Spatiotemporal variations of Chinese lakes and their driving mechanisms since the Last Glacial Maximum: A review and synthesis of lacustrine sediment archives

In this article,the author provides the first synthesis and classification of available environment-indicating proxies for lacustrine sediment.A review of spatio-temporal variations in lakes from the Tibetan Plateau,the dry areas of Northwestern China,the Yunnan-Guizhou Plateau and the plains of Eastern China since the LGM is then provided.The driving mechanism for variations in lake processes and characteristics is also discussed based on various temporal scales.The author then proposes that future investigations be conducted to:(1) strengthen the study of theoretics and interpretation of environment-indicating proxies,(2) enhance the study of high-resolution time series and spatial variability of lake environment evolution,(3) provide more attention on the influence of human activities on lake environments,and(4) boost construction of the Quaternary lake database of China.     

滇桂黔石漠化片区土地生态系统服务价值时空演变研究

土地生态系统服务价值评价对于优化土地利用格局、改善地表覆被、实现区域可持续发展,具有重要的指导意义。以特殊生态脆弱区——滇桂黔石漠化片区为研究区域,综合运用土地利用转移矩阵、价值当量法和地理探测器等方法,探究片区1990—2018年土地生态系统服务价值的时空演变特征及其驱动因子。结果表明：研究期内,滇桂黔石漠化片区城市建设成效显著,石漠化治理效果良好。建设用地和水域面积分别增加116.38%和76.40%,以石漠化裸岩石质地为主的未利用地则减少47.45%并主要转化为草地和林地。但耕地和林地面积的减少态势应引起警惕;滇桂黔石漠化片区生态系统服务价值呈逐年增加态势,生态系统服务价值由1990年的10 423.82亿元逐年提高至2018年的10 631.62亿元,但增长幅度较小且内部差异明显,总体维持西南较高、南部次之、北部较低的空间分异特征,生态系统功能改善仍任重道远;滇桂黔石漠化片区生态系统服务价值的空间分布差异受自然地理要素和社会经济要素共同作用,其中人类活动程度影响深刻。距离县中心、人口密度和年均气温始终是解释力排前三的单因子,且所有具备较强解释力的交互因子均包含距离县中心。     

Relationship between climatic conditions and the relative abundance of modern C3 and C4 plants in three regions around the North Pacific

Using −24‰ and −14‰ as the endpoints of stable carbon isotopic composition of total organic carbon (δ¹³C_TOC) of surface soil under pure C₃ and C₄ vegetation, and surface soil δ¹³C_TOC data from eastern China, Australia and the Great Plains of North Amer- ica, we estimate the relative abundance of C₃/C₄ plants (i.e., the ratio of C₃ or C₄ biomass to local primary production) in modern vegetation for each region. The relative abundance of modern C₃/C₄ vegetation from each region is compared to the corresponding climatic parameters (mean annual temperature and precipitation) to explore the relationship between relative C₄ abundance and climate. The results indicate that temperature controls the growth of C₄ plants. However, even where temperature is high enough for the growth of C₄ plants, they will only dominate the landscape when precipitation declines as temperatures increase. Our results are consistent with those of other investigations of the geographic distribution of modern C₄ plant species. Therefore, our results provide an important reference for interpretation of past C₃/C₄ relative abundance records in these three regions.     

An analysis of the spatial and temporal changes in Chinese terrestrial ecosystem service functions

Since Westman(1977) and Ehrlich(1982) put forward the concepts of "the service of nature" and "ecosystem service functions",respectively,methods for conducting value accounting for them,and their practical application have become the subjects of intense study.Based on an overview of available research findings,we discuss three scientific hypotheses.First,the terrestrial ecosystem offers both positive and negative service functions.Second,changes in terrestrial ecosystem service functions lie not only in the number of ecosystem types and the coverage area of each type,but also in their quality.Third,the value of terrestrial ecosystem service functions should be assessed both in terms of the value stocked and the value added.We collected land use data from China during the period 1999-2008,and Normalized Difference Vegetation Index data based on remote sensing images from the Global Inventory Modeling and Mapping Studies for the same period.We then calculated and analyzed spatial and temporal changes in China’s terrestrial ecosystem service values over the 10-year period.Considering temporal change,the total value(stocked) of China’s terrestrial ecosystem service functions decreased from 6.82 trillion Yuan RMB in 1999 to 6.57 trillion Yuan RMB in 2008.During that period,the positive value decreased by 240.17 billion Yuan RMB and the negative value increased by 8.85 billion Yuan RMB.The decrease in total value lies mainly in the humidity control,soil formation,and waste recycling functions.The total value(added) of China’s terrestrial ecosystem service functions increased by 4.31 billion Yuan RMB in 2000,but decreased by 0.13 billion Yuan RMB in 2008(based on the constant price of China in 1999).The value(added) was a negative figure.From the perspective of spatial change,we can see that the supply of China’s terrestrial ecosystem service functions fell slightly over the past 10 years,mainly in Northeast and Southern China.As a result of human activities on ecosystems,the loss of ecosystem service functions’ value was relatively prominent in Shanxi and Gansu provinces,compared with an increase in value in Shaanxi Province.Terrestrial ecosystem service functions’ value per unit area was relatively high in mid-and East China,showing a prominent spatial change over the 10-year period,but low in Western China.Some conclusions are drawn after an in-depth analysis of the factors causing the spatial and temporal changes in China’s terrestrial ecosystem service functions,in the hope that our suggestions will be helpful for the management of China’s terrestrial ecosystems.     

