北极巴罗地区300年以来的孢粉记录及其气候变化

根据北极巴罗地区Elson泻湖300年以来的孢粉记录,揭示出小冰期以来的该地区植被的生态变化和气候变化,相对温暖期分别出现在公元1720年、1800年、1922年、1953年和1992年以后,结果和其他研究成果是比较一致的。孢粉总浓度的变化和生态变化相对应,孢粉总浓度可以作为北极巴罗地区温度变化替代性指标。温度升降是北极地区植被覆盖率变化的主要原因。20世纪人类已经对北极地区植被产生重要影响。     

末次冰期以来湛江湖光岩玛珥湖孢粉记录及古环境变化

通过对湛江湖光岩玛珥湖钻孔孢粉记录的研究认为,末次冰期以来,该区植被类型从早期的南亚热带季风常绿阔叶林依次演替为,中亚热带常绿、落叶阔叶林→南亚热带季风常绿阔叶林→中亚热带常绿—落叶阔叶—针叶混交林(湖边草地)→热带季雨林→半常绿季雨林。气候最寒冷的时期温度比目前至少降低了4—6℃以上。全新世早期相对于旱。     

新疆吉木萨尔县四厂湖剖面孢粉分析及其意义

根据位于古尔班通古特沙漠东南缘沙漠内部四厂湖剖面沉积物中的孢粉分析,结合剖面岩性特征分析和历史资料记录,揭示了该处近1000多年以来的环境变化。该地近1000多年以来,植被经历了由荒漠植被演替为浅湖和沼泽植被,又回到荒漠植被的3个阶段。而在广域上,一直是荒漠植被,与现代古尔班通古特沙漠东南缘的荒漠植被相当。该地在唐朝以前已经有沙漠发育,在唐朝中期—元朝,这里有发源于东天山河流的尾闾湖存在,唐朝—元朝将近400～500年间,可能是气候相对比较湿润的阶段。在清朝,尾闾湖主要出现在现沙漠南缘。在近50年,由于下新湖水库等水利工程的修建,使古尔班通古特沙漠东南缘的小湖完全干涸。四厂湖剖面反映了沙漠南缘相对稳定,虽有向南移动趋势,但移动速度较缓,说明气候变化不大,后期水系的明显变化是由于人为影响的结果。     

神农架大九湖12．5kaBP以来的孢粉与植被序列

在神农架海拔1700m的大九湖盆地12．5kaBP以来晚第四纪中,高密度地取得3个钻孔的孢粉样品,建立起晚第四纪高分辨率孢粉组合序列,划分出15个综合孢粉带,代表15个不同时代类型的古植物群落,根据植被演替及其所反映的气候变化过程,本文还讨论了第四纪植被与气候阶段的划分问题,认为高分辨率孢粉－植被序列的建立与研究可以反映多种时间尺度,特别是小尺度的环境变化与事件,从而更详细地揭示其演变轨迹与特点。     

成都平原4 000aBP以来的孢粉记录与环境变化

成都平原晚全新世以来沉积的泥质层发现丰富的孢粉。根据孢粉成分组合特征和生态类型可划分出5个孢粉组合带,结合剖面上6个14^C测年数据,提出在过去的4000a研究区植被类型及气候环境经历了5个阶段的变化：3800-3600aBP为亚热带常绿阔叶林,气候暖偏湿;3600-3400aBP为含常绿树种的落叶阔叶林,气候温暖湿润;3400-2600aBP为草／湿地,气温下降,环境更潮湿;2600-900aBP为落叶阔叶林,温度又开始逐渐回升,气候温和偏湿;900-300aBP再次变为草／湿地,偏干冷的气候环境。     

东北二龙湾玛珥湖晚更新世晚期植被与环境变化的孢粉记录

东北二龙湾玛珥湖孢粉记录显示,34 ka B.P.以来,该区植被和气候经历了以下变化:34-29.3 ka B.P.,发育山地寒温性针叶林,气候冷湿.29.3-12.6 ka B.P.,该区以寒温性针叶林、桦树林为主,气候转向冷干发展,尤其在20.6-18.7 ka B.P.(LGM)时,表现最为突出.12.6-8.9 ka B.P.,该区植被为针阔叶混交林,气候由冷干向温湿逐渐过渡,8.9-4.6 ka B.P.,为落叶阔叶林,气候温暖湿润.4.6 ka B.P.至今,发育针阔叶混交林,气候向温凉转干方向发展.研究表明,MIS3a阶段,以二龙湾为代表的中国东北东部气候以冷湿为主要特征,而末次冰期对该区的影响直到12.6 ka B.P.以后才结束.     

