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981.
基于同一区划方法、指标体系,使用1961—2014年辽宁省52站气象观测资料,分析辽宁省气温、气候区划指标、范围及界线的变动特征。结果表明:辽宁省年均气温在1988年发生一次突变,突变后气温开始显著上升;≥10 ℃积温日数比较显著地响应气温突变,而干燥指数、7月平均气温变化不显著。在空间分布上区划指标值均存在不同程度的变化。① 全省≥10 ℃积温日数均出现增加,但在中西部地区显著增加;② 在盘锦-抚顺一线以北(南),气候总体呈不显著变湿(干)趋势;③ 7月平均气温呈缓慢上升趋势。区划范围及界线位置出现更加显著地变化:① 暖温带范围主要向北向东扩展,中温带向东收缩;② 半湿润区范围主要向北向西扩展,半干旱区向西北方向收缩,湿润区范围基本不变;③ Tb范围显著向北向东扩展,Ta范围向北向东收缩。在此基础上分析了气候格局变化的可能气候成因,发现突变后≥10 ℃积温日数期间500 hPa高度场增加与4月和10月东亚冬季风减弱,4—10月东北冷涡持续天数增加和7月500 hPa高度场增加,可能分别是温度带,Tb区、Ta区和半湿润区、半干旱区变化的原因。  相似文献   
982.
以分布式认知理论为基础,采用质性研究法、数量分析法以及GIS空间分析技术,探讨日喀则市藏族、汉族居民对城市空间环境认知的异同性。研究表明,藏族对城市空间环境的认知得分高于汉族对城市空间环境的认知得分。藏族、汉族对城市空间环境的认知水平可分为高、中、低3类。认知空间呈现圈层结构与混合结构模式,可分为藏汉一致性、藏族独立以及汉族独立3种认知空间类型。影响居民对城市空间环境的认知因素有共性因素和差异性因素。景观走廊质量、宜居性、基础设施两项是藏族居民关注的主要影响因素,汉族居民更关注公共服务设施的服务能力以及对当地文化的融入感。  相似文献   
983.
利用福州中心城区的社会调查、POI、道路网、用地性质等数据,在社区尺度探究城市建成环境对居民休闲型中高强度体力活动的影响。研究发现:低密度土地利用与体力活动时长呈正向关联,功能单一和邻近主干道则对体力活动起到抑制作用。体力活动目的地对不同人群具有差异化影响,体育用地和付费运动场所仅能促进中高阶层和中高收入者的体力活动,而周边公共运动设施的丰富程度更具普适性意义。通过纳入运动偏好和单独分析保障房、单位大院及房改房住户达到规避居住自选择的目的,证明上述建成环境特征对体力活动的影响是独立且稳健的。  相似文献   
984.
Understanding the feeding selectivity on phytoplankton by shellfish is currently a big challenge.In order to investigate the feeding behavior of bay scallop(Argopecten irradians)on phytoplankton,we compared its compositions of phytopigments in digestive glands with those in the surrounding seawater,and conducted five consecutive investigations between July and November 2016 in a bay scallop culture area along coast of Qinghuangdao City,northwest of the Bohai Sea,China.Phytopigments in four-size fractionated phytoplankton of seawater(micro-(20-200 μm);nano(L)-[10-20 μm];nano(S)-[2.7-10 μm],and pico-[2.7 μm])and digestive glands of A.irradians were examined to investigate the selective feeding of A.irradians.Results show that fucoxanthin and peridinin constituted the major part of taxonomically diagnostic carotenoids(TDCs)in the micro-and nano(L)-phytoplankton in seawater.Compared with total phytoplankton biomass of seawater(TPB,sum of the four sizes),a substantial decrease of fucoxanthin proportion to total DCs in digestive glands was observed while that of peridinin,19'-butanoyloxyfucoxanthin,alloxanthin and 19'-hexanoyloxy-fucoxanthin showed an obvious increase when those pigments were mainly confined to micro-sized phytoplankton(20-200 μm).However,zeaxanthin and prasinoxanthin were mainly confined to nano(s)-and pico-phytoplankton,of which the proportions in digestive glands were usually lower in TPB.The contribution of lutein to total DCs in digestive glands(with an average of 7.23%)increased compared with TPB of seawater(with an average of 0.63%)during all five sampling times.  相似文献   
985.
