中全新世以来福建东北地区植被与环境变化

本文提供了福建宁德市霞浦县沿海平原XPZK3钻孔的年代和孢粉记录用于研究中全新世以来福建东北地区的植被与环境变化。中全新世以来,研究区植被中亚热带木本成分逐步降低而落叶阔叶成分逐渐增多,反映气温逐步降低,与东亚季风和北半球温度变化的趋势相同,反映在轨道尺度上北半球夏季太阳辐射对东亚季风的影响。DCA分析显示,中全新世以来,人类活动是影响研究区植被变化的最主要因素,5 000 cal. yr BP以来,松属、草本植物花粉和蕨类孢子的逐步增加反映人类活动对植被的干扰逐步加重,尤其是1 370 cal. yr BP(南北朝)以来,反映人类活动的孢粉占主要地位,人类活动对植被产生了重要影响。     

干旱区石羊河流域河水孢粉组合特征

石羊河流域初春和仲夏两季不同地点,洪水期、平水期30个河水样孢粉分析显示, 没有人类影响的情况下,河水样孢粉组合是由河流上游径流区的植物孢粉和采样点附近植被孢粉组成的,前者在孢粉组合中至少占30%～60%.河水搬运孢粉的能力非常强,可长距离、大量地搬运孢粉.孢粉组合中河水贡献孢粉的含量较高,如:云杉属(Picea Dietr.)花粉河水的贡献率在中下游可达16.5%和7.7%.采样时间、地点影响河水的孢粉组合和浓度,洪水期是孢粉搬运的主要时期.河水经过水库后,其中孢粉绝大多数沉积在水库中.     

干旱区石羊河流域河水孢粉组合特征

石羊河流域初春和仲夏两季不同地点 ,洪水期、平水期 30个河水样孢粉分析显示 ,没有人类影响的情况下 ,河水样孢粉组合是由河流上游径流区的植物孢粉和采样点附近植被孢粉组成的 ,前者在孢粉组合中至少占30 %～ 6 0 %。河水搬运孢粉的能力非常强 ,可长距离、大量地搬运孢粉。孢粉组合中河水贡献孢粉的含量较高 ,如 :云杉属 (PiceaDietr.)花粉河水的贡献率在中下游可达 16 .5 %和 7.7%。采样时间、地点影响河水的孢粉组合和浓度 ,洪水期是孢粉搬运的主要时期。河水经过水库后 ,其中孢粉绝大多数沉积在水库中。     

白洋淀地区全新世以来植被演替和气候变化初探

 根据对白洋淀白4号孔的孢粉分析、放射性碳年代测定和野外考察研究表明,白洋淀形成于中全新世。晚全新世以来,随着气候的变凉变干,古白洋淀开始收缩和解体,但在人类活动的利用改造下,使逐渐解体的白洋淀得以保留下来。依据气候地层学的观点,并结合放射性碳年代测定,白洋淀地区的全新世地层可以划分为四期：即古全新世(距今11000—9000年),气候温和湿润;早全新世(距今9000—7500年),气候偏凉偏干;中全新世(距今7500—3000年),气候温暖湿润;晚全新世(距今3000年至今),气候温凉偏干。     

