2021年度自然科学基金申请书关键词透视地理科学研究前沿热点与发展方向

地理科学是提升人类对地球表层认知、探索人地关系、解决资源、环境、发展所面临的复杂问题的重要支撑。引领科学发展,支撑领域人才队伍的建设与培育,是国家自然科学基金委员会的使命与职责。追踪地理科学领域前沿,优化学科布局并开展战略引导是基金委地理科学学科工作的重要任务。以2021年国家自然科学基金地理科学领域4 479项申请书为样本,运用词云分析方法,对申请书的关键词进行统计分析,剖析了地理科学及各分支学科的研究热点。结果表明：“深度学习”“气候变化”“生态系统服务”“高光谱遥感”“青藏高原”“可持续发展”等是2021年地理科学研究内容与方法的热点关键词。在分支学科间交叉融合方面,信息地理学与人文地理学的共现关键词主要有“空间分析模型”“地理信息系统”“遥感”“机器学习”等;自然地理学与人文地理学的共现关键词主要有“生态系统服务”“土地利用”“土地利用变化”“可持续发展”“情景分析”等;自然地理学与信息地理学的共现关键词主要有“遥感监测”“尺度效应”“机器学习”“数字土壤制图”等。未来,国家自然科学基金委员会将从关键词设置、学科间交叉融合等途径入手,进一步从战略层面优化地理科学研究布局,引导科学家聚焦地理学基础理论与热点前沿问题,服务碳中和、乡村振兴等国家重大战略需求。     

Anthropogenic origin of a change in the fire-climate relationship in northern China after ~2000 yr BP: Evidence from a 15,500-year black carbon record from Dali Lake

There are debates regarding whether a wet and warm climate or a dry and cold climate dominated Holocene fire activity in northern China on the millennial timescale, and when human activities overtook climate change as the dominant control on fire occurrence in the region. Here we present a high-resolution fire history for the past ~15,500 years from a sediment core in Dali Lake, located in the foothills of the Greater Hinggan Mountains, one of the areas of highest fire risk in China. The results demonstrate that fire activity was rare during the last deglaciation (~15,500-11,700 yr BP), gradually increased at the beginning of the Holocene, and reached its highest level during ~9000-5000 yr BP, after which there was a decreasing trend. However, after ~2000 yr BP this decreasing trend ended, and the most prominent feature is a peak in fire activity during the Medieval Warm Period (MWP). Overall, fire activity corresponded well to changes in the East Asian summer monsoon (EASM) precipitation on the millennial timescale during ~15,500-2000 yr BP, but this relationship changed after ~2000 yr BP. We propose that fire activity in northern China on the millennial timescale during ~15,500-2000 yr BP was dominated by the biofuels reserve under the control of the EASM precipitation. In contrast, with the intensification of human activities after ~2000 yr BP, human activity caused a ~62%-73% increase in fire activity, which altered the fire-climate relationship that had previously prevailed in northern China. Our results indicate that a wet-warm climate (increased EASM intensity), rather than a dry-cold climate, was the dominant control on fire activity in northern China during 15,500-2000 yr BP on the millennial timescale, but that human activities played an important role in fire occurrence after ~2000 yr BP.     

长三角城市土地扩张与人口增长耦合态势及其驱动机制

长三角是中国城市土地快速变动和人口快速集聚的热点地区,厘清并协调城市土地扩张与人口增长间的关系,对统筹区域土地资源合理配置,调控人口流动及实现新型城镇化意义重大。以长三角16个城市为研究对象,采用重心耦合模型和基于人均约束性构建的协调性系数,对1994-2012年城市土地扩张与人口增长的总体耦合态势及演变、空间耦合特征及格局进行分析,并探讨影响城市土地扩张与人口增长耦合的驱动机制。结果表明：① 长三角城市土地扩张速度整体快于人口增长速度,二者增长具有明显的阶段特征和显著的空间差异特征。② 长三角城市土地扩张与人口增长耦合关系处于不断变化过程中,人地耦合关系整体上呈现出增强—减弱—增强的态势,土地重心与人口重心间的距离不断缩小,土地扩张与人口增长间协调性逐步增强;城市土地扩张与人口增长空间耦合类型中,人口过快增长型和人地基本协调型数量有所减少,但其在空间分布上呈现集中的趋势;土地快速扩张型的数量有所增加,在空间上呈现扩散的趋势,各城市人地配置协调程度不高。③ 经济发展、产业结构升级调整、交通发展与区位条件变化、政策因素等是影响长三角城市土地扩张与人口增长及其耦合变化的重要驱动因素。     

