2001—2020年黄河流域植被覆盖变化及其影响因素

基于MODIS NDVI植被指数和气象数据集,以集合经验模态分解、趋势分析和随机森林回归分析等方法,分析了黄河流域2001—2020年植被覆盖时空变化特征,并对其气候驱动因素进行探讨。结果表明：（1）2001—2020年黄河流域植被覆盖整体呈显著增长趋势,增速为0.055/10a （P<0.05）,2010年之前增速（0.067/10a）大于2010年之后的增速（0.051/10a）。（2）空间上,植被覆盖增加区域主要分布在陕北黄土高原、甘肃省东南部、内蒙古自治区河套平原等退耕还林还草生态工程实施区域,而植被覆盖显著下降区域则集中在关中平原城市群、黄淮海平原以及青藏高原等区域。（3）气温、降水和CO₂浓度等对黄河流域植被生长起到正向促进作用,且绝对敏感性依次降低,而大气饱和水汽压差、太阳辐射等对植被生长起到抑制作用。本研究结果可为评估气候变化对黄河流域植被覆盖变化的综合影响提供参考依据。     

台风水汽稳定同位素组成与天气过程的关系——以2015 年13 号台风“苏迪罗”为例

基于台风“苏迪罗”（1513）影响前后南京实时高频监测的水汽稳定同位素数据,并结合再分析资料、HYSPLIT后向轨迹模型分析了大气水汽δ¹⁸O与天气过程之间的关系以及大气水汽过量氘所指示的水汽来源。结果表明,1）整个台风影响过程水汽δ¹⁸O先保持基本不变后一直下降的趋势,而水汽过量氘则呈现完全相反的变化趋势。2）根据台风“苏迪罗”影响前后南京水汽δ¹⁸O变化特征,将其划分为3个阶段：Ⅰ阶段水汽δ¹⁸O较高与南京地区较为稳定的大气条件相对应,水汽过量氘值较低指示南京地区主要受海洋水汽影响;Ⅱ阶段台风环流及其残压和北方南下冷空气相互作用造成南京地区强降水,水汽凝结和降雨蒸发的共同作用导致水汽δ¹⁸O不断贫化,较高的水汽过量氘表明南京地区主要受海洋和局地混合水汽的影响;Ⅲ阶段可能是中尺度下沉气流导致南京地区极端偏负的δ¹⁸O和高水汽过量氘。     

中国荒漠植物-土壤系统生态化学计量学研究进展

荒漠生态系统是中国陆地生态系统的重要组成部分,具有独特的结构和功能.生态化学计量学重点关注C、N、P元素比例及权衡关系,已成为揭示生态系统养分循环及其限制等生态过程的有力工具.植物自身体现出对养分元素的调控能力和对环境变化的响应及适应性,土壤C∶N∶P可表征土壤养分供应能力和储量变化,植物-土壤系统中N、P的养分循环关...     

环渤海地区农村空心化程度与耕地利用集约度的时空变化及其耦合关系

利用环渤海地区分县社会经济数据和土地利用数据, 采用神经网络确定权重的方法, 对该区分县农村空心化程度和耕地利用集约度进行综合测评, 并以山东省为例, 进行两者耦合规律探索。结果表明:① 环渤海地区农村空心化区域差异明显。高度空心化且进入稳定期的地区主要集中在“C”型沿海地区;平原传统农区, 农村空心化正处空心化的成长、兴盛期;农村空心化低值区主要集中落后山区。② 耕地利用集约度时空差异明显。辽中平原粮食主产区、冀中南粮食主产区、鲁西鲁南粮食主产区集约度较高;低集约度主要集中在太行山区、长白山区、沂蒙山区、坝上高原等落后地区。③ 农村空心化与耕地利用集约度变化存在着耦合联动关系。空心化出现、成长期, 农村劳动力向城镇转移, 农村地区隐性失业问题得以解决, 耕地利用集约度不断提升;农村空心化发展至兴盛期, 农村地域发展面临主体弱化, 耕地利用集约度有所下降;至空心化稳定期, 健全的土地流转机制和农业现代化的持续推进, 耕地利用集约度将反弹上升, 最终趋于波动稳定。     

长江经济带工业废水排放的时空格局演化及驱动因素

利用探索性空间分析方法（ESDA）和迪氏分解模型（LMDI）研究长江经济带2002~2013年工业废水排放的时空格局演化和主要驱动因素。① 时空格局演化方面,时间上工业废水排放先上升后下降,在2005年达到峰值。空间上,排放量自上游向下游增加;高排放城市减少,中排放城市增多;工业废水排放自下游向中上游转移,并由大城市向中小城市扩散;呈现明显的空间集聚状态。② 驱动因素方面,经济发展效应和技术进步效应分别是工业废水排放增多和降低的主导因素;产业结构效应的影响取决于产业发展政策的调整;人口规模效应影响较小。     

天山上地幔结构及其对壳内构造运动的作用

以深部地球物理资料为基础,介绍了天山地震带上地幔的基本结构,讨论了天山不同地区上地幔介质的动力学性质和可能的驱动机制。认为水平挤压形变是造成西天山和天山毗邻西昆仑附近区域上地幔岩石圈缩短和增厚的主要原因;而在中天山和东天山靠近准噶尔盆地南缘一带,除了板块运动造成的水平挤压力之外,上地幔热物质有可能上浮甚至侵入到地壳之中。它们与水平运动一样,对壳内脆性介质的构造活动起到非常重要的作用,特别是地壳底部莫霍面附近的低速滑脱层成为震源区深部构造的一个明显标志。此外,自从印度 亚洲大陆碰撞以来,天山部分地区固结冷却的山根有可能在多重挤压变形和小尺度热对流的共同作用下,脱离它们的原有的层位而沉入上地幔     

