vegetation history climate change and human activities over the last 6200 years on the liupan mountains in the southwestern loess plateau in central china abstract fossil pollen data from tianchi lake on the liupan mountains in the loess plateau in china were used to investigate the interplay of climate change vegetation history and human activities the chronology of an 11 m long sediment core was controlled by 19 accelerator mass spectrometry radiocarbon dates on terrestrial plant macrofossils the pollen record shows a long term change from a closed canopy forest to open landscape over the last 6200 years from mixed deciduous coniferous forest dominated by betula quercus picea and pinus at 6200 2900 cal yr bp to transitional steppe forest co dominated by trees betula picea and pinus and herbs mostly artemisia at 2900 1100 cal yr bp and to open landscape dominated by artemisia and poaceae after 1100 cal yr bp this general pattern of vegetation change indicates a drying climate trend consistent with other independent climate records mostly from the monsoon region that show a weakening summer monsoon since the mid holocene the gradual increase in both poaceae pollen and microscopic charcoal since about 2000 cal yr bp and a sharp increase in poaceae but a decrease in charcoal at 1000 cal yr bp indicate two phases of human impacts on vegetation the results from pollen and charcoal analysis together with archaeological and historical evidence suggest that human activities over the last 2000 years have significantly accelerated deforestation that was initiated by a drying climate since the mid holocene

aeolian sediments evolution controlled by fluvial processes climate change and human activities since lgm in the qaidam basin qinghai tibetan plateau abstract aeolian sediments are widely distributed in the eastern qaidam basin qb the main habitats for human in the hyper arid basin during the holocene especially since 3 ka the evolution of aeolian sediments is an important factor for the environmental change and influence human activities and migration however many questions e g when the aeolian sediments start to accumulate what controls their initiation and how their evolution responds to climate change and human activities still need further studies in this study we present a detailed optically stimulated luminescence osl chronology for both aeolian and underlying fluvial sediments from the tiekui desert in the eastern qb to discuss aeolian and fluvial processes climatic changes desert evolution and human activities dating results show that 1 underlying fluvial sediments were formed during 23 9 12 1 ka and the erosion caused by the fluvial process may provide an explanation for the absence of aeolian sediments during and before this period 2 aeolian sediments accumulated from ca 9 8 ka to modern times with loess development from 9 8 ka to 1 6 ka and 1 4 0 7 ka and dune sand accumulation at 1 6 1 4 ka and 0 7 0 ka through the comparison with the local and global palaeoclimatic records we suggest that desert evolution in this region was sensitive to climatic changes induced by the asian summer monsoon detailed local historical records of the past 2000 years suggest that desert evolution was also influenced by human activities

holocene climate changes in the monsoon arid transition reflected by carbon concentration in daihai lake of inner mongolia two sediment cores recovered in the central part of daihai lake in north central china were analysed at 2 to 4 cm intervals for total inorganic and organic carbon tic and toc concentrations the tic concentration is inferred to reflect temperatures over the lake region and an increase in the tic concentration implies an increase in the temperature toc concentration is considered to reflect the precipitation in the lake basin and higher toc concentrations denote more precipitations thus ams 14c time series of the tic and toc records of daihai lake sediments uncovers a detailed history of changes in temperature and precipitation in north central china during the last c 12 000 yr the holocene an epoch of postglacial warmth started c 11 500 cal yr bp and can be subdivided into three stages the early c 11 500 8100 cal yr bp middle c 8100 3300 cal yr bp and the late holocene c 3300 0 cal yr bp the climate was warm and dry during the early holocene warm and wet during the middle holoce

the 2010 yushu earthquake triggered landslide hazard mapping using gis and weight of evidence modeling the yushu county qinghai province china april 14 2010 earthquake triggered thousands of landslides in a zone between 96 20 32 9 e and 97 10 8 9 e and 32 52 6 7 n and 33 19 47 9 n this study examines the use of geographic information system gis technology and bayesian statistics in creating a suitable landslide hazard zone map of good predictive power a total of 2 036 landslides were interpreted from high resolution aerial photographs and multi source satellite images pre and post earthquake and verified by selected field checking before a final landslide inventory map of the study area could be established using gis software the 2 036 landslides were randomly partitioned into two subsets a training dataset which contains 80 1 628 landslides for training the model and a testing dataset 20 408 landslides twelve earthquake triggered landslide associated controlling parameters such as elevation slope gradient slope aspect slope curvature topographic position distance from main surface ruptures peak ground acceleration distance from roads normalized difference vegetation index distance from drainages lithology and distance from all faults were obtained from variety of data sources landslide hazard indices were calculated using the weight of evidence model the landslide hazard map was compared with training data and testing data to obtain the success rate and predictive rate of the model respectively the validation results showed satisfactory agreement between the hazard map and the existing landslide distribution data the success rate is 80 607 and the predictive rate is 78 855 the resulting landslide hazard map showed five classes of landslide hazard i e very high high moderate low and very low the landslide hazard evaluation map should be useful for environmental recovery planning and reconstruction work

sedimentological characteristics and application of machine learning techniques for landslide susceptibility modelling along the highway corridor nahan to rajgarh himachal pradesh india abstract the aim of this study is to investigate the causes of landslides in the himalayan region and analysis of their sedimentary characteristics the himalayan region is unique to topographic as well as geological formations each range has different litho tectonic setting such as the siwalik the lesser andthe great himalayan ranges particularly the lesser himalayan ranges are highly susceptible to landslide during the monsoon season in this study a highway corridor is selected passing through the siwalik and the lesser himalayan range the study comprises of two parts a investigates landslide sedimentary characteristics such as particle size plasticity limit slope geometry and land cover b comparative analysis of four machine learning methods to find out a best suitable model for landslide susceptibility analysis in order to achieve the objectives detailed landslide inventory of the area is prepared based on repeated field visits and multi dated satellite imageries the field investigation reveals that debris fall and debris flow mostly confined a along the road in proximity to the streams particularly in scrubs and wasteland and b along the streams due to river undercutting process sedimentological characteristics are examined to understand the grain size plasticity limit rock mass strength and its relationship to slope failure mechanism landslide susceptibility is analyzed using boosted regression tree brt generalized linear model glm random forest rf and support vector machine svm for the study area these model results are validated using landslide test dataset with the area under curve auc method the auc values of brt 0 85 glm 0 786 rf 0 904 and svm 0 865 reveals the high prediction rate for spatial modelling of landslide in the area the validation results show satisfactory agreement between the computed landslide susceptibility maps and the existing landslides occurred along the highway corridor

a 750 year fire history based on lake sediment records in central yellowstone national park usa a 750 year fire history was reconstructed for the central plateau of yellowstone national park from the deep water sediments of five lakes the charcoal record from a large lake provided a chronology of regional fires data from four small lakes were used to study local and extralocal fires the co occurrence of abundant charcoal and high magnetic susceptibility values at the same stratigraphic level was used as evidence of a local catchment fire and a charcoal peak without high magnetic susceptibility was ascribed to an extralocal fire or a local fire without a related erosion event the fire history was compared with the dendrochronologic fire record for the last 450 years and the close agreement provided the justification to extend the chronology back in time large areas of the region burned in ad 1988 c 1700 c 1560 and c 1440 from c 1220 to 1440 and c 1700 to 1987 intermediate to small areas burned the near absence of fires in the twentieth century prior to the large fires of 1988 is evi

on the assessment of the management priority of sediment source areas in a debris flow catchment in many alpine catchments the monitoring and hazard mitigation of debris flow events require enormous economic and social resources to confront these problems a subjective estimation of the most hazardous zones of the basin could be useful in the best sustainable planning of protective measures in this paper a new methodology is proposed that develops a management priority index mpi to rank sediment source areas by their quantitative capability to deliver debris flow volumes to a point of interest within the catchment the mpi sets the intervention priority based on a combination of three sub indicators a susceptibility indicator evaluating the overall catchment predisposition to generate debris flow a triggering indicator and a volume budget indicator assessing the rate of deliverable volume to a selected outlet mpi was applied to the basin of the rio gadria catchment venosta valley bolzano italy an alpine basin with an unlimited sediment supply that is characterized by multiple very active shallow landslides and bare soil zones the proposed ranking method was successfully verified using post event surveys and through evidence from consolidation check dams built over many years in the basin copyright 2014 john wiley sons ltd

late pleistocene fire in the ili basin central asia and its potential links to paleoclimate change and human activities abstract evidence of late pleistocene fire activity in central asia is important for understanding the underlying processes and controls of fire here two microcharcoal records from two separate loess sections covering the last 70 thousand years kyr in the ili basin are reported the results show that total microcharcoal concentrations are similar in both records and are correlated with insolation indicating consistent basin wide fire trends related to moisture changes driven by insolation in addition two anomalous fire events were identified at 45 35 ka and 6 0 ka we argue that these events are possibly related to ancient human activities rather than to pure natural factors such as sedimentation wind taphonomic change or climate change

postglacial vegetation and fire history eastern klamath mountains california usa pollen and high resolution charcoal data from bluff lake and crater lake california indicate simi lar changes in climate vegetation and fire history during the last 15 500 years pollen data at bluff lake suggest that the vegetation between c 15 500 and 13 100 cal bp consisted of subalpine parkland with scattered pinus and abies after 13 100 cal bp a relatively closed forest of p monticola p contorta and abies developed and fire event frequency was low the inferred climate then was cooler and wetter than present pinus and quercus vaccinifoliadominated at both sites during the early holocene when conditions were warm and dry as climate became wetter and cooler in the late holocene abies spp at both sites and tsuga mertensi ana at crater lake increased in importance displacing pinus and quercus the two lake records have similar trends in fire history with high event frequencies at c 8400 4000 and 1000 cal bp and low values at c 4800 cal bp the fire and vegetation history at both sites suggests a similar response to large scale changes in climate during the holocene

