A Preliminary Study on Vegetation and Climate Changes in Dianchi Lake Area in the Last 40000 Years

This paper presents results of pollen analysis on sediments of core Cao 2 from Dianchi Lake. Four pollen zones are defined, namely zone I, which is further divided into four subzones, zone Ⅱ, zone Ⅲ and zone Ⅳ. Zone Ⅰ(ca. 47600–11800 yrs B. P.) is characterized by low land pollen sedimentation rates and constant presence of Abies pollen. In zone Ⅱ (ca. 11800–6900 yrs B. P.) broad-leaved tree pollen increases and Abies pollen gradually disappears. In zone Ⅲ (ca. 6900–3800 yrs B. P.) evergreen broad-leaved-tree pollen and total land pollen influx reach their maximum values while, Tsuga pollen decreases. Zone Ⅳ shows a great decreases in pollen influx of various pollen types and a increase in Monolete psilate spores. In the past 40000 years vegetation in this area trend changes from a dominantion of coniferous tree to an evergreen broad-leaved forest, co-existing or mixing deciduous broadleaved forest and coniferous forest. In the past 3800 years, due to climate changes and / or human activities, the vegetation cover in this area has been greatly reduced. The above vegetation changes indicate a climate change process from cool and humid, to warm and humid and finally to mild and dry.     

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。     

Vegetational Development and Climatic Changes in the Last 10000 Years in Beijing

In the previous paper authors found the vegetational and climatic changes in the past 30,000–10,000 years in Beijing. This paper is based on the informations of the sporo-pollen assemblages obtained from the Gaolizang, Dawangzhang, Yinjiahe, Xiwu- tiyng etc. with drilling cores in the vicinity of Beijing. About 12,000–10,000 years ago deciduous broad-leaved trees were flourishing in Beijing. At that time the climate was warm and rather wet. 10,000–8,000 years ago, the herbaceous plants, such as Artemisia, Compositae were flourishing in plain of Beijing and mountainous region was dominant in subalpine conifer forest, consisting of Pinus, Picea and Abies, According to the needle-leaved forest increasing at that time we think about 9,000 B. P. that climate was cool and wetter. In the past 8,000–6,000 years, needle-leaved and deciduous broad-leaved mixed forest, consisting of Pinus, Quercus and Betula thrived under a warm and wetter climate, the bogs were better developed in plain. During 6,000–2,000 years, in general review on the sporopollen assemblages of the Beijing we think that the climate was warm, especial about 5,000 years ago, the flora was mainly composed of deciduous broad-leaved trees, such as Ulmus, Quercus, Morus and Betula. But during 5,600 years ago or so, spruce-fir forest became predominant in the low land and the plain of Beijing again. At that time the annual mean temperature was lower than that of the present. It was corresponed to new glacial period. The flora mainly composed of Pinus was obviously reduced since 2,000 years. The glassland even increased in Beijing.     

On the Evolution of the Palynoflora and Climatic Environment During Late Pleistocence in Tengger Desert,China

Palynoflora studies on the Duantouliang section, located at 39º40'N, 103º55'E in Northwestern Tengger Desert, China showed that, based on the spore-pollen assemblages, the major vegetation and climatic environment between 42 000 to 23 000 a BP could be divided into the following different periods: Ⅰ. From 42 000 to 38 000 a BP, the spore-pollen assemblages displayed that the mixed conifer/deciduous broad-leaved forests developed on the mountain and its foothill regions where the bare Gobi-desert are at present; At that time, Populus and Salix forests and grassland surrounded the Paleaolake, the climate condition was much warmer and humid than today; Ⅱ. From 38 000 to 37 000 a BP, the climate was warm and moist, it was the most suitable period for the plant growth, the studied area was dominated by the temperate and warm-temperate mixed broad-leaf deciduous and needleleaf forest, there was meadow spreaded on the river sides and lake beaches; Ⅲ. From 31 000 to 30000 a BP, the needleleaf forests and cold-temperate Salix oritrepha shrubs were flourishing, and the climate at that time was relatively cold;Ⅳ. From 30000 to 28000 a BP, the temperatures began increasing, the high lake levels was formed during this time, and the vegetations were meadows and swamps; V. From 28 000 to 23 000 a BP, temperate Cupressaceae and Betula mixed conifer/deciduous forests grew on mountain and foothill region, grassland developed on plain areas, Salix was on lake and river sides. This indicates a warm and moist climate condition but it was drier than the earliest period.     

