A Comparison of the Environmental Changes of the Post-European Period with those of the Preceding 2000 Years at Lake Keilambete,South-western Victoria

Several parameters representing aspects of vegetation, fire, erosion and lacustrine productivity are investigated to compare the environmental changes of the historic period against those of the last 2000 years at Lake Keilambete in south-western Victoria. The average sedimentation rate post-dating European settlement was found to be c .2.5 times that of the analysed pre-European period and the nature of this sediment is distinctly different. Pollen representation was generally stable prior to the European period, but instability increased subsequently, reflecting the influence of pastoralism and the increase in exotic plant species. An increased concentration (and variability) of carbonised particles in the historic period, despite the faster rate of sedimentation, suggests a complex change in the fire regime of the region. The productivity of Lake Keilambete has varied in the past (e.g. it was elevated between c .1750 and 1250 years BP) but the response to European land use was diminutive. The expression of the quantified sedimentary parameters as average accumulation rates suggests a marked difference in the rate of landscape processes between the pre- and post-contact periods. The environmental change of the post-European period suggests that this landscape was particularly susceptible to the land-use strategies of the European settlers.     

Controls on sediment export from the Waipaoa River basin, New Zealand

A stability model of drainage basin mass balance is used to interpret historic and prehistoric patterns of sediment production, storage and output from the Waipaoa River basin, New Zealand and assess the sensitivity of basin sediment yield to land use change in the historic period. Climate and vegetation cover changed during the late Holocene, but the drainage basin mass balance system was stable before the basin was deforested by European colonists in the late 19th and early 20th centuries. In this meso‐scale dispersal system sediment sources and sinks are closely linked, and before that time there was also little variability in the rate of terrigenous mass accumulation on the adjacent continental shelf. However, despite strong first‐order geologic controls on erosion and extensive alluvial storage, sediment delivery to the continental shelf is sensitive and highly responsive to historic hillslope destabilization driven by land use change. Alluvial buffering can mask the effects of variations in sediment production within a basin on sediment yield at the outlet, but this is most likely to occur in basins where alluvial storage is large relative to yield and where the residence time of alluvial sediment is long relative to the time scale of environmental change. At present, neither situation applies to the Waipaoa River basin. Thus, the strength of the contemporary depositional signal may not only be due to the intensity of the erosion processes involved, but also to the fact that land use change in the historic period destabilized the drainage basin mass balance system.     

Fine Resolution Palaeoecology Confirms Anthropogenic Impact During the Late Holocene in the Lower Hawkesbury Valley,NSW

This study reconstructs environmental conditions at Mill Creek, within the lower Hawkesbury-Nepean Valley, by the use of fine resolution palaeoecological studies of sediments. Archaeological surveys and historical accounts are used to investigate ecosystem response to known human activities. Research found that during prehistoric times (between 820 BP and the 1790s), the study area was well vegetated with dry sclerophyll communities on the valley sides, and a highly productive wetland community occupied the moist valley floor. Valley sides were generally stable, and little fire was evident in the landscape. Sediment was mainly deposited on the valley floor from the Hawkesbury-Nepean River during flood. After European settlement in the 1790s, sedimentation rates and charcoal preserved within sediments increased significantly, probably due to agricultural and clearing practices, both locally and upstream. Consequently, vegetation communities were altered. In 1967, the study area became part of Dharug National Park. Forestry and agricultural activities were excluded from the catchment, and the fire regime was reduced in frequency. Present-day vegetation communities appear to be becoming more like those that prevailed during prehistoric times. However, sedimentation rates remain elevated due to continued disturbance to the greater Hawkesbury River catchment. Recent poor water quality, coupled with a succession of floods on the Hawkesbury River, has increased wetland productivity levels, and their spatial extent, at Mill Creek.     