太湖平原西北部全新世以来植被与环境变化

太湖平原西北部卜弋桥Zk01孔上部8m地层孢粉资料显示该地区自全新世以来植被与气候主要经历了三个阶段:1)11000—9500cal.aB.P.,地带性植被为壳斗科为主的亚热带常绿落叶针阔混交林。森林成分以栎属(Quercus)、青冈属(Cyclobalanopsis)、栗属(Castanea)、栲属(Castanopsis)/石栎属(Lithocarpus)和松属(Pinus)为主,同时混生有少量的枫香属(Liquidambar)、冬青属(Ilex)、水青冈属(Fagus)、桦属(Betula)、榆属(Ulmus)等乔灌木。本阶段孢粉浓度较高,气候较温暖湿润,为早全新世升温期;2)9500—3900cal.aB.P.,植被演替为中亚热带性质的常绿阔叶林。此阶段特别是8000cal.aB.P.以来,植被以青冈属为主的常绿分子获得大发展为特点。当时森林繁茂,气候暖湿且较为稳定,对应于中全新世大暖期(适宜期);3)3900cal.aB.P.以来,森林植被表现为次生性质的亚热带针阔混交林。青冈属、栎属骤减,松属、禾本科(Poaceae)及水龙骨科(Polypodiaceae)含量明显增升。本阶段孢粉浓度减为最低,据研究区周边的孢粉资料推测此时期气候温凉湿润。本阶段晚期森林植被受到人类的干扰,与人类活动密切相关的农作物如禾本科(35—45μm)、十字花科和菊科等花粉类型含量持续增多,表明研究区自全新世晚期以来出现了明显的人类活动的迹象。Zk01钻孔点位处古河道,磁化率和粒度证据揭示了研究点沉积环境全新世早期为河流相,水动力较强,中期水动力条件显著增强,晚期减弱。最后,结合孢粉资料和沉积环境简述了植被变化与沉积环境之间的关联。     

河北卢龙饮马河流域全新世冲积物孢粉分析及对全新世植被时空变化的初步探讨

 依据河北省卢龙县闫深港4.6m厚的冲积物剖面，揭示了较高时间分辨率的孢粉分析，参照现代冲积物孢粉与植被的对应关系，探讨了距今11000年以来饮马河流域植被的时空变化。11000～9000aBP的森林覆盖率约10％，9000～7000aBP约30％～40％，7000～4000aBP约20％～40％，3000～2500aBP约10％～20％。在9000aBP左右出现了云杉、冷杉花粉的高峰值，表明饮马河流域曾出现垂直植被带的变化。     

新疆乌伦古湖全新世以来高分辨率的孢粉记录与环境变迁

根据新疆乌伦古湖钻孔剖面高分辨率的孢粉研究,得出全新世以来研究区的气候经历了四个大的阶段：约9．99～7．72cal．kaBP期间,气候温暖干旱;7．72—3．62cal．kaBP,气候由温和偏湿逐渐转向温暖偏干;3．62—1．24cal．kaBP,气候由寒冷干旱逐渐转向寒冷偏湿到温和湿润;1．24cal．kaBP至今,气候总体上温和干旱。在这四个大阶段的气候背景下,还存在8．90cal．kaBP和8．35cal．kaBP左右、3．62—2．80cal．kaBP期间、0．82—0．45cal．kaBP期间和约0．23cal．kaBP时的突然变冷事件。本剖面的孢粉组合在约9．99—7．72cal．kaBP期间反映的是湖区的植被,早期为以芦苇为主的水生植物群落,随后演替成以黑三棱为主的水生植物群落;自7．72cal．kaBP以后,孢粉组合反映的是区域植被,与气候相应的区域植被依次经历了荒漠草原→荒漠→荒漠草原→草原或荒漠草原→草原→荒漠→荒漠草原的多次演替。     

最近12000年来青藏高原植被的时空分布

青藏高原 30个点湖泊的孢粉记录综合研究显示 :在进入全新世之前 (12kaBP以前 ) ,除最东南部外 ,高原从东到西均发育为荒漠草原植被。全新世早期 (12 .0 - 9.0kaBP)高原东南部 (10 4° - 98°E)为落叶阔叶林 /针阔叶混交林 ;中部 (98° - 92°E)为草甸或灌丛草甸 ,再向西至 80°E左右为草原植被 ;全新世中期 (9.0 - 3 .2kaBP)高原由东向西古植被依次发育为针阔混交林和硬叶阔叶林 (10 4° - 98°E)→针阔混交林 (98° - 94°E)→灌丛草甸 (94° -92°E)→草原 (92°- 80°E) ;全新世晚期 (3.2kaBP以后 )由东向西古植被依次为硬叶阔叶林→针阔混交林→草甸→草原→荒漠。     

最近12 000年来青藏高原植被的时空分布

青藏高原30个点湖泊的孢粉记录综合研究显示: 在进入全新世之前(12 ka BP以前),除最东南部外,高原从东到西均发育为荒漠草原植被.全新世早期(12.0-9.0 ka BP)高原东南部(104°-98° E)为落叶阔叶林/针阔叶混交林; 中部(98°-92° E)为草甸或灌丛草甸,再向西至80° E左右为草原植被; 全新世中期(9.0-3.2 ka BP)高原由东向西古植被依次发育为针阔混交林和硬叶阔叶林(104°-98° E)→针阔混交林(98°-94° E)→灌丛草甸(94°-92° E)→草原(92°-80° E);全新世晚期(3.2 ka BP以后)由东向西古植被依次为硬叶阔叶林→针阔混交林→草甸→草原→荒漠.     

