近20余年来西北地区植被变化特征分析

利用1982—2003年8 km分辨率的NDVI数据集,选中国西北地区森林、草原、灌溉农业、雨养农业区不同类型植被为研究区,分析了植被年、年际变化特征,并对植被覆盖空间变化进行动态研究.结果表明:森林、草原、灌溉农业区和以春小麦为主的雨养农业区NDVI年变化为单峰型曲线,以冬小麦为主的雨养农业区NDVI曲线呈双峰型;同一类型的植被NDVI受纬度或海拔高度的影响,绿峰出现时间存在1个月的位相差.22 a来森林植被NDVI多呈下降趋势,草原植被区为上升趋势;雨养农业区变化不大,灌溉植被区呈显著的上升趋势.西北东部雨养农业区植被波动频率和幅度最大,是受降水影响最敏感的地区;森林植被次之;有灌溉条件的绿洲植被,年际间波动最小.22 a间西北地区植被以增加趋势为主,增加面积约为20.5%,主要分布在新疆和河西走廊绿洲、黄河沿岸灌区以及青海草区,水分条件充足的绿洲是NDVI增加最显著的区域;NDVI减少地区面积为4.77%,主要分布在西北东部.     

Coastal Inundation due to Sea Level Rise in the Pearl River Delta,China

This paper examines the increased potential risk of tidalinundations in the Pearl River delta, China, due to futurerises in sea level. The research is based on tidal recordsof 54 tide gauges distributed across the delta plain, andemploys mathematical calculations to predict potentialrises of water level in different parts of the delta undera number of flood scenarios. After assessing a 72-yeartidal record of Hong Kong and factors such as estuarinebackwater effects and long-term geological subsidence,it suggests that a 30 cm rise in relative sea level at themouth of the estuary is possible by 2030. Based on theprediction and five freshwater discharge scenarios, thepotential impacts on water levels across the delta plain arecalculated. Three zones are identified as least affected,heavily affected and severely affected. The impacts arealso translated into return periods of water level. It issuggested that in a large part of the delta plain, returnperiods will be shortened and hence will be increasinglyvulnerable to tidal inundation. Finally, managementimplications are discussed along with assessment ofthe adequacy of the existing tidal flood defences, as well asevaluation of the cost implications if they are to be improved.     

过去21a中国西北植被覆盖动态监测与模拟

利用1981至2001年8kmAVHRR数据,采用均值法、差值法和一元线性回归模拟法,分析西北植被年内变化、年际变化特征,并模拟近21aNDVI最大化值的变化趋势线和NDVI增长幅度.统计结果表明,中国西北植被覆盖在7～8月达到年内最丰盛;近21a来植被覆盖存在普遍退化的趋势,且后10a变化幅度大于前10a变化幅度;在局部区域有植被改善的趋势,改善幅度小于退化幅度.模拟结果表明,植被改善的区域主要分布在新疆西部和北部地区.     

14,000 Years of Sediment, Vegetation, and Water-Level Changes at the Makepeace Cedar Swamp, Southeastern Massachusetts

Data from a transect of four cores collected in the Makepeace Cedar Swamp, near Carver, Massachusetts, record past changes in deposition, vegetation, and water level. Time series of palynological data provide a 14,000-yr record of regional and local vegetation development, a means for biostratigraphic correlation and dating, and information about changes in water level. Differences in records among cores in the basin show that water level decreased at least 1.5 m between 10,800 and 9700 cal yr B.P., after which sediment accumulation was slow and intermittent across the basin for about 1700 yr. Between 8000 and 5600 cal yr B.P., water level rose 2.0 m, after which slow peat accumulation indicates a low stand about the time of the hemlock decline at 5300 ± 200 cal yr B.P. Dry conditions may have continued after this time, but by 3200 cal yr B.P., the onset of peat accumulation in shallow cores indicates that water level had risen to close to its highest postglacial level, where it is today. Peat has accumulated across the whole basin since 3200 cal yr B.P. Data from Makepeace and the Pequot Cedar Swamp, near Ledyard, Connecticut, indicate an early Holocene dry interval in southern New England that began 11,500 yr ago near the end of the Younger Dryas interval. The dry conditions prevailed between 10,800 and 8000 cal yr B.P. and coincide with the arrival and later rise to dominance of white pine trees (Pinus strobus) both regionally and near the basins. Our results indicate a climatic cause for the “pine period” in New England.     