elemental carbon record of paleofire history on the chinese loess plateau during the last 420 ka and its response to environmental and climate changes an elemental carbon ec record covering the last 420 ka was reconstructed using chemical oxidation method on a loess and paleosol sequence from the lingtai section on the chinese loess plateau the ec record reveals the paleofire history and its relationship with climate and vegetation changes on the chinese loess plateau our results show that the ec abundance is generally higher in the paleosols than in the loess layers showing a glacial interglacial pattern which is coincident with biomass changes this variation pattern indicates that paleofires were intensified when biomass accumulated and climate changed abruptly especially from wet to dry conditions the ec abundance increases sharply at similar to 130 kab p indicating a dramatic change in the vegetation and climate variation patterns the occurrence of a peak value with the highest average ec abundance in the holocene may reflect the occurrence of a major climate event at similar to 6 kab p and may also be partly due to more frequent anthropogenic fire usages c 2007 elsevier b v all rights reserved

mid holocene climate change and its effect on prehistoric cultural evolution in eastern qinghai province china abstract we studied the mid holocene climate change in eastern qinghai province china and its impact on the evolution of majiayao 3980 2050 bc and qijia 2183 1635 bc cultures near the important neolithic site of changning the investigation focused on analyses of grain size magnetic susceptibility ratios of elemental contents and pollen assemblage from a loess paleosol sequence the results indicate that the climate was wet during 5830 4900 cal yr bp which promoted the development of early mid majiayao culture in eastern qinghai province however 4900 4700 cal yr bp were drought years in the region responsible for the decline and eastward movement of prehistoric culture during the period of transition from early mid to late majiayao culture the climate turned wet again during 4700 3940 cal yr bp which accelerated the spread of qijia culture to the middle reaches of the huangshui river including the changning site

application of lidar and discriminant analysis to determine landscape characteristics for different types of slope failures in heavily vegetated steep terrain horseshoe run watershed west virginia abstract a landslide inventory map was created for horseshoe run watershed west virginia using high resolution topographic data obtained from airborne lidar a total of 152 landslides were remotely mapped and classified as planar slides rotational slumps debris flows debris fans debris slides and active slopes based on morphologic characteristics interpreted from lidar derived shaded relief maps with field verification at several locations seven landscape variables were calculated for the watershed from the high resolution 0 5 m topographic data elevation slope angle slope aspect distance from roads distance from streams plan curvature and profile curvature statistical analyses were conducted to determine the mean and standard deviations for each variable and corresponding slope failure type discriminant analyses were conducted on the different types of failed slopes with a maximum 86 accuracy level to determine which landscape characteristics contribute to each type of landslide results from the discriminant analyses indicate that statistically significant differences exist between the failure classes mapped within the watershed and that slope angle slope aspect and landscape curvature are important variables influencing the type of process the results from this study have important implications for predicting where certain types of slope failures may occur based on landscape characteristics

prehistoric human activity and its environmental background in lake donggi cona basin northeastern tibetan plateau lake donggi cona is a key area for the exploration of the prehistoric settlement of the inner tibetan plateau because of its location in the joint of the higher inner tibetan plateau and the upper

changes in fire regimes on the chinese loess plateau since the last glacial maximum and implications for linkages to paleoclimate and past human activity abstract a high resolution black carbon bc record from 27 5 kyr bp to present was reconstructed using a chemical oxidation method on loess and paleosol samples from the lijiayuan section of the chinese loess plateau the black carbon mass sedimentation rates bcmsr and carbon isotopic record reveal a paleofire history and its relationship with climate and vegetation changes at the study site the bcmsr record was decomposed into two components background bcmsr and the bcmsr peaks the background bcmsr represents regional fires and shows high fire activities occurred contemporaneous with the younger dryas older dryas heinrich events and greenland stadials as registered in the loess grain size record this suggests a rapid response of regional fires on the loess plateau to abrupt climate changes spectral analysis of background bcmsr showed two meaningful periodicities of 1620 and 1040 years close to the cyclicity of the east asian monsoon as recorded in the stalagmite 18o record in central china this indicates a tight control of millennial scale wet dry changes in the monsoonal climate on regional fires on the loess plateau by contrast the bcmsr peaks are considered to reflect local fire episodes the occurrences of local fires were more frequent during the last glacial period with a maximum frequency of 6 episodes 1000 years during the last glacial maximum lgm 22 3 to 14 6 kyr bp when the climate was drier and more continuous grassy fuels existed on the landscape during the last glacial interglacial transition lgit period 14 6 to 11 0 kyr bp fire frequency was largely reduced due to an increase in precipitation and more woody vegetation if the lgit period is taken as an analog for the projected near future then future global warming alone may not produce large wildfires in northwestern china wildfires remained infrequent during the early to middle holocene biomass burning increased after 4 0 kyr bp when the climate became drier and land use was more intensive bc carbon isotope ratios may well reflect changes in the vegetation being burnt i e grasses versus trees yielding results consistent with the associated pollen data in the region

advance retreat history of the east asian summer monsoon rainfall belt over northern china during the last two glacial interglacial cycles abstract in northern china the history of desert migration provides a good measure of the east asian summer monsoon variations since the desert margin environment is very sensitive to changes in summer monsoon rainfall desert margin migration can be well documented in the downwind loess deposits since the grain size of chinese loess is principally controlled by source to sink distance and hence the loess grain size is an effective proxy for reconstructing the history of the east asian summer monsoon in order to investigate the pattern and migration of the summer monsoon rainfall belt over northern china during the past two glacial interglacial cycles contour maps of loess grain size were constructed for mis 2 3 4 5 6 and 7 all the grain size isolines show a near north south gradient for both glacials and interglacials indicating a dominant dust source region in north and an approximately north south dust transport pathway for dust deposits in the main body of the loess plateau at least for the past two glacial interglacial cycles the reconstructed southeast desert margin for mis 2 3 4 5 6 and 7 roughly parallels the present isohyets implying that the pattern of the east asian summer monsoon rainfall belt during the past two glacial interglacial cycles is similar to the present i e a northeast southwest trend for the isohyets of the summer monsoon despite the glacial interglacial cycles using the grain size isolines of mis 2 as a reference we derive a northerly desert retreat of 160 km 19 km 225 km and 223 km for mis 3 4 5 and 7 respectively and a southerly desert advance of 29 km for mis 6 that could be preliminarily regarded as the relative migration distance for the east asian summer monsoon rainfall belt in addition the inferred climate conditions in mis 3 are cool and humid in northern china while the driest and coldest interval of the last two glacial periods occurs in mis 6

linkages between climate fire and vegetation in southwest china during the last 18 5ka based on a sedimentary record of black carbon and its isotopic composition abstract fires are sensitive to climate changes and in addition they have a major influence on the global carbon cycle land surface properties and chemical composition of the atmosphere which in turn can affect the climate system projecting the impacts of future climate changes on fire mediated biogeochemical processes requires understanding of how various climatic factors influence regional fire regimes however long term variations in fire activity and their controls are poorly known in this study we report the concentration of black carbon bc and its isotopic composition 13cbc in an upland lake sediment core from southwest china in order to elucidate linkages between changes in fire regime climate and vegetation over the past 18 5 ka the results show that the sedimentary bc content recorded variations in fire activity and exhibits a close negative correlation with the amount of precipitation delivered by the indian summer monsoon ism during heinrich event 1 18 5 15 0 cal ka bp the younger dryas 12 8 11 1 cal ka bp and the mid to late holocene the weakening of the ism led to greatly increased fire activity in southwest china in the last 1 0 ka the bc record may have been affected by human activity in the catchment which may have caused an increased influx of minerogenic material to the lake thereby diluting the sedimentary bc concentration the general trend of changing vegetation compositions inferred from the 13cbc values also tracks the variations of the ism suggesting a change from mixed c3 c4 plant ecosystems during the last glacial maximum to c3 plant dominated forest during the holocene however the abundance of c4 plants may be overestimated during the bolling allerod warm interval and the early holocene due to the fact that fires were probably limited to the savanna ecosystem in the valleys and low lying basins

anthropocene archaeology of the yellow river china 5000 2000 bp in this paper we use geoarchaeological and paleoenvironmental data from three localities in the yellow river valley china taosi sanyangzhuang and the yiluo valley to argue that human activi

origin of eolian sand mobilization during the past 2300 years in the mu us desert china abstract eolian sand dunes and sand sheets are extensive in the semiarid regions of northern central china previous studies indicated that these eolian sands mainly formed during historical times however the sand sources and their reworking processes have not been well studied and even the reasons for their occurrence are still controversial field investigation and sedimentary evidence indicate that both the inner mu us desert and its southern marginal region both sources of modern eolian sand are largely associated with reworking of sands of the last glaciation based on geological documentary and archaeological data three phases of land cultivation during the past 2300 years together with historical droughts high wind energy and the easily reworked sand sources largely account for the occurrence of active sand dunes and sand sheets in the mu us desert

clastic facies models and facies analysis summary the term facies is used either descriptively for a certain volume of sediment or interpretatively for the inferred depositional environment of that sediment facies models are intellectual aids to the understanding of sedimentary environments and the origin of ancient sedimentary rocks many different models can be constructed to explain a given set of data depending on which aspect of the facies requires the most illumination and on the types of techniques used in the analysis when dealing with ancient rocks facies modelling is the last stage in the process of facies analysis which consists of the detailed description of exposed or cored sediments their classification into objectively defined facies the compilation of the characteristics of each facies the deduction of the processes of deposition of each facies the examination of the spatial relationships between facies and the recognition of facies associations the interpretation of the overall depositional environment of the association and the detailed interpretation and modelling of individual facies short cuts can lead to fallacious interpretations reliable facies models cannot be produced without careful facies analysis a facies model may be plausible yet totally inapplicable to the facies from which it was supposedly derived

