Late survival of woodland contrasts with rapid limnological changes following settlement at Kalmanstjörn,Mývatnssveit,northeast Iceland

The settlement of Iceland is known to have had profound impacts on vegetation and landscape stability, but there remain uncertainties around the spatial variability and timing of environmental change, and the impacts of settlement on aquatic ecosystems. Here a new multiproxy palaeoenvironmental reconstruction spanning the last 3000 years is presented from Kalmanstjörn, a small lake in Mývatnssveit, northeast Iceland. Sedimentology, pollen and non-pollen palynomorphs, and geochemical proxies, dated using tephrochronology, are used to reconstruct terrestrial vegetation, landscape stability and aquatic ecosystems. The data reveal complex environmental dynamics after settlement. At this site, substantial tree populations persisted until the late 15th century, in strong contrast to the rapid deforestation shown by almost all other records from Iceland. The eventual loss of woodland may have been caused by changes in direct human activity and the location of extensive grazing, in combination with Little Ice Age climatic cooling. The loss of woodland was accompanied by increased soil erosion. Conversely, the lake ecosystem showed an immediate response to settlement, becoming more productive for several centuries, perhaps in response to increased availability of nutrients from grazing herbivores. The late persistence of woodland in the Kalmanstjörn record adds to our understanding of the spatial variations in ecosystem responses to settlement in Iceland, while the evidence for decoupling of the aquatic and terrestrial systems suggests that palaeolimnological reconstructions focusing on aquatic ecosystem responses may be important new sources of information on the wider ecological consequences of human settlement.     

Fire in the virgin forests of the Boundary Waters Canoe Area,Minnesota

Fire largely determined the composition and structure of the presettlement vegetation of the Boundary Waters Canoe Area as well as the vegetation mosaic on the landscape and the habitat patterns for wildlife. It also influenced nutrient cycles, and energy pathways, and helped maintain the diversity, productivity, and long-term stability of the ecosystem. Thus the whole ecosystem was fire-dependent.At least some overstory elements in virtually all forest stands still date from regeneration that followed one or more fires since 1595 A.D. The average interval between significant fire years was about 4 yr in presettlement times, but shortened to 2 yr from 1868 to 1910 during settlement. However, 83% of the area burned before the beginning of suppression programs resulted from just nine fire periods: 1894, 1875, 1863–1964, 1824, 1801, 1755–1959, 1727, 1692, 1681. The average interval between these major fire years was 26 yr. Most present virgin forests date from regeneration that followed fires in these years. Significant areas were also regenerated by fires in 1903, 1910, 1936, and 1971. Most major fire years occurred during prolonged summer droughts of subcontinental extent, such as those of 1864, 1910, and 1936. Many fires were man-caused, but lightning ignitions were also common. Lightning alone is probably a sufficient source of ignitions to guarantee that older stands burned before attaining climax. Dry matter accumulations, spruce budworm outbreaks, blowdowns, and other interactions related to time since fire increase the probability that old stands will burn. Vegetation patterns on the landscape were influenced by such natural firebreaks as lakes, streams, wetlands, and moist slopes. Red and white pine are most common on islands, and to the east, northeast, or southeast of such firebreaks. Jack pine, aspen-birch, and sprout hardwood forests are most common on large uplands distant from or west of such firebreaks.A Natural Fire Rotation of about 100 yr prevailed in presettlement times, but many red and white pine stands remained largely intact for 150–350 yr, and some jack pine and aspen-birch forests probably burned at intervals of 50 yr or less. There is paleoecological evidence that fire was an ecosystem factor before European man arrived, and even before early man migrated to North America. Probably few areas ever attained the postulated fir-spruce-cedar-birch climax in postglacial times. To understand the dynamics of fire-dependent ecosystems fire must be studied as an integral part of the system. The search for stable communities that might develop without fire is futile and avoids the real challenge of understanding nature on her own terms.To restore the natural ecosystem of the Canoe Area fire should soon be reintroduced through a program of prescribed fires and monitored lightning fires. Failing this, major unnatural, perhaps unpredictable, changes in the ecosystem will occur.     