云贵高原抚仙湖近13300年的花粉/炭屑记录*

抚仙湖是云贵高原著名的断陷深水湖,其沉积物蕴藏着流域地质历史时期丰富的环境信息。对钻取自该湖的900cm 湖泊沉积物岩芯进行花粉/炭屑分析及花粉数据的主成分分析表明,抚仙湖流域的植被、气候与火灾在过去的13 300年经历了5个阶段的变化：(1)13 300—10 400cal．a BP,植被以松林为主,伴有山地暗针叶林和常绿阔叶林,表明该时期气候较为冷湿,森林火灾多发,在后期随着温度和湿度的降低,森林火灾愈加频繁。(2)10 400—5 700cal．a BP,松林收缩,常绿阔叶林扩张,出现一定数量的落叶阔叶林,显示该时期气候偏暖偏干;此阶段早期随着气候变暖变干森林火灾的发生延续上阶段高发的状态,直到9 500cal．a BP后随着湿度的增加森林火灾明显减少。(3)5 700—1 800cal．a BP,松林变化较小,常绿/落叶阔叶林比重增大,首次出现了暖热性的枫香林,显示该时期暖湿的气候特征,火灾发生频率低。(4)1 800—500cal．a BP,松林扩张,阔叶林收缩,本阶段后期草本植被比重开始增加,显示该时期气候相对冷干,森林火灾发生频率较高。(5)500cal．a BP至今,松林收缩,落叶阔叶树种增多,草本植物花粉明显增多,显示该时期气候温凉偏干,森林火灾发生频率降低。     

Holocene climate and environmental history of Brurskardstjørni,a lake in the catchment of Øvre Heimdalsvatn,south-central Norway

The Holocene lake history, vegetation history and climate history of Brurskardstjørni, an alpine lake in the Jotunheimen Mountains of south-central Norway, are reconstructed. The reconstructions are based on fossil pollen, plant macrofossils, diatoms, chironomids and sediment characteristics. Subsequent to deglaciation, the lake was formed at about 11,000 cal years BP. A diverse chironomid assemblage quickly colonised the lake, whereas the first diatoms were found about 400 years later. At that time, the lake water was turbid with a high pH. The surrounding soils were immature and unstable and dominated by open pioneer vegetation. Compared to the present, summer temperatures were warmer and there was less winter precipitation. From about 10,000 cal years BP, local organic production increased rapidly and from about 9,500 cal years BP a few macrofossils and a high pollen influx of birch suggest that the tree-line was close to the lake. Pine most likely reached its highest tree-line altitude around 9,000 cal years BP and has receded since that time. From about 5,000 cal years BP, the total amount of trees and shrubs decreased and the landscape became more open, probably due to decreasing temperatures and increasing effective moisture lowering the birch tree-line. Coinciding with a cooling during the last 3,000 years, lake-water pH decreased. There is large incongruence between the Holocene July temperatures inferred from pollen and chironomids. The biological proxies responded to a combined effect of environmental change and biotic interactions. This response is interpreted with reference to taxon–environment relationships in the modern calibration data sets and with reference to the latent structure and ecological demands of the fossil assemblages.     

青藏高原东南部18ka以来气候与水文变化

青藏高原东南部众多封闭小湖的湖相沉积记录着重要的地理信息,是恢复当地晚更民以来古环境演变的理想材料。西藏海登湖和仁同分辨率的花粉组合,ＡＭＳ＾１４Ｃ测年及磁化率和有机质含量测定,揭示了研究区与鳊季风密切相关的古植被,古气候和古水文变化历史。高分辨率的花粉记录反映,在１６ｋａＢｍ,Ｐ,以前花粉组合以黎科（Ｃｈｅｎｏｐｏｄｉａｃｅａｅ）和蒿属（Ａｒｔｅｍｉｓｉａ）为主,花粉浓度很低,应为荒漠草原植被。     

Palynoflora at Late Miocene?aEarly Pliocene from Leijiahe of Lingtai,Gansu Province,China

Vegetation and climate changes of Late Miocene-Early Pliocene have been deduced based on pollen research from Wenwanggou and Xiaoshigou sections near Leijiahe village (ca 35°04′15″N,107°43′30″E). The two sections are quite famous of rich micromammalian fossils. Before ca. 6.5 Ma, open forest-grassland was distributed in the studied area indicating a temperate and humid condition at that time. In the period between ca.6.5 and 5.8 Ma BP (Late Miocene) predominance of Chenopodiaceae and Artemisia implies that desert or desert-grassland was developed in the area and the climate should be cold and dry. During the time interval from ca.5.8 to 3.4 Ma BP mixed conifer and broad leaved deciduous forest with a few subtropical tree taxa had replaced the arid desert vegetation indicating a warm and humid climate. The climate aridity event of Late Miocene can be correlated with the global climatic event.     

