陇中黄土高原近3万年以来孢粉记录的植被与气候变化研究

The Middle Gansu of Loess Plateau is located at hilly and gully region of west of the Liupan Mountain, which the ecological environment is very fragile. It is one of the sensitive areas of Asian monsoon climate. Recently, in this region, a deposition sequence of Alluvial-Lacustrine-Aeolian loess that formed in late Quaternary has been found. This sequence, because of its higher deposition rate, clear bedding, continuous deposition, and abundant dating material, will take a good advantage to study the high resolution climate change and abrupt climatic events since the last Quaternary. This project, based on the study of the relationship between surface pollen and vegetation types, will focus on the pollen and other’s indexes study on representative stratigraphic section of this sequence, reconstruct the evolutionary of paleovegetation and paleoclimate during the last 30000 years, then provide a longer high resolution biological climate evolution sequence for the environmental change. In order to reveal the regional climate change characteristics of the MIS - 2 stages and the Holocene in the study area, and compared with the relevant research results of adjacent area and The global, discuss the similarities and differences and the reasons. This work not only can provide scientific basis for strategic plan for restoration and management of ecological environment in the core area of the national ecological security of the Loess Plateau currently, but also have a great significance to further study on response mechanism of regional vegetation to global climate change and forecast of future climate and environment change.

陇中黄土高原地处六盘山以西的黄土丘陵沟壑区，生态环境极为脆弱，是季风气候和全球变化的敏感区之一。近年来在该区发现一系列第四纪晚期以来形成的河流-湖沼-风成黄土沉积序列，这些地层沉积速率较高且层理清晰、沉积连续，测年材料较为丰富，为我们通过高分辨率研究进一步探讨晚第四纪以来的气候环境变化规律及突发气候事件提供了良好有利条件。本项目将在表土孢粉与植被数量关系研究的基础上，重点对该区的代表性地层剖面进行高分辨率的孢粉及其它代用指标研究，重建该区近3万年以来的古植被及古气候演化历史，为区域环境变化研究提供一个较长的高分辨率生物气候演化序列。以此揭示研究区MIS-2阶段及全新世的区域气候变化特征，并与邻近区域及全球有关研究成果进行对比，探讨其异同点及其形成原因。这不仅可为当前黄土高原国家生态安全核心地区生态环境修复治理的战略部署提供科学依据，而且对进一步深入探讨区域植被对全球气候变化的响应机制、预测未来气候环境变化趋势具有重要意义。

陇中黄土高原地处六盘山以西的黄土丘陵沟壑区，生态环境极为脆弱，是季风气候和全球变化的敏感区之一。末次冰盛期以来，地球系统经历了一次从冷到暖完整的气候旋回，是过去全球变化研究的一个重要时段。本项目重点基于23个14C年龄及其校正年代建立的年表，对陇中黄土高原硝沟（XG）剖面的冲积-湖积-风成黄土序列的1343个粒度样品、893个TOC样品和711个花粉样品进行了高分辨率多指标对比分析，不仅重建了该区末次冰盛期以来的古植被演替及古气候演化历史，揭示了近3万年以来发生的主要古气候事件，而且探讨了区域气候变化的周期性及可能机制。取得的主要成果：（1）高分辨率花粉记录研究表明，末次冰盛期以来该区的植被演替过程为：荒漠草原（寒冷的盛冰期）→针叶疏林/森林草原（逐渐增温的冰消期）→针阔叶混交林为主的森林草原→针阔叶混交林（温暖的盛间冰期）→针叶疏林草原→干草原/荒漠草原；相应的气候演化过程为：冷干→较温湿→较暖湿→暖湿→温凉偏干→较冷干。（2）高分辨率花粉、粒度及TOC指标不仅记录了北大西洋地区所报道的近3万年来的主要气候事件，而且在千年和百年尺度上揭示出许多剧烈的高频气候振荡。总体来看，末次冰盛期是一个相当干燥寒冷的时期；冰消期是一个逐渐变湿变暖的时期；全新世可分为3个阶段：早期（~11.5 - 6.7 cal. ka BP）最温暖湿润，中期（~6.7 - 3.0 cal. ka BP）急剧降温变干，晚期（~3.0 cal. ka BP以来）最寒冷干燥。H3、H2、H1、YD及全新世系列冷干气候事件等叠加在上述气候变化的总体趋势之上。（3）对该序列花粉总浓度的小波分析结果显示出5个显著的准周期：~5500a、~2200a、~900a、~380a及~210a；对比分析表明，除~5500a准周期与大西洋经向翻转环流有关外，其它4个准周期均与太阳活动有间接的因果关系。该研究不仅可为当前黄土高原生态环境修复治理的战略部署提供科学依据，而且对进一步深入探讨区域植被对全球气候变化的响应机制、预测未来气候环境变化趋势具有重要意义。