statistically significant at the 1% level. Neither the La Niña-like state of the MWP nor the El Niño-like state of the LIA is reproduced in the model. Both the reconstructed and the simulated Antarctic Oscillations had a negative phase in the early period of the last millennium and a positive phase in the late period of the last millennium. The Asian-Pacific Oscillation was generally strong during the WMP and weak during the LIA, and the correlation coefficient between the simulation and reconstruction is 0.50 for the period 1000?C1985 AD. The analysis suggests that the specified external forcings significantly affected the evolution of atmospheric oscillation during the last millennium.     

Synchronization of animal population dynamics by large-scale climate

The hypothesis that animal population dynamics may be synchronized by climate is highly relevant in the context of climate change because it suggests that several populations might respond simultaneously to climatic trends if their dynamics are entrained by environmental correlation. The dynamics of many species throughout the Northern Hemisphere are influenced by a single large-scale climate system, the North Atlantic Oscillation (NAO), which exerts highly correlated regional effects on local weather. But efforts to attribute synchronous fluctuations of contiguous populations to large-scale climate are confounded by the synchronizing influences of dispersal or trophic interactions. Here we report that the dynamics of caribou and musk oxen on opposite coasts of Greenland show spatial synchrony among populations of both species that correlates with the NAO index. Our analysis shows that the NAO has an influence in the high degree of cross-species synchrony between pairs of caribou and musk oxen populations separated by a minimum of 1,000 km of inland ice. The vast distances, and complete physical and ecological separation of these species, rule out spatial coupling by dispersal or interaction. These results indicate that animal populations of different species may respond synchronously to global climate change over large regions.     

亚欧阻塞高压的变化特征及其与重庆夏季降水的联系

使用国家气候中心(NCC)沿用的北半球阻塞高压监测公式,利用NCEP/NCAR逐日500hPa环流场再分析资料,计算出1961-2011年逐日阻高指数,分析了北半球阻塞高压出现的关键地区阻高指数的年际和年代际变化特征及其与重庆夏季降水的联系.结果表明,三个关键区阻高的季节分布以鄂霍次克海阻高在冬季和夏季出现的频率最高,而春季和秋季则是乌拉尔山阻高活动频繁的季节,贝加尔湖地区阻高活动不及前两个区域活跃.从变化趋势来看,乌拉尔山阻高和鄂霍次克海阻高有增强的趋势,贝加尔湖阻高有减弱的趋势.各关键区的阻高日数都存在2~5年的显著性周期特点.三个关键区对重庆夏季降水的影响各有其特点,贝加尔湖和鄂霍次克海的阻塞形势对重庆夏季降水的影响较大,鄂霍次克海阻高日数对重庆夏季降水的影响比其强度对重庆夏季降水的影响关系更加显著,夏季鄂霍次克海阻高日数偏多(少),重庆夏季降水偏多(少).     

求解一类非线性规划问题的新途径

给出了一类约束函数单调而目标函数非单调的非线性规划问题的一种新的求解方法。首先给出了将其目标函数单调化的一种方法，然后．通过这个方法将这类非线性规划问题转化为等价的单调规划问题，进而利用已有的关于单调函数的凸化、凹化方法，可将其转化为等价的凹极小问题或反凸规划问题以及标准DC规划问题．再利用已有的关于这些规划问题求全局极小点的方法，可以求得原问题的全局极小点。