班戈错盐湖古湖岸堤石英光释光年代学及其古环境指示意义研究

古湖岸堤是湖泊湖面变化的地貌学证据,通过古湖岸堤沉积年代学研究可重建地质时期湖泊演化历史。青藏高原内陆湖泊众多,保存了大量的第四纪时期古湖岸堤,是研究过去湖泊演化和气候变化信息的重要载体。对青藏高原班戈错盐湖北岸和东岸的低位连续古湖岸堤开展了地貌调查和光释光年代学研究。结果表明班戈错自末次冰消期(13. 5±1. 2 ka BP)以来,湖面整体呈波动下降过程,期间出现了4期湖面稳定阶段,分别在末次冰消期(13. 5±1. 2～11. 2±1. 0 ka BP)、全新世早中期(10. 1±0. 8～6. 5±0. 5 ka BP)、全新世后期(4. 2±0. 4～3. 1±0. 2 ka BP)以及全新世晚期(1. 7±0. 1～1. 2±0. 1 ka BP)。全新世晚期约1. 7 ka BP以后湖面迅速退缩,湖泊蒸发浓缩进入盐湖阶段。在末次冰消期班戈错高湖面形成主要与北半球太阳辐射强度增加引起气温升高,导致区域冰雪融水量增加相关,而在全新世湖面变化主要受印度季风强度变化控制。     

近30年全国消失湖泊243个

“近30年来,全国原面积1平方公里以上的湖泊消失了243个,其中江苏11个、浙江2个、上海1个……”中科院南京地理与湖泊研究所研究员马荣华昨天告诉笔者,“湖泊消失或者湖泊生态系统恶化,将直接影响湖岸周边居民的生活和经济活动。”马荣华参与了第二次全国湖泊调查,这是我国科学家首次调研近半个世纪来中国湖泊的存亡与变化。     

巴丹吉林沙漠典型湖冰冻结-消融的空间模式差异

利用多源遥感数据解译、野外考察、原位观测等方法,分析了巴丹吉林沙漠腹地湖泊群湖冰冻结-消融空间模式及其差异的主要影响因素。结果表明：该沙漠存在4种冻结-消融空间模式,湖冰自湖岸蔓延至湖心、冻结早的区域融化晚;湖冰自湖岸蔓延至湖心、冻结早的区域融化早;湖冰自湖泊一岸扩展至另一岸、冻结早的区域融化晚;湖冰自湖泊一岸扩展至另一岸、冻结早的区域融化早。大部分面积较小湖泊的冻结-消融空间模式为从湖岸冻结至湖心,冻结早的区域消融晚。不同冻结-消融空间模式之间的差异反映了泉水与地下水对湖泊的补给作用,同一盆地内部或同一沙山两侧孪生湖泊湖冰物候特征的差异主要受湖泊形态特征、湖泊溶解性固体总量（TDS）、局地气候条件的影响,有泉水或地下水出露、TDS越低、水位越浅、风力越小的区域冻结越早。泉水、地下水与湖水混合后使湖水TDS降低,更易于冻结,这是巴丹吉林沙漠大部分湖泊冰的最初生成形式,表明巴丹吉林沙漠湖冰物候在一定意义上是湖泊群接受区域深层地下水补给的直接反映。     

中全新世以来查干淖尔古湖面波动

内陆湖泊水位变化是对区域气候和水文变化的一种响应,古湖岸堤是过去湖泊水位变化的最直接证据。野外考察发现内蒙古高原查干淖尔湖周围存在海拔为1 026、1 023m和1 018m的3级古湖岸堤。根据光释光定年,其形成年代分别是6.83±0.37、4.26±0.29ka BP和2.42±0.15ka BP。利用DEM模型恢复得到的对应时期古湖面积分别是270、230km2和120km2。在6.83~4.26ka BP时段,查干淖尔古湖高湖面稳定在1 023~1 026m,比现代湖面约高7m,该时段气候相对湿润,4.26ka BP以来湖面持续下降,与区域性甚至全球性气候变化有着深刻的关系。     