A Preliminary investigation on the Vegetational and Climatic Changes Since 11, 000 Years in Qinghai Lake An Analysis Based on Palynology in Core QH85-14C

Qinghai Lake is the largest inland saline lake in China. it is situated in the northeastern part of the Qinghai Xizang Plateau. This paper is based on the information of the sporo-pollen assemblages of 47 samples from the drill core and surface samples. The general treads of vegetational and climatic changes since 11,000 years B. P. may be subdivided in ascending order as follows: In the first stage which corresponds to zone Ⅰ of the sporo-pollen assemlage, the vegetation during the past of 11,000–10,000 years was represented by a temperate shrub, semi-shrub and steppe, consisting of Chenopodiaceae. Artemisia, Nitraria, Ephedra and Gramineae were predominant. At the same time, some subalpine conifers, Pinus, Picea and Betula, would grow by the side of rivers and lakes, the climate was warmer and wetter than that of the Late Pleistocene. Due to the rising temperature in this zone, the Pleistocene-Holocene boundary might be estimated at about 11,000 years B. P.. The vegetation of the first stage belonges to temperate steppe with a few trees: In the second stage (ZoneⅡ of pollen), the vegetation was characterized by a temperate forest steppe during this period of 10,000 to 8,000 years B. P. Forest area apparently increased and some broadleaf deciduous and need leaf evergretn trees, such as Quercus, Betula, Pinus and Picea, grew by lakes and on mountains. At this time, the climate was warmer and wetter than that of the first stage. In the third stage (Zone Ⅲ) between B,000 and 3,500 years B. P, The vegetation was composed of a temperate mixed broad-leaf deciduous and needle-leaf evtrgreen forest. The needle-leaf evergreen forest consisting of Picea, Pinus, Abies, Betula grew in temperate zone mountains. The climate was relatively warm and wet. The fouth stage (zone IV), the vegetation was dominated by shrub semishrub, dwarf semishrubs, steppe and semi-arbors. Some trees consisting of Betula, Picea, and Pinus decreased in number in the lake regions. Some subalpine cold temperature evergreen trees, such as Abies and picea disappeared from the lake region. This indicated that the climate was warmer and drier during the past 3500–1500 years B. P. than the third zone. In the fifth stage (pollen zone V), the vegetation comprised steppe and desert from 1500 years ago to the present time. Some arborealtrus such as Betula and Pinus were less increased about 500 years B. P. at this time the temperate and wet slightly, rose up. From the above analysis, it is clear that the Qinghai lake region has been confronted with the vegetational and climatic changes since ll,000 years B. P. Therefore, the palynoflora of the Qinghai lake has its significance in Geography and vegetational history.     

Holocene vegetation and water level history in two bogs of the Cordillera de Talamanca, Costa Rica

Pollen records of Holocene sediment cores from the Costa Rican Cordillera de Talamanca (La Chonta bog, 2310 m and La Trinidad bog, 2700 m) show the postglacial development of the montane oak forest zone from ca. 9500 to 1500 yr BP. During the early Holocene (ca. 9500–700 yr BP), alder vegetation covered the La Chonta and La Trinidad bogs and their adjacent hills. The upper forest line is inferred to be at 2800–3000 m elevation. A Podocarpus-Quercus forest characterised the middle Holocene (ca. 7000–4500 yr BP). The upper forest line is located at >3000 m reaching the present-day altitudinal distribution. A Quercus forest characterised the late Holocene (ca. 4500–1500 yr BP). Compared to modern conditions, the early Holocene has similar average temperatures, but the moisture level was probably higher. Pollen evidence for the late Holocene indicates drier environmental conditions than today. In order to improve the paleoecological interpretation, we described the local vegetation and used moss samples as pollen traps at both montane bogs along strong soil moisture gradients.The Netherlands Centre for Geo-ecological Research, ICG     

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.     