Age and impacts of the caldera-forming Aniakchak II eruption in western Alaska

The mid-Holocene eruption of Aniakchak volcano (Aniakchak II) in southwest Alaska was among the largest eruptions globally in the last 10,000 years (VEI-6). Despite evidence for possible impacts on global climate, the precise age of the eruption is not well-constrained and little is known about regional environmental impacts. A closely spaced sequence of radiocarbon dates at a peatland site over 1000 km from the volcano show that peat accumulation was greatly reduced with a hiatus of approximately 90–120 yr following tephra deposition. During this inferred hiatus no paleoenvironmental data are available but once vegetation returned the flora changed from a Cyperaceae-dominated assemblage to a Poaceae-dominated vegetation cover, suggesting a drier and/or more nutrient-rich ecosystem. Oribatid mites are extremely abundant in the peat at the depth of the ash, and show a longer-term, increasingly wet peat surface across the tephra layer. The radiocarbon sample immediately below the tephra gave a date of 1636–1446 cal yr BC suggesting that the eruption might be younger than previously thought. Our findings suggest that the eruption may have led to a widespread reduction in peatland carbon sequestration and that the impacts on ecosystem functioning were profound and long-lasting.     

Late quaternary environmental changes in the upper Las Vegas valley, Nevada

Five stratigraphic units and five soils of late Pleistocene to Holocene age crop out in dissected badlands on Corn Creek Flat, 30 km northwest of Las Vegas, Nevada, and at Tule Springs, nearer to Las Vegas. The record is dominantly fluvial but contains evidence of several moister, marsh-forming periods: the oldest (Unit B) dates perhaps to the middle Wisconsin, and the more widespread Unit D falls between 30,000 and 15,000 yr B.P. Unit D therefore correlates with pluvial maximum lacustrine deposits elsewhere in the Great Basin. Standing water was not of sufficient depth or extent during either period to form lake strandlines. Between 14,000 and 7200 yr B.P. (Unit E), standing surface water gradually decreased, a trend also apparent in Great Basin pluvial lake chronologies during the same period. Groundwater carbonate cementation and burrowing by cicadas (Cicadae) accompany the moist-phase units. After 7200 yr B.P., increased wind action, decreased biotic activity, and at least 25 m of water-table lowering accompanied widespread erosion of older fine-grained deposits. Based on pack-rat midden and pollen evidence, this coincides with major vegetation changes in the valley, from sagebrush-dominated steppe to lower Mohave desertscrub.     

Paleoecological perspectives on human adaptation in central Panama. I. The Pleistocene

Paleoecological data from two sites in central Pacific Panama have allowed the reconstruction of Late Pleistocene climate and vegetation in lowland areas, the timing of important environmental changes, and the generation of predictions concerning Paleoindian settlement and subsistence. The last 9000 years of the glacial period, from 20,000 B.P. until 11,050 B.P. were marked by climates cooler and drier than today's. The period from ca. 16,000 B.P. until 11,000 B.P. appears to have been the coolest and driest. We postulate that the major effects of these conditions were to have brought montane vegetation 900 m lower than its present range and to create tracts of open landscape along the Pacific coast. Forests, however, were widespread in extent and many lowland forest taxa apparently persisted, creating the basis for the rejection of refugial theory as an explanatory model for early human occupation. Neither the admittedly limited archaeological or paleoecological data indicated the presence of pre-Clovis populations in Panama, and we chose to view Clovis as the first human expression on the Isthmus. Correlation of reconstructed environmental setting with Paleoindian site location suggests that Clovis adaptations were fluid and flexible, and utilized a wide variety of vegetation types. Occupation and modification of tropical forest appear to have been integral parts of Clovis subsistence and settlement strategies.     