洞庭湖区湿地生物资源特征及生态系统评价

洞庭湖湿地是我国最大的淡水湖泊湿地生态景观系统,生态资源十分丰富,其中植物资源1428种,鸟类资源216种,鱼类资源119种,哺乳类22种,两栖爬行类27种及其它大量的野生生物资源。根据生物资源的分布状对湖区湿地生态系统进行了分类,即环湖丘岗生态系统,湖州草滩生态系统,湖岸带生态系统,浅水层生态系统、深水层生态系统。在此基础上,对湖区湿地生态系统的功能效益进行了综合评价。按直接利用价值和间接利用价值进行了分类,最后对湿地生物资源保护和开发中存在的问题,并就今后本区湿地生物资源的保护和利用提出了一些设想和建议。     

柴达木盆地可鲁克湖沉积物表层花粉散布规律及其对区域植被的指示意义

可鲁克湖是柴达木盆地东部荒漠区重要的生态屏障,对全球气候变化响应十分敏感。利用沉积物化石花粉重建湖泊生态系统演变历史及其对全球气候变化响应过程和机制的分析是当前重要的研究方向,本研究系统采集了可鲁克湖沉积物表层样品开展花粉分析。研究结果显示,花粉组合以藜科、禾本科、蒿属、莎草科为主。花粉总浓度在湖泊沉积中心及偏西南区域显著偏高,其中藜科、莎草科、蒿属、白刺属、麻黄属、紫菀属花粉与总浓度变化特征较为一致,而禾本科花粉在湖泊东南部显著富集。湖泊沉积物中的藜科和蒿属花粉较好地指示了柴达木盆地东部灌木-矮灌木荒漠和荒漠草原整体植被特征,而禾本科和莎草科花粉主要指示湖岸周边隐域性沼泽和河滩草甸植被群落;白刺属花粉对湖泊北岸一级阶地上的白刺群落发育和湖面变化具有较好的指示意义,谷物类禾本科和十字花科花粉能较为灵敏地反映湖泊附近的农耕活动,桦木属和云杉属花粉则主要由风力和河流远距离输入。研究揭示了可鲁克湖水深、水动力条件、湖岸周围植被群落分布以及风力作用是影响花粉散布和沉积的重要影响因素,此项研究也为青藏高原湖泊沉积物花粉组合的精确解译提供了重要数据资料和分析依据。     

艾比湖的湖岸地貌及其反映的湖面变化

艾比湖为一典型的内陆干旱区封闭型湖泊,干旱区的湖泊对气候和环境变化的响应非常敏感,该湖自形成以来的变化湖岸地貌中留下了很好的记录,对湖积堤和湖成阶地的系统研究以及对湖各平原的分析结果展现了艾比湖的湖在变化过程。     

海平面变化与南极大陆沿海西福尔丘陵湖泊环境演变

对东南极大陆沿海西福尔丘陵 ( Vestfold Hills,68°38′S,78°0 6′E)若干主要湖泊及其周边环境进行了现代生态学和古生态学研究。分析了不同类型湖泊的地理地貌环境和理化要素的动态特征、生态群落结构类型。利用湖岸古化石的生态组成与放射性同位素测定资料 ,推断了晚更新世以来随着全球海平面变化 ,该地区所经历的海侵、海退及其地理地貌改变过程 ,尤其重现了本区 1 80 0 0年以来因两次海侵而发生的湖泊生态演替过程。本文首次推出了该区海成湖泊 4种环境演化模式 ,认为这些湖泊环境演化模式不仅是区域环境生态历史演变的缩影 ,而且也是现今南极局部环境变化和全球气候变化的具体反映     

青海湖小冰期降水量估算

通过对处于构造活动相对稳定的青海湖湖滨地带湖岸堤的野外考察,获取了海晏湾和哈达湾两处湖岸堤的14C年龄;在地理信息系统的支持下,得到这两处岸堤的海拔高度和湖泊面积,应用水热平衡模型,估算了当时流域的降水量。200 a B.P.的青海湖湖岸堤海拔高度为3 201 m,湖泊面积为4 870 km2,流域降水量为416 mm,表明青海湖该时段小冰期气候具有比现在湿润的特征,同时,降水量估算的结果也支持了青海湖流域气候受亚洲西南季风影响的观点。     