河北迁安盆地中全新世以来的植被变化及人类活动的影响

依据位于燕山南部迁安盆地蚕姑庙村和余家洼村具放射性碳年代测定支持的埋藏泥炭剖面的孢粉分析资源，揭示了迁安盆地5000a BP以来自然植被变化和人类活动对自然环境的影响。在4600～3100a BP期间，迁安盆地曾经生长着以栎为主的落叶阔叶林，至3100a BP以后，森林中阔叶树成分显下降，喜凉耐干的松树比例增加，1600a BP后，迁安盆地人类农耕活动进一步加剧，森林遭受到大规模的破坏，孢粉分析资料揭示迁安盆地人类栽培板栗的历史可以追溯到1600a BP左右，种植水稻的历史可以追溯到700a BP左右。     

基于RS和GIS的干旱区内陆河流域生态系统质量综合评价——以石羊河流域为例

石羊河流域是河西走廊东段重要生态区,也是用水矛盾最突出、生态环境问题最严重的地区之一,对其进行生态系统质量的评价,可为干旱区内陆河流域的生态保护工作提供借鉴.依据生态系统质量概念,以统计数据、遥感数据和土地覆被数据为基础,从生态系统的3方面(生产力、稳定性和承载力)构建评价指数,基于非参数Kruskal-Wallis卡方(χ²)检验和熵值法确定指标权重,结合RS、GIS和SPSS软件对2000、2005、2010和2015年石羊河流域不同生态系统类型的质量及各指数进行综合评价及变化分析.结果表明: 2000—2015年,石羊河流域生态系统质量均值为57.76,呈现显著下降趋势,年降幅为0.72,空间分布呈上游优于中游、中游优于下游的状态;生态系统生产能力、稳定性和承载力均值分别为67.52、45.37、58.53,生产能力和稳定性小幅上升,承载力逐渐下降.就各生态系统类型来看,森林生态系统质量最高,年均值为78.12,年降幅最小,为0.28;其次是草地、农田和城镇生态系统,年均值分别为62.45、58.76、50.29;湿地生态系统质量最低,年降幅最大,达0.98.     

Holocene altitudinal shifts in vegetation belts and environmental changes in the Sierra Madre Occidental, Northwestern Mexico, based on modern and fossil pollen data

A modern pollen rain study was performed in a 300 km-long altitudinal transect (~ 28° N latitude) from 300 to 2300 m elevation. The higher elevation modern communities: epithermal oak–pines, pine–oak forest, pine forest, and mixed conifer forest were easy to distinguish from their pollen content. In contrast, lower elevation subtropical communities: thornscrub and tropical deciduous forest were difficult to separate, because they share many pollen taxa. Nevertheless we identify high frequencies of Bursera laxiflora as an important component of the tropical deciduous forest.Additionally, fossil pollen was analyzed at three sites located between 1700 and 1950 m altitude at ~ 28° latitude north in the Sierra Madre Occidental of northwestern Mexico. The sites were in pine–oak (Pinus–Quercus), pine, and mixed-conifer forests respectively. Shifts in the altitudinal distribution of vegetation belts were recorded for the last 12,849 cal yr BP, and climate changes were inferred. The lowest site (pine–oak forest) was surrounded by pine forest between 12,849 and 11,900 cal yr BP, suggesting a cold and relatively dry Younger Dryas period. The early Holocene was also cold but wetter, with mixed conifer forest with Abies (fir) growing at the same site, at 1700 m elevation, 300 m lower than today. After 9200 cal yr BP, a change to warmer/drier conditions caused fir migration to higher elevations and the expansion of Quercus at 1700 m. At 5600 cal yr BP Abies was growing above 1800 m and Picea (spruce) that is absent today, was recorded at 1950 m elevation. Fir and spruce disappeared from the 1950 m site and reached their present distribution (scattered, above 2000 m) after 1000 cal yr BP; we infer an episodic Holocene migration rate to higher elevations for Abies of 23.8 m/1000 cal yr and for Picea of 39.2 m/1000 cal yr. The late Holocene reflects frequent climate oscillations, with variations in the representation of forest trees. A tendency towards an openness of the forest is recorded for the last 2000 yrs, possibly reflecting human activities along with short-term climate change.     

