Late Holocene monsoon climate as evidenced by proxy records from a lacustrine sediment sequence in western Guangdong,South China

The study of a 300-cm-thick exposed lacustrine sediment section in the Hedong village in Zhaoqing area which is located in sub-tropical west Guangdong Province in South China, demonstrates that the lacustrine sedimentary sequence possibly contains evidence for exploring variation of Asian monsoon climate. Multi-proxy records, including the humification intensity, total organic carbon, and grain size fractions, reveal a general trend towards dry and cold conditions in the late Holocene that this is because of a decrease in solar insolation on an orbital scale. Three intensified Asian summer monsoon (ASM) intervals (∼3300–3000 cal yr BP, ∼2600–1600 cal yr BP, and ∼900–600 cal yr BP), and three weakened ASM intervals (∼4000–3300 cal yr BP, ∼3000–2600 cal yr BP, and ∼1600–900 cal yr BP) are identified. Our humification record (HD_cal) shows a good correlation on multi-centennial scale with the tree ring Δ¹⁴C record, a proxy of solar activity. A spectral analysis of HD_cal reveals four significant cycles, i.e., ∼1250 yr, 300 yr, 110 yr, and 70 yr, and most of these cycles are related to the solar activity. Our findings indicate that solar output and oceanic–atmospheric circulation probably have influenced the late Holocene climate variability in the study region.     

Stratigraphy and facies development of the marine Late Devonian near the Boulongour Reservoir,northwest Xinjiang,China

Late Devonian to Early Carboniferous stratigraphic units within the ‘Zhulumute’ Formation, Hongguleleng Formation (stratotype), ‘Hebukehe’ Formation and the Heishantou Formation near the Boulongour Reservoir in northwestern Xinjiang are fossil-rich. The Hongguleleng and ‘Hebukehe’ formations are biostratigraphically well constrained by microfossils from the latest Frasnian linguiformis to mid-Famennian trachytera conodont biozones. The Hongguleleng Formation (96.8 m) is characterized by bioclastic argillaceous limestones and marls (the dominant facies) intercalated with green spiculitic calcareous shales. It yields abundant and highly diverse faunas of bryozoans, brachiopods and crinoids with subordinate solitary rugose corals, ostracods, trilobites, conodonts and other fish teeth. The succeeding ‘Hebukehe’ Formation (95.7 m) consists of siltstones, mudstones, arenites and intervals of bioclastic limestone (e.g. ‘Blastoid Hill’) and cherts with radiolarians. A diverse ichnofauna, phacopid trilobites, echinoderms (crinoids and blastoids) together with brachiopods, ostracods, bryozoans and rare cephalopods have been collected from this interval. Analysis of geochemical data, microfacies and especially the distribution of marine organisms, which are not described in detail here, but used for facies analysis, indicate a deepening of the depositional environment at the Boulongour Reservoir section. Results presented here concern mainly the sedimentological and stratigraphical context of the investigated section. Additionally, one Late Devonian palaeo-oceanic and biotic event, the Upper Kellwasser Event is recognized near the section base.     

Mobilization and redistribution of elements in soils developed from extreme weathering basalt on Hainan Island

Major, trace and organic elements of a South China were reported to investigate elements laterite profile developed on Neogene basalt on Hainan Island, mobilization and redistribution in tropical regions. The results indicate that strong acid environment and organic matter （OM） can remarkably improve the transfer of insoluble elements. Among all the elements, Th is the least mobile. As for the general conservative elements during incipient chemical weathering, such as Ti, Zr, Hf and Nb, the removals are up to 30%-40% in the upper profile. And for Fe, A1, Cu and Ni, that tend to be combined with secondary minerals and to be retained in temperate zone, they are re- moved from the upper profile, transferred downwards, and then precipitated in the lower profile. In addition, atmos- pheric inputs, including sea salt aerosols and dust, have a profound effect on the budgets of elements that are susceptible to leaching losses （e.g. K, Na and Sr）. Excluding the possibilities of groundwater and erosion, the remarkable increase of K, Na and Sr concentrations in the upper profile, together with dramatically upward increasing trends of the percentage changes of Sr/Th, K/Th and Na/Th ratios, show that atmospheric inputs, especially sea salt aerosols, contribute much extraneous seawater derived elements, such as K, Na and Sr to the soils. The overall elemental be- haviors in this profile suggest that organic matter and atmospheric inputs play a very important role in the mobiliza- tion and redistribution of elements during extreme weathering in tropical regions.     

