喀斯特系统生物地球化学循环及对全球变化的响应

生物地球化学循环是地球系统物质循环的核心,是维系地表生态系统稳定和人类社会可持续发展的重要基础。然而,气候变化以及人类的过度干扰可能会显著改变表层地球系统中的生物地球化学循环过程,尤其是脆弱的喀斯特生态系统。特殊的多孔隙关键带结构也加速了喀斯特地区物质循环及其对外界环境变化的响应,影响了不同尺度的物质循环和生物地球化学过程。本研究主要综述了宏观尺度（气候变化）、中尺度（人类活动）和微观尺度（微生物活动）的环境变化对喀斯特地区生物地球化学循环的影响。结果表明多要素变化导致喀斯特地区物质循环受到强烈影响,气候变化、人类活动和微生物活动及其耦合关系对喀斯特地区生物地球化学循环的调控作用具有重要意义。最后,本研究强调了现有研究的局限性并指出未来研究的挑战与方向,即未来应从系统研究（如地球关键带）的视角出发,将多尺度观测－分析与综合模型集成研究并举,从而构建多源多尺度耦合的过程和系统模型,进而为阐明喀斯特系统的演变规律和动力学机制、实现喀斯特地区的生态保护和高质量发展提供理论基础。     

多元地球化学指标指示的32～9 ka B.P.罗布泊地区环境及其对全球变化的响应

对位于新疆罗布泊地区罗北洼地的CK-2钻孔柱样,自距顶0.94 m到10.35 m部分,以5 cm间距采样,6个样的质谱,铀系法年龄为32～9 ka B.P.,用仪器-化学分析法得到了样品中Na、K、Ca、Mg、Fe、cu、Hg、Zn、Mn、Sr、As、Pb、P、Cl和TOC共15种元素的含量.通过对元素含量变化和主成分序列分析,探讨了罗布泊地区在32～9 ka B.P.期间,经历的从末次盛冰期(阶段Ⅰ)、暖干期(阶段Ⅱ)、末次冰期晚期(阶段Ⅲ),到全新世早期(阶段Ⅳ)的不同程度冷湿与暖干的变化阶段.与格陵兰冰芯(GISP2)和深海沉积物氧同位素序列对比结果表明,罗布泊地区经历了MIS3晚期、MIS2和早M1S1早期.在罗布泊环境演化序列中也出现了发生在北大西洋冰漂碎屑的Heinrich事件(H3、H2和H1)和新仙女木(YD)事件,以及快速回暖的D/O事件(IS4、IS3、IS2和IS1).这表明高纬度的大气环流影响到中纬度西风带的强度、相位和位移,制约了我国西北干旱化地区气候环境变化的格局.为此,罗布泊地区的湖相沉积环境不仅记录了受到西风带、青藏高原隆升以及远离东亚和南亚季风影响所具有区域性的冷湿与暖干的水热配置特点,并且还具有全球变化的印迹.     

Human response to environmental change in the perspective of future, global climate

Human response to severe environmental stress is conceived and implemented by individuals, but must be approved by the group. These decisions are made with respect to perceived circumstances. Societies are enmeshed within adaptive systems that provide a matrix of opportunities and constraints for a wide range of potential behavioral variability. Such systems repeatedly readjust to short-term crises, e.g., droughts, but persistent and severe environmental stress may require substantial revision of adaptive strategies. The Sahel drought of 1968–1973 is an example of a brief but severe crisis, recurring along the Saharan margins perhaps once every 30 years. Closer inspection shows links between intensified intertribal warfare and ecological stress in the lower Omo Valley. The decline of the Egyptian New Kingdom during the 12th century B.C., in response to economic stagnation, sociopolitical instability, dynastic weakness, foreign pressures, and poor Nile floods over 50–70 years, represents a more complex and fundamental modification, with systemic simplification lasting 450 years. Such insights can be applied to future, global climatic change due to increasing atmospheric CO₂. Simulation and paleoclimatic experience suggest a drier climate for the North American and Soviet breadbaskets, to threaten world food supplies at a time of maximum demographic pressures and declining resources. Public perception and remedial planning should receive the attention of Quaternary scientists, in order to preempt an involuntary, global, systemic simplification.     