landslide susceptibility mapping using lidar and dmc data a case study in the three gorges area china the objective of this study is to map landslide susceptibility in zigui segment of the yangtze three gorges area that is known as one of the most landslide prone areas in china by using data from light detection and ranging lidar and digital mapping camera dmc the likelihood ratio lr and logistic regression model lrm were used in this study the work is divided into three phases the first phase consists of data processing and analysis in this phase lidar and dmc data and geological maps were processed and the landslide controlling factors were derived such as landslide density digital elevation model dem slope angle aspect lithology land use and distance from drainage among these the landslide inventories land use and drainage were constructed with both lidar and dmc data dem slope angle and aspect were constructed with lidar data lithology was taken from the 1 250 000 scale geological maps the second phase is the logistic regression analysis in this phase the lr was applied to find the correlation between the landslide locations and the landslide controlling factors whereas the lrm was used to predict the occurrence of landslides based on six factors to calculate the coefficients of lrm 13 290 553 pixels was used 29 5 of the total pixels the logical regression coefficients of landslide controlling factors were obtained by logical regression analysis with spss 17 0 software the accuracy of the lrm was 88 8 on the whole the third phase is landslide susceptibility mapping and verification the mapping result was verified using the landslide location data and 64 4 landslide pixels distributed in extremely high zone and high zone in addition verification was performed using a success rate curve the verification result show clearly that landslide susceptibility zones were in close agreement with actual landslide areas in the field it is also shown that the factors that were applied in this study are appropriate lithology elevation and distance from drainage are primary factors for the landslide susceptibility mapping in the area while slope angle aspect and land use are secondary

optical dating of tibetan human hand and footprints an implication for the palaeoenvironment of the last glaciation of the tibetan plateau 1 the tibetan plateau is a cold and arid environment with poor archaeological finds it is generally assumed to have been covered by ice sheet during the last ice age nineteen handprints and footprints of homo sapiens on hot spring travertine and the remnant of a fireplace have been found at an elevation of 4200 m on the tibetan plateau based on the optically stimulated luminescence of quartz extracted from samples of the baked and unheated travertine the age of the prints and the fireplace are around 20 000 these finds suggest that there were humans living in this area around the time of the last glacial maximum lgm and that the ice sheet did not cover the entire tibetan plateau at this time

holocene climatic instability a prominent widespread event 8200 yr ago the most prominent holocene climatic event in greenland ice core proxies with approximately half the amplitude of the younger dryas occurred 8000 to 8400 yr ago this holocene event affected regions well beyond the north atlantic basin as shown by synchronous increases in windblown chemical indicators together with a significant decrease in methane widespread proxy records from the tropics to the north polar regions show a short lived cool dry or windy event of similar age the spatial pattern of terrestrial and marine changes is similar to that of the younger dryas event suggesting a role for north atlantic thermohaline circulation possible forcings identified thus far for this holocene event are small consistent with recent model results indicating high sensitivity and strong linkages in the climatic system

holocene lake mega chad palaeoshorelines from space during the holocene a giant lake known as lake mega chad lmc extended over more than 350 000 km2 in southern sahara morphodynamic features of sedimentary systems outlining the lmc palaeoshorelines have been identified by the joint analyses of new topographic images digital elevation model acquired by radar interferometry and landsat thematic mapper images here we characterize for the first time at the scale of the chad basin a wave dominated sedimentary system including river deltas longshore sandridges beach ridges spits and a wave ravinement surface they provide new evidence of the environmental impact of quaternary climate changes in the sahelo saharan area continental trade winds controlled the longshore drift in the northern part of the palaeolake two distinct lmc episodes dated as lower and middle holocene are clearly identified contemporaneous with the two phases of wetter conditions usually recognized in central and northern africa

spatial distribution and susceptibility zoning of geohazards along the silk road xian lanzhou the region between xi an and lanzhou is the first and most important part of the so called silk road in china however this section is highly susceptible to geohazards including landslides debris flows etc as a result of complex geological formations steep landforms seasonal heavy rainfall and intensive anthropogenic activity that characterize this region these geohazards have resulted in significant damage to the local infrastructure and economy and are becoming increasingly frequent with time to identify the distribution of characteristics of geohazards and susceptibility zoning in this region a frequency analysis and logistic analysis were used to study the spatial distribution of geohazards the key factors of surface topography and geology associated with geohazards were considered including slope gradient height differential profile curvature slope aspect and rock hardness first the distribution and frequency of geohazards were discussed in relation to the five factors second each factor s influence was evaluated by logistic regression and the relative importance of each of the variables was discussed finally geohazard susceptibility zoning was mapped using logistic regression and geography information system tools the results of the susceptibility zoning model were validated using the locations that had recorded geohazards in recent decades the accuracy of the model was greater than 86 8 the model validation proved that there was good agreement between the susceptibility mapping and historically recorded geohazards the logistic regression model produced acceptable results using a receiver operating characteristics curve in which the total area under the receiver operating characteristics curve was 0 879 the results of this study can assist in preliminary planning for land use particularly with reference to construction projects in high risk areas

spatial and temporal variety of prehistoric human settlement and its influencing factors in the upper yellow river valley qinghai province china abstract we report an investigation of forty two prehistoric sites in the upper yellow river valley located in guide jianzha hualong xunha and minhe qinghai province china including forty four new radiocarbon dates from twenty four sites review published archaeological surveys and radiocarbon dates analyze landform features and discuss the reasons for spatial and temporal variety of regional prehistoric human settlement our results suggest that people occupied the upper yellow river valley during the early holocene but a continuous archaeological record begins only after about 5500 cal yr bp thereafter the intensity of prehistoric human settlement in the area is varied neolithic human settlement spread northwestward to high altitude areas of the upper yellow river valley during early mid majiayao and qijia periods but moved southeastward to lower locations in the area during late majiayao period during the bronze period two coeval archaeological cultures the kayue and xindian occupied the upper yellow river region kayue archaeological sites are numerous and widely distributed in the high areas of the upper yellow river while xindian sites are restricted to the lowest basin of the region variation in site density and location are likely the result of changing paleoclimate and technology

what the past can say about the present and future of fire wildfires are an integral part of most terrestrial ecosystems paleofire records composed of charcoal soot and other combustion products deposited in lake and marine sediments soils and ice provide a record of the varying importance of fire over time on every continent this study reviews paleofire research to identify lessons about the nature of fire on earth and how its past variability is relevant to modern environmental challenges four lessons are identified first fire is highly sensitive to climate change and specifically to temperature changes as long as there is abundant dry fuel we can expect that in a warming climate fires will continue to grow unusually large severe and uncontrollable in fire prone environments second a better understanding of slow interannual to multidecadal socioecological processes is essential for predicting future wildfire and carbon emissions third current patterns of burning which are very low in some areas and very high in others are often unprecedented in the context of the holocene taken together these insights point to a fourth lesson that current changes in wildfire dynamics provide an opportunity for paleoecologists to engage the public and help them understand the potential consequences of anthropogenic climate change

architectural fades analysis of nonmarine depositional systems in the upper triassic chinle formation southeastern utah the upper triassic chinle formation in southeastern utah consists of nonmarine strata deposited in a back arc cratonic basin architectural analysis of exposures in subparallel canyons reveals an intricately interbedded fluvial deltaic lacustrine system characterized by 1 mobile fluvial channel belts consisting of stacked channel complexes 2 overbank deposits of levees paleosols marshes and small flood plain lakes interfingered with crevasse splays and lacustrine deltas and 3 extensive lacustrine strata deposited over the entire study area stratigraphic panels using closely spaced measured sections drawn either perpendicular or parallel to depositional dip show lateral facies relations within the extra channel strata and the relations to channel complexes successions of panels through several canyons depict the three dimensional architecture of the chinle depositional system

holocene east asian monsoon variation inferred from species assemblage and shell chemistry of the ostracodes from hulun lake inner mongolia a sediment core from hulun lake inner mongolia was analyzed for species assemblages and shell chemistry of ostracodes to investigate changes in the hydrology and climate of the east asian summer monsoon margin during the holocene darwinula stevensoni was abundant ilyocypris spp scarce littoral ostracodes absent and mg ca sr ca and 18o were low 11 100 to 8300 yr ago indicating high lake levels and cool fresh waters darwinula stevensoni declined largely ilyocypris spp throve littoral ostracodes were rare and chemical indicators remained in low values 8300 to 6200 yr ago suggesting that the lake continued high stands but water became warm the lake then contracted and water became cool brackish 6200 to 4300 yr ago littoral ostracodes flourished 4300 to 3350 yr ago marking the lowest lake levels of the entire holocene the lake level recovered and water salinity decreased 3350 to 1900 yr ago from 1900 to 500 yr ago the lake maintained the preceding status albeit lowered stands and increased salinities 1100 to 800 yr ago during the recent 500 yr the lake expanded and water salinity decreased the data imply that the east asian summer monsoon did not intensify until 8300 yr ago and weakened dramatically 4300 to 3350 yr ago