论气候变暖背景下干旱和干旱灾害风险特征与管理策略简

The drought is a most severe natural disaster worldwide, which leads to great risk in human being. The drought disaster and risk have more prominent because of obvious climatic warming in the last hundred years. At present, the understanding of the internal laws of the occurrence of drought and drought risk is not comprehensive, and the recognition of the characteristics of the drought and drought risk under climatic warming is obscure. In this paper, we summarized systematically the domestic and overseas research progress of the drought and drought disaster risk, introduced the principle of the drought disaster transfer process and the essential features of drought disaster, analyzed synthetically the main characteristics and interactions among the key factors of the drought disaster risk, discussed the effect of climatic warming on drought and drought disaster risk, and probed into the basic requirement of drought disaster risk management. Above all, we provide the main protective measurements of the drought disaster and the main strategy of drought disaster risk management.     

陆生植物氮同位素组成与气候环境变化研究进展

近年来,由于植物氮同位素组成(δ15N)记载了气候环境变化的信息,因而被广泛应用于全球变化研究中,成为古气候环境再造和了解现代气候环境变化信息的有力工具。然而,人们对气候环境引起的δ15N变化及其指示的气候环境意义并不完全清楚,这就有可能限制植物δ15N在古气候环境变化等领域研究中的应用。在概述植物氮同位素分馏和植物不同氮源的氮同位素分布的基础上,分析了温度、降水、大气CO2浓度和海拔高度等气候环境因子对陆生植物δ15N的影响以及它们的关系。指出了目前研究中存在的问题及其研究前景,认为在全球变化研究中利用植物氮同位素技术不仅可以重建古气候环境(如重建大气CO2浓度变化),揭示历史时期温度、降水的变化,而且还可以在一定的时间和空间上综合反映生态系统氮循环的特征。     

Research Progress in Responses of Modern Terrestrial Plant Carbon Isotope Composition to Climate Change

Global climate change has been one of the most concerned environmental problems in the world since the 1980s. Since stable carbon composition (¹³C) in plant tissues can record abundant information on climate changes, it has been widely used as an important climate proxy in global change studies and becomes a powerful tool for obtaining paleoclimate information, understanding paleoenvironment reconstruction and modern climate change, and predicting future climate trends. However, a lot of potential uncertainties have always involved in the reconstruction of paleoclimate and paleoenvironment by carbon isotope of the past period sediment or fossils. Among them, the most dominant uncertainty is due to our poor understanding of the relations between carbon isotope ratios of plants and climatic factors and the climatic and environmental significance indicated by modern plant ¹³C. This may limit the application of plant ¹³C in the study of climatic and environmental changes. Based on the Summary of plant ¹³C fractionation and carbon isotope distribution of different photosynthetic plants, the effects of environmental factors, e.g., temperature, precipitation, atmospheric CO₂ concentration, and altitude on terrestrial plant ¹³C and their relationships were reviewed in this paper, and the response mechanism of plant ¹³C to climate changes were also analyzed. Furthermore, the current existing problems and the future prospects in carbon isotope study were discussed. It is pointed out that strengthening some studies such as the response of C₄ plants ¹³C to climate environmental parameters, the transformation relation of different scale plant ¹³C, intersection and permeation of related disciplines, and various proxies and scientific method, will undoubtedly make us have a more accurate understanding of the climate history and eventually broaden the development of the field during the process of global change study by plant carbon isotope techniques.     

