人类起源及演化与地球系统环境演化相互关联的科学研究不仅是传统第四纪研究的关键内容之一,也是当今宜居地球研究的首要问题。文章回顾了黄土高原及邻近地区第四纪地层中发现的重要古人类遗存(包括古人类化石和旧石器)的主要成就,阐述了前人提出的“黄土石器工业”和“黄土地质考古带”研究思路的萌生和发展历程,介绍了学者们运用黄土-古土壤序列对第四纪不同类型沉积物中埋藏的古人类遗存研究的概况。在此基础上,根据前人的大量资料以及笔者自身数十年积累的第一手调查研究数据,提出了一种新的科学思路:针对“全球变化”研究中的薄弱环节,运用独一无二的中国黄土连续序列的“地圈”优势,去寻找“生物圈”古人类活动的连续“序列性”踪迹,研究古气候古环境演化对古人类生存环境的制约及其反馈等重大科学问题。以新的思路和科学问题为宗旨,运用黄土-古土壤序列标准年代框架标尺,以蓝田地区上陈、公王岭、陈家窝、吉家湾-甘峪-刁寨剖面的含石器或古人类化石的26个黄土-古土壤组合旋回(其中包括21个古土壤层和15个黄土层)为基础数据,初步构建了一个年代大约2.12~0.01 Ma B. P.的较高分辨率的古人类古文化演化序列——“黄土-古土壤-古人类遗存序列”框架,期望为人类演化和黄土环境研究拓展新路。
Climate change brings new challenges to the sustainable development of agriculture in the new era.Accurately grasping the patterns of climate change impacts on agricultural systems is crucial for ensuring agricultural sustainability and food security.Taking the Loess Plateau(LP),China as an example,this study used a coupling coordination degree model and spatial autocorrelation analysis to portray the spatial and temporal features of crop-cropland coupling relationship from 2000 to 2020 and explored the impact law of climate change through geographically and temporally weighted regression(GTWR).The results were as follows:1)the crop-cropland coupling coordination degree of the LP showed a gradual upward trend from 2000 to 2020,forming a spatial pattern with lower values in the central region and higher values in the surrounding areas.2)There was a positive correlation in the spatial distribution of cropcropland coupling coordination degree in the LP from 2000 to 2020,and the high value-low value(H-L)and low value-low value(L-L)agglomerations continued to expand eastward,while the spatial and temporal evolution of the high value-high value(H-H)and low value-high value(L-H)agglomerations was not obvious.3)The impacts of climatic elements on crop-cropland coupling coordination degree in the LP showed strong heterogeneity in time scales.The inhibitory impacts of summer days(SU)and frost days(FD)accounted for a higher proportion,while the annual average temperature(TEM)had both promoting and inhibiting impacts.The impacts proportion and intensity of extreme heavy precipitation day(R25),continuous drought days(CDD),and annual precipitation(PRE)all experienced significant changes.4)In space,the impacts of SU and FD on the crop-cropland coupling coordination degree varied with latitude and altitude.The adaptability of the LP to R25 gradually strengthened,and the extensions of CDD and increase of PRE led to the increasing inhibition beyond the eastern region of LP,and TEM showed a promoting impact in the Fenwei Plain.As a
Check dams are widely constructed on China's Loess Plateau,which had a total number of 58,776 by the end of 2019.Great achievements in check dam construction have been gained regarding the economic and environmental impacts.This study reviews the remarkable benefits of check dams on the land reclamation and environmental improvement on the Loess Plateau,and sediment reduction entering the Yellow River.However,the flood incidents on check dams have been frequently reported for the past decades,which has attracted more attention in the context of climate change and extreme rainfall events recently.Advances in the flood migration techniques achieved by the research group led by the first author have been highlighted to migrate the breach risk of check dams due to floods.The“family tree method”has been proposed to determine the survival status and critical rainfall threshold of each check dam in the complicated dam system.An updated dam breach flood evaluation framework and the corresponding numerical algorithm(i.e.,DB-IWHR)have been developed.Moreover,innovative types of water-release facilities for check dams,including geobag stepped spillway and prestressed concrete cylinder pipe in the underlying conduit,have been proposed and developed.Finally,the perspectives concerning the check dam construction on the Loess Plateau have been put forward.
