青藏高原北部孢粉记录的全新世以来环境变化

根据青藏高原北部同纬度地区,同一个垂直自然带内的西藏羊湖的湖相沉积、青海昆仑河河流相沉积、青海豆错(苦海)湖的湖相沉积记录的全新世以来孢粉(spore-pollen)资料的对比分析,表明:①极度干旱荒漠区的代表植被麻黄属(Ephedra)花粉平均百分含量,三个地区分别为:7.7%,4.2%,7.5%,总体上,羊湖地区的数值高于昆仑河地区与苦海地区。②代表气候湿润的禾本科(Gram ineae)花粉平均百分含量,三个地区分别为:1.2%、4.9%、12.0%,从西向东数值逐渐升高。③代表气候湿润的蒿属(Artem isia)花粉平均百分含量,三个地区分别为:22.2%,43.6%,48.8%,从西向东数值逐渐升高。④代表气候干旱的藜科(Chenopod iaceae)花粉平均百分含量,三个地区分别为:52.1%,42.4%,11.5%,从西向东数值逐渐降低。⑤依据蒿属、藜科花粉百分含量,计算出环境变化指标,蒿属/藜科(A/C)值,三个地区的平均值分别为:0.45,1.23,5.59,从西向东比值逐渐升高,⑥麻黄属/蒿属值,在全新世晚期,三个地区都呈上升趋势,但幅度存在差异,分别为:0.45,0.34,0.28,从西向东数值逐渐降低。综观上述6个方面的变化规律,青藏高原北部全新世以来,干旱的程度从西向东逐渐降低;对青藏高原北部东西方向现今植被和环境的实际考察并结合上述变化规律,未来高原北部干旱变化的趋势将继续由西向东推移。

Holocene environmental changes of northern Qinghai-Tibetan Plateau based on spore-pollen analysis

Based on the contrastive analysis of spore-pollen data since Holocene,recorded in the same latitude and vertical natural zones: Yang Lake deposition,Tibetan Autonomous Region,Kunlun Rive deposition and Doucuo(Kuhai) Lake deposition,Qinghai Province.The results in these three regions have been given that(1)Ephedra,as dry and desert vegetation,the average percents are 7.7 in Yang Lake,4.2 in Kunlun Rive,7.5 in Doucuo(Kuhai) Lake,and the datum in Yang Lake is higher than others;(2)Gramineae,as humid vegetation,the average percents are 1.2 in Yang Lake,4.9 in Kunlun Rive,12.0 in Kuhai Lake,increasing gradually from west to east;(3)Artemisia,as humid vegetation,the average percents are 22.2 in Yang Lake,43.6 in Kunlun Rive,48.8 in Kuhai Lake,increasing gradually from west to east,too;(4)Chenopodiaceae,as dry vegetation,the average percents are 52.1 in Yang Lake,42.4 in Kunlun Rive,11.5 in Kuhai Lake,however,decreasing gradually from west to east;(5)Artemisia/Chenopodiaceae(A/C),the average data,as environmental changing index,are 0.45 in Yang Lake,1.23 in Kunlun Rive,5.59 in Kuhai Lake,increasing gradually from west to east,and there is higher data scope during 3.0~4.3 ka BP in these two lake sediment profiles,then decreasing;(6)Ephedra/ Artemisia,data are all increased,but the amplitude is different,such as 0.45 in Yang Lake,0.34 in Kunlun Rive,0.28 in Kuhai Lake,decreasing gradually from west to east.These Characteristics have indicated that the dry level decreased gradually from west to east and its evolving tendency is still from west to east including a short wet period,in the northern of Qinghai-Tibetan Plateau since Holocene,after reconstructing from spore-pollen data of Paleovegetation and Paleoenvironment.