2000—2020年蒙古高原湖泊变化及其影响因素分析

基于Landsat遥感影像,提取蒙古高原2000—2020年每年1 km²以上湖泊面积信息,分析其时空变化特征。结果表明：(1)2009年之前湖泊面积和数量呈减少趋势,2009年之后呈增加趋势,整体上2000—2020年湖泊面积和数量呈减少趋势。(2)不同等级湖泊变化差异较大,特大型和中型湖泊变化相对稳定,大型湖泊减少幅度最大。(3)不同区域湖泊变化也不同,西北部湖泊变化较稳定,中东部湖泊变化较剧烈。(4)研究区湖泊空间分布集聚性呈异因同向的减弱趋势。(5)湖泊面积与年均气温、年降水量、年蒸发量、植被指数和4层土壤水分的相关关系较为显著,且2个时间段内表现的影响程度有明显差异。掌握蒙古高原湖泊时空变化情况及其原因,对蒙古高原乃至全球的气候调节和生物多样性保护研究提供可参考依据。     

The effect of the Changjiang River on water regimes of its tributary Lake East Dongting

The blocking or reversing effect of the downstream trunk river on its tributary lakes is an essential aspect of river-lake hydraulics. To measure how and the extent to which a trunk river can influence its tributary lakes, we made a case study in Changjiang River and one of its tributary lakes, Lake East Dongting (Lake ED) during a 35-year study period (1980–2014). Specifically, we investigated Lake ED’s discharge ability into Changjiang River using stage-discharge relationship curves, and hence the changes of the lake discharge ability under different hydrologic conditions of the Changjiang River. The results show that (1) the Changjiang River does exert a huge impact on the water regimes of Lake ED. And this impact varies seasonally. A variation of 3000 m³/s in Changjiang River’s runoff would change the lake water level by about 1.1 m in dry seasons, by 0.4 m in wet seasons, and by 0.6 m during severe summer floods. (2) Changes in the Changjiang River runoff triggered by the Three Gorges Dam since 2003 have led to dramatic water regime variations in Lake ED. Other factors, including reduction of lake inflow and the lake bed erosion, also exacerbated the water regime variations in Lake ED.     

2000—2019年新疆大型湖泊湖冰物候时空变化特征

湖冰物候变化特征是全球气候变化过程的重要指示器。通过长时间序列MODIS数据、Landsat数据提取的湖泊数据集,综合分析了2000—2019年新疆大型湖泊湖冰物候的变化特征。结果表明：（1） 近20 a新疆大型湖泊的开始冻结日呈现提前和推迟2种变化趋势,开始冻结日呈现推迟趋势的湖泊分别为博斯腾湖、赛里木湖、艾比湖、吉力湖、乌伦古湖、萨利吉勒干南库勒湖和鲸鱼湖,且大部分湖泊的开始冻结日推迟趋势在0.51~1.53 d·a^-1之间;开始冻结日呈现提前趋势的湖泊有3个,分别为阿牙克库木湖（变化趋势为-1.04 d·a^-1）、阿克赛钦湖（变化趋势为-0.41 d·a^-1）、阿其克库勒湖（-0.31 d·a^-1）。（2） 湖冰完全覆盖期是重要的湖冰参数,湖冰覆盖期的延长或者缩短能够直接表示区域气候变化过程,新疆大部分湖泊湖冰覆盖期表现为缩短趋势,其中分布在新疆中北部的艾比湖、吉力湖和博斯腾湖等湖泊的湖冰覆盖期缩短较为明显,变化趋势分别为-1.76 d·a^-1、-2.13 d·a^-1和-0.81 d·a^-1;冰完全覆盖期延长的湖泊有3个,分别为阿牙克库木湖、阿其克库勒湖和鲸鱼湖,变化趋势分别为3.51 d·a^-1、1.54 d·a^-1和1.37 d·a^-1,这些湖泊均匀分布在昆仑山高原北翼。（3） 新疆大型湖泊湖冰物候变化特征是受其自身条件（湖泊形态因子、湖泊面积等）及气候变化（气温、降水量等）等多种因素共同作用的结果。本研究探讨了气候变化环境下的新疆大型湖泊湖冰物候的冻融趋势及其变化模式,同时应用不同遥感数据和研究方法识别了湖冰,证实了MODIS数据反演湖冰物候的可行性。     