The dynamic mechanism of post-rift accelerated subsidence in Qiongdongnan Basin, northern South China Sea

A 1-D unloaded tectonic subsidence (air-loaded tectonic subsidence) model is proposed and applied to the Qiongdongnan Basin. Results show that three episodes of subsidence exist in Cenozoic, that is, syn-rift rapid subsidence (Eocene–Oligocene) with subsidence rate at 20–100 m/m.y., post-rift slow thermal subsidence (early-middle Miocene) around 40 m/m.y., and post-rift accelerated subsidence (since late Miocene) 40–140 m/m.y., which is substantially deviated from the exponentially decayed thermal subsidence model. For exploring the mechanism of post-rift accelerated subsidence, the faulting analyses are conducted and results show that there is a dramatically decrease in the numbers of active faults and fault growth rate since 21 Ma, which indicates that no active brittle crust extension occurred during post-rift period. Furthermore, previous studies have demonstrated that the stretching of the upper crust is far less than that affecting the whole crust. Therefore, we infer that the lower crust thinned during the post-rift period and a new model of basin development and evolution is put forward to explain the post-rift accelerated subsidence and depth-dependent crust thinning in the Qiongdongnan Basin, which is supported by gravity data.     

1969年渤海7．4级地震区地质构造和发震构造的初步研究

根据石油地质勘探资料和地震学等研究的成果,对1969年渤海7.4级地震的构造条件作了具体而较深入的分析,填补了华北渤海大震区地震构造研究的空白.震区位于渤海湾新生代裂陷盆地的东部,地处北北东向营潍断裂带与北西向北京-蓬莱断裂带交汇的地区.早第三纪断陷阶段,该区于地壳上部主要发育北北东、北西和东西向3组断裂,呈铲状和平面状形态,正断性质,多属断陷主断裂.晚第三纪以来的拗陷阶段,先存断裂有不同程度的活动;同时还新发育一条北东向黄河口-庙西北断裂带.7.4级地震的震源断层走向为北东45°,倾向南东,近于直立,呈右旋走滑性质,埋藏于15～34km的深度范围.大震的发震断裂不是营潍断裂带,而是黄河口-庙西北新生断裂带.     

区域伸展体制下盆—山构造耦合关系的探讨——以渤海湾盆地和太行山为例

根据地质、地球物理和构造地貌等资料研究了渤海湾盆地和太行山之间的耦合关系。盆地和山脉是在晚白世形成的结山准平原上经新生代裂陷作用产生的。盆地阶段性下沉与山区间歇性抬升彼此相应，相反相成。盆山之间的太行山山前断裂带是上地壳中的大型拆离构造，沿它拉张滑脱而盆降、山隆；区内现今地壳上地幔结构等差异可能是盆－山构造发育过程中形成的，总体为分层拆离、脆韧转换和伸展－收缩组合而成的岩石圈结构构造剖面。盆地和山脉具统一的形成机制和同一动力条件，盆地深部软流圈上隆和侧向分流导致岩石圈地幔和下地壳自下而上同向锁流变，不仅托曳传力使上覆壳层拉张裂陷成盆，而且往西推挤山区相同层圈的物质使之缩短增厚并隆升，为盆地伸展让位；山半随盆地发育而形成。     