landslide susceptibility certainty mapping by a multi method approach a case study in the tertiary basin of puy en velay massif central france the present study discusses the use of integrated variables along with a combination of multi method forecasts for landslide susceptibility mapping the study area is located in the south eastern french massif central a volcanic region containing tertiary sedimentary materials that are prone to landslides the flowage type landslides within the study area are very slow moving phenomena which affect the infrastructures and human settlements the modelling process is based on a training set of landslides 70 of total landslides and a set of controlling factor slope lithology surficial formation the topographic wetness index the topographic position index distance to thalweg and aspect we create a composite variable or integrated variable corresponding to the union of geology and surficial formation in order to avoid the conditional dependence between these two variables and to build a geotechnical variable we use five classical modelling methods index weight of evidence logistic regression decision tree and unique condition unit with the same training set but with different architectures of input data made up of controlling factors all the models are tested with a validation group 30 of total landslides using the area under the receiver operating characteristic curve auc to quantify their predictive performance we finally select a single best model for each method however these five models are all equivalent in quality despite their differences in detail so no single model stands out against another finally we combine the five models into a unique susceptibility map with a calculation of median susceptibility class the final auc value of this combined map is better than that for a single model except for unique condition unit and we can evaluate the certainty of the susceptibility class pixel by pixel in agreement with the sparse literature on this topic we conclude that i integrated variables increase the performance of classical modelling processes and ii the combination of multi method forecasts is a pragmatic solution to the inherent problem of choosing the most suitable method for the available data and geomorphological context

late cenozoic fire enhancement response to aridification in mid latitude asia evidence from microcharcoal records fire provides an important indicator of paleoclimatic change however little information relating to late cenozoic fire history has been gathered in mid latitude asia including inner asia and east asia a key region for understanding the development of the arid monsoon climate system as well as the driving forces behind it here we first report the records of microcharcoal concentrations mc covering the holocene 10 0 ica and late pleistocene 0 8 0 ma which we use to analyze the fire activity patterns at an orbital time scale then we compile the late cenozoic mc record to investigate the long term fire history by analyzing four cores from the yangtze river delta yrd area east asia representing 8 0 ma and three sites in inner asia representing 18 2 ma the results show that the i mc remained higher during the relatively dry late holocene glacial stages than that during the humid middle holocene interglacial stages at individual sites ii mc increased with time in both inner asia and east asia after 18 and 8 ma respectively and iii mc always remained higher in the dry inner asia than in the contemporaneous wet east asia all these characteristics imply that late cenozoic fire occurrence in mid latitude asia experienced a gradual increasing trend along with the global temperature ice volume change and indicates a continuous aridification trend across mid latitude asia the global cooling rather than the tibetan plateau uplift might have played a key role in this observed trend c 2016 elsevier ltd all rights reserved

stable carbon isotope records of black carbon on chinese loess plateau since last glacial maximum an evaluation on their usefulness for paleorainfall and paleovegetation reconstruction abstract stable carbon isotope composition of soil organic matter 13 c som has been widely used to infer past environmental or vegetation c 3 c 4 changes however as a carbonaceous product of incomplete burning of biomass the carbon isotope signature of black carbon bc has received little study and a limited usage on this purpose moreover the environmental or vegetation indication of bc carbon isotope composition 13 c bc in sedimentary records remains ambiguous although the 13 c bc is supposed to reflect carbon isotope composition of vegetation being burnt this deserves site specific studies here we analyzed 13 c bc and 13 c som on loess paleosol samples from lijiayuan and yangling sections on chinese loess plateau clp spanning the last glacial maximum to decipher the environmental or vegetation meaning of 13 c bc at each study site opposite changing patterns were observed on the 13 c bc values for the two sections the 13 c bc at yangling in southern part of the clp varied from 19 18 to 21 93 mean 20 62 with more positive values occurred during the middle holocene than those during the lgm demonstrating more c 4 plants occupied in the region during the warm humid middle holocene this is consistent with the changing pattern widely documented in 13 c som records over the clp during the same period by contrast the 13 c bc at lijiayuan in northwestern part of the clp changed within the range of 21 83 24 64 mean 23 34 and displayed more negative values during the early middle holocene with respect to the lgm period the 13 c bc at lijiayuan were about 2 5 lower than those at yangling indicating a northward decrease of c 4 plants on the clp the anti phased changes of 13 c bc at lijiayuan were considered to reflect variations in paleorainfall because the vegetation is dominated by c 3 plants at the study site and carbon isotope compositions of c 3 plants decrease as rainfall increases compared with 13 c som record at the same profile 13 c bc seem biased against capturing c 4 signal during mid holocene possibly due to dominance of c 3 plants at the study site during fire seasons and a potentially extra source of bc from forest fires occurred on surrounding mountains by contrast 13 c bc tend to exaggerate c 4 signal during the lgm attributed to a possible shift of fire season from spring to summer these findings suggest that we probably underestimate the abundance of c 4 plants during mid holocene and overestimate c 4 biomass during the lgm using bc carbon isotope composition

a relationship between dunes fire and climate recorded in the holocene deposits of quebec during the past 5 000 yr bp the tropics have experienced an increase in aridity and aeolian activity in both maritime and continental areas1 4 in contrast the onset and subsequent development of post hypsithermal climates in northern latitudes were primarily conducive to global cooling it is suggested here that aeolian activity in cold environments represents a direct response to this long term cooling trend that began after 6 000 5 000 yr bp at the end of the climatic optimum5 9 this study establishes the holocene chronology of sand dunes near the outer forest limit in northern quebec fig 1 i show here that fires initiate the aeolian activity and that the fire dune relationship is typical of cooling period on this basis a palaeoclimatic reconstruction since the climatic optimum is proposed

effects of sample size on the accuracy of geomorphological models abstract commonly the most costly part of geomorphological distribution modelling studies is gathering the data thus guidance for researchers concerning the quantity of field data needed would be extremely practical this paper scrutinises the relationship between the sample size the number of observations varied from 20 to 600 and the predictive ability of the generalized linear model glm generalized additive model gam generalized boosting method gbm and artificial neural network ann in two data settings i e independent and split sample approaches the study was performed using empirical data of periglacial processes from an area of 600 km2 in northernmost finland at grid resolutions of 1 ha 100 100 m and 25 ha 500 500 m a rather sharp increase in the predictive ability of the models was observed when the number of observations increased from 20 to 100 and the level of robust predictions was reached with 200 observations the result indicates that no more than a few hundred observations are needed in geomorphological distribution modelling at a medium scale resolution ca 0 01 1 km2

lake surface fluctuations since the late glaciation at lake daihai north central china a direct indicator of hydrological process response to east asian monsoon climate abstract sediment retrieved by coring from the center of enclosed lake daihai in north central china and lacustrine sediments obtained from lake terrace outcrops were employed to reconstruct the lake surface fluctuations and the relationships with monsoon climate since the late glaciation based on accelerator mass spectrometry ams radiocarbon chronology before ca 13 ka bp the surface of the lake was lower indicating a deficiency of effective precipitation and dry climate the result of relatively decreased monsoon precipitation during ca 13 11 ka bp the lake surface ascended to a relatively higher level marking a significant increase of effective precipitation the climate became humid indicating strengthened monsoon rainfall then the lake surface experienced a sharp decline ca 11 10 ka bp this could suggest a severe reduction of effective monsoon precipitation and drier climate ca 10 9 0 ka bp the lake surface area expanded temporarily as the level rose denoting the amelioration of monsoon related effective precipitation and a relatively humid climate subsequently the lake surface declined at ca 9 0 7 3 ka bp reflecting the prevalence of dry climate and relatively decreased monsoon precipitation higher lake level and larger lake depth indicated large scale expansion of the lake surface at ca 7 3 3 2 ka bp despite some secondary fluctuations this implied plentiful monsoon related effective precipitation and more humid climate in the lake basin since ca 3 2 ka bp the lake surface has experienced a severe fall except for a minor rise around 2 0 ka bp indicating dry climate as a whole from waning monsoon precipitation and relatively increased evaporation the effective precipitation variations revealed by lake surface fluctuations in lake daihai since the late glaciation are not only related to forcing factors such as insolation and temperature driven air masses from the continent and the ocean but are also influenced by regional feedback from topography vegetation coverage and hydrological status

water erosion susceptibility mapping by applying stochastic gradient treeboost to the imera meridionale river basin sicily italy abstract soil erosion by water constitutes a serious problem affecting various countries in the last few years a number of studies have adopted statistical approaches for erosion susceptibility zonation in this study the stochastic gradient treeboost sgt was tested as a multivariate statistical tool for exploring analyzing and predicting the spatial occurrence of rill interrill erosion and gully erosion this technique implements the stochastic gradient boosting algorithm with a tree based method the study area is a 9 5 km 2 river catchment located in central northern sicily italy where water erosion processes are prevalent and affect the agricultural productivity of local communities in order to model soil erosion by water the spatial distribution of landforms due to rill interrill and gully erosion was mapped and 12 environmental variables were selected as predictors four calibration and four validation subsets were obtained by randomly extracting sets of negative cases both for rill interrill erosion and gully erosion models the results of validation based on receiving operating characteristic roc curves showed excellent to outstanding accuracies of the models and thus a high prediction skill moreover sgt allowed us to explore the relationships between erosion landforms and predictors a different suite of predictor variables was found to be important for the two models elevation aspect landform classification and land use are the main controlling factors for rill interrill erosion whilst the stream power index plan curvature and the topographic wetness index were the most important independent variables for gullies finally an roc plot analysis made it possible to define a threshold value to classify cells according to the presence absence of the two erosion processes hence by heuristically combining the resulting rill interrill erosion and gully erosion susceptibility maps an integrated water erosion susceptibility map was created the adopted method offers the advantages of an objective and repeatable procedure whose result is useful for local administrators to identify the areas that are most susceptible to water erosion and best allocate resources for soil conservation strategies