Postglacial vegetation history as recorded from the subalpine Lake Ribno (NW Rila Mts), Bulgaria

A pollen analysis conducted on a 600 cm core from Lake Ribno (2184 m) in the Northwestern Rila Mountains, supplemented by 13 radiocarbon dates, has revealed the basic stages in its postglacial vegetation dynamics. The lateglacial vegetation, composed of Artemisia, Chenopodiaceae and Poaceae, with stands of Pinus and Juniperus-Ephedra shrubland, dominated in the stadials and partly retreated during the B?lling/Aller?d interstadial (14700–12900 cal. yrs. BP). The afforestation in the early Holocene (11600–7800 cal. yrs. BP) started with pioneer Betula forests, with groups of Pinus and Juniperus at mid-high altitudes, and Quercus forests with Tilia, Ulmus, Fraxinus, Corylus below the birch zone. A coniferous belt composed of Pinus sylvestris, P. peuce and Abies was shaped under the conditions of a more humid climate (7800–5800 cal. yrs. BP). The last trees that invaded the study area were Fagus after 4300 cal. yrs. BP and Picea abies after 3400 cal. yrs. BP. Evidence for destructive changes in the vegetation and indications of agricultural and stock-breeding activities (pollen of Triticum, Secale, Plantago lanceolata, Rumex, Juglans) was continuously recorded since the Late Bronze Age (3400–3200 cal. yrs. BP). The postglacial vegetation history in the Northwestern Rila Mountains demonstrated close similarities with that of the Northern Pirin Mountains.     

四万年来南海北部周边地区植被演替序列—孢粉生物群区化方法恢复古植被的尝试

就南海北部海域17940孔的孢粉资料,利用孢粉生物群区化方法和因子分析方法,对南海北部周边地区4万年以来的植被演替序列进行研究。结果表明：对于深海沉积物,在排除远距离搬运的花粉尤其是松属（Pinus L.)花粉的噪音后,可以利用孢粉生物群区化方法恢复周边大陆古植被演替序列。因子分析表明,湿度和温度的变化是影响南海北部周边大陆植被演化的主要因子。在40500－11100aBP南海北部沿海大陆地区的古植被,主要为常绿阔叶林（WAMF）,山地针叶林（MRGF）分布于低山、丘陵、而广泛出露的大陆架上则发育了以蒿属(Artemisia L.)为主的草原（STEP）景观：末次冰期时环境变化的突出特征山地针叶林（MRGF）、常绿阔叶林（WAMF）与草原（STEP）之间的频繁交替,反映了气候冷湿和温干的千年级尺度的迅速变化,可以与Heinrich事件以及Dansggard-Oscherge事件进行对比。其中在7.0m处（12700aBP)所恢复的山地针叶林（MRGF）景观反映了一次气候变冷变湿的事件,可能与新仙女木事件相对应。全新世早期和末期较多出现热带雨林（TRFO0以及热带季雨林（TSFO）景观,而全新世中期以常绿阔叶林（WAMF）为主,缺乏热带雨林（TRFO）以及热带季雨林（TSFO）景观,可能表明在全新世中期尽管温度升高,但湿度有可能降低。     

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.     

Vegetation Evolution in the Northern South China Sea Region Since 40 ka BP?aAn Attempt To Reconstruct Palaeovegetation Based on Biomization (in English)

egetation evolution in the northern South China Sea region since 40 500 a BP is reconstructed using biomization procedure based on pollen data from deep sea core 17940. The result shows that, it is feasible to reconstruct palaeovegetation using biomization procedure, when pollen, particularly Pinus pollen, transported by wind over long distance is excluded. Results from factor analysis suggest that humidity and temperature are the two main factors determining vegetation evolution on land around the northern South China Sea. From 40 500 a BP to 11 100 a BP, broad-leaved evergreen forest (WAMF), and montane conifers(MGRF) occurred on hills and low mountains; while steppe (STEP) predominated on the exposed shelf. The main feature of the vegetation evolution is the frequent alternation between MGRF (or WAMF) and STEP, implying abrupt changes in millennium scale between humid/cold and dry/temperate climate. All abrupt climate events could be broadly correlated with Henrich events and Dansggard-Oscherge events. One of the events around 12 700 a BP, sees the occurrence of MGRF, suggesting that climate turned humid and cold rapidly. This may be correlated with the Younger Dryas event; Broad-leaved evergreen (WAMF) predominates since 11 000 a BP. During the early Holocene and late Holocene tropical rainforest (TRFO) or tropical seasonal forest (TSFO ) occurred several times.     

Tree line identification from pollen data: beyond the limit?