雅鲁藏布江流域降水时空变化特征

雅鲁藏布江流域是全球气候变化的敏感区,该流域降水变化对青藏高原的水系统、生态系统和山地灾害系统的演变具有重要影响。本文通过流域水文分析,将雅鲁藏布江流域的三大水资源区细分为9个分区。基于雅鲁藏布江流域1979—2018年降水数据,综合分析了雅鲁藏布江流域及9个分区的年、干湿季、月降水量以及日、小时尺度极端降水的时空变化特征,探讨了降水和典型大尺度大气环流因子的相关性。结果表明：① 1979—2018年间,在流域尺度上,各时间尺度降水整体上均呈上升趋势。其中,年降水量上升趋势最大,为2.5 mm·a^-1;年、干湿季降水量以及典型小时尺度极端降水（Rx3hour、Rx12hour）均在95%信度水平下显著上升。在水资源分区尺度上,各分区不同时间尺度降水的变化趋势呈现更明显的非一致性,所有分区除小时尺度极端降水均呈上升趋势外,其余时间尺度降水的趋势变化方向各异。② 雅鲁藏布江流域降水存在明显的空间分异性,且降水空间分异性会随着降水指标时间尺度的缩短而增强。各时间尺度降水整体上均呈现出自东部向西部逐渐减少的趋势,流域东南部（分区Ⅲ-2）始终是高值中心,流域中西部（分区Ⅰ-2、Ⅱ-1）存在区域性高值中心。③ 北半球副热带高压和北半球极涡对雅鲁藏布江流域降水变化具有显著影响。研究结果有助于掌握当地降水的多尺度变化特征,可为雅鲁藏布江流域和青藏高原地区的水循环研究、水资源开发利用和山洪灾害防治等提供科学基础。     

尺度转换视角下易武斗茶会的构建与变迁

选取易武斗茶会为研究案例,以尺度转换为理论分析工具,通过参与式观察法和半结构化访谈法,深入分析易武斗茶会的发展历程并展示推动其发展演变的多元社会主体的不同行动与实践。研究发现：① 易武斗茶会的演变过程中存在2种尺度转换的方式,一种是为迎合普洱茶市场细分而进行的尺度下推,另一种是根据地方发展需求而进行的尺度上推。② 易武斗茶会尺度转换是在地方政府的推动、茶企的支持、茶农的配合以及茶客的偏好下共同驱动的。③ 多元主体的行动在推动易武斗茶会尺度转换的过程中满足了各自群体的利益诉求,地方依凭茶叶经济实现了本土发展。从节事的角度对中国茶文化进行深入分析研究,为茶村如何通过地方性节事活动实现本土发展提供理论依据与案例借鉴。     

1637—1643年华北地区极端干旱事件中的粮食危机

粮食作为自然生态系统与社会经济系统的关联点,能够有效地揭示极端干旱事件对自然-经济-社会复合生态系统影响的过程和机理。以粮价异动为切入点,通过粮价通胀指数和“无透雨”的持续时间,分析农业旱情及其对粮食生产的影响,对1637—1643年华北地区极端干旱事件中的粮食安全进行深入剖析。结果显示:华北地区无透雨天数超过150 d,年降水量与5—9月降水量的距平值均≤-30%,水分异常短缺,土壤严重失墒,危及粮食生产安全。因此,降水量距平值≤-30%是华北地区粮食生产安全的临界阈值。此次极端干旱事件是历史同类事件之最,连续无透雨日数最长,地表径流枯竭记录最多,水资源的短缺导致伴生灾害相继发生,超过生态系统的忍耐极限,粮食生长期缩短,减产歉收,绝产绝收,粮食供给链条断裂。粮价通胀指数最低9.50,最高26.70;货币发行与粮食供给失衡,通货膨胀严重,粮价飞涨,市场倒闭,粮食安全体系崩塌,自然-经济-社会复合生态系统发生质变成为历史必然。     

我国东南沿海午后短时降水极端峰值强度与湿度和地表气温的关联

利用中国东南沿海地区55个站点的逐时降水、日平均地面温湿场、低空气温露点差及OISST海表温度资料,对午后短时降水的极端峰值强度与湿度和地表气温的关联进行分析。结果表明,东南沿海地区午后短时降水极端峰值强度随气温的变化趋势存在明显变化,日最高气温低于29℃时,峰值强度随气温升高而上升;日最高气温高于29℃时,峰值强度随气温升高而下降。分析水汽条件作用发现,峰值强度在高温条件下随气温的升高而下降的现象与相对湿度变化有关,日最高气温较高时,相对湿度随气温的升高而大幅减小。初步分析可知,当陆地达到较高温度并进一步增温时,附近海域海表温度变化不大,使得洋面水汽含量增加较少。在陆地水汽主要来自于海洋的情况下,伴随陆地的进一步升温,地表相对湿度将减小。