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基于天山北坡西部温泉哈夏林区间隔100m海拔高度采集的雪岭云杉梯度样本的断面积生长量资料,分析该区域树木生态弹性变化。干旱事件是区域生态弹性最主要的干扰因子,高温事件也是干扰因子之一。干扰因子的强度会造成生态弹性梯度特征的变化。在极端干旱年份,哈夏林区梯度生长弹性特征最显著,即中高海拔为强抵抗力和弱恢复力,而低海拔则呈相反态势,并出现生长衰退现象。中旱事件时不同海拔均为强抵抗力和较强的恢复力。高温年份低海拔呈现弱抵抗力和弱恢复力。在发生持续干旱时,不同海拔高度的树木生长均受到遏制,但低海拔衰退强度大于高海拔区域,高海拔区域树木对干旱的适应能力要强于中低海拔。 相似文献
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The ecological implications of a Yakutian mammoth's last meal 总被引：1，自引：0，他引：1
Bas van Geel Andr Aptroot Claudia Baittinger Hilary H. Birks Ian D. Bull Hugh B. Cross Richard P. Evershed Barbara Gravendeel Erwin J.O. Kompanje Peter Kuperus Dick Mol Klaas G.J. Nierop Jan Peter Pals Alexei N. Tikhonov Guido van Reenen Peter H. van Tienderen 《Quaternary Research》2008,69(3):361-376
Part of a large male woolly mammoth (Mammuthus primigenius) was preserved in permafrost in northern Yakutia. It was radiocarbon dated to ca. 18,500 14C yr BP (ca. 22,500 cal yr BP). Dung from the lower intestine was subjected to a multiproxy array of microscopic, chemical, and molecular techniques to reconstruct the diet, the season of death, and the paleoenvironment. Pollen and plant macro-remains showed that grasses and sedges were the main food, with considerable amounts of dwarf willow twigs and a variety of herbs and mosses. Analyses of 110-bp fragments of the plastid rbcL gene amplified from DNA and of organic compounds supplemented the microscopic identifications. Fruit-bodies of dung-inhabiting Ascomycete fungi which develop after at least one week of exposure to air were found inside the intestine. Therefore the mammoth had eaten dung. It was probably mammoth dung as no bile acids were detected among the fecal biomarkers analysed. The plant assemblage and the presence of the first spring vessels of terminal tree-rings of dwarf willows indicated that the animal died in early spring. The mammoth lived in extensive cold treeless grassland vegetation interspersed with wetter, more productive meadows. The study demonstrated the paleoecological potential of several biochemical analytical techniques. 相似文献
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本文利用EOF展开,对我国西部树轮指数和降水场进行了讨论,分别计算了降水和树轮的第一、第二主成份的周期。结果表明我国西部树轮和降水在空间与时间上都有着较好的对应关系。在此基础上,通过稳健回归方法对树轮和降水的传输函数进行了研究。 相似文献
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We present a reconstruction of June–July minimum temperatures since AD 1245 for the Mackenzie Delta region based on a 29-site network of white spruce (Picea glauca) ring-width series. Most but not all trees experienced a divergent temperature–growth response, similar to the divergence that has affected other white spruce trees across Yukon and Alaska. However, divergence in the study region began as early as AD 1900 and we have documented our methods to avoid including divergent signals in the reconstruction. Calibration/verification testing based on local temperature data, and multi-century coherence with nearby and large-scale temperature proxy records, confirm that our reconstruction is robust. The reconstruction shows cool conditions in the late 13th, early 18th and early 19th centuries, corresponding with solar minima and increased volcanism. These cool periods are interrupted by warm periods consistent with early to mid-20th century warmth. The late 20th century is the warmest interval, and the last decade is estimated to be 1.4°C warmer than any decade before the mid-20th century. The reconstructed climate history corroborates other proxy-based inferences and supports the notion that high-latitude regions such as the Mackenzie Delta have experienced rapid warming in recent decades that is exceptional in the last eight centuries. 相似文献
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用树轮密度及宽度资料重建新疆吉木萨尔县的季节降水和最高温度 总被引：18，自引：0，他引：18