基于空间距离指数的中国西北干旱内陆河流域生态敏感性时空演变特征——以石羊河流域为例

生态敏感性是生态系统对自然环境变化和人类活动干扰的反映程度及生态环境问题发生难易程度和可能性大小的重要因素之一。以中国西北地区典型的干旱内陆河流域-石羊河流域为例,通过借鉴前人研究成果及实地调查研究,将石羊河流域生态敏感性分为生态风险敏感性、水土流失敏感性和生物多样性敏感性三个方面,并系统构建生态风险敏感性指数、水土流失敏感性指数和生物多样性敏感性指数三个定量评价指标,对石羊河流域综合生态敏感性进行研究。并通过格网编码、圈层分析,探讨近30年石羊河流域生态敏感性的时空变化。研究结果表明:(1)1987—2016年间石羊河流域生态敏感性总体上逐年降低,综合生态敏感性指数(Comprehensive ecological sensitivity index,CESI)值从1987年的1.143上升到2016年的1.287,反映出流域生态环境当前还是向着可持续发展的方向发展;(2)流域生态敏感性整体偏高,常年极度敏感区和常年重度敏感区占流域总面积的42.26%。此外,敏感性空间分异明显,流域上游及下游荒漠区敏感性相对稳定,中下游绿洲区敏感性波动变化较为频繁,且波动变化区占总面积的51.24%,这表明流域生态敏感性与人类活动及工农业生产有较为密切的关系;(3)目前流域生态敏感性整体趋于好转,但局部地区有恶化的趋势,敏感性波动降低的区域面积为11693.57km~2,占流域总面积的28.82%,敏感性波动升高的区域面积为9099.66km~2,占流域总面积的22.43%,这表明一方面在国家宏观政策的引导下,当地在生态环境保护方面做了大量工作,另一方面也表现出在全球生态环境逐渐恶化的大背景下,当地的生态环境治理工作仍然任重道远。     

Environmental changes clarified by pollen and diatom proxy records in the sedimentary archive of the northwestern Japan Sea during last 21.0 kyr

High-temporal resolution pollen and diatom records from the northwestern Japan Sea document environmental changes over the last 21.0 kyr. Vegetation and climate changes were evaluated using the forest-steppe (SFI) and the pollen temperature (T_p) indices. The highest SFI occurred between ca. 21.0 ka and 16.6 ka and indicates the presence of a relatively dry climate and large areas of forest-steppe in the region. Boreal forests covered the mountain slopes. The broad-leaved trees survived in refugia located in lower mountain belts. Beginning ca. 16.6 ka, SFI decreases, while T_p increases, especially between ca. 11.0 ka and 5.7 ka. However, variations in these indices indicate fluctuating climates during the deglaciation. Significant vegetation changes occurred in the Holocene. Mixed deciduous forests with a predominance of Quercus became widely present beginning ca. 9.8 ka. The area of forest-steppe was reduced occurring only in local habitats. Pinus became one of the most common taxa in the forest ca. 5.3 ka. The geographic features of the coring area have determined in the past the persistence throughout the record of cold-water diatom flora. Cold-water diatoms have dominated in both cool and warm intervals; however, a small increase in the percentage and species diversity of warm-water diatoms was noted for warming. Low sea level during the Last Glacial Maximum (LGM) and early Holocene changed the general patterns in the sea circulation and in the vectors of the longshore currents, which transported the waters formed in the shallow areas of the northeastern and northern parts of the Japan Sea. A slight increase in sublittoral benthic diatoms indicates a lowered sea level during the LGM. The increase in sublittoral planktonic diatoms reflects a gradual rise in sea level during the Bølling–Allerød (BA) and Younger Dryas (YD). A greater component of oceanic diatom species at Holocene indicates the inflow of Pacific waters across both the Tsushima and Tsugaru straits. This study of pollen and diatom records demonstrates a clear response to climatic fluctuations and sea level changes in the Japan Sea during the Late Pleistocene and Holocene.     