Late Holocene climate change and human disturbance on Andros Island, Bahamas

A 2 m sediment core from Church's Blue Hole on Andros Island, Bahamas provides the first paleoecological record from the Bahama Archipelago. The timing of events in the lower portion of the core is uncertain due to inconsistencies in the radiocarbon chronology, but there is evidence that a late Holocene dry period altered the limnology of Church's Blue Hole and supported only dry shrubland around the site. The dry period on Andros may correlate with a widespread dry period in the Caribbean from 3200 to 1500 yr BP. After the dry period ended, a more mesic climate supported tropical hardwood thicket around Church's Blue Hole. At c. 740 radiocarbon yr BP there is a sudden rise in charcoal concentration and a rapid transition to pinewoods vegetation, while at c. 430 radiocarbon yr BP charcoal concentration drops, but is higher again near the top of the core. Although climatic shifts could have caused these changes in vegetation and charcoal concentration, the changes post-date human colonization of the Bahamas and may reflect human arrival, followed by the removal of humans c. 1530 AD and the recolonization of Andros Island c. 200 years later.This is the 12th in a series of papers published in this special AMQUA issue. These papers were presented at the 1994 meeting of the American Quaternary Association held 19–22 June, 1994, at the University of Minnesota, Minneapolis, Minnesota, USA. Dr Linda C. K. Shane served as guest editor for these papers.     

亚洲中部干旱区丝绸之路沿线环境演化与东西方文化交流

基于环境记录、考古发现,以及同位素资料,对亚洲中部干旱区丝绸之路沿线的全新世以来的环境变化和东西方文化交流进行了梳理。结果表明,研究区独特的地理环境和环境变化过程,深刻地影响着文化的发展和传播。河西走廊受季风影响,表现出季风—西风过渡带干湿变化的模式,晚全新世气候趋向干旱;从新疆到中亚的丝绸之路沿线的环境变化比较一致：在早全新世（BC 6000以前）主要为干旱环境,植被以荒漠类型占优势;中晚全新世,湿润程度增加,草原植被扩展。新疆和中亚全新世中晚期较为湿润的环境为东西文化交流提供了较适宜的环境基础。得益于环境条件的改善,东西方文化交流融合的进程在BC 2000以后明显加速。在BC 2500-2000期间,东西方农业文化在丝绸之路沿线接触融合,是史前丝绸之路的首次贯通;在BC 2000-1000期间,丝绸之路沿线绿洲地带形成了以小麦—/大麦—粟黍—畜牧为特征的混合型经济特征,并扩散到欧亚草原带,和周围的畜牧业形成鲜明的对照,并持续到历史时期。这种空间分异,是地理环境和东西方文化交流共同作用的结果。在史前时期,东西方农业的相向传播和融合,基本沿着山前地带的绿洲蛙跳式前进。到了历史时期,政治版图的变化是影响丝绸之路的首要因素,但环境变化仍然是不可忽略的因素。     

A Late Holocene Vegetation and Environment Record from Byenup Lagoon,South-western Australia

South-western Australia has a Mediterranean-type climate and its infertile soils support a highly diverse angiosperm flora. Little is known of the vegetation history of this region, and this means that little can be said of the roles of environmental stability, climate change, or human impact on the maintenance or development of the high biodiversity of the region. This study presents a pollen and fossil charcoal record from two peat profiles from a freshwater lagoon region near Lake Muir, east of Manjimup, in south-western Australia. The record shows a glimpse of an early Holocene where a mix of Casuarina and eucalypts with an understorey of heath and some open herbaceous vegetation, including chenopods, occurred. Fire was not an important factor at this time. The main record begins from about 4800 BP, and shows a vegetation mix of Corymbia calophylla and Eucalyptus marginata, with the latter becoming dominant by about 3500 BP. Corymbia calophylla again becomes prominent in the last few centuries. A heathy understorey is present throughout the last 4800 years, but was apparently less dense during phases when C. calophylla was more prominent. Melaleuca woodland has been the main vegetation type around the wetland areas and areas of inundation since the mid-Holocene. Major fire periods at Byenup, around 4200 BP and between about 3000 and 2000 BP, did not result in major vegetation changes. An analysis of cation content in the sediments suggests that weathering and erosion rates have been relatively stable throughout the record, but an increase in phosphorus and possibly organic matter in the surface layers suggests that agricultural practices have led to changes in the chemistry of sediments. It is hypothesised that an increase in effective precipitation about 4800 BP led to the initiation of the continuous part of the sediment record at Byenup. This increase most likely resulted from a more effective westerly wind stream. Changes since this time are more likely a result of changing fire regime and the interaction of species, rather than climate shifts.     