气候变化和人类活动对伊塞克湖水位变化的影响及其演化趋势

结合气象、水文、冰川变化和人类活动序列资料,应用水量平衡方法分析了气候变化和人类活动对吉尔吉斯坦伊塞克湖1927—2008年水位变化的影响.结果表明:降水量和入湖径流量是湖泊水位变化的决定因素.在水量平衡各要素中,降水量和入湖径流量与湖泊水位变化的正相关关系最为密切,而灌溉耗水对目前湖泊水位的变化的影响仅处于次要地位.由于气候变化,流域高山区气温上升显著,湖面降水量和入湖径流量增加明显,导致湖面于1998年停止下降,开始回升,到2008年底已经上升了0.59 m.按照所有SRES情景预估的未来升温情况,伊塞克湖水位还将会因为雨雪比例的增大及冰川融水的大量增加而上升.因此,伊塞克湖水位现在已经处于自然波动恢复状态中,不需要从其他流域向伊塞克湖调水来恢复湖水位,但要注意灌溉回归水可能会对湖水造成一定的污染.     

苏拉威西海周边地区全新世植被演化及气候变化

全新世时期的环境和气候变化是全球气候模拟、预测中不可或缺的资料.对苏拉威西海西北部MD98-2178孔(3.6200°N,118.7000°E,水深1 984 m)全新世的样品进行孢粉分析和浮游有孔虫氧稳定同位素测试,重建全新世苏拉威西海周边地区植被演化和气候变化图景.根据孢粉记录得到:在全新世早期至7 ka BP时,各孢粉组合浓度剧烈下降,指示海平面处于上升阶段;在7~4 ka BP时,各孢粉组合浓度都处于低谷,体现为高海平面期;在4 ka BP之后,孢粉记录则显示海平面有小幅的下降.在全新世中期,即5~4 ka BP,热带高山雨林花粉含量明显上升,表明是温度低值期.蕨类孢子记录显示降雨量在全新世早期是持续增加的,但在全新世中期之后,降雨量有所减少,这与陆地孢粉记录和印尼石笋记录的结果相似,体现全新世该地区降雨量受海陆格局和太阳活动共同影响.      

东海内陆架近两百年来有孔虫组合变化及原因

基于东海内陆架泥质区DH7-2孔岩心,使用激光粒度分析仪、体视显微镜开展了沉积物粒度和有孔虫组成的分析和鉴定,并利用高能γ能谱仪进行了沉积物岩心的210Pb年代标定,探讨了近二百年来有孔虫组合变化及其影响因素.研究表明:近200年来有孔虫组合变化可以划分为3个阶段,1822—1900年,主要受到该时期较强东亚冬季风的影...     

Paleoenvironmental Evolution of the Beilun River Estuary, Northwest South China Sea, During the Past 20,000 Years Based on Diatoms

The paleoenvironmental history of the Beilun River estuary on the coast of Beibu Gulf in the northwest South China Sea is reconstructed based on fossil diatoms, isotopic dating, sedimentary grain size data, mineralogy and geochemistry in three sediment core samples. Results show that the estuary has experienced significant environmental changes since deposition began about 20,000 yr ago. Freshwater runoff of the Beilun River initially was strong. However, the freshwater runoff reduced significantly after a transgressive event. Subsequently the estuary’s position began to migrate to the northeast. At the end of the Late Pleistocene the estuary shifted gradually towards the southwest. In the Early-Mid Holocene, the estuary’s geomorphology was shaped by seawater transgressing into the ancient river channel. The basin was filled continuously but slowly to form the present Beilun River estuary. Holocene transgression in this area could be divided roughly into three stages, including oscillation period 1, the maximum transgression period, and oscillation period 2.     