亚洲内陆干旱区巴里坤湖记录的H1突变事件

对亚洲内陆干旱区Heinrich (H)事件发生时的气候状况和植被响应过程的研究有利于加深对内陆干旱生态系统与气候突变事件关系的理解.本研究以新疆巴里坤湖BLK11A岩芯450~610 cm段的沉积物为研究载体,基于AMS 14C年代控制,通过岩性、粒度、 X射线荧光光谱元素钛含量( XRF-Ti)和孢粉变化特征等对H1突变事件(17~15 cal. ka B. P.)发生时流域的气候特征和植被分布状况进行了重建.研究结果表明: 1)H1时期湖泊岩性以砂质或者粉砂质的浅湖相为主,湖泊水位较低.沉积物粒度分布频率曲线表现出与流域现代扬尘一致的双峰分布特征,同时XRF-Ti含量增加,两者共同指示了流域局地扬尘发生频率增加,且对湖泊物质输入起主导作用;2)该时期耐旱的荒漠植被比例显著增加,植被覆盖度降低,流域生物量也相应降低,代表了流域植被显著退化;3)结合中纬度欧亚内陆干旱区其他地质记录,发现这一区域H1时期整体以冷干气候为主,风沙活动加强,湖泊萎缩,植被退化.主要原因为西风携带水汽的减少,使得能够到达该内陆区域的降水减少,另一方面温度降低导致了冰雪融水补给的减少,两者共同导致了内陆干旱区植被和环境的退化.     

Storegga tsunami sand in peat below the Tapes beach ridge at Harøy, western Norway, and its possible relation to an early Stone Age settlement

One of the early problems with the Storegga tsunami deposit was how to distinguish it from deposits of the midHolocene (Tapes) transgression. An excavation on Harøy, an island on the outermost western coast of Norway, shows a distinct, clean sand bed embedded in peat and clearly separated from the overlying Tapes beach deposits. This sand bed continues in the peat landwards of the beach ridge for at least 60 m. Radiocarbon dates of the peat show that the sand was deposited some time between 6900 and 7700 yr BP. The sedimentary structures of the bed, the ¹⁴C dates, and the fact that this is the only sand bed in the peat, suggest that the sand bed was deposited by a short-lived event, the Storegga tsunami. On the neighbouring island, Fjørtoft, a Stone Age settlement, dated to 7500 yr BP, was discovered in the early 1970s. The settlement was found underneath a sand bed that later had been covered by the Tapes beach ridge deposits. When discovered, the sand covering the settlement was inferred as eolian sand. However, this investigation shows that the Storegga tsunami deposited a widespread sand bed on the land surface around this time with a similar grain size distribution to eolian sand. It is therefore suggested that the sand bed covering this settlement was deposited from the Storegga tsunami. Both the stratigraphy and ¹⁴C dates demonstrate that the Tapes transgression maximum was reached well after the Storegga tsunami on Harøy, between 6500 and 6100 yr BP.     

Quantitative estimates of temperature changes over the last 2700 years in Michigan based on pollen data

Temperatures for the past 2700 yr are estimated using well-dated pollen data from northwestern lower Michigan. The pollen data were sampled from sediment cores of four lakes along a 75-km transect, with fine-grained morainic soils around the two western lakes and sandy outwash soils around the lakes to the east. Climatic reconstructions based on the pollen data from the sandy sites show less temperature change than the reconstructions from the other sites, because variations in the composition of the vegetation at the sandy sites are edaphically restricted. One of the cores studied was dated by counting visible annual laminations (varves). The cores from the other lakes were dated based on three radiocarbon dates per core as well as the historically determined age of the settlement horizons. All the time scales were cross-checked using pollen-stratigraphic correlation between the four sites. A calibration function was developed using a network of modern pollen and climate data covering all of lower Michigan. Based on this calibration function, the 2700-yr reconstruction for Marion Lake indicates an estimated growing-season temperature range of 1.3°C between extreme 30-yr means. Mild conditions persisted prior to ca. A.D. 400, but a cold interval occurred between ca. A.D. 500 and 800. The well-marked warm period evident from ca. A.D. 1000 to 1200 was the last time when temperatures were about equal to the 1931–1960 mean. A prolonged longed cooling occurred after A.D. 1200 and reached 1°C below the 1931–1960 mean by the 1700s. A warming of 0.5°C is indicated from ca. A.D. 1750 to 1850. The estimated temperatures for the 1830s at Marion Lake agree with the instrumental data for that period and this provides some validation of the calibration-function results.     