Paleoecology and its application to fire and vegetation management in Kootenay National Park, British Columbia

High-resolution analysis of macroscopic charcoal and pollen ratios were used to reconstruct a 10,000 yr history of fire and vegetation change around Dog Lake, now in the Montane Spruce biogeoclimatic zone of southeastern British Columbia. Lake sediment charcoal records suggest that fire was more frequent in the early Holocene from 10,000 to 8200 calendar yrs BP, when climate was warmer and drier than today and forest fuels were limited. Fire frequency increased and reached its maximum during the early to mid-Holocene from 8200 to 4000 calendar yrs BP, corresponding to the dry and warm Hypsithermal period in the Rocky Mountains. During the Hypsithermal period forests around Dog Lake were dominated by Pseudotsuga/Larix,Pinus and open meadows of Poaceae that were subject to frequent fire. From 4000 calendar yrs BP to present, fires became less frequent with the onset of cooler and wetter Neoglacial climate and an increase in wet-closed Picea and Abies forests in the valley. Changes in fire frequency are supported by dry-open/wet-closed pollen ratio data indicating that forest type and disturbance regimes vary with changing climate. The fire frequency and forest cover reconstructions from Dog Lake are a first attempt at defining a range of natural variability for Montane Spruce forests in southeastern British Columbia. Fire and vegetation management in Kootenay National Park can now use this century to millennial-scale range of variability to define the context of current forest conditions and potential changes under global warming scenarios.     

The Response of Aboriginal Burning Practices to Population Levels and El Niño–Southern Oscillation Events during the mid- to late-Holocene: a case study from the Sydney Basin using charcoal and pollen analysis

Pollen and macroscopic charcoal have been analysed from a sedimentary sequence representing approximately 6100 years from a site within Wollemi National Park. This is located to the north-west of Sydney and forms a part of the Greater Blue Mountains World Heritage Area. The overall aim of the work was to examine the prehistoric interrelationships between vegetation, fire and human activity. There were relatively minor changes in the vegetation over the last ～6000 years, perhaps reflecting the climate- and fire-resilient nature of the sclerophyllous vegetation found on Hawkesbury Sandstone throughout the Sydney Basin. Casuarinaceae declined in the late Holocene, a trend that has been detected in numerous palaeoecological studies throughout south-eastern Australia. This decline was unrelated to fire, which has been a persistent feature at the site over the entire analysed sequence. The fire regime at the site changed from 5.7 ka, which is interpreted as reflecting the onset of increased climatic variability associated with El Niño-Southern Oscillation (ENSO) events. Another dramatic change in the fire regime occurred at 3 ka, which was coeval with archaeological changes in the region. It is possible that the change in fire activity from 3 ka represented an alteration to Aboriginal management strategies associated with an increasing population and/or the increased risk of conflagrations in an ENSO-dominated climate.     

A 7000-Year Record of Environmental Change,Bear Lake,Rocky Mountain National Park,USA

Few long-term records of the fire history of Rocky Mountain National Park exist. Data from a lake sediment core was used to reconstruct changes in vegetation and fire frequencies over the last 7000 cal yr. Bear Lake is a high-elevation lake surrounded by subalpine vegetation in Rocky Mountain National Park, Colorado. Pollen data indicate that a warm and dry climate prevailed between ca. 7000 and 5000 cal yr BP. Temperatures increased until shortly before ca. 3500 cal yr BP when evidence for a marked decline is seen. Cooler-than-present conditions were maintained until ca. 1700 cal yr BP, when conditions transitioned to more like those of the present-day climate. Based on macroscopic charcoal analyses, fire frequency had varied between two and five episodes per 1000 years. The largest peak in charcoal was at ca. 590 cal yr BP. The fire return interval has varied with climate over time; however, we calculate a fire return interval of 325 years over the past 7000 years. Given these results, fire activity is likely to increase under current Intergovernmental Panel on Climate Change climate projections of an increase in annual temperatures.     