Sea Level Changes in the Last Several Thousand Years, Penghu Islands, Taiwan Strait

Holocene shore-face and beach-face deposits form plains <5 m above present sea level along Taiwan Strait. We measured the¹⁴C ages of detrital mollusk shells and coral in such deposits at the Penghu Islands. Twelve carbonate samples—mainly from the largest island, Makung—were dated. Age measurements for two coral samples and one mollusk sample from the same outcrop imply that the¹⁴C ages of mollusk shells give the best approximation of depositional age. The highest Holocene relative sea level in the Penghu Islands occurred about 4700 years ago with a height about 2.4 m above the present sea level. Thereafter, relative sea level appreciably fell without detectable fluctuations to its recent position. Our sea level data are consistent with other studies from the central and western Pacific, except for the timing of peak sea level position. This variation may reflect local crustal response to hydroisostatic effects on the continental shelf.     

内蒙古克什克腾旗地区距今16 000 a以来的孢粉组合特征与环境变迁

本文通过对三义黄土剖面孢粉资料的分析，初步重建了内蒙克旗地区16000a以来植被及环境的变迁过程。约16010～15380a B P，植被稀疏，气候寒冷而干燥；约15380～11270a B P，植被以草本植物为主，气候变得更加干旱；约11270～9940a B P，气候总体上由先前的冷干开始向暖湿方向发展，植被仍以草原为主；约9940～2320a B P，植被得到进一步发展，气候表现出温暖湿润的特征；约2320a B P至今，植被仍以草原为主，气候向温凉方向发展。     

Dynamic Changes of Lakes in Tibet Plateau and the Climate Interaction in the Past Forty Years

正Lake change,as a mirror of climate change,has obvious indication and warning effect on climate.By extracting information of all lakes in Tibet Plateau from Landsat of the 1970’s,the 1990’s,around 2000 and 2010 based on RS and GIS,and,in combination with on-the-spot investigations to a few representative lakes,the authors     

近300a来古里雅冰芯记录的气候突变事件

根据古里雅冰芯高分辨率气候环境信息记录,利用小波气候突变的检测方法,对近300a来的气候突变事件进行了检测.结果表明,在百年尺度上,近300a来古里雅冰芯中所记录的δ¹⁸O(温度代用指标)发生了2次突变,分别在1788年和1932年;净积累量(降水量的代用指标)也发生了2次突变,分别在1805年和1939年;降水突变发生的时间迟于温度突变发生的时间.时间尺度越短,发生突变的次数则越多,这也体现了气候变化的层次性.因此,较好地确定隐含在气候资料中冷暖(干湿)期突变的位置,从冷暖(干湿)期的变更上去把握气候变化,将有助于认识气候变化的机理.     

A Profile of International Climate Change Science in the Past One Hundred Years*

Climate change is one of the most active research fields currently, which has attracted extensive attention from the international community. In order to better understand the development situation and research status of international climate change science, in this paper we took the SSCI and SCI databases as data sources, collected the relevant literatures since 1900 based on the key words related to climate change, and made some statistics and analysis of the literatures of the past one hundred years to reveal the development process of climate change research as well as the development and evolution of its research topics and hot spots. The results showed that the climate change research began in the late 18 th century and early 19 th century, and the academic debate about global warming and global cooling started in the early 1970s. The international programs and projects led by a range of international organizations and intergovernmental bodies have contributed significantly to the rapid development of climate change research. The United States and the United Kingdom have long been the core countries of climate change research. The proportion of Chinese papers has risen rapidly in the last decade. The intensity and scope of scientific research cooperation are constantly expanding. Current research focuses on climate model/modeling, climate simulation, climate policy, climate sensitivity, climate change impacts, climate change adaptation, climate change mitigation, and rate of climate change.     