Early and middle Holocene ecosystem changes at the Western Carpathian/Pannonian border driven by climate and Neolithic impact

Travertine deposits are unique archives for multidisciplinary studies of past climate changes, associated vegetation development and the evolution of human societies. Despite their high potential in palaeoecological and palaeoclimate reconstructions, investigations of travertines are rather scarce in central Europe and particularly in Slovakia. Therefore, this study focused on a travertine deposit situated on the border between the Pannonian Basin and the Western Carpathians in a small valley in Santovka village (SW Slovakia), which is unique due to the presence of archaeological artefacts with known radiocarbon ages in the palaeoecological profile. Using a multidisciplinary approach combining macrofossil, pollen, mollusc, lithological and geochemical analyses, this study investigated climate–human–vegetation interactions. The Holocene onset was marked by the early arrival of oak trees; however, forest‐steppe with a high representation of pine predominated until 9880 cal. a BP, followed by an expansion of temperate trees. The local ecosystem changed around 8600 cal. a BP when the valley was probably dammed by a travertine accumulation, probably resulting in the existence of a small travertine lake. This was associated with wetter climatic conditions, which were also documented in other sites in the Western Carpathians at that time. Surrounding temperate forest possibly retained a certain degree of openness, or local steppe habitat may have persisted on adjacent loess terraces until the neolithization of the area. Archaeological evidence represented by a ceramic shard dated to 7339 cal. a BP suggests the first appearance of humans at the site, yet pollen analysis records a significant change in vegetation first at 6650 cal. a BP. The local ecosystem records an abrupt change linked with human settlement earlier, at c. 7000 cal. a BP. Deforestation activities of the Neolithics resulted in the formation of an open calcareous fen occupied by numerous light‐demanding mollusc species. The present study provides new important data about the spread of temperate trees at the onset of the Holocene, about further vegetation changes caused by activities of the first Neolithic farmers and about climate changes in the region of southwestern Slovakia.     

青藏高原植被动态与环境因子相互关系的研究现状与展望

青藏高原是中国乃至全球对气候变化最敏感的地区之一,是全球平均海拔最高的地理单元,对周边地区起到重要的生态安全屏障作用。近年来,当地植被受到气候变化和人类活动的双重压力。本文基于文献检索分析青藏高原的植被生理、生态特征对气候变化和人为干扰的响应,并利用荟萃分析定量综述植被覆盖度变化对土壤理化性质的影响。在此基础上分析青藏高原植被与环境因子相互关系的研究尺度与方法。结果表明:(1)气温、降水、辐射等自然因素和放牧、农耕、筑路等人为活动均对青藏高原植被的碳交换、水分利用效率、元素含量与分布格局、物候、多样性等指标产生显著影响,植被的变化也同时影响着土壤的水热交换、水文过程和理化性质等;(2)在植被退化过程中,由高覆盖度向中覆盖度转变时对土壤理化性质产生的不利影响强于由中覆盖度转为低覆盖度时,高覆盖度地区的植被保护需要引起更多关注;(3)现有研究更多关注单一要素、单一尺度,未来应关注多要素间的相互耦合,通过合作与共享获取数据,开展多尺度对比和尺度效应研究,系统梳理和分析植被与环境因子的相互关系可为制定科学合理的生态修复策略提供科学依据。     