A high-resolution clay mineralogical record in the northern South China Sea since the Last Glacial Maximum,and its time series provenance analysis

High-resolution clay mineralogical analysis of Core MD05-2904 in the northern South China Sea (SCS) covering the period since the Last Glacial Maximum shows that illite (29%–48%), smectite (14%–45%), chlorite (17%–28%), and minor kaolinite (6%–14%) comprise the clay mineral assemblage, and that time series variation does not present glacial-interglacial cyclicity. Provenance analysis indicates three end-member sources: almost all smectite derives from Luzon, all kaolinite is sourced from the Pearl River, and illite and chlorite originate from both the Pearl River and Taiwan. By comparing clay mineral compositions in surface sediments from the three major source areas and of the SCS, we reconstructed a time series of clay mineral contribution from the major provenances to the northern slope of the SCS using the linear separation method for illite crystallinity. There were three stages of provenance change. (1) During 24.1–17.5 ka BP, contributions from Taiwan and Luzon were similar (30%–40%), while that from the Pearl River was only 25%. (2) During 17.5–14.0 ka BP, the contribution from Luzon decreased rapidly to 20%–25%, while that from Taiwan increased to 35% from an average of 25% at 18 ka BP, and that from the Pearl River increased largely to 40%. (3) During the Holocene, differences in contributions from the three major provenances increased: the contribution from Luzon increased slightly and then remained at 27%–35%, that from Taiwan increased rapidly and then remained at 55%–60%, and that from the Pearl River decreased to 15%. The change in clay mineral contributions from different provenances is influenced mainly by clay mineral production, monsoon rainfall denudation, oceanic current transport, and sea-level change.     

Spatial and temporal variations of zooplankton composition and quantity distribution in the upper waters around Nansha Islands

This study aims to examine spatial and temporal variations of zooplankton species composition, density and biomass distribution and community structure, based on the data obtained from three separate cruises carded out in November 1997, April and July 1999. Results show that 244 species of zooplankton and 8 groups of planktonic larvae were identified, which were dominated by copepods, followed by amphipods, ostracods and medusae. The total species were 201 and 198 for the cruises of November 1997 and July 1999, respectively, and no obvious seasonal variation of species richness was observed. The distribution of zooplankton species richness decreased from pelagic to coastal waters. Average richness of species in each station was higher in the cruises of November 1997（62） and April 1999（61） than in the cruise in July 1999 （56）, which was mainly a result from the pelagic or coastal water mass movement made by the monsoon. Zooplankton in the upper waters （0--100 m） around Nansha Islands belonged to the typical tropic pelagic fauna, most of them were pelagic warm-water species, followed by coastal warm-water species and euryhaline warm-water species. The number of dominant species ranged from 5 to 7 in each cruise. No obvious seasonal succession of dominant species was ob- served. Sagitta enflata, Cypridina narni, Cosmocalanus darwinii, Pleuromamma gracilis and Echino-pluteus larva were the main dominant species. The average of zooplankton biomass and density in three cruises were 31, 32, 28 mg·m^-3 and 31, 39, 35 ind·m^-3, respectively. Copepods were the most abundant, followed by chaetognaths. Zooplankton high biomass distributed mainly in the northwestern waters around Nansha Islands, and generally occurred in the areas of oceanic front and upweUing. The main reason for zooplankton quantity without obvious seasonal variation was the relative steady temperature dynamics in the waters around Nansha Islands.     

