The Mid-Pleistocene Climate Transition Recorded in a 1.6 Myr-Period Lacustrine Sediment Sequence from Mazatage, Tarim Basin

The mid-Pleistocene climate transition （MPT） has been widely reported in worldwide geological events. As a key issue of the Quaternary geology, it has attracted much attention from the paleoclimate community. MPT refers to a period lasting for several hundreds of thousand years, during which the dominant climate periodicity gradually extended from 41 kyr to 100 kyr （Ruddiman et al., 1989）,

Climate Transition Risk and Development Finance： A Carbon Risk Assessment of China＇s Overseas Energy Portfolios

The role of development finance institutions in low-income and emerging countries is fundamental to provide long-term capital for investments in climate mitigation and adaptation. Nevertheless, development finance institutions still lack sound and transparent metrics to assess their projects＇ exposure to climate risks and their impact on global climate action. To attempt to fill this gap, we develop a novel climate stress-test methodology for portfolios of loans to energy infrastructure projects. We apply the methodology to the portfolios of overseas energy projects of two main Chinese policy banks. We estimate their exposure to economic and financial shocks that would result in government inability to introduce timely 2~C-aligned climate policies and from investors＂ inability to adapt their business to the changing climate and policy environment. We find that the negative shocks are mostly concentrated on coal and oil projects and vary across regions from 4.2 to 22 percent of the total loan value. Given the current leverage of Chinese policy banks, these losses could induce severe financial distress, with implications on

Clay mineral assemblages of the oceanic red beds in the northern South China Sea and their responses to the Middle Miocene Climate Transition

The Middle Miocene Climate Transition(MMCT,~14 Ma)is the largest cooling event in the Cenozoic“Coolhouse”,which significantly impacts the global chemical weathering pattern.In this paper,the responses of the MMCT global cooling event in the deep South China Sea were studied by clay mineral assemblages analysis of the oceanic red beds(ORB)at International Ocean Discovery Program(IODP)Expedition 368 Site U1502.The results show that the clay mineral assemblages of the ORB at Site U1502 are mainly composed of smectite(56–88%),illite(7–29%),and kaolinite(6–20%),without chlorite.The contents of these clay minerals and illite crystallinity show a four-stage variation pattern during early-middle Miocene(22.8–10.8 Ma).Smectite decreased from average 81%during 22.8–16.2 Ma and 16.2–14.4 Ma to average 67%during 13.8–10.8 Ma,with a rapid decrease of~14%during 14.4–13.8 Ma.On the contrary,illite and kaolinite increased rapidly by~8%and~6%,respectively,during 14.4–13.8 Ma.Illite crystallinity increased from average 0.18°Δ2θduring 22.8–16.2 Ma to average 0.19°Δ2θduring 16.2–14.4 Ma,and then decreased rapidly by~0.02°Δ2θduring 14.4–13.8 Ma.The provenance analysis of clay minerals shows that illite and kaolinite mainly originated from South China landmass due to physical erosion,while smectite mainly came from the Luzon arc as the product of chemical weathering.Therefore,smectite/illite ratio and illite crystallinity are used as proxies of chemical weathering intensity in the early-middle Miocene.High values of the ratio and the crystallinity represent the enhanced chemical weathering,whereas low values indicate the weakened chemical weathering or the strengthened physical erosion process.The smectite/illite ratio and illite crystallinity both decreased rapidly during 14.4–13.8 Ma,indicating the chemical weathering in the surrounding area of the South China Sea weakened rapidly,which we believe is the result of the MMCT event forcing.In addition,their values increased slightly during 16.2–14.4 Ma,which is in response to the relatively enhanced chemical weathering during the Middle Miocene Climate Optimum(MMCO).The variation pattern of clay mineral assemblages of the early-middle Miocene ORB in the South China Sea and its rapid transformation during the MMCT reveal that the Cenozoic cooling played a specific role in controlling the chemical weathering of the Earth’s surface.