淀山湖太湖形成的古生物证据

通过对湖泊周围钻孔样品的微体古生物分析,根据化石群的生态特征,结合岩性、孢粉、¹⁴C等资料探讨晚更新世中期以来淀山湖、太湖沉积环境的演变过程,并比较其异同。现代湖泊的形成于全新世晚期。     

Former glacial lakes of the Bunger Hills,Antarctica

The Bunger Hills in East Antarctica occupy a land area of approximately 400 km². They have been exposed by Holocene retreat of the Antarctic ice sheet and its outlet glaciers. The accompanying sea level rise flooded the marine inlets that now separate the northern islands and peninsulas from the major part of the hills. During deglaciation the continental ice sheet margin retreated south‐eastwards with several temporary halts, during which ice‐dammed lakes were formed in some valleys. These lakes were maintained long enough to permit formation of beaches of sand and gravel, and for the erosion of shore platforms and low cliffs in bedrock. Around the western end of Fish Tail Bay impressive shoreline features 20 m above sea level define a former ice‐dammed lake that was 5.5 km long. A similar 7 km long former ice‐dammed lake was formed at Lake Dolgoe. The more extensive and deeper glacial lake is revealed by well‐developed and preserved shoreline features cut at 29 m which is 16 m above present lake level. In addition, several small ice‐dammed lakes existed temporarily near Lake Shchel and in the valley to the west. Lake Fish Tail existed more than 6,900 ¹⁴C years ago and Lake Shchel probably more than 6,680 ¹⁴C years ago. It is inferred that the shore platforms and beaches were formed by lake ice and wave action over considerable periods when the lakes were impounded by steep cold ice margins. There appears to have been a balance between meltwater input and evaporative loss from the lakes in the cold dry continental climate. There is no evidence for rapid lake level fluctuations, and there was very little input of clastic sediment. This resulted in poor development of deltaic and rhythmically laminated lake floor deposits. It is suggested that such deposits are more characteristic of ice‐dammed lakes formed in association with wet‐based temperate ice than those associated with dry‐based polar ice.     

两个相连湖泊的微生态系统——云南高原湖泊中浅水的星云湖和深水的抚仙湖研究

抚仙湖是中国云南省的一个深水湖，连接着富营养化的浅水湖－－星云湖，星云湖排放含绿藻的水进入抚仙湖。两湖位于省会昆明附近，由于地方文化、集约化农业、以及旅游业的发展，两湖已经富营养化。因为湖泊体积容量的级别差异，深水湖的富营养化几乎没被注意，抚仙湖秋季下层滞水带缺氧已经关注了20年，似乎下层滞水带是深水湖富营养化的指标或趋势。抚仙湖看起来目前情况尚好，可以说寡营养，然而，外界负荷是潜在的，且是以稳定的加速度进行的。在此对浅水湖富营养化的原因进行了讨论，包括在其它云南湖泊观察到富营养化的过程，再者，对两个连相湖的藻和蓝藻碎片的大小构成进行比照。为了与深水的抚仙湖状况进行比较，简略介绍了一个日本的深湖及其径流系统。其中，涡流和它的微生态系统，在两者中相关性很好。对于以涡流生态系统的见解判断微生态系统的深水湖富营养化问题将给予概括。     