Ran  Weimin  Luan  Xiwu  Lu  Yintao  Liu  Hong  Yang  Jiajia  Zhao  Yang  He  Wenchang  Yan  Zhonghui 《中国海洋湖沼学报》2019,37(1):47-61

Analysis of 2D seismic data over 4 500 km in length from the Madura Strait Basin in the East Java Sea reveals seismic reflection characteristics of reefs and associated sedimentary bodies, including asymmetrical or symmetrical dome reflections, slope progradational reflections, chaotic reflections and discontinuous strong reflections inside the reef, which onlap the flank of the reef. It is concluded that the developmental paleo-environment of most reefs is mainly conducive to shallow marine carbonate platform facies and platform margin facies, based on well core data, variations in seismic facies and strata thickness. The formation and evolution of all reefs are primarily influenced by the tectonic framework of the Madura Strait Basin. Platform margin reefs are principally controlled by two types of structures: one is a series of E-W trending Paleogene normal faults, and the other is an E-W trending Neogene inversion structures. In addition, wave actions, tidal currents and other ocean currents play an accelerated role in sorting, rounding and redeposition for the accumulation and evolution of reefs. Tertiary reefs in the MSB can be divided into four types: 1) an open platform coral reef of Late Oligocene to Early Miocene, 2) a platform margin coral reef controlled by normal faults in Late Oligocene to Early Miocene, 3) a platform margin Globigerina moundreef controlled by a “hidden” inversion structure in Early Pliocene, and 4) a platform margin Globigerina mound-reef controlled by thrust faults in the early Pliocene. Patterns of the formation and evolution of reefs are also suggested.

  相似文献   
986.
The geographic al variations in life history characteristic s of small yellow cro aker Larimich thys polyactis,caused by experienced different environmental conditions,have been observed in China seas.Previous studies based on spatial distribution,migration route,and body morphometrics suggested a complex stock structure.In this study,to clarify the source of a spawning stock,we investigated the reproduction strategy and inter-structure of the Haizhou Bay(HZB)spawning stock in the middle Yellow Sea from both egg survey and adult otolith increment analysis.Egg and adult samples were collected from three surveys during spawning season in 2013.Distinct spatial and temporal variations were detected in egg distribution and size,and otolith shape analy sis of adult fishes revealed two morphotypes with different increment growth using random forest cluster.The results indicate the existence of two components within the same spawning stock in HZB from different wintering grounds,and accordingly special protection should be required for this stock given the significance to maintain connectivity between adj acent subpopulations.  相似文献   
987.
Dam removal is becoming an effective approach for aquatic biodiversity restoration in damming river in order to balance the aquatic ecosystem conservation with large-scale cascade damming. However, the effects of dam removal on fish communities in Asian mountainous rivers, which are dominated by Cypriniformes fishes, are still not well known. To determine whether dam removal on a mountainous river benefit restoration of fish diversity, we investigated the response of fish assemblage to dam removal using a before-after-control-impact design in two tributaries of the Lancang River(dam removal river: the Jidu River, and control river: the Fengdian River). Fish surveys were conducted one year prior to dam removal(2012) and three years(2013–2015) following dam removal. We observed rapidly and notably spatio-temporal changes in fish biodiversity metrics and assemblage structure, occurring in the Jidu River within the first year after dam removal. Overall, fish species richness, density and Shannon-Wiener diversity all increased immediately in above-and below-dam sites, and maintained a stable level in subsequent years, compared to unchanged situation in the control river. All sites in the Jidu River experienced shifts in fish composition after dam removal, with the greatest temporal changes occurred in sites below-and above-the former dam, resulting in a temporal homogenization tendency in the dam removed river. These findings suggest that dam removal can benefit the recovery of habitat conditions and fish community in Asian mountainous rivers, but the results should be further evaluated when apply to other dammed rivers since the dam age, fluvial geomorphology and situation of source populations could all affect the responses of fish assemblages.  相似文献   
988.
