重庆喀斯特地区现代花粉组合与植被的关系

重庆喀斯特地区4种不同地貌单元的81份表土和苔藓样品的孢粉分析结果表明:(1)研究区植物孢粉组合共由109科属组成。除金佛山外,其他植被退化严重地区样点均以草本和蕨类植物占据优势(剔除石漠化治理大量引种的马尾松、柳杉和侧柏等乔木花粉),其次是乔木植物花粉(主要为马尾松),灌木植物花粉含量很低,显示该区植被退化严重;(2)孢粉组合的PCA分析能够很好地将研究区的现代孢粉组合区分开来,较好地反映了重庆喀斯特地区不同地貌单元的植被特征,特别是石漠化区植被退化严重的孢粉组合特征。生态保护较好、自然植被发育的金佛山地区具有106科属的乔木、灌木与草本孢粉类型,以及高含量的乔木花粉,而喀斯特石漠化地区的鸡公山(46科属)、青木关镇(56科属)和南平镇(50科属)则表现为乔灌木孢粉类型较少;(3)银杉作为金佛山特有的孑遗植物,其花粉含量明显低于松属花粉,说明其花粉不利于远距离传播;(4)随着土地利用强度的增加,现代孢粉组合中乔灌木花粉含量和种类越少,草本和蕨类植物孢粉含量越多,且以耕地杂草为主。因此,土地利用方式的变化是喀斯特石漠化区次生植被及其现代孢粉组合变化的主要影响因素。研究可为重庆喀斯特地区土地利用策略的制定,重庆及其周边地区第四纪古植被、古气候和古环境重建研究,以及中国孢粉数据库建设提供基本数据和科学依据。

Modern palynomorph assemblages and their relationships with vegetation in karst areas of Chongqing, Southwestern China

Palynological analysis was carried out on 81 samples of topsoils and mosses collected from four different landforms in the karst areas of Chongqing City, Southwestern China. The results are summarized here. (1) A total of 109 pollen taxa (genera or family) were identified, which were dominated by herbs and ferns, followed by trees (mainly Pinus massoniana); shrub pollen content was the lowest (excluding Mt. Jinfo). These results revealed serious degradation of vegetation in the study area. (2) PCA analysis could distinguish the modern samples, which better reflects the characteristics of pollen assemblages in the karst areas, especially in the rocky desertification areas. In Mt. Jinfo with good ecological protection and natural vegetation development, we found 106 families of trees, shrubs and herbaceous pollen types, and a high content of arboreal pollen. On the contrary, fewer types of trees and shrubs were found in the karst rocky desertification areas, such as Mt. Jigong (46 families), Qingmuguan Town (56 families), and Nanping Town (50 families). (3) As the unique relict plant of Mt. Jinfo, the percentage of Cathaya argyrophylla pollen was much lower than that of Pinus pollen, indicating that its pollen is not suitable for long-distance transmission. (4) The proportions of trees and shrubs pollen decreased with the increasing land use intensity, while those of herbs and ferns increased, which were heavily dominated by pollen of weeds. Therefore, we conclude that the change in land use is the main factor affecting the secondary vegetation and pollen assemblages in the karst areas we studied. The results can provide some guidance for land use decision-making for the Chongqing karst areas, and can also provide some basic data and reference for Quaternary paleo-vegetation, paleoclimate and paleoenvironment reconstructions in Chongqing and its surrounding areas, and for the construction of the China Pollen Database.