Vegetation dynamics in central Africa since 18,000 yr BP: pollen records from the interlacustrine highlands of Burundi, Rwanda and western Uganda

A standardized analysis of palaeoecological data, in the form of six pollen sequences and forty- four radiocarbon ages, has permitted a region-wide reconstruction of Late Quaternary vegetation dynamics for the interlacustrine highlands of central Africa.
A landscape widely dominated by ericaceous scrub and grasslands, but also supporting sparse patches of open-canopied montane forest, possibly in those areas with a topography most favourable to the growth of trees, is indicated for the last glacial maximum of 18,000 yr bp . Major expansions in the extent of upper altitudinal forms of montane forest occurred from around 12,500 yr bp , while lower moist montane forest—the expected climax for much of the region today—did not become prominent until 11,000 yr bp to 10,000 yr bp . From the palaeoecological evidence at least, it appears that the major east Central forest refuge, proposed by some workers on the basis of current species' distribution patterns, did not extend to the eastern flanks of the Albertine Rift.
A late glacial–early Holocene transition is only fully chronicled in two of the sites. However, it appears that the expansion of lower montane forest had a time-transgressive pattern across the region, and was not simply from low to high altitude. The composition of forests during the early Holocene appears to have been different to that in the later stages of the present interglacial, as taxa presently associated with wetter and/or more open forest types were much more common. Pollen data also indicate that higher altitude parts of the interlacustrine highlands were more attractive to the earliest (possibly Bantu-speaking) farmers and metal-workers. There is evidence of wide-spread forest clearance around the beginning of the present millennium, possibly as a result of substantial changes in socio-economic conditions, and patterns of settlement, associated with the onset of the Late Iron Age.     

内陆河流域中、下游绿洲耕地变化及其驱动因素——以石羊河流域中游凉州区和下游民勤绿洲为例

以野外实际调查资料以及社会经济统计资料,结合研究区1986年和2000年的TM影像数据,分析了石羊河流域中游凉州区和下游民勤绿洲近20a来的耕地变化及其驱动因子,结果表明：（1）两个绿洲的耕地面积都呈增加趋势,且民勤绿洲耕地增加速度更为显著;在空间上新增耕地主要集中在荒漠和绿洲的交错地带,耕地的增加凉州区以沙地作为主要来源,而民勤则以牺牲林草地为代价.（2）从耕地变化驱动力来看,人口增加是直接动因,同时农业科技进步和社会经济的发展为耕地面积的扩大提供了前提条件;此外,耕地面积的变化在凉州区与地表水量关系密切;而在民勤则与大风、沙尘暴天气等生态环境问题以及绿洲内的降水、蒸发等气象因素有显著关系.充分表明石羊河流域中游绿洲经济的繁荣发展以下游民勤绿洲的急剧衰退为代价.     

Reconstruction of climate change during the Holocene in western and central Europe based on pollen records of indicator species

On the basis of distribution maps showing the first pollen occurrences in the Holocene of the well-known climate indicators Hedera, Ilex and Viscum as well as data for Corylus, a series of maps have been prepared that show summer and winter isotherms at various time intervals during the Holocene. From these maps climate curves for Amsterdam, the Netherlands have been set out. These were compared with curves for the Eemian at the same site. In both of these warm periods there is evidence for increased seasonality in the early phases which were relatively continental. Changes in insolation could account for such differences. Summer optima occurred earlier than winter optima. Changes in land-sea distribution are important, especially with regard to the patterns in winter climate. During the latter half of the Eemian, the climate was distinctly more oceanic than in the Holocene. Early in the Holocene, an influx of warm ocean water resulted in higher winter temperatures in the Gulf of Biscay, the Irish Sea, and areas east of Skagerrak-Kattegat. Temperature decline after the climatic optimum was greatest in the north, i.e. at 60°N, where a depression in the order of 2°C in summer and 2–3°C in winter occurred. Temperature decline was less farther south, i.e. at ca. 50°N, where a distinct west-east gradient in temperature change can be observed.     