鹤庆深钻孢粉记录揭示的气候变化与西南季风演化

本文在鹤庆深钻孢粉分析的基础上,把各孢粉类型划分成不同的孢粉生态组,结合孢粉多样性指数,系统重建云南鹤庆地区2.78 Ma以来的占气候演化所经历的8个大的阶段,与西南季风在滇西北地区8次大的变化相对应:即在2.729-2.608Ma和0.118Ma-11.83ka BP期间,气候整体湿润,冬、夏季降水的季节性较强,反映西南季风相对较强盛;1.447-0.342Ma期间,气候整体逐渐变湿,冷暖、干湿变化幅度逐渐变大,气候组合特征逐渐变复杂,反映西南季风逐渐增强,其波动幅度也逐渐变大,并于0.991-0.342Ma期间达到最强盛,其波动幅度也最大;而在2.780-2.729Ma、2.608-1.447Ma和0.342-0.118Ma期间,气候普遍相对温暖干旱,西南季风相对较弱.     

上海松江广富林遗址的孢粉记录

上海广富林地区广富林遗址IT1238和IT0446剖面的孢粉记录,并根据14C数据和遗址层位所建立的年代标尺,通过孢粉分析结果表明,在5300cal.aB.P.之前,本区尚无人类活动的迹象,遗址点周围主要生长由栎树和榆科等植物构成的常绿和落叶阔叶混交林,气候温暖湿润。良渚文化中前期,在花粉谱上出现了农作物的证据,说明当地已有人类进驻,并开展农业活动;大量水生植物花粉的分布说明当时水体面积扩大,降水量增多。良渚文化晚期以后,栎树林几近消失,水生植物减少,而蒿、藜增加,可能是由于水体面积的减少,以及区域气候变得干冷所致。广富林遗存、战国和东汉文化层时期的状况,在一定程度上延续了良渚文化晚期的特征。在战国和东汉文化层时期,栎树林有所恢复,人类活动在后期有所增强。     

达里诺尔湖沉积物中无机碳的形态组成

以达里诺尔湖沉积物为研究对象,运用连续浸取法分析测定了沉积物中不同形态的无机碳,开展了沉积物中无机碳形态的分布特征研究,初步探讨了沉积物中不同形态生源要素与无机碳的相互关系.研究表明,表层和柱芯沉积物中无机碳的主导形态均为NH2OH·HCl相;空间分布上,湖心区为各形态无机碳的高值区,东部和北部湖区为低值区;计算结果表明,碳酸钙在湖水中可达过饱和,揭示达里诺尔湖具备形成自生碳酸盐沉淀的条件;沉积柱芯中氮、磷和生物硅与无机碳的相互关系反映了营养水平升高可促进水体对碳酸钙过饱和条件的形成,藻类光合作用对水体理化性质的改变是导致碳酸盐沉淀的重要因素之一.     

黄海大气中的孢粉及其对海底沉积物中孢粉组合的影响

１９７８—１９７９ 年在黄海上空共收集到孢粉３２１ 粒,属２３ 个属种。春季大气中所含孢粉数量最多,秋季次之,夏季和冬季较少。大气中木本花粉含量达７４％ ,草本花粉２３％ ,孢子３％ 。通过大气中孢粉与１９９０ 年黄海表层沉积物中孢粉组合的对比,反映出大气中孢粉与海洋沉积物中孢粉属种具有明显的对应关系。海洋沉积物中的孢粉分布显现近岸草本花粉含量高,远海木本花粉含量高的规律     

Miocene to Pliocene vegetation reconstruction and climate estimates in the Iberian Peninsula from pollen data

Pollen analysis of Miocene and Pliocene sediments from the Iberian Peninsula shows a progressive reduction in plant diversity through time caused by the disappearance of thermophilous and high-water requirement plants. In addition, an increase in warm-temperate (mesothermic), seasonal-adapted “Mediterranean” taxa, high-elevation conifers and herbs (mainly Artemisia) occurred during the Middle and Late Miocene and Pliocene. This has mainly been interpreted as a response of the vegetation to global and regional processes, including climate cooling related to the development of the East Antarctic Ice Sheet and then the onset of the Arctic Ice Sheet, uplift of regional mountains related to the Alpine uplift and the progressive movement of Eurasia towards northern latitudes as a result of the northwards subduction of Africa. The development of steppe-like vegetation in southern Iberia is ancient and probably started during the Oligocene. The onset of a contrasted seasonality in temperature during the Mid-Pliocene superimposed on the pre-existing seasonality in precipitation, the annual length of which increased southward. The Mediterranean climatic rhythm (summer drought) began about 3.4 Ma and caused the individualization of modern Mediterranean ecosystems. Quaternary-type Mediterranean climatic fluctuations started at 2.6 Ma (Gelasian) resulting in repeated steppe vs. forest alternations. A latitudinal climatic gradient between the southern and the northern parts of the Iberian Peninsula existed since the Middle Miocene.     