Aim The boreal tree line is a prominent biogeographic feature, the position of which reflects climatic conditions. Pollen is the key sensor used to reconstruct past tree line patterns. Our aims in this study were to investigate pollen–vegetation relationships at the boreal tree line and to assess the success of a modified version of the biomization method that incorporates pollen productivity and dispersal in distinguishing the tree line. Location Northern Canada (307 sites) and Alaska (316 sites). Methods The REVEALS method for estimating regional vegetation composition from pollen data was simplified to provide correction factors to account for differential production and dispersal of pollen among taxa. The REVEALS‐based correction factors were used to adapt the biomization method and applied as a set of experiments to pollen data from lake sediments and moss polsters from the boreal tree line. Proportions of forest and tundra predicted from modern pollen samples along two longitudinal transects were compared with those derived from a vegetation map by: (1) a tally of ‘correct’ versus ‘incorrect’ assignments using vegetation in the relevant map pixels, and (2) a comparison of the shape and position of north–south forest‐cover curves generated from all transect pixels and from pollen data. Possible causes of bias in the misclassifications were assessed. Results Correcting for pollen productivity alone gave fewest misclassifications and the closest estimate of the modern mapped tree line position (Canada, + 300 km; Alaska, + 10 km). In Canada success rates were c. 40–70% and all experiments over‐predicted forest cover. Most corrections improved results over uncorrected biomization; using only lakes improved success rates to c. 80%. In Alaska success rates were 70–80% and classification errors were more evenly distributed; there was little improvement over uncorrected biomization. Main conclusions Corrected biomization should improve broad‐scale reconstructions of spatial patterns in forest/non‐forest vegetation mosaics and across climate‐sensitive ecotones. The Canadian example shows this is particularly the case in regions affected by taxa with extremely high pollen productivity (such as Pinus). Improved representation of actual vegetation distribution is most likely if pollen data from lake sediments are used because the REVEALS algorithm is based on the pollen dynamics of lake‐based systems.     

The Holocene at Lac de Creno, Corsica, France: a key site for the whole island

Two Holocene lake sequences from Lac de Creno, Corsica were analysed on the basis of 119 pollen spectra and with the support of 13 ¹⁴C-calibrated dates. The lower part of one of these sequences, corresponding to the late- glacial period, has been published previously. The first third of the Post-glacial is characterized by very particular forest dynamics, namely the absence of a role for deciduous Quercus and Corylus , the presence of mesophilous vegetation types dominated by Taxus , and the major forest role of Erica arborea at lower and mean altitude. At about 7440 cal BP, the occurrence of a major anthropogenic action brought about significant changes in the vegetation, notably an increase of deciduous Quercus and the expansion of Quercus ilex . Later, three major human-induced events are identified: the first, at about 2290 cal BP, is the cause of a short local expansion of Abies ; the second, at about 1150 cal BP, is the degradation of deciduous forests to the benefit of Fagus ; the third, at about 310 cal BP, corresponds to the disappearance of Fagus and its replacement by Pinus . Pollen data indicate that Q. ilex , Abies and Fagus are not indigenous in Corsica but spread there during the Postglacial ; this probably took place at about 6980 cal BP for Q. ilex .     

Vegetation history with implication of climate changes and human impacts over the last 9000 years in the Lake Nanyi area,Anhui Province,East China

Palynological analyses in combination with radiocarbon dating on a Holocene borehole from the Lake Nanyi, Anhui Province, East China demonstrate a well-documented local vegetation evolution since 9000 cal BP, which is the first record of Holocene climate change and human impact in this region. Since 9000 cal BP a mixed evergreen and deciduous broad-leaved forest dominated by Cyclobalanopsis and Quercus developed in this area, indicating a warm climate condition with enhanced insolation. A mixed evergreen and deciduous broad-leaved forest was fully developed between 6600–4500 cal BP, which corresponds to the Holocene Climate Optimum with the strong influence of East Asian summer monsoon (EASM). After 3000 cal BP the broad-leaved forest decreased rapidly, while land herbs and ferns increased. It seems that the climate condition in East China was similar to the present after Holocene Climate Optimum. Pollen results show a potential interface between environment changes and human activities. Pollen diagram demonstrates that human impacts on the natural vegetation remained weak at the early stage but significantly enhanced upwards. The distinctive fluctuations of the pollen contents among AP (trees and shrubs), and the possible agriculture indicators might infer the potential human behaviors for environment changes. Due to the enlargement of organized farming and increase in population, natural forest was eventually replaced by farmland since 3000 cal BP. This study would increase our knowledge of Holocene vegetation transition related to the monsoon dynamics on a long timescale in East China and provide an environmental background for more detailed studies on cultural developments in the middle and lower reaches of the Yangtze River region.     