palaeoclimatic changes in the qinghai lake area during the last 18 000 years abstract multi proxy analysis of a sediment core from qinghai lake including pollen carbonate toc tn and 13 c of organic matter was used to document regional climatic changes during the last 18 000 years climate was very cold and dry before 16 9 cal kyr bp the warm and wet period which began at about 14 1 cal kyr bp culminated at 6 5 cal kyr bp and came to its end at about 4 5 cal kyr bp after that the climate gradually became colder and drier during the transitional period from the late glacial to the holocene the climate fluctuated frequently the short term climatic oscillations including the bolling allerod younger dryas and the cooling event at ca 8 2 cal kyr bp appear to be recorded in the qinghai lake sedimentary record the climatic evolution in the qinghai lake area during the past 18 000 years indicates that solar insolation changes on the ten thousand year scale are the likely driving force of the east asia monsoon

changes in fire regimes since the last glacial maximum an assessment based on a global synthesis and analysis of charcoal data fire activity has varied globally and continuously since the last glacial maximum lgm in response to long term changes in global climate and shorter term regional changes in climate vegetation and human land use we have synthesized sedimentary charcoal records of biomass burning since the lgm and present global maps showing changes in fire activity for time slices during the past 21 000 years as differences in charcoal accumulation values compared to pre industrial there is strong broad scale coherence in fire activity after the lgm but spatial heterogeneity in the signals increases thereafter in north america europe and southern south america charcoal records indicate less than present fire activity during the deglacial period from 21 000 to 11 000 cal yr bp in contrast the tropical latitudes of south america and africa show greater than present fire activity from 19 000 to 17 000 cal yr bp and most sites from indochina and australia show greater than present fire activity from 16 000 to 13 000 cal yr bp many sites indicate greater than present or near present activity during the holocene with the exception of eastern north america and eastern asia from 8 000 to 3 000 cal yr bp indonesia and australia from 11 000 to 4 000 cal yr bp and southern south america from 6 000 to 3 000 cal yr bp where fire activity was less than present regional coherence in the patterns of change in fire activity was evident throughout the post glacial period these complex patterns can largely be explained in terms of large scale climate controls modulated by local changes in vegetation and fuel load

holocene changes in fire frequency in the daihai lake region north central china indications and implications for an important role of human activity abstract black carbon bc content in a sediment core from daihai lake inner mongolia was analyzed to reconstruct a high resolution history of fires occurring in northern china during the holocene and to examine the impacts of natural changes and human activities on the fire regime the black carbon mass sedimentation rate bcmsr was disintegrated into two components the background bcmsr and the bcmsr peak with the bcmsr peak representing the frequency of fire episodes both the background bcmsr and the magnitude of the bcmsr peak display a close relation with the percentage of tree pollen from the same sediment core suggesting that regional vegetation type would be a factor controlling the intensity of fires the inferred fire episode frequency for the holocene exhibits two phases of obvious increases i e the first increase from

shorelines in the sahara geomorphological evidence for an enhanced monsoon from palaeolake megachad the sahara desert is the most extensive desert on earth but during the holocene it was home to some of the largest freshwater lakes on earth of these palaeolake megachad was the biggest landsat tm images and shuttle radar topography mission srtm digital topographic data reveal numerous shorelines around palaeolake megachad at its peak sometime before 7000 years ago the lake was over 173 m deep with an area of at least 400 000 km2 bigger than the caspian sea the biggest lake on earth today the morphology of the shorelines indicates two dominant winds one northeasterly that is consistent with the present day winds in the region the other originated from the southwest we attribute it to an enhanced monsoon caused by a precessionally driven increase in northern hemisphere insolation subsequent desiccation of the palaeolake is recorded by numerous regressive shorelines in the sahara desert

a holocene pollen record from the northwestern himalayan lake tso moriri implications for palaeoclimatic and archaeological research this paper presents a new fossil pollen record from tso moriri 32 54 n 78 19 e 4512 m a s l and seeks to reconstruct changes in mean annual precipitation map during the last 12 000 years this high alpine lake occupies an area of 140 km2 in a glacial tectonic valley in the northwestern himalaya the region has a cold climate with a map 300 mm and open vegetation the hydrology is controlled by the indian summer monsoon ism but winter westerly associated precipitation also affects the regional water balance results indicate that precipitation levels varied significantly during the holocene after a rapid increase in map a phase of maximum humidity was reached between ca 11 and 9 6 cal ka bp followed by a gradual decline in map this trend parallels the reduction in the northern hemisphere summer insolation comparison of different palaeoclimate proxy records reveal evidence for a stronger holocene decrease in precipitation in the northern versus the southern parts of the ism domain the long term trend of ism weakening is overlaid with several short periods of greater dryness which are broadly synchronous with the north atlantic cold spells suggesting reduced amounts of westerly associated winter precipitation compared to the mid and late holocene it appears that westerlies had a greater influence on the western parts of the ism domain during the early holocene during this period the westerly associated summer precipitation belt was positioned at mediterranean latitudes and amplified the ism derived precipitation the tso moriri pollen record and moisture reconstructions also suggest that changes in climatic conditions affected the ancient harappan civilisation which flourished in the greater indus valley from approximately 5 2 to 3 cal ka bp the prolonged holocene trend towards aridity punctuated by an interval of increased dryness between ca 4 5 and 4 3 cal ka bp may have pushed the mature harappan urban settlements between ca 4 5 and 3 9 cal ka bp to develop more efficient agricultural practices to deal with the increasingly acute water shortages the amplified aridity associated with north atlantic cooling between ca 4 and 3 6 and around 3 2 cal ka bp further hindered local agriculture possibly causing the deurbanisation that occurred from ca 3 9 cal ka bp and eventual collapse of the harappan civilisation between ca 3 5 and 3 cal ka bp

holocene wildfires related to climate and land use change over the weihe river basin china abstract charcoal particles preserved in the loess palaeosol profiles provide records of wildfires during the holocene total organic carbon magnetic susceptibility and charcoal analysis and osl dating were carried out in the holocene loess palaeosol profiles at two sites in the weihe river basin the analytical results show that natural wildfires occurred frequently during the last glaciation when climate was dominated by northwest continental monsoon and steppe vegetation expanded southerly to the weihe river basin wildfire occurrence decreased during climatic amelioration in the early holocene during the holocene climatic optimum between 8500 b p and 3100 b p natural wildfire occurrence was reduced greatly pedogenic alteration to the accumulated dust was intensified because of the humid warm climate brought on by southeast maritime monsoon localized fire events in connection with human activities of the neolithic occurred in several episodes over the region during the late holocene when climate become drier wildfire occurrence over the upland hills shows a pattern different from that in the guanzhong basin over the upland hills in the north charcoal concentrations show a decreasing trend in the recent loess and topsoil it indicates infrequent biomass burning during the last 3100 years this is attributable to nomadic occupation of the loess hills during the bronze age and the development of a land use pattern of livestock farming in most part of the history over the loess tableland in the guanzhong basin in the south abruptly increased charcoal concentrations in the recent loess and topsoil show very high level of biomass burning this is attributable to the increasingly intensified land reclamation for cereal cultivation from the bronze age this study provides new insights into wildfires over the semi arid and sub humid regions in connection with climate and land use change

quaternary environmental changes in the drylands of china a critical review abstract this paper reviews our current understanding of quaternary climate and landscape changes in the desert areas of northern china a key portion of the middle latitude drylands on earth combining earlier studies with our recent research and experience we offer a comprehensive picture of the state of chinese deserts during the quaternary and in the interest of enhancing future research identify knowledge gaps and areas of uncertainty lacustrine deposits found over an area ranging from china s western taklamakan desert to the eastern hunshandake sandy lands suggest that extensive lakes occurred in china s deserts during the pleistocene analysis of digital elevation models from srtm shuttle radar topography mission data supports this interpretation and shows the significant extent of these former lakes new estimates of mean annual evaporation of ca 1000 mm from lake surfaces and ca 100 mm from land surfaces confirms that local and regional rainfall is critical for maintenance of desert lakes in this temperate zone especially during intervals when the mean annual rainfall is more than 100 mm rapid shifts between sand seas and lakes in geologically and environmentally diverse settings suggest that the drylands of china are very sensitive ephemeral systems and not long lasting as previously thought available chronologies suggest that there were large lakes in the western taklamakan desert and the chadamu basin during mis marine isotope stage 3 at 30 ka probably related to a period of strong influence of northern hemispheric westerly winds channels and elevation models revealed by srtm data and remains of lacustrine sediments also indicate that there was a large lake in the hunshandake sandy lands in the eastern portion of the desert belt during the quaternary there is significant evidence that during the middle holocene strong summer monsoons led to a relatively large increase in moisture availability in the entire desert belt of northern china lacustrine records from the badain jaran desert in western inner mongolia suggest that it was generally dry before 10 cal ka becoming wetter from 10 to 4 cal ka and dry again afterwards study of palaeosols widely occurring in dune stratigraphy in the eastern portion of the desert belt suggests that there was a period of wet and warm climate in this region during the mid holocene optimum at a minimum between 6 ka and 4 ka but possibly lasting longer recent observations dealing with the generation and transport of dust from central asia indicate that the causal relationship between sand seas and loess sequences is not as close as previously assumed these results suggest that there is an urgent need to examine whether the frequency and amplitude of climatic variation in chinese deserts are somehow similar to that having occurred in the sahara desert of north africa deserts in northern china were also important focal regions for neolithic cultures during intervals when environmental conditions supported a denser vegetative cover there is evidence that some areas of woody vegetation to the west of badain jaran desert were deforested by humans by ca 4000 yr b p although it is still debatable whether humans have had a significant impact in other areas at that time opinions on the severity of desertification vary and are sometimes contradictory due to the lack of long term field based investigations

