中文摘要：

人类对现代植被的影响已经成为解释过去人类活动及其环境效应的关键问题。对西北干旱区40个农田和荒地表土样品花粉组合的研究表明：农田花粉平均浓度（7227粒／g）明显低于荒地（32704粒／g）；农田中农作物花粉含量高于荒地，但并不占绝对优势，农田花粉组合不仅反映农田本身的植被组成，而且还反映地方或区域植被组成状况；农田中灌木花粉含量低于荒地，杂草花粉类型比荒地丰富；藜科、蒿属、麻黄花粉都占有较高比例，普遍呈超代表性；不同的农作物花粉百分比指示该样品所在地或周围不同的农作物类型。聚类分析进一步表明了农田／荒地花粉组合特征的一致性：葡萄花粉在葡萄地的含量均相当高，而在其他植被类型中很少出现，花粉组合特征一致性较好；棉田棉花花粉含量低，其他植物花粉含量高，花粉组合特征与荒地相似，很难与荒地区分开来；如果农田和荒地比较接近，农田农作物花粉含量又比较低，则两种植被类型花粉组合特征就较为相似。

英文摘要：

Assessment of human impact on modern vegetation has become a key issue in explaining the past human activities and their environmental effects. Studies on 40 surface pollen assemblages of farmlands and wildlands in arid northwestern area of China show that the pollen concentration of farmlands is lower than that of wildlands, which are 7227 grains/g and 32704 grains/g respectively. The percentages of agricultural pollen types from farmlands are larger than those of wildlands, while the agricultural pollen types are not dominant in both of the assemblages. The pollen assemblages in farmlands reflect not only local plant compositions of the lands but also regional vegetation information. The percentages of shrubs pollen of farmlands are lower than that of wildlands, and weed pollens are more abundant. Chenopodiaceae, Artemisia and Ephedra pollen widely present in all the samples. The percentages of different agricultural pollens indicate different vegetation in local and regional areas. The results of cluster analysis furthermore indicate a consistency of pollen assemblages between farmlands and wildlands. The percentages of vitaceae pollen are dominant and pollen assemblages are consisted well in grape lands, while not present in other vegetation types. The percentages of malvaceae pollen are quite low and other species are the main pollen types, with poor consistency to the local vegetation cover. If the farmlands and wildlands are close and the percentages of agricultural pollen of farmlands are low, pollen assemblages of the two land types are similar.