陕北气候变化与生态植被变迁

分析了128万年以来陕北气候变化及其生态植被变迁。结果表明,陕北黄土高原气候经历了多次冷、暖、干、湿的周期变化。陕北植被变迁在地质时期以及历史时期早期,主要由气候条件所控制,植被类型随气候的冷暖干湿变化而变迁。随着人类活动的加剧,气候条件不再是影响植被变迁的唯一因素,人类活动对植被的影响愈来愈明显。明清时期,气候冷干,旱灾频繁．陕北生态环境脆弱,大规模垦殖和滥烧使自然植被迅速减少,陕北自然植被遭到毁灭性破坏。20世纪50年代,陕北逐步开始生态环境治理,在对生态环境治理的同时,又对部分地区自然植被进行破坏。20世纪80年代以后,生态环境总体上趋于好转。     

The change of sediment composition during recovery of two Finnish lakes induced by waste water purification and lake oxygenation

Total oxygen deficit occurred regularly during stagnation periods in the deepest part of Lake Kallavesi in the period 1973–1986. The sediment was black and anaerobic during the first sampling in 1987. After beginning of artificial lake oxygenation and efficient purification of waste waters of a paper board mill in 1986 the oxygen deficit decreased gradually and a light brown oxidized uppermost sediment layer appeared and began to thicken. The following changes in the sediment composition were observed during 1987–1996: loss on ignition, total nitrogen and BOD₇ concentrations decreased in the uppermost sediment layer (0–2 cm) and BOD₇ concentration increased in the next sediment layer beneath (2–10 cm). There were no significant change in phosphorus and iron concentrations.Lake oxygen, total phosphorus and suspended solids concentrations fluctuated in a noticeable degree in Lake Huruslahti depending on waste water input and artificial oxygenation during the years 1980–1993. Oxygen condition was good at times of successful waste water elimination and lake oxygenation while deterioration of either resulted oxygen deficiency as well as increase of total phosphorus and suspended solids concentration. Most of the internal load entered with suspended solids during periods of total oxygen deficiency.An explanation for the findings in Lake Huruslahti could be microbiological. Gas formation inside sediment lift organic material towards top of the sediment and into the water, but after the lake recovery the material retain in the sediment. Also in Lake Kallavesi microbiological gas formation resuspended sediment particles with phosphorus into the overlaying water prior to oxygenation. During oxygenation microbiological processes in uppermost sediment utilize the anaerobic metabolic products, organic acids and methane, and block gas formation. Organic substances remain in the top sediment decomposing gradually in the uppermost layer.     

Determinants of pollen dispersal in the East Asian steppe at different spatial scales

Two sites from the East Asian steppe, the Mu Us Sandland as a regional case and the Anguli Nuur catchment as a local one, were chosen to detect roles of vegetation, climate, landform, and human disturbance on pollen dispersal. 1) Vegetation: The semi-arid steppe vegetation is characterized by Artemisia and Chenopodiaceae pollen under various vegetation conditions; however, no evident correlation between pollen percentages and corresponding plant species cover is found. 2) Climate: Samples under different Mean Annual Precipitations (MAPs) clearly distinguish themselves in the Mu Us Sandland, implying MAP-determined surface pollen spectra in regional scale. 3) Landform: Surface pollen assemblages in the azonal psammophytic vegetation and lowland meadow, show insignificant variance from the zonal steppe vegetation. The azonal halophilous vegetation, mostly distributed in the lowland or near the lake shore, leads to higher than average percentages of Chenopodiaceae pollen. Signal of exotic Pinus pollen is also strengthened in the lowland and lake sediment. 4) Human disturbance: The role of human disturbance on surface pollen assemblages is weak, as shown in the Mu Us Sandland.

This study also provides theoretical bases for quantitative reconstructions of palaeoclimate and palaeovegetation based on fossil pollen spectra from lake sediments and lowland soils in the semi-arid East Asian steppe. We suggest that calibration against locally dispersed pollen taxa is necessary to reliably reconstruct changes in vegetation pattern through time, for example, a factor of 1.75 for the widely used A/C (Artemisia/Chenopodiaceae) ratio is suggested according to the pollen assemblages in the surface layers of the lake sediment vs. slope soil in Anguli Nuur. However, uncertainties also exist for such calibration considering the dynamics of local-scale azonal vegetation.     