archaeology of the anthropocene in the yellow river region china 8000 2000 cal bp although archaeological analysis emphasizes the importance of climatic events as a driver of historical processes we use a variety of environmental and archaeological data to show that human modif

an expert knowledge based approach to landslide susceptibility mapping using gis and fuzzy logic this paper presents an expert knowledge based approach to landslide susceptibility mapping in an effort to overcome the deficiencies of data driven approaches the proposed approach consists of three generic steps 1 extraction of knowledge on the relationship between landslide susceptibility and predisposing factors from domain experts 2 characterization of predisposing factors using gis techniques and 3 prediction of landslide susceptibility under fuzzy logic the approach was tested in two study areas in china the kaixian study area about 250 km 2 and the three gorges study area about 4600 km 2 the kaixian study area was used to develop the approach and to evaluate its validity the three gorges study area was used to test both the portability and the applicability of the developed approach for mapping landslide susceptibility over large study areas performance was evaluated by examining if the mean of the computed susceptibility values at landslide sites was statistically different from that of the entire study area a z score test was used to examine the statistical significance of the difference the computed z for the kaixian area was 3 70 and the corresponding p value was less than 0 001 this suggests that the computed landslide susceptibility values are good indicators of landslide occurrences in the three gorges study area the computed z was 10 75 and the corresponding p value was less than 0 001 in addition we divided the susceptibility value into four levels low 0 0 0 25 moderate 0 25 0 5 high 0 5 0 75 and very high 0 75 1 0 no landslides were found for areas of low susceptibility landslide density was about three times higher in areas of very high susceptibility than that in the moderate susceptibility areas and more than twice as high as that in the high susceptibility areas the results from the three gorge study area suggest that the extracted expert knowledge can be extrapolated to another study area and the developed approach can be used in large scale projects results from these case studies suggest that the expert knowledge based approach is effective in mapping landslide susceptibility and that its performance is maintained when it is moved to a new area from the model development area without changes to the knowledge base c 2014 elsevier b v all rights reserved

chinese loess and the paleomonsoon abstract this paper presents a general review of the recent research advances of the east asian paleomonsoon based mainly on studies of the loess soil sequences in the chinese loess plateau in the last 2 6 million years the paleomonsoonal history may be divided into about 166 events on a time scale of the earth s orbital variations during the last glacial period millenial scale oscillations of the monsoon system were prominent which can be fairly well correlated with the dansgaard oeschger cycles recognized in the greenland ice cores the monsoonal rainfall belt has experienced a wide repeated advance retreat change during the glacial interglacial cycles of the pleistocene both temporal and spatial changes of the monsoon system in the quaternary could have been linked closely to global ice volume variations

postglacial vegetation climate and fire history along the east side of the andes lat 41 42 5 s argentina abstract the history of the low elevation forest and forest steppe ecotone on the east side of the andes is revealed in pollen and charcoal records obtained from mid latitude lakes prior to 15 000 cal yr bp the vegetation was characterized by steppe vegetation with isolated stands of nothofagus the climate was generally dry and the sparse vegetation apparently lacked sufficient fuels to burn extensively after 15 000 cal yr bp a mixture of nothofagus forest and shrubland steppe developed fire activity increased between 13 250 and 11 400 cal yr bp contemporaneous with a regionally defined cold dry period huelmo mascardi cold reversal the early holocene period was characterized by an open nothofagus forest shrubland mosaic and fire frequency was high in dry sites and low in wet sites the data suggest a sharp decrease in moisture eastward from the andes a shift to a surface fire regime occurred at 7500 cal yr bp at the wet site and at 4400 cal yr bp at the dry site preceding the expansion of austrocedrus by 1000 1500 yr the spread of austrocedrus is explained by a shift towards a cooler and wetter climate in the middle and late holocene the change to a surface fire regime is consistent with increased interannual climate variability and the onset or strengthening of enso the present day mixed forest dominated by nothofagus and austrocedrus was established in the last few millennia

black carbon in soils and sediments analysis distribution implications and current challenges this review highlights the ubiquity of black carbon bc produced by incomplete combustion of plant material and fossil fuels in peats soils and lacustrine and marine sediments we examine various definitions and analytical approaches and seek to provide a common language bc represents a continuum from partly charred material to graphite and soot particles with no general agreement on clear cut boundaries formation of bc can occur in two fundamentally different ways volatiles recondense to highly graphitized soot bc whereas the solid residues form char bc both forms of bc are relatively inert and are distributed globally by water and wind via fluvial and atmospheric transport we summarize chronologically the ubiquity of bc in soils and sediments since devonian times differentiating between bc from vegetation fires and from fossil fuel combustion bc has important implications for various biological geochemical and environmental processes as examples bc may represent a significant sink in the global carbon cycle affect the earth s radiative heat balance be a useful tracer for earth s fire history build up a significant fraction of carbon buried in soils and sediments and carry organic pollutants on land bc seems to be abundant in dark colored soils affected by frequent vegetation burning and fossil fuel combustion thus probably contributing to the highly stable aromatic components of soil organic matter we discuss challenges for future research despite the great importance of bc only limited progress has been made in calibrating analytical techniques progress in the quantification of bc is likely to come from systematic intercomparison using bcs from different sources and in different natural matrices bc identification could benefit from isotopic and spectroscopic techniques applied at the bulk and molecular levels the key to estimating bc stocks in soils and sediments is an understanding of the processes involved in bc degradation on a molecular level a promising approach would be the combination of short term laboratory experiments and long term field trials

natural and anthropogenic forest fires recorded in the holocene pollen record from a jinchuan peat bog northeastern china abstract pollen and charcoal particles from a jinchuan peat northeastern china were examined to investigate the fire origin and interaction between climate vegetation fire and human activity during the holocene pollen results show that i a broadleaved deciduous forest was dominant during the early holocene ii from 5500 cal yr b p there was a gradual increase in coniferous trees mainly pinus and a decrease in broadleaved deciduous trees e g quercus juglans and ulmus zelkova iii after 4200 cal yr b p the deciduous forest was replaced by a mixed forest of coniferous and deciduous trees iv coniferous trees including pinus abies and picea further increased after 2000 cal yr b p reflecting a cooler and drier climate after 5500 4200 cal yr b p two layers of abundant microfossil charcoal particles 250 10 m and the coexistence of macrofossil particles 2 mm suggest two local fires fire event 1 5120 66 cal yr b p and fire event 2 1288 8 cal yr b p ad 662 8 charcoal layer 1 with a large amount of monolete psilate spores is superimposed on the long term trend of vegetation changes indicating a natural origin for fire event 1 that was probably facilitated by drying environmental conditions since the mid holocene cerealia type pollen and a low percentage of monolete psilate spores were observed in charcoal layer 2 indicating that fire event 2 was caused by clearing we suggest that fire event 2 may be related to the spread of the han farming culture accompanied by the territorial expansion of the tang dynasty to the studied area in ad 668

charcoal records of fire history in the holocene loess soil sequences over the southern loess plateau of china abstract charcoal preserved in accretionary loess soil profiles within the southern part of the loess plateau has recorded fire history and landscape evolution connected with climatic variations and human activities local wildfires occurred frequently during the late last glacial period and the early holocene before 8500 years bp when steppe vegetation expanded from the inner mongolian plateau southerly over the loess plateau during the holocene climatic optimum between 8500 years bp and 3100 years bp natural wildfires were largely reduced pedogenesis of the luvisols and isohumisols was intensified because of the increased monsoonal precipitation and soil moisture localized fires in connection with human activities occurred in different patterns at the study sites fire seems to have been applied to vegetation clearance for land reclamation for millet cultivation at many places during the neolithic and early bronze age levels of biomass burning were very high during the late holocene when the climate became drier and historical land use became more intensive at some sites the intensity of human disturbance by fire and cultivation increased continuously during the last 3100 years at the other sites local fires occurred most frequently between 3100 years bp and 1500 years bp during the major period of land reclamation for cereal cultivation human burning of the landscape has been reduced since then

landslide susceptibility assessment using logistic regression and its comparison with a rock mass classification system along a road section in the northern himalayas india landslide studies are commonly guided by ground knowledge and field measurements of rock strength and slope failure criteria with increasing sophistication of gis based statistical methods however landslide susceptibility studies benefit from the integration of data collected from various sources and methods at different scales this study presents a logistic regression method for landslide susceptibility mapping and verifies the result by comparing it with the geotechnical based slope stability probability classification sspc methodology the study was carried out in a landslide prone national highway road section in the northern himalayas india logistic regression model performance was assessed by the receiver operator characteristics roc curve showing an area under the curve equal to 0 83 field validation of the sspc results showed a correspondence of 72 between the high and very high susceptibility classes with present landslide occurrences a spatial comparison of the two susceptibility maps revealed the significance of the geotechnical based sspc method as 90 of the area classified as high and very high susceptible zones by the logistic regression method corresponds to the high and very high class in the sspc method on the other hand only 34 of the area classified as high and very high by the sspc method falls in the high and very high classes of the logistic regression method the underestimation by the logistic regression method can be attributed to the generalisation made by the statistical methods so that a number of slopes existing in critical equilibrium condition might not be classified as high or very high susceptible zones

