长江三峡大宁河流域3000年来的环境演变与人类活动

长江三峡大宁河流域张家湾东周-汉代古遗址的孢粉学和沉积学等分析结果表明3000年来该区环境演变与人类活动的互动影响，连续的孢粉和粒度记录证实，该区古人类活动初期处于暖湿的气候，东周-汉代时期转变为温凉略干的温带气候，东周-汉代后，该区经历了一次规模较大的大宁河洪水泛滥期，导致汉代文化层中断。此后不久，由于人类活动剧烈，自然植被严重破坏，水土流失比较严重，山洪灾害频繁，导致汉代之后该区没有连续的文化层堆积，而由于人类活动剧烈，自然植被严重破坏，水土流失比较严重，山洪灾害频繁，导致汉代之后该区没有连续的文化层堆积，而由于短暂洪水暴发引起大面积坡面片流，导致坡积物的大量堆积，汉代之后该区频繁的兴涝灾害和山洪灾害体现了人地关系的复杂性。     

Population,urbanization and economic scenarios over the Belt and Road region under the Shared Socioeconomic Pathways

The countries throughout the Belt and Road region account for more than 60% of the world's population and half of the global economy. Future changes in this area will have significant influences on the global economic growth, industrial structure and resource allocation. In this study, the proportion of the urban population to the total population and the gross domestic product were used to represent the levels of urbanization and economic development, respectively. The population, urbanization and economic levels of the Belt and Road countries for 2020–2050 were projected under the framework of the IPCC's shared socioeconomic pathways(SSPs), and the following conclusions are drawn.(1) The population, urbanization and economic levels in the Belt and Road region will likely increase under all five pathways. The population will increase by 2%–8%/10 a during 2020–2050 and reach 5.0–6.0 billion in 2050. Meanwhile, the urbanization rate will increase by 1.4%–7.5%/10 a and reach 49%–75%. The GDP will increase by 17%–34%/10 a and reach 134–243 trillion USD.(2) Large differences will appear under different scenarios. The SSP1 and SSP5 pathways demonstrate relatively high urbanization and economic levels, but the population size is comparatively smaller; SSP3 shows the opposite trend. Meanwhile, the economy develops slowly under SSP4, but it has a relatively high urbanization level, while SSP2 exhibits an intermediate trend.(3) In 2050, the population will increase relative to 2016 in most countries, and population size in the fastest growing country in Central Asia and the Middle East countries will be more than double. Urbanization will develop rapidly in South Asia, West Asia and Central Asia, and will increase by more than 150% in the fastest growing countries. The economy will grow fastest in South Asia, Southeast Asia and West Asia, and increase by more than 10 times in some counties with rapid economic development.     

Effects of land use and cultivation time on soil organic and inorganic carbon storage in deep soils

The vertical distribution and exchange mechanisms of soil organic and inorganic carbon(SOC, SIC) play an important role in assessing carbon(C) cycling and budgets. However, the impact of land use through time for deep soil C(below 100 cm) is not well known. To investigate deep C storage under different land uses and evaluate how it changes with time, we collected soil samples to a depth of 500 cm in a soil profile in the Gutun watershed on the Chinese Loess Plateau(CLP); and determined SOC, SIC, and bulk density. The magnitude of SOC stocks in the 0–500 cm depth range fell into the following ranking: shrubland(17.2 kg m~(-2)) grassland(16.3 kg m~(-2)) forestland(15.2 kg m~(-2)) cropland(14.1 kg m~(-2)) gully land(6.4 kg m~(-2)). The ranking for SIC stocks were: grassland(104.1 kg m~(-2)) forestland(96.2 kg m~(-2)) shrubland(90.6 kg m~(-2)) cropland(82.4 kg m~(-2)) gully land(50.3 kg m~(-2)). Respective SOC and SIC stocks were at least 1.6-and 2.1-fold higher within the 100–500 cm depth range, as compared to the 0–100 cm depth range. Overall SOC and SIC stocks decreased significantly from the 5 th to the 15 th year of cultivation in croplands, and generally increased up to the 70 th year. Both SOC and SIC stocks showed a turning point at 15 years cultivation, which should be considered when evaluating soil C sequestration. Estimates of C stocks greatly depends on soil sampling depth, and understanding the influences of land use and time will improve soil productivity and conservation in regions with deep soils.     

