分析周原全新世土壤剖面木炭屑与野火活动关系探索.docVIP

分析周原全新世土壤剖面木炭屑与野火活动论文摘要：　研究陕西周原全新世黄土剖面磁化率曲线、总有机碳曲线、木炭屑曲线和野火活动及其与生态演变的关系结果表明,马兰黄土堆积时期气候干旱,在当时半荒漠草原上当地时常有自然野火发生;全新世大暖时期(8500~3100aB.P)气候湿润,生物成壤作用强度大,呈现森林或森林草原自然景观,野火活动极少发生;先周人迁居到周原地区(3100aB.P)开始,人类用火及其放火烧荒开垦农田等活动,加之气候变得干旱,生物化学成壤作用减弱,致使生态环境发生重大变化,自然生态景观向半自然、半人工景观演替;1500aB.P开始可耕种土地几乎开垦殆尽,生态景观完全被人工农田生态景观所代替;而近几百年来随着密度和聚落的增加,人类生活用火和垃圾随之加大,人类对土壤环境的干扰进一步增强。论文关键词：　野火　生态演替　全新世　关中盆地　木炭屑 　　Key ?words：　Wildfire,Change of ecology,Holocene,Guanzhong Basin,Charcoal 　　Abstract：The relationships among soil charcoal in Holocene,wildfire and its change of ecological environment were studied.The results show that in the phase of piling of Malan loess,the climate was arid and wildfire often occurred onsemi-desert grassland.During the period of soil formation,bio-pedogenic processes were so active that forests or forest-grassland formed with the arrival of humid warmer climate of the Holocene Megathermal.Therefore,the wildfire activitiesseldom occurred.However,by the time of 3100aB.P,with the settlement of Zhouyuan people and human manipulation ofthe environment through the use of the fire,great changes had taken place,varying from natural ecology to semi-naturaland semi-artificial ecology.Since 1500aB.P,the arable farmland almost disappeared,resulting in artificial ecology in placeof natural ecology.For hundreds of years,with the growth of the world population,tremendous requirements of fires hadincreased with a large amount production of rubbish and human activities had also caused great damage to the soil environ-ment. 　　野火普遍存在于自然界中[1],它既直接影响生态环境结构和功能的演替,又维持并促进生态环境平衡[2]。目前许多科学家利用记录、现代火记录、火疤木研究以及沉积物中孢粉、炭屑分析等方法,试图恢复过去野火发生的过程。但文献资料和火疤木时间跨度较短,难以用于探讨更长尺度的生态环境演变和气候动态变化。反映火灾历史时木炭屑记录要求对完整剖面的沉积物连续取样,以避免多次火灾事件的木炭屑混在一起或某些火灾事件被忽略掉,利用沉积物木炭屑分析探讨长期区域野火活动对生态环境的影响有其独特优势。本研究选择黄土高原南部关中盆地周原扶风地区典型剖面木炭屑、磁化率和总有机碳等多项指标,探讨了全新世野火活动与生态环境演变的关系。 　　1　研究区域概况与研究方法 　　周原扶风地区位于黄土高原南部、关中盆地西部,研究区匠阳村剖面位于扶风县北台塬面上,海拔高度685m,出露于约4~5m高的陡坎,临近先周歧邑遗址外围。该剖面黄土-古土壤序列发育完整连续且层位稳定,界限分明,结合野外观察记录和实验室内分析,可将本剖面全新世地层划分为0~40cm现代表土层(MS)、40~80c