长江河口北支潮位与潮差的时空变化和机理

考虑长江河口径流、潮汐和风场共同作用,数值模拟和定量分析北支潮位和潮差时空变化和动力机制.北支月平均潮位呈现出从1月到7月逐渐增大,从8月到12月逐渐减小的变化趋势,主要决定于径流量产生的余水位.潮差具有季节变化,一年中出现两次极大值和两次极小值.两次极大值出现在3月(农历二月)和9月(农历八月),两次极小值出现在6月...     

西北地区暴雨时空变化及异常年夏季环流特征

利用中国西北地区248个观测站1981-2010年逐日降水量资料、NCEP/NCAR再分析资料,对西北地区暴雨的时空变化及环流异常特征进行了分析.结果表明:暴雨主要出现在陕西、甘肃东南部、宁夏东南部,暴雨出现次数依次由东南向西北减少.暴雨的年际差异较大,年内主要集中在7-8月,两个月的暴雨日数占全年的64%,7月最多,8月次之,区域性暴雨7月下旬最多.西北地区大范围暴雨过程偏多年份夏季(7月和8月),西太平洋副热带高压偏强,西脊点伸到110?E附近,亚洲中高纬度多低值系统活动,低层(700 hPa)来自南海的偏东气流与青藏高原南侧的偏西气流合并为偏南气流向北伸展到西北地区东部,将充沛的水汽输送到这一区域,到达35?N附近与西北气流相遇;反之,西北地区大范围暴雨过程偏少年份夏季(7月和8月),西太平洋副热带高压偏弱,远离大陆,亚洲高纬度多高值系统活动,低层是一支偏北气流控制西北地区东部.     

Spatial and temporal variations of light rain events over China and the mid-high latitudes of the Northern Hemisphere

Based on observed daily precipitation data, monthly gridded radiosonde upper air temperature and sea surface temperature data from the UK Met Office Hadley Centre, monthly surface air temperature from the Climatic Research Unit at the University of East Anglia and the NCEP/NCAR monthly reanalysis data, this study investigates the spatial and temporal variations of light rain events over China and the mid-high latitudes of the Northern Hemisphere during 1961-2010, and discusses the relationship between the change of light rain events and atmospheric stability, sea surface temperature and atmospheric circulation. The light rain events over East China display a decreasing trend of 3.0%/10 a in summer and winter half years. Over Northwest China, an increasing trend of 4.1%/10 a is found in winter half years, but there is no trend in summer half years. Using empirical orthogonal function (EOF) analysis, it is found that the first two principal components of light rain events over the mid-high latitudes of the Northern Hemisphere show long time scale variations in summer and winter half years. The first EOF modes (EOF1s) for summer and winter half years both depict a long-term increase in light rain events over North America and Southern Europe as well as Northwest China (except in summer half years), and a long-term decrease over most of the Eurasia (Central Europe, Eastern Europe, North Asia and East China). The second EOF mode (EOF2) for summer half year shows that light rain events increase over North America, Southern Europe and South China, but decrease over Eurasia north of 45°N from 1961 to early 1980s, while the trends reverse from late 1980s to 2010. The second EOF mode (EOF2) for winter half years indicates that light rain events increase over North America and South and North China, but decrease over Eurasia north of 40°N from 1961 to early 1980s, while the trends reverse from late 1980s to 2009. Correlation analysis and linear regression analysis suggest that EOF1s may be related to the change in atmospheric static stability associated with global warming, and EOF2s are possibly linked to the AMO.     

湖北省温度与降雨对全球变化响应的时空差异分析

以湖北省国家级气象站点1959年～2008年逐日气温和降水量数据为依据,运用累积距平、滑动平均、Mann-Kendall检测法以及空间插值法等方法分析湖北省温度与降水时空变化特征,分析影响和制约变化的因素.结果表明,湖北省近50 a来,年平均气温总体呈上升趋势,气温与降雨具有明显的代际时间梯度与空间变异性,站点间气温与降雨变化率具有显著的区域差异性.     