Pollen, phytoliths, arthropods and high-resolution 14C sampling from Rano Kau, Easter Island: evidence for late Quaternary environments, ant (Formicidae) distributions and human activity

A 20-m sediment core from Rano Kau, Easter Island provides plant microfossil, arthropod fossil and high-resolution ¹⁴C sampling evidence for late Quaternary environments, ant (Formicidae) distributions and human activity. The record commences prior to or during the LGM, providing the two oldest dates for Rano Kau thus far, 20,340 ± 160 and 34,260 ± 440 BP. The vegetation at the time was mostly Arecaceae (palm)-dominated grassland-woodland, suggesting cooler/drier conditions than present. Near the start of the Holocene c. 12,500 cal BP, climate alleviation is indicated by Asteraceae shrubland increasing at the expense of grassland. There is an early to mid-Holocene sediment hiatus. The record recommences c. 3,500 cal BP, with in-washed clayey soils bearing charcoal and phytoliths of Polynesian-introduced Musa (banana) and mixed with wetland detritus, reflecting slumping as a result of forest clearance and gardening. Dates of material of other plants from the clay/detritus layers containing the Musa phytoliths are older than expected, within the range 3,680–2,750 cal BP, well before settlement of Eastern Polynesia. This could reflect horticultural material settling in an older part of the sediment column or age increase by reservoir effects. A long section of overlying unconsolidated detritus provides a progressively younger upward sequence from 2,840–2,870 to 930–810 cal BP, but dates are variable after 1,290–1,180 cal BP, where charcoal, disturbance-related pollen and older than expected ant exoskeletons demonstrate the inclusion of pre-aged material from the floating vegetation mat or upslope erosion in the sediment column. Arecaceae pollen declines sharply after 930–810 cal BP. Arthropod analysis reveals two new weevil species for Easter Island, and two ant taxa, Tetramorium bicarinatum and Pheidole sp., the latter of which is also new for the island. Three of the four age determinations on ant remains suggest that ants were present prior to c. 2,500 cal BP, and probably associated with the period following the resumption of sediment accumulation c. 3,500 cal BP. Unless the apparent ant ¹⁴C ages have been increased by reservoir effects, these results question the long-accepted assumption that all Eastern Polynesia’s ant species have been introduced.     

Fire and vegetation history during the last 3800 years in northwestern Montana

Foy Lake in northwestern Montana provides a record of annual-to-decadal-scale landscape change. Sedimentary charcoal and pollen analyses were used to document fire and vegetation changes over the last 3800 years, which were then compared to similar records from AD 1880 to 2000. The long-term record at Foy Lake suggests shifts between forest and steppe as well as changes in fire regime that are likely the result of climate change. Fire activity (inferred from the frequency of charcoal peaks) averaged 18 fire episodes/1000 years from 3800 to 2125 cal year BP, and increased from 16 fire episodes/1000 years at 2125 cal year BP to 22 episodes/1000 years at 750 cal year BP, a period when the pollen data suggest that steppe vegetation yielded to increasing patches of forest cover. Between 2125 and 750 cal year BP, increased forest cover produced more background charcoal than before and after this period, when vegetation was dominated by steppe. Between 750 and 75 cal year BP steppe has expanded and fire episode frequency averaged 33 episodes/1000 years, increasing to a maximum of 40 episodes/1000 years at ca. 300 cal year BP and then decreasing to present levels. Since AD 1880, the pollen record indicates an increase in shrubs and grasses from AD 1895 to 1960 as a result of vegetation changes associated with timber harvesting and livestock grazing. No fires have been documented in the Foy Lake watershed since AD 1880. Charcoal from the extralocal fires of AD 1910, burning over 4,111,249 ha in Idaho, Montana, and Wyoming, however, is present in Foy Lake. Between AD 1970 and 2000, increased arboreal pollen in the record is consistent with observations that the forest has become more closed. The activities of Euro–Americans have led to a decline in forest cover between AD 1880 and 1970, followed by a recent increase as trees are now growing in areas previously occupied by steppe. Euro–Americans are likely the cause of a reduction in fire activity in watershed since AD 1880.     