基于流量监测的西藏东南部然乌湖水量平衡季节变化及其补给过程分析

青藏高原分布着亚洲大陆最大的湖泊群,其湖泊变化对气候变化响应敏感。基于遥感数据的湖泊面积变化不足以反映外流湖对气候变化的响应,需借助湖泊水量平衡过程分析来进一步研究各补给要素的变化。本文利用2015年4月-11月然乌湖水文气象监测数据,通过建立流量—水位关系,依据连续的水位数据重建了观测期内然乌湖主要径流的水文过程线,并结合SRM模型分析了然乌湖的水量平衡过程及季节变化。结果表明,观测期内然乌湖入湖水量约为18.49×10⁸ m³,其中冰川融水约为10.06×10⁸ m³,冰川融水占然乌湖补给的54%以上,湖面降水、湖面蒸发对湖泊水量平衡过程影响微弱。流域降水对湖泊的补给具有明显的季节特征。春季受西风南支扰动影响,然乌湖地区降水量大,降水是春季然乌湖的主要补给源。夏季和早秋由于气温升高,冰川消融量大,冰川融水是湖泊补给的主控因素。在未来气候变暖的条件下,冰川融水将会在湖泊补给中占据更大比例,并可能使得流域内的冰湖水量增加,产生潜在灾害风险。     

"富营养化湖泊治理及湖泊管理昆明国际讨论会"综述

湖泊富营养化是国际上普遍存在而倍受关注的问题。以国家列为“三河三湖”重点环保项目整治的滇池为首的云南九大高原湖泊中,有6个已富营养化。在云南省即将大规模开展湖泊治理工作之际,为借鉴国际湖泊治理及管理的方法及成功的经验,2001年11月召开了此次会议。有众多国际湖泊学权威在内的10个国家的163名专家出席会议。重点讨论了5个主题：湖泊治理及管理研究;湖泊环境变化的沉积记录;湖水氮、磷负荷与湖泊生态健康;湖泊污染与治理;湖泊富营养化过程。专家们对云南高原湖泊的治理提出了4个方面的建议：以改善、恢复湖泊生态系统结构的方法控制富营养化;清淤一定要慎重;加强湖泊富营养化过程与机制的研究;加强流域管理研究。会议最后发表了《昆明宣言》,建议建立云南高原湖泊国际研究中心。     

Historical changes in sediments of Pyramid Lake,Nevada, USA: consequences of changes in the water balance of a terminal desert lake

Sediment cores from the shallow and deep basins of Pyramid Lake, Nevada, revealed variations in composition with depth reflecting changes in lake level, river inflow, and lake productivity. Recent sediments from the period of historical record indicate: (1) CaCO₃ and organic content of sediment in the shallow basin decrease at lower lake level, (2) CaCO₃ content of deep basin sediments increases when lake level decreases rapidly, and (3) the inorganic P content of sediments increases with decreasing lake volume. Variations in sediment composition also indicate several periods for which productivity in Pyramid Lake may have been elevated over the past 1000 years. Our data provide strong evidence for increased productivity during the first half of the 20th Century, although the typical pattern for cultural eutrophication was not observed. The organic content of sediments also suggests periods of increased productivity in the lake prior to the discovery and development of the region by white settlers. Indeed, a broad peak in organic fractions during the 1800's originates as an increase starting around 1600. However, periods of changing organic content of sediments also correspond to periods when inflow to the lake was probably at extremes (e.g. drought or flood) indicating that fluctuations in river inflow may be an important factor affecting sediment composition in Pyramid Lake.     