The Lancang-Mekong River has attracted much attention from researchers, but the cooperation on water issues in this river basin has been limited, even after the establishment of the Mekong River Commission(MRC). Cooperation on water resources has been determined as one of the key priority areas in the Lancang-Mekong Cooperation Mechanism, but there are no details of targets. In order to establish the priorities of water cooperation under the mechanism, we adopted nine categories to classify the objectives of 87 water cooperation events based on the ‘Lancang-Mekong Water Cooperative Events Database' from 1995 to 2015. Based on the occurrence of cooperative events, cooperative objectives, cooperative scales, and approaches to cooperation, we conducted statistical, correlation, and text analyses. Our analyses indicated the following results: under the impact of economic conditions inside and outside the river basin, full cooperation appeared more difficult than bilateral and multilateral cooperation. Each of the partners adopted different preferences for cooperation targets. Cooperation with more definite objectives was easier to establish than cooperation with broader and more complex objectives. The potential objectives for water cooperation were navigation, hydropower, joint management, data sharing, flood control and water use. Because hydropower development is controversial, and because water cooperation is avoided by most existing regional cooperation mechanisms due to its complexity, we suggest the following priority areas for water cooperation in the Lancang-Mekong River Basin. 1) Navigation and flood control/drought relief are attractive objectives for all the riparian countries across the whole watershed. 2) Data sharing should be a priority for cooperation in the watershed due to its laying the foundation for the equitable and reasonable utilization of transboundary waters. 3) Hydropower is an objective best implemented mainly through bilateral cooperation, and on tributaries.  相似文献   
989.
Xiong  Ying  Chen  Yun  Peng  Fen  Li  Jingzhi  Yan  Xiaojing 《地理学报(英文版)》2019,29(8):1346-1362
Journal of Geographical Sciences - Urban land intensive use is an important indicator in harmonizing the relationship between land supply and demand. The system dynamics (SD) can be used to...  相似文献   
990.
With the goal of model fitting species abundance distribution patterns of the tree, shrub and herb layers of the natural Toona ciliata community in Xingdoushan Nature Reserve, Enshi Autonomous Prefecture, Hubei Province, we used the data collected from the field survey and employed different ecological niche models. The models tested were the broken stick model (BSM), the overlapping niche model (ONM) and the niche preemption model (NPM), as well as three statistic models, the log-series distribution model (LSD), the log-normal distribution model (LND) and the Weibull distribution model (WDM). To determine the fitted model most suitable to each layer, the fitting effects were judged by criteria of the lowest value of Akaike Information Criterion (AIC), Chi-square and the K-S values with no significant difference (P>0.05) between the theoretical predictions and observed species abundance distribution values. The result showed: (1) The fitting suitability and goodness of fit of the tree, shrub and herb layers by using the three ecological niche models were ranked as: NPM>BSM>ONM. Of the three statistical models, by accepting the fitting results of the three layers, WDM was the best fitting model, followed by LND. By rejecting the fitting tests of the herb layer, LSD had the worst fitting effect. The goodness of the statistical models was ranked as: WDM>LND>LSD. In general, the statistical models had better fitting results than the ecological models. (2) T. ciliata was the dominant species of the tree layer. The species richness and diversity of the herb layer were much higher than those of either the tree layer or the shrub layer. The species richness and diversity of the shrub layer were slightly higher than those of the tree layer. The community evenness accorded to the following order: herb>shrub>tree. Considering the fitting results of the different layers, different ecological niche models or statistical models with optimal goodness of fit and ecological significance can be given priority to in studying the species abundance distribution patterns of T. ciliata communities.  相似文献   
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