Bryozoan-rich stromatolites (bryostromatolites) from the Silurian of Gotland and their relation to climate-related perturbations of the global carbon cycle

Bryozoan–stromatolite associations (bryostromatolites) formed conspicuous reef structures throughout the Sheinwoodian (Wenlock) to Ludfordian (Ludlow) stratigraphy on Gotland but have not been described so far. They are mainly composed of encrusting bryozoans forming a complex intergrowth with porostromate and spongiostromate microbes and are different from the abundant stromatoporoid–coral–algal reefs with respect to their composition. In the bryostromatolite different growth stages can be identified. The observed succession can be taken as evidence for cyclic environmental changes during reef formation. Stenohaline reef-dwelling organisms, such as echinoderms, sponges, corals and trilobites, indicate fully marine salinities. Ten localities exposing bryostromatolites were discovered. Individual bryostromatolites are small with few decimetres up to one metre in size, and occur solely in shallow marine areas. Common features of these reefs on Gotland are cauliflower-like growth, a high bryozoan diversity, a high abundance of phosphatic fossils and components such as bryozoan pearls and inarticulate phosphatic brachiopods, enhanced bioerosion, Palaeomicrocodium crusts, vadose silt and gypsum pseudomorphs. The high abundance of Palaeomicrocodium, as well as the alternation with other crust-forming contributors, suggest that it could have been formed directly at the palaeo-sea surface, probably in times of minor but high-frequency sea-level fluctuations. Vadose silt and pseudomorphs after gypsum in reef cavities indicate subaerial exposure shortly after reef growth. The high amount of phosphatic components indicates a high nutrient input, probably by dust. All bryostromatolites were formed in times of strongly elevated δ¹³C values. The unusual combination of sedimentological and palaeoecological features, as well as their occurrence exclusively during strong positive δ¹³C excursions, are evidence that the bryostromatolite development responded to climatic/oceanographic changes, which may have played an important role in reef control.     

中国天山地区降水对全球气候变化的响应

天山地区的降水变化及其对全球气候变化的响应是近年来研究的热点。利用中国天山地区40个气象站1951-2014年的月降水数据,运用线性倾向估计、相关分析等气候诊断方法,分析了该区域的降水变化,探讨了主要气候指数与降水同步变化的相关关系。结果表明：年降水呈现出"西多东少,北多南少,高山多外围少"的特征,年降水变化率为6.0 mm·（10a）^-1。SASMI与年降水表现为显著正相关,PDO、PNA和AO与年降水表现为弱正相关,且有局限性。在枯水期,SASMI与天山北坡及部分中高山地带的降水表现为弱正相关,而在西天山南坡表现为弱负相关,ENSO与中、西天山南北坡的中低山带的降水变化相关性较高。在丰水期,SASMI与天山南坡和高山区降水变化相关性较高,PDO与中、西天山南北坡的低山带部分站点的降水变化相关性较高。     

The Tambora eruption in 1815 provides a test on possible global climatic and chemical perturbations in the past

A coupled one-dimensional radiative-convective-photochemical diffusion model, which takes into account the influence of ocean inertia on global radiative perturbations is used to investigate the possible climatic and other atmospheric effects of a major volcanic eruption, thought to be similar in magnitude to that of the Tambora eruption, Indonesia, which took place in 1815. A volcanic cloud was introduced in the model stratosphere between 20–25 km and the global average peak aerosol optical thickness was assumed to be 0.25. Both the aerosol optical thickness and aerosol composition, which determine the optical properties, were allowed to vary in the model atmosphere during the life cycle of the volcanic cloud. The results indicate that the global average surface temperature decreases steadily from the date of eruption (7–12 April 1815) with maximum cooling of 1° K occurring in the spring of 1816. The calculations also show significant warming of the stratosphere, with temperature increasing up to 15° K at 25 km in less than six months after the date of eruption. The important effects of the Tambora eruption on stratospheric ozone and UV-B radiation at the surface are also mentioned.     