A change from grass pollen induced allergy to tree pollen induced allergy: 30 years of pollen observation in Switzerland

Pollen monitoring with a Hirst like pollen trap for 30 years in Basel, Switzerland allows understanding of the behaviour of the different plants producing allergenic pollens. It becomes evident that in this time period the different tree pollen like Hazel and Birch increased, whereas in the control, the observed amount of a herb pollen like Artemisa did not change. Moreover, it was observed that in the different trees flowering took place earlier namely at the beginning of the year. This was especially impressive for Hazel, where flowering was shifted ofmore than one month. These aerobiological observations were supported and confirmed by some epidemiological studies, showing that tree pollen allergy has become more important in the last years compared to grass pollen allergy and herb pollen allergy. The reason for the increase of tree pollen counts and the shift in the flowering time depends on the observed increase of the annual temperature, an increased input of nutrients like CO₂or NO_x but probably also a real increase of certain trees, like birch for example, in parks and avenues. This revised version was published online in June 2006 with corrections to the Cover Date.     

A comparison of sedimentary DNA and pollen from lake sediments in recording vegetation composition at the Siberian treeline

Reliable information on past and present vegetation is important to project future changes, especially for rapidly transitioning areas such as the boreal treeline. To study past vegetation, pollen analysis is common, while current vegetation is usually assessed by field surveys. Application of detailed sedimentary DNA (sedDNA) records has the potential to enhance our understanding of vegetation changes, but studies systematically investigating the power of this proxy are rare to date. This study compares sedDNA metabarcoding and pollen records from surface sediments of 31 lakes along a north–south gradient of increasing forest cover in northern Siberia (Taymyr peninsula) with data from field surveys in the surroundings of the lakes. sedDNA metabarcoding recorded 114 plant taxa, about half of them to species level, while pollen analyses identified 43 taxa, both exceeding the 31 taxa found by vegetation field surveys. Increasing Larix percentages from north to south were consistently recorded by all three methods and principal component analyses based on percentage data of vegetation surveys and DNA sequences separated tundra from forested sites. Comparisons of the ordinations using procrustes and protest analyses show a significant fit among all compared pairs of records. Despite similarities of sedDNA and pollen records, certain idiosyncrasies, such as high percentages of Alnus and Betula in all pollen and high percentages of Salix in all sedDNA spectra, are observable. Our results from the tundra to single‐tree tundra transition zone show that sedDNA analyses perform better than pollen in recording site‐specific richness (i.e., presence/absence of taxa in the vicinity of the lake) and perform as well as pollen in tracing vegetation composition.     

近30年河北大海陀自然保护区山地草甸植被(NDVI)变化及其对气候的响应

河北大海陀自然保护区地处我国暖温带落叶阔叶林区,草甸植被多处于山地顶部,对外界干扰敏感。为了研究该地区的草甸植被变化以及其对气候变化的响应,收集了该地区近30年的TM遥感影像资料,1980—2015年的气候数据,包括年平均气温、7月份平均气温、1月份平均气温、年降水量、6—8月平均降水量等多个气候指标,以及大海陀自然保护区及其周边地区的地形数据等,用滑动平均法、M-K检验法、相关分析法及偏相关分析法等方法分析了大海陀自然保护区草甸植被NDVI及其与气候响应。结果表明:(1)近30年来,大海陀自然保护区草甸植被NDVI呈先上升后下降的趋势,在2004年NDVI达到最高,随后逐渐下降。(2)大海陀自然保护区草甸区域的年降水量变化整体表现为波动循环的趋势,总体略有上升,但没有达到显著水平;年均温变化表现为上升趋势,且达到了极显著水平,该地区的气温上升趋势主要由以1月为主的冬季温度升高而引起。(3)草甸植被NDVI与年均温成显著的负相关关系,与年降水量的关系不明显。     

Climate change predicted to cause severe increase of organic carbon in lakes

Riverine transport of organic carbon (OC) to the ocean is a significant component in the global carbon (C) cycle and the concentration of total organic carbon (TOC) in rivers and lakes is vital for ecosystem properties and water quality for human use. By use of a large dataset comprising chemical variables and detailed catchment information in ～1000 Norwegian pristine lakes covering a wide climatic range, we were able to predict TOC concentrations with high accuracy. We further predict, using a ‘space‐for‐time’ approach and a downscaled, moderate, climate change scenario, that northern, boreal regions likely will experience strong increases in OC export from catchments to surface waters. Median concentrations of OC in these lakes will increase by 65%, from the current median of 2.0–3.3 mg C L^?1. This is a long‐term effect, primarily mediated by increased terrestrial vegetation cover in response to climate change. This increase OC will have severe impacts on food‐webs, productivity and human use. Given the robustness of the estimates and the general applicability of the parameters, we suggest that these findings would be relevant to boreal areas in general.