依据新疆吉木萨尔县天山云杉树木年轮宽度、最大密度和最小密度标准化年表,讨论了晚材宽度、最大密度和最小密度,与月平均最高温度和降水的响应函数基本特征,采用逐步回归方法,确定了利用晚材宽度指数、最大密度指数和最小密度指数重建该地６～９月份降水,以及利用最大密度指数和最小密度指数重建该地４～９月份平均最高温度。重建结果可靠且与实际情况较为一致。分析发现,该地区在过去１５０年中,月平均最高温度和降水有明显的阶段性变化。 相似文献
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Cores of thick leaf spruce from the western Qilian Mountains were subjected to densitometric analysis to obtain data for seven tree-ring parameters (tree-ring width, earlywood width, latewood width, maximum density, minimum density, mean earlywood density and mean latewood density). The chronologies were analyzed individually and then compared with each other. Most of these variables show moderately high values of common variance and mean interseries correlation except latewood and maximum densities. The relationships between the different tree-ring parameters and climate data are also presented. The growth/climate response analyses reveal that the radial growth of thick leaf spruce is the mainly controlled by total annual precipitation (July-June). Herein the residual ring width chronology was used to reconstruct annual (July-June) precipitation of Jiuquan for the period 1768-2009 A.D., and it accounted for 45.0% of the precipitation variance. Multi-taper spectral analysis reveals the existence of significant 11.1-year, 4.9-year, and 2.0- to 3.4-year periods of variability. Spatial analysis shows that the precipitation of Jiuquan has strong common signals for the northern margin of the Tibetan Plateau and Hexi Corridor. Drought events in our reconstruction are compared to the historical archives and other moisture-sensitive tree ring width series in the Hexi Corridor. The results reveal common climatic extremes over much of the Hexi Corridor. Many of these events have had profound impacts on the peoples of the Hexi Corridor over the past several centuries. 相似文献
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利用吉尔吉斯斯坦东部chon-kyzyl-suu附近的两个树轮宽度年表,与CRU气温、降水资料和PDSI资料进行相关分析和响应分析,重建该地区过去百年的降水和PDSI,分析近百年吉尔吉斯斯坦东部干湿变化特征。结果表明：（1）该地区树轮宽度对降水和PDSI响应较好,利用树轮宽度年表可以较好地重建该地区过去百年上年7月到当年6月的降水和PDSI序列;（2）近百年该地区干湿变化具有明显的6 a、13 a和21 a左右的变化准周期;在1913年前后、1943年前后和1972年前后发生了由多到少的气候突变,在1950年前后发生了由少到多的气候突变;（3）吉尔吉斯斯坦东部过去百年干湿变化与中国境内天山山区降水变化一致：1890s偏干,1900s是最为湿润的10 a,1910s是最为干旱的10 a,1917年是近百年来最干旱的1 a,1920s-1930s偏湿,1940s偏干,1950s-1960s偏湿,1970s偏干,1980s-2000s偏湿,尤其是1980年以后到现在,天山山区经历了近百年最为漫长的增湿期;重建的近百年吉尔吉斯斯坦东部干湿变化能较好的代表西天山大部分区域尤其是西天山北坡吉尔吉斯斯坦境内的干湿变化。 相似文献
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Ancient kauri (Agathis australis) buried in bogs across Northland, New Zealand, provide potential for a continuous high-precision radiocarbon calibration curve that extends to the full chronologic range of the dating method. Here we report four new tree-ring series which in addition to previous work represent some 5312 years across Oxygen Isotope Stage 3, a period during which human evolution, migration and extinction took place against a backdrop of extreme and abrupt global climate and environmental change. We compare our radiocarbon-dated series against three different calibration datasets and find considerable differences in the wiggle-matched solutions, demonstrating the difficulty in undertaking high-precision correlation between ice, marine and terrestrial sequences. One way around the apparent impasse is the use of 10Be in the Greenland and Antarctic ice cores to precisely link to kauri 14C from which a decadally/bidecadally-resolved floating ‘calibration’ dataset can be generated. 相似文献
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不同胶结宽度粒间胶结特性试验研究 总被引：2，自引：0，他引：2
胶结砂土中水泥含量、能源土中水合物的含量会导致其宏观力学特性的差异,从微观层面可以解释为颗粒之间胶结物含量的不同所导致的粒间力学性质的差异所致。为研究不同胶结物含量的胶结颗粒的力学特性,进行了不同胶结宽度的粒间胶结试验,试验结果表明：（1）峰值压缩荷载随胶结宽度的减小呈非线性变化,宽高比对峰值荷载有明显影响;（2）峰值拉伸荷载随胶结宽度减小而线性减小,宽高比对其影响不大;（3）峰值剪切荷载和峰值扭矩由两部分组成,即胶结部分和摩擦部分。且其变化趋势相似,随着法向荷载的增大,峰值荷载先随之增大,在达到临界应力比后,峰值荷载开始减小,当应力比达到1,即胶结破坏时,胶结部分不再发挥作用,此时粒间荷载由摩擦部分提供;（4）在压-剪-扭试验中,不同初始偏心距情况下得到的峰值荷载在剪力-扭矩平面内呈椭圆状。 相似文献