定西鲁家沟全新世以来的气候变迁及人地关系演化研究

Climatic variations and human activities in Lujiagou,Dingxi Region over the past 11200 yesrs

根据鲁家沟黄土剖面粒度、磁化率、有机质和碳酸盐含量等气候代用指标的变化和14C测年结果,分析和讨论了该区全新世以来的气候演化的过程。结果表明:11.2calk aB.P.以来的气候可划分为3个阶段:1)全新世早期(11200-7560cal aB.P.),气候开始转暖转湿,但整体上较为寒冷;2)全新世中期(7560-3600cal aB.P.),气候温暖湿润;3)全新世晚期(3600-1167cal aB.P.),气候变得干旱,夏季风强烈减退。该区全新世以来的气候变化是不稳定的,存在频繁的次级波动。大约从7800cal ka B.P.开始定西地区就有人类活动。在6000cal a B.P.左右温暖湿润的气候可能为古人类的生存和发展提供了优越的自然条件,人类活动范围扩大。由于当时生产力水平低下,人类也只是在居住地附近垦殖耕种。因此,人类活动并没有对环境产生明显影响。晚全新世以来,气候总体向干旱化发展的同时,叠加了人类活动的影响。尤其是唐宋以来,人类不合理的开垦土地、滥垦滥伐,使大面积的天然植被不复存在,致使生态环境不断遭到破坏,导致气候环境亦不断恶化。人类活动对气候环境变化的影响程度大大超过了气候环境自身由于自然原因而产生的变化。

The paleoenvironment was established by analysis of grain size、magnetic susceptibility、organic matter and carbonate content of the sediments at Lujiagou section,Dingxi in Gansu province and 14C dating.The results showed that climatic changes in the past 11200cal aB.P.implicated by climatic indexes from the section were instable in this area and could be divided into three periods：the early Holocene（11200-7560cal aB.P.）,the summer monsoon was strengthening,the climate was becoming warmer and wetter;a warm and wet climate dominated the middle Holocene（7560-3600cal aB.P.）;during the late Holocene（3600-1167cal aB.P.）,the climate became drier and cooler,the dust-fall was strengthening.We also discussed relationships of environmental changes and human activities,especially late Holocene.Beginning of the late Holocene before,the impact of human activities on environment was very weak.Since Tang and Song dynastics,the drying climate and the impact of the human activities during the historical periods could not be separated,the ecological environment in Dongxi region was aggravated.Environmental degeneration was the result of the natural law and the impact of human activities piling on the natural law,but the impact of human activities on environmental changes was more than natural law.