The response of the environment of the Angara-Lena Plateau to global climate change in the Holocene

The paper is focused on the regularities and character of the response of the regional landscapes of the Angara-Lena Plateau to variations in the global climate system during the Holocene. They were revealed by integrated studies of four peat bogs of the plateau—an important area for the understanding of the environmental dynamics in the entire Baikal region. Age models for the records obtained were provided by 16 radiocarbon dates. A spatiotemporal correlation of spore-pollen indices with the trend of 5¹⁸O records from the global stratotypes was used to find out the possible causes of changes in the landscapes and climate of the Angara-Lena Plateau in the context of past changes in the global climate system. The plateau environment showed a dramatically varying response to global climate variations in the Middle-Late Holocene. Moreover, the observed intervals of reorganization in the regional environment took place in a quasi-millennial regime, in accordance with global climate rearrangement. However, not all the studied regions of the Angara-Lena Plateau exhibited a synchronous or analogous response to global environment change. This emphasizes the complicated character of regional climate manifestations in the Holocene and necessitates the use of paleogeographical data from a wider range of territories.     

Assessment of the response of subaqueous methane hydrate deposits to possible climate change in the twenty-first century

Doklady Earth Sciences -     

天山南坡清水河与阿拉沟流域径流变化特征及其对气候变化的响应

依据1956-2012年天山南坡清水河流域的克尔古提水文站以及阿拉沟流域的阿拉沟水文站资料,采用Mann-Kendall非参数检验法和交叉小波变换法,分析了清水河与阿拉沟出山径流的趋势、突变、周期变化等特征,并进一步探讨了出山径流对气候变化的响应。结果表明：清水河与阿拉沟流域年径流量均呈上升趋势,其中1988年为径流突变年,该年前后年均径流变化态势不同,1988年以后径流升幅显著。同时,流域径流过程呈现多时间尺度的周期变化,以32 a以上大周期为主,2 a和8 a小周期变化为辅。因流域下垫面特征等差异,清水河出山径流对降水变化的响应程度强于阿拉沟,而阿拉沟出山径流对气温敏感性高于清水河。且受冰川径流调节作用与多年冻土退化的影响,阿拉沟径流过程对气温的滞后性强于清水河。     

洞庭湖区土壤实测碳量的分布规律及其对全球变化的响应

研究区域土壤碳库的分布特征对于全球变化研究、土壤肥力和生态系统的功能评价具有重要意义。在缺乏长期实测资料情况下,国内外多以模型、第二次土壤普查资料或较稀的实测数据进行研究。文中利用洞庭湖区生态地球化学调查实测数据,研究影响该区土壤碳分布的因素认为区域土壤碳量处于全国的中、高级水平;地质地貌条件是影响土壤无机碳量分布的最重要因素;土壤类型对土壤碳量有影响;本区水土流失强度对表层土壤总有机碳量影响不大;经济林、竹林的土地利用方式及防治土壤潜育化有利于土壤的碳储存;从TOC等沉积的时空演化规律说明,本区环境变化是对全球环境变化的响应,为区域土地利用、促进土壤碳固定及全球环境变化研究提供了依据。     

Sub-bottom temperature perturbations due to temperature variations at the boundary of inhomogeneous lake or oceanic sediments

