Testing the Landscape Reconstruction Algorithm for spatially explicit reconstruction of vegetation in northern Michigan and Wisconsin     

Shinya Sugita  Tim Parshall 《Quaternary Research》2010,74(2):289-300

The Landscape Reconstruction Algorithm (LRA) overcomes some of the fundamental problems in pollen analysis for quantitative reconstruction of vegetation. LRA first uses the REVEALS model to estimate regional vegetation using pollen data from large sites and then the LOVE model to estimate vegetation composition within the relevant source area of pollen (RSAP) at small sites by subtracting the background pollen estimated from the regional vegetation composition. This study tests LRA using training data from forest hollows in northern Michigan (35 sites) and northwestern Wisconsin (43 sites). In northern Michigan, surface pollen from 152-ha and 332-ha lakes is used for REVEALS. Because of the lack of pollen data from large lakes in northwestern Wisconsin, we use pollen from 21 hollows randomly selected from the 43 sites for REVEALS. RSAP indirectly estimated by LRA is comparable to the expected value in each region. A regression analysis and permutation test validate that the LRA-based vegetation reconstruction is significantly more accurate than pollen percentages alone in both regions. Even though the site selection in northwestern Wisconsin is not ideal, the results are robust. The LRA is a significant step forward in quantitative reconstruction of vegetation.  相似文献   

Millennial-scale vegetation changes during the last 40,000 yr based on a pollen record from Lake Biwa, Japan     

Ryoma Hayashi  Hikaru Takahara  Keiji Takemura 《Quaternary Research》2010,74(1):91-202

A high-resolution pollen record covering the last 40,000 yr (BIW95-4) from Lake Biwa, western Japan, shows regional vegetation responses to millennial-scale climate changes. From 40 to 30 ka, Cryptomeria japonica was dominant around the lake among pinaceous conifers and deciduous broad-leaved trees. During this period, fluctuations of C.japonica are correlated with Dansgaard-Oeschger (D-O) cycles recognized from the anhysteretic remanent magnetization (ARM) record. Increases in the abundance of this taxon may have been caused by wetter summer conditions influenced by the East Asian monsoon or increased snowfall on the Sea of Japan side of the Japanese archipelago. Between 29 and 14 ka, pinaceous conifer forests mainly composed of Pinus subgenus Haploxylon, Tsuga, and Picea trees developed. At approximately 23 ka, Picea trees increased in abundance as ARM values decreased. This expansion of Picea trees has been correlated with Heinrich event (HE) 2 in the North Atlantic. At about 14 ka, the distribution of broad-leaved forest (mainly composed of deciduous oaks) began to expand after D-O 1. Evidence of significant vegetation change related to the abrupt Younger Dryas cooling event has not been found.  相似文献   

基于孢粉的中全新世以来共和盆地人类活动探讨          下载免费PDF全文

李生梅  侯光良  许长军  魏海成  金孙梅 《盐湖研究》2020,28(4):56-63

采用1310个中国北方表土孢粉,共和盆地达连海化石孢粉数据,利用现代类比法,重建7.0cal kaBP共和盆地的人类活动指数(HI),结果显示:7~5.4 cal kaBP,人类活动非常微弱,盆地内主要为细石器狩猎采集活动,对自然环境影响非常有限；5.4~4.6 cal kaBP人类活动开始显现,宗日文化的定居、农业活动,已经开始对自然环境产生影响；进入3.8~2.0 cal kaBP的青铜时代,HI指示人类活动显著增强,这与当时社会及自然环境背景紧密相关,当时卡约文化遗址数量多达260余处,人口增长,畜牧业确立与普及,风沙活动较弱；1.8~1.2 cal kaBP HI达到峰值,此时汉—唐时期盆地内出现了城址,聚落建制和规模大大提高,人口数量较为稳定,畜牧业发展达到鼎盛,风沙活动较为微弱,人类活动强度达到顶峰；1.0 cal kaBP之后,人类活动相对减弱,这与盆地内风沙活动开始增强,聚落和人口减少,及其畜牧业衰落有关。重建的HI阶段性变化特征与盆地内人类活动的考古和历史记录较为吻合,揭示共和盆地人类活动强度变化,主要受聚落、人口、经济活动形式和沙地变化等自然—社会因素共同驱动,也说明采用孢粉记录来指示过去人类活动变化是可行的。  相似文献   

Holocene vegetation, fire and climate history of the Sawtooth Range, central Idaho, USA     