Biogeochemistry of silica in Devils Lake: implications for diatom preservation

Diatom-salinity records from sediment cores have been used to construct climate records of saline-lake basins. In many cases, this has been done without thorough understanding of the preservation potential of the diatoms in the sediments through time. The purpose of this study was to determine the biogeochemistry of silica in Devils Lake and evaluate the potential effects of silica cycling on diatom preservation. During the period of record, 1867–1999, lake levels have fluctuated from 427 m above sea level in 1940 to 441.1 m above sea level in 1999. The biogeochemistry of silica in Devils Lake is dominated by internal cycling. During the early 1990s when lake levels were relatively high, about 94% of the biogenic silica (BSi) produced in Devils Lake was recycled in the water column before burial. About 42% of the BSi that was incorporated in bottom sediments was dissolved and diffused back into the lake, and the remaining 58% was buried. Therefore, the BSi accumulation rate was about 3% of the BSi assimilation rate. Generally, the results obtained from this study are similar to those obtained from studies of the biogeochemistry of silica in large oligotrophic lakes and the open ocean where most of the BSi produced is recycled in surface water. During the mid 1960s when lake levels were relatively low, BSi assimilation and water-column dissolution rates were much higher than when lake levels were high. The BSi assimilation rate was as much as three times higher during low lake levels. Even with the much higher BSi assimilation rate, the BSi accumulation rate was about three times lower because the BSi water-column dissolution rate was more than 99% of the BSi assimilation rate compared to 94% during high lake levels. Variations in the biogeochemistry of silica with lake level have important implications for paleolimnologic studies. Increased BSi water-column dissolution during decreasing lake levels may alter the diatom-salinity record by selectively removing the less resistant diatoms. Also, BSi accumulation may be proportional to the amount of silica input from tributary sources. Therefore, BSi accumulation chronologies from sediment cores may be effective records of tributary inflow.     

Formation and early history of Lakes Pepin and St. Croix of the upper Mississippi River

Study of Lake Pepin and Lake St. Croix began more than a century ago, but new information has permitted a closer look at the geologic history of these two riverine lakes located on the upper Mississippi River system. Drainages from large proglacial lakes Agassiz and Duluth at the end of the last glaciation helped shape the current valleys. As high-discharge outlet waters receded, tributary streams deposited fans of sediment in the incised river valleys. These tributary fans dammed the main river, forming riverine lakes. Lake Pepin was previously thought to be a single long continuous lake, extending for 80 km from its dam at the Chippewa River fan all the way up to St. Paul, with an arm extending up the St. Croix valley. Recent borings taken at bridge and dam locations show more than a single section of lake sediments, indicating a more complex history. The Minnesota and Mississippi Rivers did not always follow their current paths. Valleys cut into bedrock but now buried by glacial sediment indicate former river courses, with the most recent of these from the last interglacial period marked at the surface by chains of lakes. The morphology of the Mississippi valley bottom, and thus the morphology of Lake Pepin as it filled the valley, is reflect in part by the existence of these old valleys but also by the presence of glacial outwash terraces and the alluvial fans of tributary streams. A sediment core taken in Lake Pepin near Lake City had a piece of wood in gravels just below lake sediments that dated to 10.3 ka cal. BP, indicating that the lake formed as the Chippewa River fan grew shortly after the floodwaters of Lakes Agassiz and Duluth receded. Data from new borings indicate small lakes were dammed behind several tributary fans in the Mississippi River valley between the modern Lake Pepin and St. Paul. One tributary lake, here called Early Lake Vermillion, may have hydraulically dammed the St. Croix River, creating an incipient Lake St. Croix. The tributary fans from the Vermillion River, the Cannon River, and the Chippewa River all served to segment the main river valley into a series of riverine lakes. Later the growth of the Chippewa fan surpassed that of the Vermillion and Cannon fans to create a single large lake, here called late Lake Pepin, which extended upstream to St. Paul. Sediment cores taken from Lake Pepin did not have significant organic matter to develop a chronology from radiocarbon dating. Rather, magnetic features were matched with those from a Lake St. Croix core, which did have a known radiocarbon chronology. The Pepin delta migration rate was then estimated by projecting the elevations of the top of the buried lake sediments to the dated Lake Pepin core, using an estimated slope of 10 cm/km, the current slope of Lake Pepin sediment surface. By these approximations, the Lake Pepin delta prograded past Hastings 6.0 ka cal BP and Red Wing 1.4 ka cal BP. This is one of eight papers dedicated to the “Recent Environmental History of the Upper Mississippi River” published in this special issue of the Journal of Paleolimnology. D. R. Engstrom served as guest editor of the special issue.