A thousand years of environmental change and human impact in the alpine zone at Mt Kosciusko,New South Wales

This study reconstructs erosion, productivity, fire and vegetation records at Club Lake, in the alpine zone of Kosciusko National Park (the highest mountain region in Australia), and uses them to compare the prehistoric and historic periods. While disturbance in the prehistoric period was found to be minimal and mainly activated by fire, the impact of land uses after European arrival initiated a change in the erosion and fire regime and brought new grazing animals and exotic plant species. These triggered temporal changes in eutrophication and the nature of erosion, and significant vegetation changes. There was a reduction in the stability and persistence of species representation, especially in herbfield vegetation, and little recovery is evident despite the cessation of summer grazing. It is apparent that the area is very sensitive to disturbance by human impact and large fires.     

Impact of Holocene climate change on the prehistoric cultures of Zhejiang region,East China

The temporal-spatial distribution features of prehistoric cultures since the Holocene in Zhejiang region were comparatively analyzed based on GIS spatial analysis. Results show that the prehistoric cultures expanded gradually in this region before 4000 cal. a BP. The notable expansions occurred twice, one in the Majiabang-Hemudu cultural period, the other in the Liangzhu cultural period. Meanwhile, the prehistoric cultures were disseminated from west to east coast along river valleys. After 4000 cal. a BP, as represented by the Maqiao Culture, the distributed area of each prehistoric culture contracted. This is obviously due to the termination of spreading trends to east coast, which was simultaneously accompanied by two different modes of production and economic transitions in the north and south Zhejiang region respectively. The distribution of prehistoric cultures was closely related with Holocene sea-level fluctuations, especially on the banks of Hangzhou Bay, where the distribution changes of prehistoric cultural sites were greatly affected by sea-level changes, with the closest relationships between them. After 7000 cal. a BP, the process of lowered sea-level and regression-epeirogenesis provided wider terrestrial living spaces for prehistoric inhabitants. Based on the comparative analyses of the changes of prehistoric cultures and the environmental evolution information recorded in the Qianmutian subalpine peat of Mt. Tianmu and muddy area on the inner shelf of the East China Sea, it is indicated that the changes of prehistoric cultures were synchronized with environmental changes in Zhejiang region. Before 4000 cal. a BP, the eastward expansion of prehistoric cultures in Zhejiang occurred under the background of the Holocene Optimum, and was the expansion and extension under the joint influences of agricultural civilization and maritime civilization. However, after 4000 cal. a BP, the geographical contraction of prehistoric cultures in Zhejiang occurred under the back ground of dry-cold climate trend and deterioration of coastal marine environment. It is evidenced from the above fact that the development, expansion and contraction of prehistoric cultures are positively correlated to environmental change. The change of the climatic environment is just the underlying reason for these changes and transitions of production modes and economic forms. Therefore, the climatic environment is the dominant factor of prehistoric culture vicissitudes in Zhejiang region, which has exerted great influence on distribution, dissemination, expansion and transmutation of the culture.     