评估全球自然对人类的贡献

自然对人类的贡献(nature’s contributions to people,NCP)是指大自然对人类生活质量的一切积极贡献和消极影响,分为10个调节型NCP、4个物质型NCP和4个非物质型NCP.但目前这些NCP的全球时空分布及其相互作用规律尚不清楚,直接制约了加强自然界多种有益贡献的生态系统管理实践.本研究构建基于指标体系的评价方法,结合生态系统演变、气候变化与人类活动全球尺度多源空间数据集,在全球范围内对1990~2018年所有18个NCPs进行空间制图,在15,204个流域单元上识别主导了NCP组合,并基于NCPs时空特征识别了全球景观变化的功能权衡关系和景观多功能性.结果表明,全球大部分NCPs的高值仅在局地出现.1992~2018年,6个调节型NCP、3个物质型NCP和2个非物质型NCP下降.29种调节型和物质型NCP组合(总共有54种组合)的主导流域占全球76%的陆地面积,而无NCP主导的流域占全球陆地面积的22%.NCPs变化的协同关系比权衡关系更为常见,但调节型和物质型NCP之间的关系普遍处于权衡状态.过渡气候地区的NCP相对少,并具有强烈的权衡关系;而低纬度地区NCPs之间的高度协同关系可能受到未来气候变化的影响.研究结果提供了对全球NCP空间变化规律的总体认知,可用于科学支撑区域景观功能的关系调控和景观多功能性提升,以增强全球人类福祉.

Effects of fire and nitrogen addition on photosynthesis and growth of three dominant understory plant species in a temperate forest

Aims Fire and atmospheric nitrogen(N)deposition have the potential to influence growth and productivity of forest canopy.However,their impacts on photosynthesis and growth traits of understory plants in forests remain largely unexplored.This study was conducted to examine the effects of burning and N addition on foliar N content,net photosynthesis and growth traits of three dominant shrub species(Vitex negundo,Lindera glauca and Symplocos chinensis)in a temperate forest in Central China.Methods The experiment used a pair-nested design,with four treatments(control,burning,N addition and burning plus N addition)and five replicates.Leaf mass area(LMA),area-based concentrations of foliar N and chlorophyll(N_(area) and Chl_(area)),net photosynthesis(A_(n)),stomatal conductance(g_(s)),maximum photosynthetic rate(A_(max))and maximal carboxylation rate(V_(cmax)),basal diameter,height and branch length(BL)of the three species were measured.Important Findings Across the three species,burning stimulated LMA,N_(area),Chl_(area),A_(n),g_(s),A_(max) and V_(cmax),and consequently enhanced basal diam-eter,height and BL.Nitrogen addition increased A_(n) and gs but did not affect LMA,N_(area),Chl_(area),A_(max),V_(cmax),basal diameter,height or BL.However,N addition strengthened the positive effects of burning on g_(s),V_(cmax),A_(n) and BL.The findings indicate the primary role of light resources in determining plant photosynthesis and growth of understory shrub species after fire and highlight that understory plants should be considered in projection of biomass accumulation and productivity of forests under environmental perturbations.

Clay minerals in the Pliocene-Quaternary sediments of the southern Yangtze coast, China: Sediment sources and palaeoclimate implications

Clay mineralogy was used as an indicator of the sediment source and prevailing climate and five suites （I-V） were identified throughout the borehole. Smectite was dominant in the bottom suite of the borehole, indicating the sediment was mainly derived from the local basalt when the study area stood as uplands during the Pliocene. The sharp reduction of smectite in suites II and III （Early Pleistocene） reflects a broader sediment provenance due to neo-tectonic subsidence of the study area. Significant climate fluctuations are indicated by distinct variations in the ratios of illite versus smectite and kaolinite, and by the illite crystallinity in suites II and IV. Especially the suite IV, which forms mottled muddy sediments that underwent pedogenesis, possibly represents glacial/interglacial cycles during the Mid-Pleistocene climate transition （MPT）. The rare presence of smectite in suite V which formed during the Late Quaternary suggests a significant contribution of fine-grained sediment derived from the upstream of the Yangtze catchment. Such changes in sediment sources are consistent with the evolution of regional sedimentary environments, which evolved towards an open coast/ deltaic setting and imply that the study area became the depositional basin of the Yangtze fine-grained sediment due to the final submergence of the Wu-Nan-Sha and Fukien-Reinan Massifs since the Late Quaternary.