For many years continental heat flow data were obtained from temperature gradients measured in boreholes and conductivity measurements made on representative cores. Because of the difficulty of obtaining deep holes in suitable regions, increasing use is being made of measurements made in the top few meters of the sediments at the bottom of continental lakes. For reliable heat flow results two conditions must be met. First, an accurate record of the temperature history at the top of the sediment should be available, preferably over a time span of 4 or 5 years; second, if the thermal properties are not constant with depth, then the depth-dependence should be known.Errors that may arise if either or both of these conditions cannot be met can be serious. Using various surface thermal histories we compare results from models assuming constant diffusivity, a diffusivity changing exponentially with depth and a layered medium, all being structures based upon observed variations near the sediment-water interface where conductivity may change by a factor of two over 2 or 3 m. In some situations, errors as large as several hundred percents may occur but in such cases it should be possible to deduce from the data that something has occurred to make the data unreliable; more realistically, there are occasions where a temperature-depth plot which is linear within normally acceptable limits of accuracy and with a gradient that is within the range of expectations may be as much as 100% in error.     

Spatiotemporal changes of global extreme temperature events (ETEs) since 1981 and the meteorological causes

Of the various types of disasters caused by extreme climate and weather, extreme temperature events (ETEs) have led to a heightened awareness due to their increasing frequency, intensity, widespread distribution, and severe health impacts. Although many previous studies have surveyed the severe impacts of specific ETEs, few systematic studies have analyzed the temporal trends and the spatial patterns of this type of ETEs at the global scale. In the present study, disaster data from 1981 to 2010 compiled by Emergency Events Database were used to obtain a global view of the distribution of and the changes in the recorded ETEs. In addition, the daily maximum/minimum temperature data provided by National Centers for Environmental Prediction /Department of Energy Reanalysis 2 were used to explore the potential meteorological causes of these events. The results showed 2.7 and 6.4 increases in the frequencies of heat waves and cold spells per decade, respectively, since the 1980s. However, a large regional variability was found worldwide. Moreover, more than 40 % of the recorded ETEs occurred in Europe, and Asia experienced 33 and 26 % of the heat wave and cold spell events, respectively. Additionally, the global pattern for the occurrence frequency of ETEs in recent decades could be largely ascribed to the meteorological indexes: the heat stress index (HSI) and the cold stress index (CSI). The frequency of heat wave events increased from 1981 to 2010, and this trend is consistent with the increase in the HSI. However, the cold spell events did not appear to be reduced, as demonstrated by the disaster records, and this finding is inconsistent with the CSI trend. This result indicates that other factors also influence the occurrence of disaster events.     

Exploring the potential of tree-ring chronologies from the Trafoi Valley (Central Italian Alps) to reconstruct glacier mass balance

Two tree-ring chronologies of stone pine ( Pinus cembra L.) and two of Norway spruce ( Picea abies Karst.) were constructed on the basis of data from three high-altitude sites in the Trafoi Valley (Central Alps, Italy) to test tree species sensitivity to climate at different sites and to explore the potential of the two species for reconstructing the mass balance of two glaciers in the same region (the Careser and Hintereis glaciers). Influence of climate on tree-ring growth and on glacier mass variations was tested by means of Pearson's correlation and response functions. At highest altitude sites, both species appeared to be sensitive to July temperatures, while stone pine also showed higher sensitivity than Norway spruce to previous winter precipitation. Comparing the dendrochronological and glaciological series, stone pine showed higher negative correlations with glacier mass balance series than Norway spruce. These different relationships reflect different species responses to climate, and stone pine is potentially useful in reconstructing past glacier mass balance in the Central Alps. Extreme climatic events induce different and even contrasting responses of tree-ring growth and glacier mass variations and may therefore bias tree-ring-based glacier mass balance reconstructions.     