Impact of Holocene climate change on the prehistoric cultures of Zhejiang region,East China

The temporal-spatial distribution features of prehistoric cultures since the Holocene in Zhejiang region were comparatively analyzed based on GIS spatial analysis. Results show that the prehistoric cultures expanded gradually in this region before 4000 cal. a BP. The notable expansions occurred twice, one in the Majiabang-Hemudu cultural period, the other in the Liangzhu cultural period. Meanwhile, the prehistoric cultures were disseminated from west to east coast along river valleys. After 4000 cal. a BP, as represented by the Maqiao Culture, the distributed area of each prehistoric culture contracted. This is obviously due to the termination of spreading trends to east coast, which was simultaneously accompanied by two different modes of production and economic transitions in the north and south Zhejiang region respectively. The distribution of prehistoric cultures was closely related with Holocene sea-level fluctuations, especially on the banks of Hangzhou Bay, where the distribution changes of prehistoric cultural sites were greatly affected by sea-level changes, with the closest relationships between them. After 7000 cal. a BP, the process of lowered sea-level and regression-epeirogenesis provided wider terrestrial living spaces for prehistoric inhabitants. Based on the comparative analyses of the changes of prehistoric cultures and the environmental evolution information recorded in the Qianmutian subalpine peat of Mt. Tianmu and muddy area on the inner shelf of the East China Sea, it is indicated that the changes of prehistoric cultures were synchronized with environmental changes in Zhejiang region. Before 4000 cal. a BP, the eastward expansion of prehistoric cultures in Zhejiang occurred under the background of the Holocene Optimum, and was the expansion and extension under the joint influences of agricultural civilization and maritime civilization. However, after 4000 cal. a BP, the geographical contraction of prehistoric cultures in Zhejiang occurred under the background of dry-cold climate trend and deterioration of coastal marine environment. It is evidenced from the above fact that the development, expansion and contraction of prehistoric cultures are positively correlated to environmental change. The change of the climatic environment is just the underlying reason for these changes and transitions of production modes and economic forms. Therefore, the climatic environment is the dominant factor of prehistoric culture vicissitudes in Zhejiang region, which has exerted great influence on distribution, dissemination, expansion and transmutation of the culture.     

全新世浙江地区气候变化对史前文化的影响(英文)

The temporal-spatial distribution features of prehistoric cultures since the Holocene in Zhejiang region were comparatively analyzed based on GIS spatial analysis. Results show that the prehistoric cultures expanded gradually in this region before 4000 cal. a BP. The notable expansions occurred twice, one in the Majiabang-Hemudu cultural period, the other in the Liangzhu cultural period. Meanwhile, the prehistoric cultures were disseminated from west to east coast along river valleys. After 4000 cal. a BP, as represented by the Maqiao Culture, the distributed area of each prehistoric culture contracted. This is obviously due to the termination of spreading trends to east coast, which was simultaneously accompanied by two different modes of production and economic transitions in the north and south Zhejiang region respectively. The distribution of prehistoric cultures was closely related with Holocene sea-level fluctuations, especially on the banks of Hangzhou Bay, where the distribution changes of prehistoric cultural sites were greatly affected by sea-level changes, with the closest relationships between them. After 7000 cal. a BP, the process of lowered sea-level and regression-epeirogenesis provided wider terrestrial living spaces for prehistoric inhabitants. Based on the comparative analyses of the changes of prehistoric cultures and the environmental evolution information recorded in the Qianmutian subalpine peat of Mt. Tianmu and muddy area on the inner shelf of the East China Sea, it is indicated that the changes of prehistoric cultures were synchronized with environmental changes in Zhejiang region. Before 4000 cal. a BP, the eastward expansion of prehistoric cultures in Zhejiang occurred under the background of the Holocene Optimum, and was the expansion and extension under the joint influences of agricultural civilization and maritime civilization. However, after 4000 cal. a BP, the geographical contraction of prehistoric cultures in Zhejiang occurred under the back-ground of dry-cold climate trend and deterioration of coastal marine environment. It is evidenced from the above fact that the development, expansion and contraction of prehistoric cultures are positively correlated to environmental change. The change of the climatic environment is just the underlying reason for these changes and transitions of production modes and economic forms. Therefore, the climatic environment is the dominant factor of prehistoric culture vicissitudes in Zhejiang region, which has exerted great influence on distribution, dissemination, expansion and transmutation of the culture.     