长江源区高寒生态与气候变化对河流径流过程的影响分析

近40 a来长江源区气候变化剧烈,是青藏高原增温最为显著的地区之一,高寒生态系统与冻土环境不断退化.采用多因素逐次甄别方法与半经验理论方法相结合,基于多年冻土的不同植被覆盖降水-径流观测场观测试验结果,分析了长江源区气候-植被-冻土耦合系统中各要素变化对河川径流的不同影响.结果表明:近40 a来长江源区河川径流呈持续递减趋势,年均径流量减少了15.2%,频率>20%的径流量均显著减少,而>550 m³·s^-1的稀遇洪水流量发生频率增加;气候变化与高寒草甸覆盖变化对源区径流变化的影响较大,分别占5.8%和5.5%;气候与植被覆盖变化对径流的显著影响是与冻土耦合作用的结果,但冻土环境与冰川变化对径流的贡献尚不能准确评价.高寒沼泽湿地和高寒草甸生态系统对于源区河川径流的形成与稳定起到关键作用,这两类生态系统的显著退化是驱动河川径流过程中变差增大、降水-径流系数减少以及洪水频率增加的主要原因.保护源区高寒草甸与独特的高寒湿地生态,对于维护源区水涵养功能和流域水安全意义重大.     

Vegetation change based on SPOT-VGT data from 1998 to 2007, northern China

Dynamic change of vegetation in northern China from 1998–2007 was explored, based on SPOT-VGT data. The results showed that the NDVI can effectively monitor vegetation change, but also the mean multi-year NDVI maximum of 0.10 basically can be considered as the threshold of vegetation cover in northern China, and those places with smaller than or equal to the threshold value mainly were covered by deserts, Gobi and lakes, salinization lands, glaciers, snow patches and bare mountains, etc. The change trends of vegetation where sub-region C and D were affected by east-Asia monsoon were similar with the characteristics of first decreasing, later increasing and finally slowly decreasing; the difference lies in that sub-region C maintained a lower vegetation state, and sub-region D reached a higher state. The vegetation change of sub-region A was anomalous with smaller fluctuation. The change trend of vegetation of sub-region B was not only extremely unstable, but also the change extent was huge. As far as the whole of northern China is concerned, vegetation has not demonstrated obvious improvement since these ecological construction and protection projects, and the area of vegetation degradation still is much larger than that of vegetation improvement from 1998 to 2007, but there was a bigger spatial difference. Field investigation and remote sensing monitoring reveal that vegetation has obviously been improved in the agro-grazing mixing zone and to the south, as well as many oases in the northwestern arid zone, while vegetation still has worsened in the steppes, especially the Ulanqab steppe, Hunshandake Sandy Land, the region along the Sino–Mongolia border within Xilingol Meng, Hulunbeir Sandy Land and the northern Tianshan mountain region in Xinjiang. Human activities only obviously showed success in local regions. The compelling challenges of restoring the eco-environment are still immense, especially in the northern grazing zone of China.     

Assessment of the feasibility of utilizing Landsat for detection and monitoring of landfills in a statewide GIS

Use of satellite data could be beneficial and cost effective in detecting and monitoring landfills in a state-wide geographic information system (GIS). To assure the feasibility of this approach, multitemporal Landsat data were used to detect several selected active and inactive landfills in central and southwest Missouri. The landfills were visually delineated from aerial photography of approximately the same two dates. A classification procedure based on homogeneity of the digital numbers was performed on each landfill scene for each time period using four spectral bands: two visible, one near-infrared, and one mid-infrared. The mid-infrared band proved more useful in delineating landfills, especially when spectral change was compared to the near-infrared band. The active landfills were spectrally different from surrounding land cover as were the two landfills which closed after the collection of the first Landsat scene. These landfills showed considerable areal change between the two selected time periods as verified by the aerial photographs. The inactive landfills were more difficult to discern from surrounding land cover types because they were grass covered and spectrally similar to pasture. Consequently, areal change could not be assigned to these older landfills because the reclamation process was practically complete.     