A hybrid integrated deep learning model for the prediction of citywide spatio-temporal flow volumes

ABSTRACT

The spatio-temporal residual network (ST-ResNet) leverages the power of deep learning (DL) for predicting the volume of citywide spatio-temporal flows. However, this model, neglects the dynamic dependency of the input flows in the temporal dimension, which affects what spatio-temporal features may be captured in the result. This study introduces a long short-term memory (LSTM) neural network into the ST-ResNet to form a hybrid integrated-DL model to predict the volumes of citywide spatio-temporal flows (called HIDLST). The new model can dynamically learn the temporal dependency among flows via the feedback connection in the LSTM to improve accurate captures of spatio-temporal features in the flows. We test the HIDLST model by predicting the volumes of citywide taxi flows in Beijing, China. We tune the hyperparameters of the HIDLST model to optimize the prediction accuracy. A comparative study shows that the proposed model consistently outperforms ST-ResNet and several other typical DL-based models on prediction accuracy. Furthermore, we discuss the distribution of prediction errors and the contributions of the different spatio-temporal patterns.     

从全球生产网络到全球金融网络：理解全球-地方经济联系的新框架

全球化带来的新国际劳动分工使全球生产网络(Global Production Network, GPN)成为研究全球经济与区域发展的重要框架。与此同时,金融在现代社会经济运行中的地位日益提升,经济金融化在全球不同尺度下深刻影响着经济活动的空间分布和网络。因此,金融已经成为GPN研究不能忽略的重要环节。更重要的是,金融化带来的逻辑也日益深刻地影响到GPN的演化和运行。尽管GPN研究日益重视金融的作用,并开始研究金融业的全球生产网络,但是随着越来越多的企业通过获得国际股权投资或者在境外资本市场上市等方式融入全球资本市场,主要从生产角度理解地方经济融入全球过程的GPN难以对该现象深入分析。全球金融网络(Global Financial Network, GFN)为刻画和分析这个过程提供了新的框架。在这个分析框架中,地方经济体通过高级商业服务业(Advanced Business Service, ABS)企业与世界城市(国际金融中心)和离岸管辖区产生联系,从而融入GFN。论文介绍了GFN的基本结构,探讨了地方经济融入GFN的主要方式及其产生的影响。最后,提出GFN未来在理论和实证方面可继续深入研究的方向。     

基于VIC模型与集合卡尔曼滤波的土壤水分同化研究

基于可变下渗能力水文模型(Variable Infiltration Capacity,VIC)和集合卡尔曼滤波(Ensemble Kalman Filter,EnKF)算法发展了一种土壤表层水分的数据同化方案,并在新疆维吾尔自治区的森林、高盖草和低盖草3种植被覆盖类型地区进行试验。在同化过程中,有强降水存在时,3种植被覆盖类型的同化值均比实际测量值高;降水较少时,高盖草和低盖草两种类型的同化值比实际测量值略低,而在森林地区,同化值比实际测量值略高。总体上,该同化方案得到的结果比VIC模拟得到的结果更接近于实际测量值,取得较好同化效果。     

云南省洱源县血吸虫病疫情分析

根据2009年血吸虫调查资料,对洱源县的血吸虫基本情况、螺情、病情、年度疫情变化进行综合研究,结果表明:洱源县的有螺地主要分布在炼铁乡、乔后镇、茈碧湖、邓川镇、右所镇、牛街乡、三营镇、凤羽乡。经过多年的防控,有螺面积从2004年的1074万m2下降至432万m2,阳性钉螺行政村由45个下降到0,阳性钉螺点由460个下降到0个,全县人畜感染率分别从2004年的9.18%、6.03%下降至2009年的0.15%、0.33%。     