evolution of miocene fluvial systems in the himalayan foredeep through a two kilometer thick succession in northern pakistan abstract sedimentological variations through a kilometer thick coarsening upward succession in the miocene himalayan foredeep basin fluvial chinji and nagri formations of the siwalik group are documented in the chinji village area on the potwar plateau of northern pakistan from the chinji formation upwards into the nagri formation 1 the proportion of major sandstone bodies increase relative to mudstone dominated beds 2 average thickness and mean grainsize of channel deposits increase 3 sediment aggradation rates increase 4 there is a reported change in sediment providence 5 paleocurrents are generally to the southeast and vary little upsection and 6 paleosols are more distinct lower in the section where there is also more evidence of ponding of water on the floodplain smaller scale 100 m thick cyclic variations in the proportion of major channel sandstone bodies also occur in both formations in the modern himalayan basin sediment dispersal away from the mountain belt is associated with 1 major rivers that flow along the basin axis 2 large rivers that drain substantial areas of the mountain belt and deposit low relief sediment fans extending hundreds of kilometers into the basin and 3 smaller rivers in fan and interfan areas that drain local areas and carry finer sediment loads sediment variations through the chinji nagri formation boundary can be related to a shifting of depositional environments within such fan and interfan areas major basin axial rivers are not exposed in this area it appears that kilometer thick upsection variations in these deposits record the progradation of the sediment fan formed by a large river system river discharge on the order of 104 m3 s over the floodplain of a smaller river system river discharge on the order of 103 m3 s large scale vertical sediment variations over hundreds of meters to kilometers appear to reflect changes in the basin subsidence and the rate of sediment input to the basin over time scales on the order of 105 106 years upsection variations can not easily be related to climatic change or eustatic variations in sea level the most likely explanation for upsection changes is tectonism deposition rates and shifting positions of river systems within the basin responded more quickly to changes in basin subsidence rate whereas increases in the proportion of sandstone bodies and increases in floodplain slopes lagged behind deposit variations in the siwalik group clearly record variations between different scale river systems delivering sediment to the basin as well as the overall basin evolution

particle size evidence for source areas of charcoal accumulation in late holocene sediments of eastern north american lakes abstract two methods of analyzing charcoal in sediment reveal changes in charcoal accumulation across temperate eastern north america during the last several hundred years in one method the analyst counts mostly small particles that reflect regional emissions in the other the analyst counts only larger particles derived mostly from such local sources as catchment fires we used these methods to compare charcoal accumulation at 14 lakes from the prairie forest border in minnesota to eastern maine the two methods gave concordant accumulation rates for sediments of pre 1850 age at each of 4 lakes analyzed by both methods this concordance is consistent with the interpretation that pre 1850 emissions were controlled by broad scale factors such as climatically controlled regional differences in fuels and moisture since 1900 large particles decreased greatly and small particles decreased slightly in minnesota and wisconsin by contrast in the northeast the large particle accumulation has remained at the low values measured in pre 1900 sediments at most sites while small particles increased everywhere east of central new york and pennsylvania the observed patterns suggest that 1 large particles primarily reflect local fires that were common in the midwest before fire suppression became effective 2 large particles were rare in the northeast especially before extensive land clearance 3 small particles reflect regional combustion that increased in the northeast after extensive use of fire for land clearance and wood burning for industrial purposes of the 19th century and 4 small particles remain abundant in the midwest long after effective fire suppression probably because these well dispersed small particles have a large source area that extends beyond the local wildfires that account for large particles before european settlement

holocene east asian monsoonal precipitation pattern revealed by grain size distribution of core sediments of daihai lake in inner mongolia of north central china abstract two sediment cores recovered in the central part of daihai lake in north central china were analysed at 2 to 4 cm intervals for grain size distribution grain size distributions of the lake sediments are inferred to be a proxy for past changes in east asian monsoon precipitation such that greater silt size percentage and higher median grain size reflect increased monsoonal precipitation rates the grain size record of daihai lake sediments spanning the last ca 10 000 yr indicates that the monsoonal precipitation in the lake region can be divided into three stages the early middle and late holocene during the early holocene before ca 7900 cal yr bp the median grain size md and the silt fraction content were relatively low and constant suggesting relatively low precipitation over the lake region the middle holocene between ca 7900 and 3100 cal yr bp was marked by intensified and highly variable monsoonal precipitation as indicated by high and variable md values and silt contents of the lake sediments during this period average precipitation rate gradually increased from ca 7900 to 6900 cal yr bp displayed intense oscillations between ca 6900 and 4400 cal yr bp and exhibited a decreasing trend while fluctuating from ca 4400 to 3100 cal yr bp although generally high during the middle holocene both the md and the silt content assumed distinctly low values at the short intervals of ca 6500 6400 6000 5900 5700 5600 4400 4200 cal yr bp implying that monsoonal precipitation might have been significantly reduced during these intervals during the late holocene since ca 3100 cal yr bp grain size values suggest that precipitation decreased however during the late holocene relatively higher md values and silt contents occurring between ca 1700 to 1000 cal yr bp may denote an intensification of hydrological cycles in the lake area changes in the east asian monsoonal precipitation were not only directly linked with the changing seasonality of solar insolation resulting from progressive changes in the earth s orbital parameters but also may have been closely related to variations in the temperature and size of the western pacific warm pool in the intensity of the el nino southern oscillation and in the path and strength of the north equatorial current in the western pacific

hydrological and climatic changes in deserts of china since the late pleistocene article i nfo article history large areas in western china were wetlands or less arid between 40 and 30 ka corresponding to the greatest lake period on the adjacent tibetan plateau during the last glacial maximum some of these western chinese deserts again experienced wetter conditions however at the same time the sandy lands in the eastern chinese desert belt experienced an activation of aeolian dunes while interpretations of the mid holocene environment in the deserts of china are controversial it is quite likely that it was more humid not only in the eastern areas influenced by monsoon climate systems but also in the western deserts where moisture is currently associated with westerlies evaluation of lacustrine records in the lakes recharged by dryland rivers and the complex interactions of these systems as well as other paleoenvironmental proxies such as the artemisia chenopodiaceae ratio should be interpreted with greater caution facing the highlighted uncertainties in our understanding of climate changes in chinese deserts it is hoped that this special issue will improve our knowledge considerably

holocene fire on the northeast tibetan plateau in relation to climate change and human activity abstract a series of holocene charcoal concentrations cc records from a slope sedimentary section in gonghe basin northeast tibetan plateau are analyzed to investigate fire characteristics e g frequency or magnitude and their linkages with paleoclimate change and ancient human activities the results reveal that changes in fire indicators are well correlated with paleoclimatic change during the past 10 0 ka bp this pattern is characterized by lower cc in the warm and humid middle holocene and higher total cc in the cold dry climate of the early and late holocene meanwhile an event characterized by abnormally high cc values at 3 6 ka bp distinct from the above trend indicates an anomalously high fire frequency which cannot easily be explained as the result of a climatic event alternatively this event is noted to correspond closely with the time of rapid human occupation of the high elevation tibetan plateau many basic domestic and agricultural activities e g slash and burn farming cooking or heating have required fire in the hostile environment of the tibetan plateau this is reflected in the higher cc following the spread of human habitation the analysis of cc might be a useful alternative method for investigating human activities when no direct evidence is available in the holocene tibetan plateau records

a high resolution absolute dated holocene and deglacial asian monsoon record from dongge cave china abstract we present a continuous record of the asian monsoon over the last 16 ka from 18o measurements of stalagmite calcite over 900 oxygen isotopic measurements providing information on shifts in monsoon precipitation are combined with a chronology from 45 precise 230th dates 18o and therefore asian monsoon intensity generally follows changes in insolation although changes in 18o are generally accommodated in abrupt shifts in contrast to smoothly varying insolation indicating that threshold effects may be important 18o decreased dramatically 3 at the start of the holocene 11 5 ka and remained low for 6 ka four positive 18o events centered at 11225 97 yr bp 1 05 10880 117 yr bp 1 15 9165 75 yr bp 1 4 and a double event centered at 8260 64 yr bp 1 1 and 8080 74 yr bp 1 0 punctuated this period of high monsoon intensity all four events correlate within error with climate changes in greenland ice cores thus the relationship between the asian monsoon and the north atlantic observed during the glacial period appears to continue into the early holocene in addition three of the four events correlate within error with outburst events from lake agassiz the decline of monsoon intensity in the mid late holocene is characterized by an abrupt positive shift in 18o which occurs at 3550 59 yr bp 1 1 in 100 yr in addition the holocene is punctuated by numerous centennial and multi decadal scale events amplitudes 0 5 to 1 up to half the amplitude of the glacial interstadial events seen in the last glacial period thus holocene centennial and multi decadal scale monsoon variability is significant although not as large as glacial millennial scale variability the monsoon shows a strong connection with northern south american hydrological changes related by changes in itcz position spectral analysis of the 18o record shows significant peaks at solar periodicities of 208 yr and 86 yr suggesting variation is influenced by solar forcing however there are numerous other significant peaks including peaks at el nino frequencies observed for high resolution portions of the record between 8110 and 8250 yr which suggest that changes in oceanic and atmospheric circulation patterns in addition to those forced by solar changes are important in controlling holocene monsoon climate in addition for this high resolution portion we observe a distinctive biennial oscillation of the asian monsoon which has been associated with the tropospheric biennial oscillation tbo

