西天山南坡表土花粉分析

Pollen in surface soil at the southern slope of western Tianshan, China

通过对西天山南坡不同植被带52个表土花粉样品的鉴定,研究表土花粉组合与现代植被分布的关系,分析蒿属/藜科比值(A/C)在该区域的指示意义.结果表明:山顶至山底可以划分为5个植被带,分别为高山荒漠带、高山草甸带、草甸草原带、山地荒漠带、典型荒漠带,代表性科属为蒿属、藜科、禾本科和麻黄属,该区域不同植被类型表土样品花粉组合差异明显.西天山南坡表土花粉在一定程度上受到北坡的影响,海拔越高影响越大.A/C值随海拔升高而先升高再降低,在高山草甸区域达到最高,可以作为反映山地垂直方向气候干湿变化的有效指标.由于A/C值波动较大,利用该比值进行气候环境重建时,需注意受人类活动等因素影响所产生的高值可能带来误判.

We analyzed 52 pollen samples of surface soils from the southern slope of western Tian-shan, China, to understand the relationship between the surface pollen and modern vegetation, and the significance of the Artemisia/Chenopodiaceae(A/C). The results showed that there were five vegetation zones from the mountain top to the foot, i.e., alpine desert zone, alpine meadow zone, meadow and steppe zone, mountain desert zone, and typical desert zone. The typical taxa were Artemisia, Chenopodiaceae, Poaceae and Ephedra. The surface pollen assemblages greatly differed across different vegetation zones in this area. Surface pollen in the southern slope of the western Tianshan Mountains was affected by the northern slope, with the impacts increasing with the increases of altitude. The A/C increased with altitude, peaked in the alpine meadow zone, and then decreased, which could effectively indicate the vertical moisture change. Given the great fluctuation of A/C value, when using this ratio to reconstruct climate and environment, attention should be paid to the fact that high values caused by human activities and other factors may lead to misjudgments.