Holocene vegetation change in northernmost Fennoscandia and the impact on prehistoric foragers 12 000–2000 cal. a BP – A review

While single pollen records are widely used in reconstructing the environment for nearby prehistoric settlements, they are less helpful when addressing large‐scale issues of variation in human settlement patterns. In order to assess the impact of vegetation change on regional prehistoric settlement and subsistence patterns in an ecotone sensitive area, we inferred the general change in main vegetation types based on palaeobotanical investigations from across northernmost Fennoscandia. Tundra vegetation was predominant during the Lateglacial and earliest parts of the Holocene. Maritime birch forests rich in ferns started to expand c. 11 000 cal. a BP and became dominant from 10 000 cal. a BP. Pine expanded from the NE of the investigation area and pine‐birch forest dominated in the inland around 8000 cal. a BP. A gradual degeneration of forest towards more open birch woodland started c. 6000 cal. a BP with the most marked change around 3500 cal. a BP. Along the northern outer coast, this eventually led to open heathland. Comparison with the archaeological setting suggests a general correlation between low forest cover and extensive mobility patterns, while widespread and varied forest cover appear to have led to a more sedentary way of life. The background for this is arguably that the forested landscapes hosted a larger diversity of resources within a shorter foraging distance, while areas and periods with low forest cover required longer travels to obtain the desired prey and materials.     

Beyond hydrogeologic evidence: challenging the current assumptions about salinity processes in the Corangamite region, Australia

In keeping with the standard scientific methods, investigations of salinity processes focus on the collection and interpretation of contemporary scientific data. However, using multiple lines of evidence from non-hydrogeologic sources such as geomorphic, archaeological and historical records can substantially add value to the scientific investigations. By using such evidence, the validity of the assumptions about salinity processes in Australian landscapes is challenged, especially the assumption that the clearing of native vegetation has resulted in rising saline groundwater in all landscapes. In the Corangamite region of south-west Victoria, salinity has been an episodic feature of the landscapes throughout the Quaternary and was present at the time of the Aboriginal inhabitants and the first pastoral settlement by Europeans. Although surface-water salinity has increased in some waterways and the area of salinised land has expanded in some landscapes, there is no recorded evidence found which supports significant rises in groundwater following widespread land-use change. In many areas, salinity is an inherent component of the region’s landscapes, and sustains world-class environmental assets that require appropriate salinity levels for their ecological health. Managing salinity requires understanding the specific salinity processes in each landscape.     

Radiocarbon-dating of transitions between marine and lacustrine sediments and their relation to the development of lakes

In three different areas in western Norway, large errors are obtained in the radiocarbon dates from lacustrine sediments close to marine/lacustrine sediment boundaries. Differences occur between radiocar-bon and pollenanalytic dates and between dates at isolation/ingression contacts for lakes of the same altitude above the present sea level. Younger radiocarbon dates are also obtained below older ones in undisturbed sediments. When divergent dates occur, the radiocarbon dates always seem to be the youngest. Large differences are also found between NaOH soluble and insoluble fractions of the same sediment samples. Insoluble fractions generally yield younger dates than the soluble. Differences are not found, however, for dates younger than about 8,000 B.P. The dating errors are connected to periods with more oligotrophic conditions with isoetides. Their roots penetrate older sediments. Due to contamination of the organic part of the sediment from partly decomposed roots, some radiocarbon dates will be too young. The isoetide vegetation and the dating errors disappear when the lakes become dystrophic.     

Exploring the effects of water on vegetation change and net primary productivity along the IGBP Northeast China Transect

To understand the mechanisms underlying the effects of climate variation, especially the effects of water on vegetation, vegetation type and distribution as well as climate data and soil type were used to simulate present vegetation distributions and net primary productivity (NPP) under present and future climate scenarios SRES-A2 and SRES-B2. A natural vegetation NPP model was also applied to calculate future vegetation NPP. The results showed that water played a dominant role not only in the distribution of vegetation, but also in the rate of change in the vegetation area. Analysis of NPP showed that precipitation had more effects on the amount of biome NPP than temperature did. Different effects were observed for the rate of change in NPP. In cases where biomes remain unaltered, the variation in annual precipitation could account for 39% of the variation in NPP. In cases where biomes changed, 45% of NPP was caused by temperature variation. Regarding the variation in transect production, −2.85% resulted from the change in vegetation structure when compared with present NPP, and 7.69% from the climate change under scenario SRES-B2; these values were −7.4 and 19.56%, respectively, under scenario SRES-A2. The results showed water served as a dominant factor controlling the vegetation distributions and NPP. However, temperature became determinant where the biomes changed, impacting the rate of change in vegetation NPP when the climate changed. The results also showed that water would have a positive effect on transect production, and the structure of vegetation had a negative effect under the projected future climate.     