Mosaic desert pavement influences water infiltration and vegetation distribution on fluvial fan surfaces

Desert pavements (DPs) are critical for maintaining ecological stability and promoting near-surface hydrological cycling in arid regions. However, few studies have focused on eco-hydrological processes of DPs in the ecological systems of fluvial fans. Although DP surfaces appear to be barren and flat, we found that the surfaces are characterized by surface mosaic patterns of desert pavement (mosaic DP) and bare ground (mosaic BG). We investigated the effects of mosaic DP on water infiltration and vegetation distribution at six sites in fluvial fans (one on a hillside and five within the sectors of fans) along a southwest belt transect in northern Linze County, in the central Hexi Corridor (China). We found significant differences in mosaic DP between the hillside and sector sites in terms of pavement thickness and vesicular horizon thickness (Av thickness), particle composition, and bulk density, although significant differences were absent for mass soil water content, gravel coverage, and surface gravel size. The mosaic DP inhibited water infiltration by the pavement layer, where the sorptivity (S), initial infiltration rate (i_int), steady-state infiltration rate (i_sat) and infiltration time (T) averaged 1.19 cm/min^-0.5, 0.64 cm/min, 0.13 cm/min and 12.76 min, respectively. Where the pavement layer was scalped, the S, i_int, and i_sat increased by 0.27 cm/min^-0.5, 0.52 cm/min, and 0.40 cm/min, respectively, and the T reduced by 7.42 min. Water infiltration was mainly controlled by the pavement layer thickness (+), Av thickness (−), surface gravel coverage (−), fine earth (+) and fine gravel (−) in the pavement layer. The DP surfaces only had a sparse covering of shrubs, but an abundance of herbs. Few shrubs were present on the mosaic DP, but a greater number of shrubs and herbs grew on the mosaic BG. It can be concluded that DPs can maintain vegetation stability for different surface mosaic patterns. This study deepens our understanding of the eco-hydrological cycle of DP landscapes in arid regions.     

Magnetic Susceptibility in Surface Sediments in the Southern South China Sea and Its Implication for Sub-sea Methane Venting

In order to understand the characteristics of magnetic variability and their possible implication for sub-sea methane venting,magnetic susceptibility (MS) of 145 surface sediment samples from the southern South China Sea (SCS) was investigated.Magnetic particles extracted from 20 representative samples were also examined for their mineral,chemical compositions and micromorphology.Results indicate that MS values range between -7.73×10-8 and 45.06x10-8 m3/kg.The high MS zones occur at some hydrecarbon-bearing basins and along main tectonic zones,and low ones are distributed mainly within the river delta or along continental shelves.Iron concretions and manganese concretions are not main contributors for high MS values in sediments,while authigenic iron sulphide minerals are possibly responsible for the MS enhancement.This phenomenon is suspected to be produced by the reducing environment where the high upward venting methane beneath the seafloor reacts with seawater sulfate,resulting in seep precipitation of highly susceptible intermediate mineral pyrrhotite,greigite and paramagnetic pyrite.It suggests that MS variability is possibly one of the geochemical indicators for mapping sub-sea zones of methane venting in the southern SCS.     

塔里木盆地西南缘的岩石组合及其构造演化

塔里木盆地西南缘可划分为喀喇昆仑、西昆仑、塔里木等三个地层区和康西瓦、库地等两个缝合带。自震旦纪以来,该区经历了震旦纪—泥盆纪和石炭纪—第四纪两大构造旋回。对应每一旋回,喀喇昆仑地层区和塔里木地层区发育有被动大陆边缘盆地和碰撞造山两种类型的岩石组合。西昆仑地层区发育了被动大陆边缘盆地、俯冲消减带和碰撞造山等三种类型的岩石组合。康西瓦缝合带是康西瓦洋经历了震旦纪—中泥盆世和早石炭世—晚侏罗世两次开合后的遗迹,它既是喀喇昆仑和西昆仑两个地层区的分界线,又是羌塘和塔里木两个板块的分界线;库地缝合带则是库地洋经历早石炭世—早二叠世一次开合的遗迹,分割了西昆仑和塔里木这两个地层区。     

Ice-core pollen record of climatic changes in the central Andes during the last 400 yr

This paper presents a high-resolution ice-core pollen record from the Sajama Ice Cap, Bolivia, that spans the last 400 yr. The pollen record corroborates the oxygen isotopic and ice accumulation records from the Quelccaya Ice Cap and supports the scenario that the Little Ice Age (LIA) consisted of two distinct phases—a wet period from AD 1500 to 1700, and a dry period from AD 1700 to 1880. During the dry period xerophytic shrubs expanded to replace puna grasses on the Altiplano, as suggested by a dramatic drop in the Poaceae/Asteraceae (P/A) pollen ratio. The environment around Sajama was probably similar to the desert-like shrublands of the Southern Bolivian Highlands and western Andean slopes today. The striking similarity between the Sajama and Quelccaya proxy records suggests that climatic changes during the Little Ice Age occurred synchronously across the Altiplano.