Cathy Whitlock  Christy E. Briles  Joshua Gage 《Quaternary Research》2011,75(1):114-124

The paucity of low- and middle-elevation paleoecologic records in the Northern Rocky Mountains limits our ability to assess current environmental change in light of past conditions. A 10,500-yr-long vegetation, fire and climate history from Lower Decker Lake in the Sawtooth Range provides information from a new region. Initial forests dominated by pine and Douglas-fir were replaced by open Douglas-fir forest at 8420 cal yr BP, marking the onset of warmer conditions than present. Presence of closed Douglas-fir forest between 6000 and 2650 cal yr BP suggests heightened summer drought in the middle Holocene. Closed lodgepole pine forest developed at 2650 cal yr BP and fires became more frequent after 1450 cal yr BP. This shift from Douglas-fir to lodgepole pine forest was probably facilitated by a combination of cooler summers, cold winters, and more severe fires than before. Five drought episodes, including those at 8200 cal yr BP and during the Medieval Climate Anomaly, were registered by brief intervals of lodgepole pine decline, an increase in fire activity, and mistletoe infestation. The importance of a Holocene perspective when assessing the historical range of variability is illustrated by the striking difference between the modern forest and that which existed 3000 yr ago.  相似文献   

Use of CART analysis to differentiate pollen of red pine (Pinus resinosa) and jack pine (P. banksiana) in New England     

Andrew M. Barton  Andrea M. Nurse  Sarah W. Hardy 《Quaternary Research》2011,75(1):18-23

The identification of fossil pollen at the generic rather than species level is hampering progress in understanding the biogeography and dynamics of paleo-vegetation. We used CART analysis to facilitate the differentiation of fossil pollen of Pinus banksiana and Pinusresinosa, which are morphologically similar and nearly always combined in paleoecological studies. The CART model, using four of the ten morphological traits measured, exhibited a high level of correct identification for pollen of each of the species and shows promise as a tool for increasing the detail of paleoecological records and inferences.  相似文献   

Mid- to late Holocene environmental and climatic changes in New Caledonia, southwest tropical Pacific, inferred from the littoral plain Gouaro-Déva     

Denis Wirrmann  Anne-Marie Sémah  Jean-Pierre Debenay  Magali Chacornac-Rault 《Quaternary Research》2011,76(2):229-242

Multiproxy analysis of three littoral cores from western New Caledonia supports the hypothesis that the main controlling factors of environmental changes are sea-level change, ENSO variability and extra-tropical phenomena, such as the Medieval Warm Period (MWP) marked by a tendency for La Niña-like conditions in the tropical Pacific. The record starts during the late Holocene sea-level rise when the terrestrial vegetation indicated wet and cool conditions. The site was a coastal bay definitely transformed into a freshwater swamp at around 3400 cal yr BP, after the rapid drawdown of sea level to its current level. Sediments and foraminiferal assemblages indicated subsequent episodes of freshwater infillings, emersion or very high-energy conditions, likely related to climatic changes and mostly controlled by ENSO variability. Between 2750 and 2000 cal yr BP, relatively dry and cool climate prevailed, while wetter conditions predominated between ca. 1800 and 900 cal yr BP. The Rhizophoraceae peak between ca. 1080 and 750 cal yr BP, coeval with the MWP, may indicate a global phenomenon. Microcharcoal particles present throughout the record increased after 1500 cal yr BP, suggesting an anthropogenic source. From ca. 750 cal yr BP the appearance of current type of vegetation marks the human impact.  相似文献   

A 94-ka Pollen Record of Vegetation Change in Qaidam Basin,Northeastern Qinghai-Tibetan Plateau     

WEI Haicheng  FAN Qishun  ZHAO Yan  MA Haizhou  AN Fuyuan  YUAN Qin 《《地质学报》英文版》2014,88(Z1):31-33

正1 Introduction The northeastern Qinghai-Tibetan Plateau(NE QTP),located at a triple junction of influences of the Asian summer monsoon,westerly jet stream and Siberian high,is of considerable significance with regard to regional responses to global climate change.Qarhan Salt Lake is the largest playa located in the central eastern  相似文献   

Holocene history and environmental reconstruction of a Hercynian mire and surrounding mountain landscape based on multiple proxies     

Lydie Dudová  Petra Hájková  Věra Opravilová  Michal Hájek 《Quaternary Research》2014