holocene treeline shifts and monsoon variability in the hengduan mountains southeastern tibetan plateau implications from palynological investigations abstract the upper 8 45 m of a sediment core from lake naleng were analysed for its pollen and charcoal content to detect vegetation climate and human activity changes on the southeastern tibetan plateau tp since the pleistocene holocene transition 11 7 cal kyr bp the application of pollen indicator taxa pollen sums biomisation and multivariate analysis helped to reconstruct environmental conditions during the holocene furthermore 64 surface samples from the southeastern tp and its foreland were analysed to investigate the relationship between modern pollen assemblages and vegetation the modern vegetation was recorded in the surface pollen assemblages by pollen indicator types although sediments also contain pollen spectra extra regional pollen transported from lower vegetation belts which is seen as a consequence of steep elevation gradients at the southeastern margin of the tp the relation between different vegetation belts and temperature from the modern sample sites was used to infer quantitative temperature trends for the holocene record spreading of forests at the beginning of the holocene marks the transition to warmer conditions from 10 7 to 4 4 cal kyr bp open abies betula forests were found at lake naleng probably reflecting a stronger than present summer monsoon temperature range reconstructions suggest a temperature that was about 2 3 c warmer and a treeline position that was 400 600 m higher than today a severe climate deterioration with temperatures about 1 2 c colder than before is documented by a retreating forest between 8 1 and 7 2 cal kyr bp forests retreated while subalpine rhododendron shrubs spread around lake naleng indicating colder conditions with temperatures 1 2 c below early and mid holocene level after 4 4 cal kyr bp the forest decline at 4 4 cal kyr bp is considered to reflect climatic conditions as low concentrations of charcoal particles found in this period exclude human induced fires as reason for the forest retreat however grazing indicators imply human influence on the environment since 3 4 cal kyr bp around lake naleng we therefore consider the rapid treeline shift seen at 3 4 cal kyr bp as partly generated by human activity and partly by climatic conditions

wildfire history and climatic change in the semi arid loess tableland in the middle reaches of the yellow river of china during the holocene evidence from charcoal records high resolution macroscopic charcoal and sediment analysis was used to reconstruct fire history and environmental changes from three loess paleosol profiles on the semi arid loess tableland landsca

a virtual graphic log for clastic sediments abstract drawing a graphic log is a standard method to describe sedimentary rocks at outcrops or from borehole cores graphic logs give a visual impression of the rocks their lithology particle size bedding contacts sedimentary structures palaeocurrents and fossil content as well as trends such as coarsening or fining upwards the format of graphic logs and their styles vary this paper includes outcrop photographs that were collected as part of a distance learning module in sedimentology and provides an opportunity for students to practice drawing a graphic log without having to venture into the field effectively bringing the field into the classroom instructions for drawing a graphic log are included there is potential for virtual logs to provide a more open science approach to outcrop interpretation enabling researchers to visit outcrops virtually and make their own descriptions and interpretations

reconstructing holocene vegetation and climate history of nam co area tibet using pollen and other palynomorphs abstract a drill core 1 8 m 34 samples was taken out of a swamp near nam co tibet china for palynological analysis c14 dating of the cores sediment at 3 different layers led to an numerical core age of about 8000 bp and the palynomorph content of prepared samples enabled reconstruction of the vegetation and climatic history of nam co area pollen of alpine steppe elements together with cyperaceae dominates the palynoflora reflecting the existing vegetation units around the lake throughout the investigated time span due to availability of water precipitation the different vegetation units extended or had to retreat and hence the amount of their pollen increased or decreased the presence of arboreal plants verified by charcoal particles suggest the existence of woodlands in the lake s surrounding area until possibly human made fires changed the environment over time holocene climate history around nam co shows several phases of a strengthening weakening or even an interruption of monsoonal activity changing conditions between dry and humid evolved from 8017 bp until 4800 bp a mostly humid and relative stable system occurred from 4800 until 700 bp whereas the last 700 years are characterized by drier conditions according to fluctuating monsoonal activity humid or arid periods have been different in duration and intensity the interaction of both parts of the monsoonal system the south asian monsoon and the east asian monsoon influenced the climatic conditions around nam co

determination of black carbon by chemical oxidation and thermal treatment in recent marine and lake sediments and cretaceous tertiary clays abstract several sample treatments and analytical methods for the measurement of black carbon in a wide variety of sediments were considered in which the removal of organic carbon is a critical step in the procedure a comparison between chemical oxidation and thermal treatment was conducted and the latter was shown to be inappropriate due to the polymerisation of organic matter using acid dichromate oxidation reactive kerogen was separated from black carbon in a variety of lake and marine and recent and ancient sediments with relatively small and quantifiable losses 1 6 of black carbon under carefully controlled reaction conditions

postglacial fire vegetation and climate history in the clearwater range northern idaho usa the environmental history of the northern rocky mountains was reconstructed using lake sediments from burnt knob lake idaho and comparing the results with those from other previously published sites in the region to understand how vegetation and fire regimes responded to large scale climate changes during the holocene vegetation reconstructions indicate parkland or alpine meadow at the end of the glacial period indicating cold dry conditions from 14 000 to 12 000 cal yr b p abundant pinus pollen suggests warmer moister conditions than the previous period most sites record the development of a forest with pseudotsuga ca 9500 cal yr b p indicating warm dry climate coincident with the summer insolation maximum as the amplification of the seasonal cycle of insolation waned during the middle holocene pseudotsugawas replaced by pinus and abies suggesting cool moist conditions the fire reconstructions show less synchroneity in general the sites west of the continental divide display a fire frequency maximum around 12 000 8000 cal yr b p which coincides with the interval of high summer insolation and stronger than present subtropical high the sites on the east side of the continental divide have the highest fire frequency ca 6000 3500 cal yr b p and may be responding to a decrease in summer precipitation as monsoonal circulation weakened in the middle and late holocene this study demonstrated that the fire frequency of the last two decades does not exceed the historical range of variability in that periods of even higher than present fire frequency occurred in the past

particle motion and the theory of charcoal analysis source area transport deposition and sampling principles from particle motion physics were applied to recurring problems of the interpretation of stratigraphic charcoal data 1 fires within catchments of lakes often produce no record in fossil charcoal curves and 2 periods characterized by no local fire e g 20th century fire suppression often display as much charcoal as times when local fire was frequent quantitative theory on source area transport deposition and sampling of charcoal shows the relationship between particle sizes counted by alternative methods of charcoal analysis pollen slides for particles 5 80 m in diameter petrographic thin sections for particles 50 10 000 m diameter and charcoal diagrams the relationship between diameter and critical and deposition velocities results in fundamental aerodynamic differences between the sizes of particles quantified by the two methods charcoal recorded on pollen slides is of a size that is difficult to lift but once entrained it remains in suspension thin section charcoal is lifted at relatively low wind velocities but it is not suspended at normal surface wind speeds thermal buoyancy during fire lofts charcoal above the forest canopy depending on particle size and wind speed pollen slide charcoal sizes are underrepresented near the fire because they remain in suspension and are preferentially exported from the burn area thin section charcoal is convected to lower heights on average and is deposited nearby following fire thin section charcoal is redistributed locally by wind and thus may enter lakes because of cohesive forces and aerodynamics more pollen slide charcoal remains on the ground and less enters lakes source areas for pollen slide charcoal are subcontinental to global and diagrams of pollen slide charcoal are biased toward nonlocal charcoal they can be used to interpret importance of fire for broad spatial and temporal scales thin section charcoal represents the catchment fire regime simulation models that generate charcoal during fire mix sediments and then sample at specified intervals indicate that 1 in the absence of sediment mixing the pollen slide method should consistently resolve individual fires that occur with an expectation of 30 50 yr 2 unless samples are continuous neither method will produce useful estimates of fire frequency and 3 even a modest amount of sediment mixing will obscure the signal

black carbon records in chinese loess plateau over the last two glacial cycles and implications for paleofires abstract to study the temporal and spatial changes in paleofires over the chinese loess plateau black carbon concentrations were analyzed on the loess paleosol samples from three sections along a north south transect using the orbitally tuned time scales of the sections the black carbon mass sedimentation rates bcmsr were calculated results show that in the last two glacial cycles the bcmsr values in glacial periods are 2 3 times higher than in interglacial periods and the bcmsr variability has a relatively strong precession associated 23 ky period suggesting that the glacial cold dry climate conditions were apt to induce natural fires over the loess plateau comparison of the bcmsr records among the three loess sections demonstrates that natural fire occurrence was much more intensive and frequent in the northern loess plateau than in the southern part coinciding with the previous conclusion that the northern plateau has experienced a drier climate regime in both glacial and interglacial periods the substantial increase in bcmsr of the upper s0 relative to the lower s0 at lingtai and weinan indicates that human activities have exerted a significant influence on fire regimes in the middle and southern loess plateau during late holocene due to the relatively intensive agricultural usage of land

how old is the human footprint in the world s largest alpine ecosystem a review of multiproxy records from the tibetan plateau from the ecologists viewpoint the age at which a human environment was made is strongly debated in quaternary science the perception of the human footprint requires an understanding of the contrast between the present cultural environment and the natural vegetation this is especially true for high altitude ecosystems such as the world s largest alpine ecosystem the 450 000 km 2 of golf course like pastures dominating the southeastern tibetan plateau this ecosystem is widely considered to be natural but only because of the unawareness of the effects of grazing management and the incorrect assessment of human signals in palaeo proxies here we posit the hypothesis that this ecosystem is a human induced replacement to test our hypothesis against defined a priori criteria we 1 monitored vegetation in grazing exclosures 2 produced floristically complete vegetation records 3 compared the vegetation records with data of the nearest climate stations 4 surveyed forest and experimental reforestation trials with endemic tree species 5 analyzed pollen and re evaluated published pollen diagrams and 6 integrated these results with palaeopedological and anthracological results of previous studies the results of long term grazing exclosure experiments the prevalence of grazing adapted plant functional types the occurrence of isolated vigorous forests in alpine pastures and the successful reforestation trials in presently treeless pastures together suggest that dominant pastures replaced forests in the montane belt and tall grassland in the alpine belt the spatial and temporal coincidence of palaeosols and archaeological sites with tree species charcoal the decline in forest pollen during the mid holocene climatic optimum and the first appearance of human indicator pollen are most parsimoniously explained by the early presence of foragers and pastoralists the onset of pastoralism in the tibetan highlands is presumed to date from the 8th millennium bp c 2013 elsevier ltd all rights reserved