Late Quaternary lake response to climate change and anthropogenic impact: biomarker evidence from Lake Constance sediments

This study used organic matter in oligotrophic Lake Constance (southern Germany) to reconstruct lake environment and to disentangle the multiple factors, such as climate change and human impacts, which influence sedimentation in large lakes. A sediment core from Upper Lake Constance, which represents 16,000 years of Late Glacial and Holocene lake history, was analysed for organic biomarkers, hydrogen index and elements calcium, strontium, and magnesium. Magnetic susceptibility was measured to establish a high-resolution stratigraphic framework for the core and to obtain further information about changes with respect to relative allochthonous versus autochthonous sedimentation. Dinosterol—a biomarker for dinoflagellates—and calcium have low concentrations in Younger Dryas sediments and consistently high concentrations between 10,500 and 7,000 cal. years BP. These variations are attributed to changes in lake productivity, but are not reflected in the proportion of total organic carbon within the sediment. During the Younger Dryas and between 6,000 and 2,800 cal. years BP, concentrations and accumulation rates of land-plant-derived C₂₉-steroids (β-sitosterol, stigmastanol and stigmasterol), in combination with a relatively low HI, indicate periods of enhanced terrigenous input to the lake. For the Younger Dryas, higher runoff can be attributed to a cold climate, leading to decreased vegetation cover and increased erosion. After 6,000 cal. years BP, high terrestrial input may be explained by enhanced precipitation. Biomarker and HI results, in combination with archaeological studies, raise the question as to whether lakeshore settlements affected sedimentation in Upper Lake Constance between 6,000 and 2,800 cal. years BP.     

9.5–2.3 ka BP燕辽地区考古文化演变及其遗址的时空分布（英文）

With basic information from 8353 archaeological sites, this study describes a holistic spatial-temporal distribution pattern of archaeological sites of the prehistoric culture sequence from 9.5 ka BP (ka BP = thousands of years before 0 BP, where "0 BP" is defined as the year AD 1950) to 2.3 ka BP in the region that extends from the Yanshan Mountains to the Liaohe River Plain(i.e., the Yan-Liao region) in northern China. Based on spatial statistics analysis – including the spatial density of the sites and Geographic Information System nearest-neighbour analysis, combined with a review of environmental and climatic data – this paper analyses cultural evolution, the spatial-temporal features of the archaeological sites and human activities against the backdrop of climatic and environmental changes in this region. The results reveal that prehistoric cultural evolution in the Yan-Liao region is extensively influenced by climatic and environmental changes. The Xinglongwa, Zhaobaogou and Fuhe cultures, which primarily developed during a habitable period from 8.5 ka BP to 6.0 ka BP with strong summer monsoons, have similar maximum density values, spatial patterns and subsistence strategies dominated by hunting-gathering. Significant changes occurred in the Hongshan and Lower Xiajiadian cultures, with a significant increase in numbers and densities of sites and a slump in average nearest-neighbour ratio when the environment began to deteriorate starting in 6.0 ka BP. Additionally, with the onset of a weak summer monsoon and the predominance of primitive agriculture, sites of these two cultures present a different type of concentric circle-shaped pattern in space. As the environment continuously deteriorated with increasing aridity and the spread of steppe, more sites were distributed towards the south, and primitive agriculture was replaced by livestock husbandry in the Upper Xiajiadian culture. The most densely populated areas of the studied cultures are centralized within a limited area. The Laohahe River and Jiaolaihe River basins formed the core area in which most archaeological sites were distributed during the strong summer monsoon period and the first few thousand years of the weak summer monsoon period.     

