陕北气候变化与生态植被变迁

分析了128万年以来陕北气候变化及其生态植被变迁。结果表明，陕北黄土高原气候经历了多次冷、暖、干、湿的周期变化。陕北植被变迁在地质时期以及历史时期早期，主要由气候条件所控制，植被类型随气候的冷暖干湿变化而变迁。随着人类活动的加剧，气候条件不再是影响植被变迁的唯一因素，人类活动对植被的影响愈来愈明显。明清时期，气候冷干，旱灾频繁．陕北生态环境脆弱，大规模垦殖和滥烧使自然植被迅速减少，陕北自然植被遭到毁灭性破坏。20世纪50年代，陕北逐步开始生态环境治理，在对生态环境治理的同时，又对部分地区自然植被进行破坏。20世纪80年代以后，生态环境总体上趋于好转。

Climate and vegetation change in the north of Shaanxi Province

The climate and vegetation change in the north of Shaanxi Province during the past 1.28 million years was analyzed in this paper.The results showed that the climate in the north of Shaanxi had changed periodically with the succession of cold,warm,dry and wet.During the early geological and historic stage,it was the climate that mainly influenced the change of the vegetation in the north of Shaanxi.Along with the development of human activity,the climate was no longer the only element influencing the vegetation,while the human activity had played a more and more important role in the vegetation change.During the Ming and Qing dynasties,the ecological environment in the north of Shaanxi became vulnerable due to the dry and cold climate.The vegetation reduced sharply because the excessive reclamation and burning and the ecosystem in the north of Shaanxi was destroyed seriously.Since 1950s,protective measures had been implemented in this area.Though there still existed some deforestation phenomena,the ecological environment in the north of Shaanxi has been gradually improved since the 1980s.