Vegetation Dynamics and Forest Landscape Restoration in the Upper Min River Watershed, Sichuan, China

The Upper Min River (UMR) watershed, with an area of 23,000 km² in the Upper Yangtze basin in Sichuan province, is ecologically and environmentally fragile. This situation is due to natural catastrophes and increasing anthropogenic disturbance. Forest cover has decreased dramatically, especially along the main Min River. Restoration of the vegetation in a watershed needs to consider the natural vegetation distribution and dynamics. In the UMR watershed, 625 sample plots were randomly placed to study the soil types, current vegetation distribution, vegetation dynamics, afforestation, and potential tree species for restoration. We investigated the relationship between vegetation types and soil orders, predicted the percentages of potential tree species for forest landscape restoration using logistic regression, identified priority areas for rapid restoration, and pinpointed areas for forest restoration where low precipitation is a constraint. The results showed that the vegetation types were well correlated with soil orders, and the latter could be used to deduce the potential vegetation for areas of degraded secondary forest. Priority areas for rapid restoration were demonstrated, and the difficult areas with precipitation as a limiting factor for vegetation restoration were specified. Suitable tree species were suggested for restoration on different soil orders at different elevations.     

Vegetation and climate changes during the last 21 000 years in S.W. Africa based on a marine pollen record

A high resolution marine pollen record from site GeoB1023, west of the northern Namib desert provides data on vegetation and climate change for the last 21 ka at an average resolution of 185 y. Pollen and spores are mainly delivered to the site by the Cunene river and by surface and mid-tropospheric wind systems. The main pollen source areas are located between 13°S and 21°S, which includes the northern Namib desert and semi-desert, the Angola-northern Namibian highland, and the north-western Kalahari. The pollen spectra reflect environmental changes in the region. The last glacial maximum (LGM) was characterised by colder and more arid conditions than at present, when a vegetation with temperate elements such as Asteroideae, Ericaceae, and Restionaceae grew north of 21°S. At 17.5 ka cal. B.P., an amelioration both in temperature and humidity terminated the LGM but, in the northern Kalahari, mean annual rainfall in the interval 17.5-14.4 ka cal. B.P. was probably 100–150 mm lower than at present (400–500 mm/y). The Late-glacial to early Holocene transition includes two arid periods, i.e. 14.4–12.5 and 10.9–9.3 ka cal. B.P. The last part of the former period may be correlated with the Younger Dryas. The warmest and most humid period in the Holocene occurred between 6.3 and 4.8 ka cal. B.P. During the last 2000 years, human impact, as reflected by indications of deforestation, enhanced burning and overgrazing, progressively intensified.     

石羊河流域水分利用效率及其对饱和水汽压差的响应

水分利用效率(WUE)是叶片通过光合作用调节水分生理过程的指标,是联系生态系统碳循环与水循环关系的关键,反映了植被生态系统对立地环境快速调整和资源的变化适应策略。基于卫星遥感和地面观测数据,利用光能利用率模型和蒸散发经验估算模型,模拟石羊河流域2000—2019年植被总初级生产力(GPP)和蒸散发(ET)数据,估算2000—2019年不同植被类型的WUE空间分布特征,研究GPP/ET/WUE与饱和水汽压差(VPD)的相关性,探讨干旱区不同类型植被对水分利用及胁迫的适应策略。结果表明：(1) 2000—2019年石羊河流域植被WUE、GPP和ET的平均值分别为0.80 gC m^-2 mm^-1、256.52 gC/m²和302.52 mm,其三者的空间分布特征表现为“南高北低”,即由流域源头至下游逐渐减少的空间分布。(2)近20年内,流域内WUE、GPP和ET的变化率的平均值分别为0.017 gC m^-2 mm^-1 a^-1,6.99 gC m^-2