研究人员通过历史数据估计未来海平面上升情况

波士顿大学的古气候学家们在2011年第4期Nature(地球科学版)杂志上发布了一项研究成果,通过对澳大利亚3 Ma前古海岸线的研究,得出该时期的海平面比现在高大约15~100英尺的结论。该结果将帮助     

Vegetation Dynamics in Rhode Island Salt Marshes During a Period of Accelerating Sea Level Rise and Extreme Sea Level Events

Sea level rise is a major stressor on many salt marshes, and its impacts include creek widening, ponding, vegetation dieback, and drowning. Marsh vegetation changes have been associated with sea level rise across southern New England, but most of these studies pre-date the current period of rapidly accelerating sea level rise coupled with episodic events of extreme increases in water levels. Here, we combine data from two salt marsh monitoring and assessment programs in Rhode Island that were designed to assess marsh responses to sea level rise and use these data to document temporal and spatial patterns in marsh vegetation during the current period of extreme water level increases. Vegetation monitoring at two Narragansett Bay salt marshes confirms the ongoing decline of the salt meadow species Spartina patens during this period as it becomes replaced by Spartina alterniflora. Bare ground resulting from vegetation dieback was significantly related to mean high water levels and led to the rapid conversion of mixed Spartina assemblages to S. alterniflora monocultures. A broader spatial assessment of RI marshes shows that S. alterniflora dominance increases at lower elevation marshes toward the mouth of Narraganset Bay. Our data provide additional evidence that S. patens continues to decline in southern New England marshes and show that losses can accelerate during periods of extreme high water levels. Unless adaptive management actions are taken, we predict that marshes throughout RI will continue to lose salt meadow habitat and eventually resemble lower elevation marshes that are already dominated by S. alterniflora monocultures.     

50年来我国水文测验工作回顾

从水文测验项目,测验设备与仪器,测验技术和方式、整编与数据库建设等方面回顾了中国水文测验５０年来的发展与取得的成就,总结了水文测验工作的重点和采取的措施,指出了目前水文测验存在的问题与不足及今后发展的方向。     

中国近海平均海面变化研究

本文在分析了中国沿海各长期验潮站年平均海面具有同升同降特点的基础上,应用方差分析方法求得年平均海面变化周期为5年、11年和19年.采用11年比较法,精选13个基本验潮站,和选择接近11年平均海面差值中数的时间段,求得中国近海近期(30余年)年平均海面上升速度为1.6±0.3mm/年.该结果与国内外大多数学者研究结果相一致,但方法简单易行.     

Astronomical Dating of the Middle Miocene Hanjiang Formation in the Pearl River Mouth Basin,South China Sea

The Hanjiang Formation of Langhian age(middle Miocene) in the Pearl River Mouth Basin (PRMB),South China Sea consists of deltaic siliciclastic and neritic shelf carbonate rhythmic alternations,which form one of the potential reservoirs of the basin.To improve stratigraphic resolutions for hydrocarbon prospecting and exploration in the basin,the present study undertakes spectral analysis of high-resolution natural gamma-ray(NCR) well-logging record to determine the dominant frequency components and test whether Milankovitch orbital signals are recorded in rhythmic successions.Analytical results indicate the orbital cycles of precession(～19 ka and～23 ka), obliquity(～41 ka),and eccentricity(～100 ka and～405 ka),which provide the strong evidence for astronomically driven climate changes in the rhythmic alternation successions.Within biochronological constraint,a high-resolution astronomical timescale was constructed through the astronomical tuning of the NGR record to recent astronomically calculated variation of Earth’s orbit. The astronomically tuned timescale can be applied to calculate astronomical ages for the geological events and bioevents recognized throughout the period.The first downhole occurrences of foraminifers Globorotalia peripheroronda and Globigerinoides sicanus are dated at 14.546 Ma and 14.919 Ma,respectively,which are slightly different from earlier estimates in the South China Sea. When compared with the global sea-level change chart,the astronomical estimate for the sequences recognized based on microfossil distributions have the same end time but the different initiation time. This is probably due to the local or regional tectonic activities superimposed on eustatic rise which postponed the effect of global sea-level rising.Astronomical timescale also resolves the depositional evolution history for the Langhian Stage(middle Miocene) with a variation that strongly resembles that of Earth’s orbital eccentricity predicted from 13.65 Ma to 15.97 Ma.We infer that the main factor controlling the variability of the sedimentation rate in the Hanjiang Formation is related to the～405-ka-period eccentricity.     