Assessing the response of runoff to climate change and human activities for a typical basin in the Northern Taihang Mountain,China

Climate change and human activities are the two main factors on runoff change. Quantifying the contribution of climate change and human activities on runoff change is important for water resources planning and management. In this study, the variation trend and abrupt change point of hydro-meteorological factors during 1960–2012 were detected by using the Mann–Kendall test and Pettitt change-point statistics. Then the runoff was simulated by SWAT model. The contribution of climate change and human activities on runoff change was calculated based on the SWAT model and the elasticity coefficient method. The results showed that in contrast to the increasing trend for annual temperature, the significant decreasing trends were detected for annual runoff and precipitation, with an abrupt change point in 1982. The simulated results of SWAT had good consistency with observed ones, and the values of \(R^{2}\) and \(E_{NS}\) all exceeded 0.75. The two methods used for assessing the contribution of climate change and human activities on runoff reduction yielded consistent results. The contribution of climate change (precipitation reduction and temperature rise) was \({\sim }37.5\%\), while the contribution of human activities (the increase of economic forest and built-up land, hydrologic projects) was \({\sim }62.5\%\).     

Late Glacial fluvial response of the Niers‐Rhine (western Germany) to climate and vegetation change

The Niers valley was part of the Rhine system that came into existence during the maximum Saalian glaciation and was abandoned at the end of the Weichselian. The aim of the study was to explain the Late Pleniglacial and Late Glacial fluvial dynamics and to explore the external forcing factors: climate change, tectonics and sea level. The sedimentary units have been investigated by large‐scale coring transects and detailed cross‐sections over abandoned channels. The temporal fluvial development has been reconstructed by means of geomorphological relationships, pollen analysis and ¹⁴C dating. The Niers‐Rhine experienced a channel pattern change from braided, via a transformational phase, to meandering in the early Late Glacial. This change in fluvial style is explained by climate amelioration at the Late Pleniglacial to Late Glacial transition (at ca. 12.5 k ¹⁴C yr BP) and climate‐related hydrological, lithological and vegetation changes. A delayed fluvial response of ca. 400 ¹⁴C yr (transitional phase) was established. The channel transformations are not related to tectonic effects and sea‐level changes. Successive river systems have similar gradients of ca. 35–40 cm km^?1. A meandering river system dominated the Allerød and Younger Dryas periods. The threshold towards braiding was not crossed during the Younger Dryas, but increased aeolian activity has been observed on the Younger Dryas point bars. The final abandonment of the Niers‐Rhine was dated shortly after the Younger Dryas to Holocene transition. Traces of Laacher See pumice have been found in the Niers valley, indicating that the Niers‐Rhine was still in use during the Younger Dryas. Copyright © 2005 John Wiley & Sons, Ltd.     

Historical global analysis of occurrences and human casualty of extreme temperature events (ETEs)

Extreme temperature events (ETEs) are important climatological natural disasters whose consequences have been largely underappreciated due to current challenges in defining them and measuring their impacts. Taking an exploratory approach, this study examines the historical records of 422 ETE occurrences across 71 countries in the period 1900–2011 from the International Disaster Database (EM-DAT) with more detailed analyses for records from 1971 to 2011. The various limitations associated with ETE data and the EM-DAT database are discussed and followed by analyses for heat and cold events. Globally, after adjusting for bias due to increased reporting, it was found that there may be genuine increases in ETE occurrences. Trends for mortality are much more uncertain, with possibly a higher increase for heat than for cold events if the high death counts of the 2003 and 2010 heat waves are included. If excluded, only mortality for cold seems to have increased over the years. Comparisons with other mortality databases suggest that EM-DAT’s global coverage may not be entirely complete. Furthermore, it may have underestimated numbers of death counts, especially for small-scale heat events and cold events in general. Further analyses by Human Development Index (HDI) categories also suggest two additional and opposing biases: an increased reporting bias for more developed nations and an underreporting bias for less developed nations. Country-level analyses based on both absolute and adjusted data suggest that a handful of countries have been most severely impacted by ETE. These mainly comprise developed nations but also include five medium- and low-HDI countries in Asia.     