全新世巢湖沉积物炭屑记录的火环境变化

通过对巢湖湖泊沉积岩芯不同粒级炭屑浓度和磁化率等指标变化的研究,揭示了全新世以来的区域火环境变化及人类活动影响。结果表明：① 全新世早期,气候由寒冷干旱向温暖湿润过渡,但仍较为干旱,炭屑浓度也相对略高,火活动比较频繁,地方性和区域性火时有发生;② 全新世中期是最温暖湿润的适宜期,炭屑浓度出现全新世以来的低值,火活动微弱,但在文化兴盛时期炭屑浓度出现峰值,则归因于人类活动的影响;③ 全新世晚期,在气候趋于凉干的环境背景下,人类活动的增强更加剧了火活动的频率和强度,炭屑浓度大幅增加;④ 近200 a炭屑浓度的降低可能与湖区附近已没有足够生物量引起火灾有关。     

Environmental magnetic studies of sediment cores from Gonghai Lake: implications for monsoon evolution in North China during the late glacial and Holocene

Environmental magnetic studies were conducted on a 9.42-m-long sediment core from Gonghai Lake, North China. Radiocarbon dating indicates that the record spans the last 15,000 cal year BP. The principal magnetic mineral in the sediments is pseudo-single domain magnetite of detrital origin with minimal post-depositional alteration. Although the variations in the concentration of detrital magnetic minerals and their grain size throughout the core reflect inputs from both soil erosion and eolian dust, it is shown that their climatic and environmental significance changes with time. In the lowermost part of the core, ~15,000–11,500 cal year BP, the magnetic minerals were supplied mainly by bedrock erosion, soil erosion and dust input when climate ameliorated after the cold and dusty last glacial maximum. The increasing magnetic susceptibility (χ) in this interval may indicate a combination of changes in the lake environment together with catchment-surface stabilization and a decreasing proportion of dust input. In the central part of the core, ~11,500–1,000 cal year BP, the detrital magnetic minerals mainly originated from dust inputs from outside the catchment when the lake catchment was covered by forest, and catchment-derived sediment supply (and thus the lake sediment accumulation rate) were minimal. The generally low concentration of magnetic minerals in this part of the core reflects the highest degree of soil stability and the strongest summer monsoon during the Holocene. In the uppermost part of the core, the last ~1,000 years, detrital magnetic minerals mainly originated from erosion of catchment soils when the vegetation cover was sparse and the sediment accumulation rates were high. Within this part of the core the high magnetic susceptibility reflects strong pedogenesis in the lake catchment, and thus a strong summer monsoon. This scenario is similar to that recorded in loess profiles. Overall, the results document three main stages of summer monsoon history with abrupt shifts from one stage to another: an increasing and variable summer monsoon during the last deglacial, a generally strong summer monsoon in the early and middle Holocene and a weak summer monsoon in the late Holocene. The results also suggest that different interpretational models may need to be applied to lake sediment magnetic mineral assemblages corresponding to different stages of environmental evolution.     

A record of vegetation dynamics and lake level changes from Lake Emakat,northern Tanzania,during the last c. 1200 years

Analyses of down-core variations in pollen and charcoal in two short cores of lake sediment and wood samples taken from the in situ remains of Nuxia congesta from Lake Emakat, a hydrologically-closed volcanic crater lake occupying the Empakaai Crater in northern Tanzania, have generated evidence of past vegetation change and lake level fluctuations. Eight AMS radiocarbon (¹⁴C) dates on bulk samples of lake sediment provide a chronological framework for the two cores and indicate that the sediment record analysed incorporates the last c. 1200 years. The in situ remains of a Nuxia congesta tree, now standing in deep water, were dated with three additional AMS ¹⁴C dates, suggesting tree growth within the interval ∼1500–1670 AD. Down-core variations in pollen from terrestrial taxa, particularly the montane forest trees Hagenia abyssinica and Nuxia congesta, indicate a broad period of generally more arid conditions in the catchment to c. 1200 AD and at a prolonged period between c. 1420 and 1680 AD. Variations in pollen from plants in lake margin vegetation indicate low lake levels, presumably as a result of reduced effective precipitation, contemporary with indications of relatively dry conditions mentioned above, but also during the late 18th and the late 19th centuries. The presence of charcoal throughout both cores indicates the frequent occurrence of vegetation fires. An increase in burning, evident in the charcoal data and dated to the early to mid second millennium AD, could relate to an expansion of human population levels and agricultural activity in the region.