We discovered the first peat section covering the entire Holocene in the Hrubý Jeseník Mountains, representing an island of unique alpine vegetation whose history may display transitional features between the Hercynian and Carpathian regions. We analysed pollen, plant macrofossils (more abundant in bottom layers), testate amoebae (more abundant in upper layers), peat stratigraphy and chemistry. We found that the landscape development indeed differed from other Hercynian mountains located westward. This is represented by Pinus cembra and Larix during the Pleistocene/Holocene transition, the early expansion of spruce around 10,450 cal yr BP, and survival of Larix during the climatic optimum. The early Holocene climatic fluctuations are traced in our profile by species compositions of both the mire and surrounding forests. The mire started to develop as a calcium-rich percolation fen with some species recently considered to be postglacial relicts (Meesia triquetra, Betula nana), shifted into ombrotrophy around 7450 cal yr BP by autogenic succession and changed into a pauperised, nutrient-enriched spruce woodland due to modern forestry activities. We therefore concluded that its recent vegetation is not a product of natural processes. From a methodological viewpoint we demonstrated how using multiple biotic proxies and extensive training sets in transfer functions may overcome taphonomic problems.  相似文献   

Continental European Eemian and early Würmian climate evolution: comparing signals using different quantitative reconstruction approaches based on pollen     

Stefan Klotz  Joel Guiot  Volker Mosbrugger   《Global and Planetary Change》2003,36(4):277-294

Analyses of Eemian climate dynamics based on different reconstruction methods were conducted for several pollen sequences in the northern alpine foreland. The modern analogue and mutual climate sphere techniques used, which are briefly presented, complement one another with respect to comparable results. The reconstructions reveal the occurrence of at least two similar thermal periods, representing temperate oceanic conditions warmer and with a higher humidity than today. Intense changes of climate processes become obvious with a shift of winter temperatures of about 15 °C from the late Rissian to the first thermal optimum of the Eemian. The transition shows a pattern of summer temperatures and precipitation increasing more rapidly than winter temperatures. With the first optimum during the Pinus–Quercetum mixtum–Corylus phase (PQC) at an early stage of the Eemian and a second optimum period at a later stage, which is characterised by widespread Carpinus, climate gradients across the study area were less intense than today. Average winter temperatures vary between −1.9 and 0.4 °C (present-day −3.6 to 1.4 °C), summer temperatures between 17.8 and 19.6 °C (present-day 14 to 18.9 °C). The timberline expanded about 350 m when compared to the present-day limit represented by Pinus mugo. Whereas the maximum of temperature parameters is related to the first optimum, precipitation above 1100 mm is higher during the second warm period concomitant to somewhat reduced temperatures. Intermediate, smaller climate oscillations and a cooling becomes obvious, which admittedly represent moderate deterioration but not extreme chills. During the boreal semicontinental Eemian Pinus–Picea–Abies phase, another less distinct fluctuation occurs, initiating the oscillating shift from temperate to cold conditions.  相似文献   

Mangrove development and its response to environmental change in Yingluo Bay (SW China) during the last 150 years: Stable carbon isotopes and mangrove pollen     

《Organic Geochemistry》2015

Located at the interface of terrestrial and marine ecosystems, mangroves are particularly sensitive to environmental change. They provide a sedimentary sink for organic carbon, whereby cores can provide detailed records of mangrove species. We aimed to trace the history of mangrove development over the past 150 years in Yingluo Bay, SW China. Sedimentation rates (avg. 0.32 and 0.37 cm/year) were calculated on the basis of ln(²¹⁰Pb_ex) vs. mass depth, and offset the rate of relative sea level rise (0.22–0.24 cm/year), leading to a seaward expansion of new mangrove habitats. Chemical tracers (δ¹³C_org and C:N) and an isotope mixing model were utilized to trace the contribution of mangrove-derived organic matter (MOM). Changes in the relative abundance of pollen from mangrove plants was used to compensate for diagenetic alteration of the stable isotope values and potential overlaps in isotope values for different sources of organic matter. The result of Pearson correlation analysis showed that the MOM was moderately positive correlated with total mangrove pollen, indicating that stable carbon isotopes and mangrove pollen provide similar information for tracing mangrove ecosystems. Based on results from this study, compositional changes in mangrove communities could be divided into two main stages: a degradation period (1870–1930 AD) and a flourishing period (1930–2011 AD), corresponding to colder temperature and warmer temperature, respectively. Owing to the location being far away from any industrial area and human activity, temperature may be a key factor for mangrove development.  相似文献