Palynological Analysis of the Late Cenozoic and Its Significance in Fulaerji,Heilongjiang Province

The pollen analytical investigation of 226.07 m,, deep QH70 core from Fulaerji district in the city of Qiqihar, Heilongjiang province have been carried out. Based on the characteristics of QH70 core sporo-pollen assemblages, seven pollen zones may be subdivided in the order as follows: The first zone (Ⅰ) belongs to early period of the Late Cretaceous. When the flora was mainly composed of gymnosperm, the next was fern and a little original angisperm. Here the climate was hot and wet and the vegetation showed tropical-subtropical in aspects. In this core the author didn't find the Palaeogene flora. The Ⅱ–Ⅲ zones belonging to the Late Tertiary are characterized by predominance of arboreal pollens, mainly consisting of Amentiferae and some conifers. The flora of the Neogene was mainly composed of Pinus, Betula, Castanea, Ulmus, Corylus, Alnus, ,Juglans, Quercus, Carya, Fagus, Tsuga etc. some subtropical species of Hamamelis, Liquidambar, Castanopsis, Melia. Myrica and Taxodiaceae which still existed. The climate was warm and humid with the annual temperature higher than that of the present. As to the last period of the third zone (Ⅲ) the assemblage of herbaceous plants and semi-shrub were predominant. The climate was changed into cool and less dry. The fouth pollen zone (Ⅳ) is represented by herbaceous plants such as Artemisia, Chenopodiaceae, Gramineae, Polygonaceae etc. indicating the Fulaerji was covered by cold-temperature grassland with a cold and dry climate. According:to temperature decreasing at this zone, magnetostratigraphy and thermoluminescence dating we may take the start of the Ⅳ zone as the mark of the beginning of Quaternary in this region. The age of the boundary between Pliocene and Pleistocene might be 2.4 million years or so. The geological age of pollen zones Ⅳ–Ⅶ, is assigned to Pleistocene. The characteritics of the sporo-pollen assemblage at these zones are quite different from one another. In the fifth pollen zone (Ⅴ), the vegetation was represented by a steppe or tundra with a cold and dry climate at its initial stage, but in the late stage the flora was characterized by a deciduous broadleaved forest and steppe, indicating the climate was warm and less humid. Pollen zones Ⅵ–Ⅶ, the herbaceous plants, such as Artemisia, Gramineae, Chenopodiaceae etc. were predominant. The climate was rather dry and cold. The plants of the boreal conifers as Picea, ilbices, Larix, Pinus and the subpolor plants such as Betula were thriving in the low land and plain on the last glacial stage demonstrating that time the climate was humid and cold. Judging from the pollen analyses of core QH70, the vegetational development and climatic changes in Fulaerji had been rapid since the Late Tertiary. It is more or less significance to use pollen analysis in hydrogeology and engineering geology.     

Late Holocene vegetation, fire, climate and upper forest line dynamics in the Podocarpus National Park, southeastern Ecuador

Late Holocene vegetation, fire, climate and upper forest line dynamics were studied based on detailed pollen and charcoal analyses. Two sediment cores, from the Rabadilla de Vaca mire (RVM) and the Valle Peque?o bog (VP), with an age of about 2100 and 1630 cal yrs b.p., respectively, were taken at the modern upper forest line in the Parque Nacional Podocarpus (Podocarpus National Park) in southeastern Ecuador. The two pollen records reflect relatively stable vegetation with slight changes in floral composition during the recorded period. Changes of the proportion between subpáramo and páramo vegetation are related to lower and higher frequency of fires. The RVM records show that the upper forest line moved to a higher elevation between 1630 and 880 cal yrs b.p., stabilising after 310 cal yrs b.p. Human impact is suggested by a high fire frequency, mainly between 1800–1600 and 880–310 cal yrs b.p. The VP records indicate no marked changes in the upper forest line. The charcoal records suggest an increased human impact from 230 cal yrs b.p. to the present. The results indicate that high fire frequency is an important factor in reducing the expansion of subpáramo vegetation and upper montane rainforest and in favouring the distribution of grass páramo. Since there is a clear correlation between fire and vegetation dynamics, it is difficult to detect how far climate change also played a significant role in upper forest line changes during the late Holocene.