Hydroecogeochemical effects of an epikarst ecosystem: case study of the Nongla Landiantang Spring catchment

A typical small-scale epikarst ecosystem usually consists of an epikarst zone, soil and vegetation. In this study, to determine the hydro-eco-geochemical effects of an epikarst ecosystem in subtropical humid area, the samples of vegetation, soil, soil microbes, rainfall, throughfall, stem flow, soil water and epikarst springs of Nongla Village, Mashan County, Guangxi in China were collected and analyzed. The research results have shown in the epikarst ecosystem, the conductivity, temporary hardness and total carbon increased continuously in hydro-ecochemical cycle; the vegetation–soil system conducted the transformation and transference of carbon in hydro-ecochemical cycle; the vegetation layer was the major source for organic carbon, while the soil layer was of the important chemical field for the conversion of organic/inorganic carbon and HCO₃ ^–, which would affect the epikarst dynamical system; for most ions, the vegetation layer and shallow soil layer presented more leaching effect than absorption, in contrast, the deep soil layer behaved oppositely. The vegetation layer and shallow soil layer leached ions, and deep soil layer absorbed them. With the plant community presenting in a positive succession, the epikarst ecosystem trended to be stabilized gradually, which made the hydro-eco-geochemical effects to be adjusted and controlled more effectively.     

Environmental change and fire in the Owen Stanley Ranges,Papua New Guinea

Kosipe, an upland valley at 2000 m altitude in the Owen Stanley Ranges of southeastern New Guinea, is known for the discovery of large stone waisted blades dated to 31 400 cal a BP. The purpose of these tools and the nature of occupation are unknown. The altitude is too high for most food crops today and may have stood close to the treeline during the last glaciation. Three pollen and charcoal diagrams from a large swamp in the Kosipe Valley provide a record of swamp and dryland changes for more than 50 000 years. There have been considerable fluctuations in vegetation on the slopes and on the swamp which reflect both environmental change and anthropogenic influences. A gymnosperm-rich forest at the base is replaced by mountain forest dominated by Nothofagus about 42 000 years ago. Fire first becomes apparent across the swamp around 40 000 years ago but is not common during the time when subalpine herbs reach their best representation. Tree fern-rich grasslands form a mosaic with montane forest in a near-treeline environment. The Pleistocene–Holocene boundary is marked by a decline in Nothofagus and increase in lower montane mixed forest taxa. Charcoal increases before this time and the swamp vegetation becomes more grass-rich. Charcoal is at its maximum through the last 3000 years possibly reflecting climate variability as well as sedentary occupation and agriculture on the swamp margin. Supplementary pollen diagrams from two higher altitude sites support the evidence from the Kosipe Swamp cores. Charcoal, local catchment erosion and increases in disturbance taxa become more widespread in the last 5000 years at these sites, suggesting that local settlement at Kosipe may have lagged behind general landscape use by populations from lower altitudes.     

Khok Phanom Di,central Thailand: Chemical analysis of pollen core KL 2 and AMS radiocarbon dates from cores KL 2 and BMR 2

Summary pollen diagrams and carbonized particle concentration figures from cores collected very near the central Thai archaeological site of Khok Phanom Di (ca. 2000-1500 B.C.) have recently been published in this journal. This paper reports on the chemical analysis of one of these cores (KL 2), the accelerator mass spectrometry radiocarbon dates from two cores (KL 2 and BMR 2), and reinterprets the pollen record in relation to the 17 dates now available from the archaeological site. the chemical analyses are the first from a lowland Southeast Asian pollen core and reinforce the conclusions of pollen analysis, while the radiocarbon dates indicate that the earlier disruption to the vegetation suggested in the previous paper pre-dates the excavation evidence. There is some evidence that archaeologically older strata than already uncovered occur at Khok Phanon Di.