塔里木河流域近40 a来气候、水文变化及其影响

塔里木河流域平原地区在近 10a明显变暖 ,较明显的增湿出现在近 2 0a,大部分平原地区近10a反而略有变干的迹象 ;2 0世纪 90年代是流域山区近 4 0a来最暖阶段 ,在天山南麓中西部山区和帕米尔高原一带 90年代增湿幅度大 ,西昆仑山北坡一带近 2 0a降水变化很小 .塔里木河流域 4条源流出山口多年平均径流量为 2 2 4 9× 10 8m3 ( 195 7— 1999年 ) ,年代际尺度上 ,5 0— 80年代基本接近多年平均值 ,而 90年代由于受山区增暖变湿影响 ,4条源流径流量达 2 4 1 9× 10 8m3 ,增幅 7 6 % .由于源流区人类活动的影响和粗放型农业 ,补给塔里木河源流条数减少 ,塔里木河干流上中游区间耗水量严重 ,中下游水量来水量在近 4 0a中持续减少 ,导致下游生态环境急剧恶化     

三大自然区过渡地带近50年来气候类型变化及其对气候变化的响应

The transition area of three natural zones (Eastern Monsoon Region, Arid Region of Northwest China, Qinghai Tibet Plateau Region) is influenced by the Asian monsoon and middle latitude westerly circulation because of its special geographical position. And it is more sensitive to global climate change. The Koppen climate classification, which is widely used in the world, and the accumulated temperature-dryness classification, which is usually used in China, were used to study the climate zones and changes in the region of longitude 97.5°~108°E, latitude 33°~41.5°N, from 1961 to 2010. The changing areas of each climate zone were compared to the East Asian Summer Monsoon index, the South Asian Summer Monsoon index, the Summer Westerly index, the East Asian Winter Monsoon index, the Plateau Summer Monsoon index, the North Atlantic Oscillation index, the Southern Oscillation index, NINO3.4 index, to explore the response of the transition area of three natural zones to each climate system. According to the results, this region will become wetter when the Summer Westerly or the East Asian Winter Monsoon is relatively strong. When the East Asian Summer Monsoon or the South Asian Summer Monsoon becomes strong, the climate in low altitude region of the study area will easily become drier, and the climate in high altitude region of the study area is easily to become wetter. When the Plateau Summer Monsoon is relatively strong, the climate in the study area will easily become drier. When the North Atlantic Oscillation is relatively strong, the study area will easily become wetter. And when the El Niño is relatively strong, or the Southern Oscillation is relatively weak, the study area will easily become drier. In general, the moisture status of this region is mainly controlled by the middle latitude westerly circulation. The enhancement of the Asian summer monsoon could increase the precipitation in the southeast part of this regional, but, according to the degrees of dryness and the types of climate change in this paper, warming effects could offset precipitation increasing and make the area drier. The transition area of three natural zones is influenced by multiple interactions of climate systems from East Asia. A single climatic index, such as air temperature or precipitation, can not completely represent the regional features of climate change. As a result, areas of climate zones can be used as an important index in the regional climate change assessment.