新疆天山南坡吐鲁番地区表土花粉的初步研究

Preliminary study on pollen distribution in the surface soil of the Turpan region in the southern slope of Tianshan Mountains,Xinjiang,China

基于对新疆天山东段南坡吐鲁番地区选取的一条沿着海拔高度从2 000––154 m的不同植被带的植物群落样方进行的调查及相应排序分析,结合所采集的36个现代表土花粉样品的孢粉组合图式,初步研究了吐鲁番地区的植被与表土花粉之间的对应关系,并将其与天山北坡的表土花粉谱进行了比较。结果表明吐鲁番地区表土花粉谱按照海拔高度自上至下可划分为4个孢粉组合带,分别对应于山地荒漠草原和荒漠带、戈壁砾石带、典型荒漠带以及盐沼植被带。与天山北坡的表土花粉垂直带谱相比,吐鲁番地区的花粉垂直带谱并不完整,缺少典型的森林和蒿属(Artemisia)荒漠孢粉带。即使在相似的孢粉带,吐鲁番地区的分布高度也高出北坡300 m左右。典型的乔木植物云杉属(Picea)、松属(Pinus)花粉在风力和水流的作用下,表现出明显的超代表性;用来指示干旱区半干旱区气候湿度变化的蒿属与藜科花粉的比值能大致反映出荒漠带的典型特征。此外,研究区内表土花粉组合与环境因子之间的排序分析结果表明,降水量是影响该区表土花粉组合的主要环境因子。与蒿属、藜科花粉相比,白刺属(Nitraria)花粉受降水量的影响较大。

Aims Our main purposes were to analyze the relationship between vegetation and pollen in the surface soil of the Turpan region,which is located in the southern slope of the eastern Tianshan Mountains,and to compare different pollen assemblages between the Turpan region and the northern slope of the Tianshan Mountains.Methods We collected 36 modern pollen samples and carried out modern vegetation survey in the Turpan region along an altitudinal gradient from 2 000 m to –154 m.Detrended correspondence analysis and Redundancy analysis were applied to analyze the distribution pattern of pollen in surface soils.Important findings We divided the pollen spectra into four pollen assemblage zones（mountain desert-steppe and desert,Gobi gravel,typical desert and salt mash vegetation）,corresponding to the major vegetation types in the Turpan region.When compared with the northern slope,the characteristics of pollen assemblages in the mountain desert-steppe and desert were similar to those in the forest-steppe on the northern slope of the Tianshan Mountains;the pollen assemblages in the Gobi gravel and the typical desert seemed to be more consistent with those in the typical desert on the northern slope;however,no analogue was found in the salt mash vegetation.Obviously,the vertical pollen spectra in Turpan region were incomplete,lacking typical forest and Artemisia desert pollen zones.Besides,similar pollen zones in the Turpan region were found at an elevation of about 300 m higher than those in the northern slope.It is remarkable that the typical tree pollen,such as Picea and Pinus,showed their extra representation in the Turpan region.On one hand,the valley forest on the southern slope of the Tianshan mountains played an important role in pollen dispersal.On the other hand,with the cold air on the northern slope over the Tianshan Mountains,pollen may be carried and deposited in the Turpan region.The rivers feeding into Aiding Lake in the Turpan region may also contribute to the distribution of Picea and Pinus pollen.Lots of pollen studies have shown that the ratio of Artemisia to Chenopodiaceae（A/C） can be used as a good indicator of the degree of humidity in the semi-arid and arid areas.Our study revealed that A/C can roughly reflect the characteristics of the desert zone in the study area.The results of Redundancy Analysis ordination on pollen assemblages and environmental factors（mean annual temperature（MAT）,mean annual precipitation（MAP） and altitude（ALT）） revealed that MAP was the main environmental factor affecting the pollen assemblages in the surface soil in the Turpan region and had more significant effects on the distribution of Nitraria pollen than on the distribution of Artemisia and Chenopodiaceae.