济阳坳陷车西洼陷异常高压与储层孔隙度的关系

根据研究区测井、测试、岩石物性等资料,讨论分析了异常高压与储层孔隙度的关系。车西洼陷沙河街组沙三段与沙四上亚段地层中存在异常地层压力,主要分布于深洼带和斜坡前缘。异常高压带地层压力与孔隙度有良好的相关性,主要表现在以下几个方面:异常高压使得储集空间得以保存;通过促进溶解作用而形成大量次生孔隙;异常高压作用下形成微裂缝,极大地改善了地层储集性能。根据异常压力与孔隙度的相关性,预测了车西洼陷沙四上亚段的孔隙度特征。     

黏土失水开裂演化过程的影响试验

裂隙性为黏土的主要特性之一。探讨黏土的开裂规律,对于分析地裂缝成因机理,开展预测研究具有重要的理论意义和工程价值。通过室内试验,研究了黏土干燥收缩过程中含水率的变化规律。分别制备不同厚度、宽度、含砂量的试样,获得不同条件下黏土失水过程含水率的变化规律。在试验所设定的条件下,土体开裂时的含水率很接近,平均约为33.48%;当样品宽度不变时,土层越厚,含水率变化速率越小;当样品厚度相同时,宽度不同,含水率变化速率几乎相同;当厚度、宽度都相同时,含水率变化速率随含砂量的增大而减小。对于同一样品,土体厚度越大,样品裂隙率越小;土体厚度相同时,样品的裂隙率随着样品宽度的增大先减小后增大,且样品的开裂周期与样品的裂隙率同步变化。     

Chemical weathering over the last 1200 years recorded in the sediments of Gonghai Lake,Lvliang Mountains,North China: a high‐resolution proxy of past climate

Increasing interest in global climate change has led to attempts to understand and quantify the relationship between chemical weathering processes and environmental conditions, especially climate. This interest necessitates the identification of new climate proxies for the reconstruction of two important Earth surface processes: physical erosion and chemical weathering. In this study, an AMS ¹⁴C‐dated 2.8‐m‐long sediment core, GH09B1, from Lake Gonghai in north‐central China was subjected to detailed geochemical analyses to evaluate the intensity of chemical weathering conditions in the catchment. Multivariate statistical analysis of major and trace elemental data of 139 subsamples revealed that the first principal component axis PCA1 explained ～53% of the variance in the assemblage of elements/oxides with significant positive correlations between PCA1 scores and the separation of mobile and soluble elements/oxides from the immobile and resistant elements/oxides, which is thus able to indicate the chemical weathering in the catchment. These results are supported by the down‐core trends of other major and trace elemental ratios of chemical weathering intensity as well as by pollen data from the same core. Variations in PCA1, chemical index of alteration (CIA), Rb/Sr ratio and other oxides ratios indicate stronger chemical weathering due to a wet climate during the Medieval Warm Period (MWP). However, the MWP was interrupted by an interval of relatively weaker chemical weathering conditions from AD 940–1070. Weak chemical weathering under a dry climate occurred during the Little Ice Age (LIA), and increased chemical weathering intensity during the Current Warm Period (CWP). Our proxy records of chemical weathering over the last millennium correlate well with the available proxy records of precipitation from Gonghai Lake as well as with the speleothem oxygen isotope record from Wanxiang Cave, but do not show a significant correlation with the temperature record in N China, suggesting that the chemical weathering intensity in the study area was mainly controlled by the amount of rainfall rather than by temperature. We conclude that high resolution lacustrine sediment geochemical parameters can be used as reliable proxies for climate variations at centennial‐decadal time scales.     

基于区域密度函数的兰—西城市区域人口聚散研究

以兰州—西宁城市区域县级行政单元三普四普五普以及2009年人口数据为依托,运用探索性空间数据分析技术研究了兰州—西宁城市区域人口分布,发现该区域存在3个人口高密度中心。根据单中心密度函数与多中心密度函数拟合结果的比较,发现采用基于平方根负指数模型的多中心区域密度函数能够很好地阐述研究区域的人口集聚与扩散。研究发现,区域内存在两种人口集聚与扩散模式,兰州城区与西宁城区呈现出向心集聚的特征,而临夏市则为弱中心式扩散。