地表覆盖对坡面流流速影响的模拟试验

植被覆盖对坡面流流速的影响,会引起坡面输沙特征的改变,但在陡坡条件下盖度与流速的响应关系尚不明确.针对目前国内外研究的不足,本研究采用变坡实验水槽在较大坡度(5°～ 25°)、流量(0.25 ～2 L/s)和盖度(0％～25％)范围内,系统研究了坡面流平均流速与盖度、坡度、流量之间的关系.结果表明:坡面流流速在0.15～ 1.35 m/s内变化,流速与盖度、坡度和流量关系密切.随着地表模拟盖度的增加,水流克服覆盖物的阻碍作用而消耗的能量越多,水流流速随之减小.随着坡度和流量的增加,坡面流重力势能与水流动能增加,因此流速随坡度和流量呈幂函数增加.通过统计回归发现,盖度对流速的影响最大,占45％左右,坡度和流量次之.三个因子可以较好模拟陡坡、定床条件下水流流速(R2 =0.93).研究结果有助于认识陡坡地表覆盖下坡面流的水动力学特性,为建立土壤侵蚀过程模型提供理论基础.     

全新世以来浙江地区史前文化对环境变化的响应

对浙江地区史前文化的时空分布进行比较研究, 发现4000 cal. a BP前本区史前文化遗址在空间上不断扩大, 较为显著的扩大曾发生过两次, 一次发生在马家浜-河姆渡文化时期, 另一次发生在良渚文化时期;同时以河流谷地为通道, 史前文化从西向东不断向沿海扩展。4000 cal. a BP后, 以马桥文化为代表的各史前文化地域明显收缩, 东向沿海扩散的趋势终止, 同时伴随有南北两种不同模式的生产方式和经济形态转变。浙江地区史前文化分布与全新世海面波动有显著的关系, 尤其是杭州湾两岸的史前文化遗址分布与海面变化的关系最密切, 7000 cal. a BP 以来的低海面-海退成陆过程为史前居民提供了广阔的陆地生存空间。浙江地区史前文化变迁与环境变化在时相上具有一致性, 对比天目山千亩田泥炭和东海内陆架泥质沉积的环境演变记录表明, 4000 cal. a BP前浙江地区史前文化的东向地域扩展是在全新世气候适宜期背景下进行的, 是农业文明和海洋文明共同作用下的扩展和延伸;而4000cal. a BP后史前文化的地域收缩是在气候干冷和沿海海洋环境恶化的背景下发生的。以上初步证明浙江地区史前文化的发展、扩张和收缩与环境变化呈显著的正相关, 而气候环境变化正是引起上述这种变化以及生产方式和经济形态变化的深层次原因。因此, 气候环境成为浙江史前文化变迁的重要影响因子, 其对文化的分布、传播、扩展和演变等都产生了重要影响。     

金沙江下游地区人类活动对土壤侵蚀的影响

土壤侵蚀发生发展过程受自然因素和社会经济因素的共同作用。社会经济因素通过驱动人类活动间接作用于侵蚀过程,已成为土壤侵蚀的主要因素。作为长江流域土壤侵蚀最为严重的地区,金沙江下游独特的自然环境条件是造成其土壤侵蚀严重的基本条件,而不合理的人类活动加剧了这一过程。通过分析金沙江下游地区植被破坏、农业耕作、工程建设这三方面的人类活动对该地区的土壤侵蚀的影响,以及针对不合理人类活动所实施的恢复措施和政策,总结目前对人类活动影响土壤侵蚀过程认识的局限以及未来研究的方向。分析认为,争取认识金沙江下游干热气候的形成机制以及对人工生态系统的全面、系统、宏观评价,是建立正确的植被恢复策略的知识基础;农业耕作方面则应转换目前的研究重心,不应把过多精力集中在技术的改进和创新上,对于政策和市场经济对当地农民行为的驱动作用应予以相当的重视,并寻求改变山区农民顺坡陡坡耕作习惯的新思路和新方法;而工程建设方面则应加强监测与基础研究,特别是公路建设引发的土壤侵蚀情况。