Assessing the transition from deforestation to forest regrowth with an agent-based model of land cover change for south-central Indiana (USA)

The Midwest and Northeast United States has experienced a net increase in forest cover since the beginning of the 20th century. However, we lack a detailed understanding of the transition to net forest cover increase because this forest regrowth occurred prior to the use of tools like household-level surveys focused on land use decision-making and availability of remote sensing data. Agent-based modeling presents an appealing means to explore what social and biophysical dynamics may have contributed to this forest regrowth process. In this paper we employ an agent-based model to analyze the process of forest regrowth in south-central Indiana from 1939 to 1993. Simulation results are presented for assumptions regarding pre-existing forest age and the stand age at which landowners harvest timber with a goal of understanding the influence of these factors on future trajectories of land cover change. The results demonstrate both the value and the burden of having many time points to evaluate the success of the model. Is the best simulation the one with the smallest net residuals across all time points? Or is the best simulation the one that best reproduces the correct trajectory of land cover change for each time interval? Model simulations that assume a harvesting frequency of 30 years all produced landscapes within 2% of the actual forest cover in 1993, the end point of the study period. However, the trajectories of these simulations did not all mimic the gradual forest regrowth found in our observed data. The model simulation with the smallest residual values across all time points assumed a initial forest age of 5 years in 1939 and a harvesting frequency of 30 years. Ultimately, we cannot definitively conclude that one model simulation is a better representation of reality than another because we have no way of comprehensively validating the model assumptions. However, we can more plausibly conclude that the age of forest regrowth in 1939 and the frequency of timber harvesting by landowners both had an influence on the successive trajectory of land cover change in the study area.     

Quantifying the response of surface urban heat island to urbanization using the annual temperature cycle model

Urban heat island(UHI),driving by urbanization,plays an important role in urban sustainability under climate change.However,the quantification of UHI’s response to urbanization is still challenging due to the lack of robust and continuous temperature and urbanization datasets and reliable quantification methods.This study proposed a framework to quantify the response of surface UHI(SUHI)to urban expansion using the annual temperate cycle model.We built a continuous annual SUHI series at the buffer level from 2003 to 2018 in the Jing-Jin-Ji region of China using MODIS land surface temperature and imperviousness derived from Landsat.We then investigated the spatiotemporal dynamic of SUHI under urban expansion and examined the underlying mechanism.Spatially,the largest SUHI interannual variations occurred in suburban areas compared to the urban center and rural areas.Temporally,the increase in SUHI under urban expansion was more significant in daytime compare to nighttime.We found that the seasonal variation of SUHI was largely affected by the seasonal variations of vegetation in rural areas and the interannual variation was mainly attributed to urban expansion in urban areas.Additionally,urban greening led to the decrease in summer daytime SHUI in central urban areas.These findings deepen the understanding of the long-term spatiotemporal dynamic of UHI and the quantitative relationship between UHI and urban expansion,providing a scientific basis for prediction and mitigation of UHI.     

San Quirce (Palencia,Spain): new chronologies for the Lower to Middle Palaeolithic transition of south-west Europe

San Quirce is an open-air archaeological site situated on a fluvial terrace in the Duero basin (Palencia, northern Iberia). This paper presents new and consistent chronologies obtained for the sedimentary sequence using post-infrared infrared stimulated luminescence (pIR-IR) dating of K-feldspars and single-grain thermally transferred optically stimulated luminescence (TT-OSL) dating of quartz. The new dating results indicate that the sequence is older than ~200 000 years and place San Quirce Level III within marine isotope stages (MIS) 8 and 7, between 274 ± 13 ka and 238 ± 13 ka. The main lithic assemblage at San Quirce comes from Level III. The predominant tool types found in this level are hammerstones, manuports and flakes, with a small proportion of cores and a significant presence of denticulates. Adaptation to local environmental conditions resulted in distinctive cultural habits, which were embedded in the cultural tradition of hominins occupying the site during the final third of the Middle Pleistocene. San Quirce preserves a simple cultural tradition that was employed by local hominins to engage in a diverse array of activities, and highlights the cultural diversity that appears to have been a characteristic feature of the Lower to Middle Palaeolithic transition 300–200 ka.