全球变化背景下森林生态系统碳循环及其管理

森林生态系统碳循环及其管理是全球变化研究的重要主题,同时也是人类维持全球生态系统的物质、能量平衡和自然资源循环再生的一个重要生态学途径。笔者在分析森林碳循环的基本特征及其与全球变化相互联系的基础上,阐述了碳循环及其管理在全球变化研究中的地位和作用,并提出了森林生态系统碳循环管理的内容、方法、措施及途径。     

天山乌鲁木齐河源区冰川擦痕级配特征及其空间分布探讨

通过对天山乌鲁木齐河源区一号冰川和七号冰川羊背石上冰川擦痕实测数据的统计分析，探讨了基岩磨光面上冰川擦痕的级配特征．得出冰川擦痕级配服从指数分布，擦痕级配指数分布的参数可以作为描述擦痕密度的指标．在此基础上进一步探讨了擦痕级配参数的空间分布特征及其对冰川动力状况的指示意义．     

鄱阳湖乐安江流域非点源磷输移的时空变化

在鄱阳湖乐安江子流域设立了17个水质采样点,通过实验室测量获得2010年10月—2011年8月河流水体总磷(TP)的浓度数据.数据分析结合模型模拟得出以下结论:监测期内,流域内河流水体TP浓度变化范围为0.024 2~0.358 4 mg/L,水质情况春季最好,秋冬季其次,夏季最差.夏季河流水体TP浓度总体上由上游至下游逐渐增加,其他季节空间上无明显变化规律.降雨径流是TP输出的主要驱动因素,河流水体TP浓度与降雨量变化趋势一致.汛期河流水体TP浓度与土地利用类型的统计模型显示,河流水体TP浓度与耕地和城乡用地面积占流域总面积的比例呈正相关关系,与林地和草地面积占流域总面积的比例呈负相关关系;其中,河流水体TP浓度对耕地、城乡用地及林地面积的变化更为敏感.     

LiFePO4/C的低成本制备及电化学性能研究

以FePO4.2H2O,Li2CO3和蔗糖为原料,采用碳热还原法合成LiFePO4/C材料.高温合成时采用木炭粉代替惰性气体保护以降低成本,对样品进行X射线衍射分析(XRD)、扫描电子显微镜(SEM)测试和电化学性能分析.结果表明:当合成温度为650℃时合成的材料具有较好的电化学性能,0.1倍率下首次放电比容量为153.0 mA.h/g,30次充放电循环后容量保持率为95%,具有良好的循环性能.     

辽南地区末次冰期以来的环境变化

本文通过对大连七顶山黄土剖面的光释光(OSL)年代、磁化率、地球化学元素、粒度特征等数据,综合分析辽南地区末次冰期以来的环境变化过程,研究结果显示:相当于黄土高原马兰黄土的堆积形成时代为距今125ka。在末次冰期早期(MIS4-5d),86-113ka,沉积物质量磁化率介于6.97-24.14×10-8m3kg-1之间,平均值为14.699×10-8m3kg-1;颗粒粒径较细(3.89-5.22准);硅铝率平均值6.756;风化淋溶系数0.4-0.73之间;退碱系数均值0.333;镁铝比均值22.901。与末次冰期晚期相比,质量磁化率值较高,化学元素各项指标值较低,明了该阶段辽南整体气候环境较为干冷,但并未达到末次冰期晚期程度。而在末次冰盛期时(22-31ka,MIS2),磁化率平均值为6.974×10-8m3kg-1,明显低于末次冰期早期,粒度均值处于3.47准-4.77准之间,主要以颗粒较粗的细砂、粗粉砂为主,粒度明显变粗,硅铝率平均为6.998;风化淋溶系数均值为0.829,退碱系数值0.66,镁铝比值均值28.725,各参数比较一致地表明该阶段研究区整体处于干冷的气候环境之下,堆积作用较活跃。而在末次冰期中期(MIS3)时,OSL年代31-86ka,该区气候条件以温暖湿润为主,黄土遭到侵蚀。     

长江经济带旅游经济的时空分异及影响因素研究

长江经济带旅游产业的整体协调发展是我国旅游空间格局优化的关键.利用长江经济带11个省市2001年～2017年的面板数据,综合采用地理空间分析和多元回归分析方法研究区域旅游经济的空间分异特征及演化规律,探讨其内在影响因素.研究发现：1) 从全流域看,长江经济带各省市旅游经济的绝对差异逐年扩大,相对差异不断缩小,旅游经济的专业化程度缓慢提升;2) 从上中下游各区域看,长江经济带不同区域旅游经济的绝对差异和相对差异均呈不同程度的下降,上游地区较低的区域经济水平突显了旅游业在国民经济中的比较优势,中游各省市绝对差异和相对差异均最小且下降幅度最大,下游的相对差异最大.3) 区域经济发展水平、基础设施状况是影响长江经济带旅游经济时空分异的主要因素,对外开放程度对此亦有贡献.4) 长江经济带旅游经济已经形成了下游网络化、中游均质化、上游专业化的空间结构,并有望向更为平衡的方向发展.