喀斯特山地典型植被恢复过程中表土孢粉与植被的关系

The relationship between pollen assemblage in topsoil and vegetation in karst mountain during different restoration period of typical vegetation community

喀斯特山地坡耕地、1 a弃耕地、灌草地、15 a疏林地、25 a次生林群落表土孢粉分析和植被样方调查结果表明:(1)研究区植物孢粉共由46科属组成,以草本和蕨类植物占据优势,含量为45.77%—68.35%,其次是乔木(主要为雪松和马尾松),含量为(2.53%—21.31%),灌木植物花粉含量最低,为1.04%—8.88%,显示该区植被退化严重;(2)恢复过程中各阶段的花粉类型丰富度差别不明显,物种多样性主要表现为草本、蕨类和灌木植物种类的变化,乔木基本保持不变;(3)喀斯特山地典型植被恢复过程的表土孢粉组合差别明显,与其相应的实际植被情况大致相同,基本反映了石漠化地区现代植被的基本状况,表明孢粉可以为该区恢复和重建自然生态环境提供参考性依据。

Karst mountains are,typically,ecologically fragile.The soil is shallow and discontinuous,with a heavy clay texture.Moisture conent is low and a C horizon is generally lacking.The result is poor stability,with slow soil formation often leading to a state of negative growth and eventual lack of renewability.This occurs especially during use of the land for arable agriculture,and its sunsequent restoration with secondary vegetation Most previous res-earch has focussed on the physical and chemical properties of the soil,micro-organisms,and hydrology,with little work on palynology or vegetational history.In the present study,we investigated Mt.Jigongshan,Beibei District,Chongqing City,using Platycladus orientalis communities of different ages to reconstruct the succession back to forest.Typical plots were chosen to analyse the vegetation at each stage.The original Zonal vegetation of the area was subtropical broadleaved forest,but this is now all removed.In its place are secondary forest trees such as Platycladus orientalis,Trachycarpus fortunei etc.,and understorey shrubs such as Pyracantha fortuneara,Coriaria sinica and Mysine africana.The herb layer is of Imperata cylindrica etc.The farming was of two to three crops per year,of wheat,corn and sweet potato.The typical time sequence is slope farmland——1year abandoned farmland-bush grassland-15year scattered woodland-25year woodland.The vegetation and the pollen/spore content of the surface soil was recorded in each of these five types.Results：（1） 46 pollen/spore taxa were recorded,with herbs and ferns dominant（58%-96%）,then trees（mainly Cedrus deodara and Pinus massoniana） with 3%-21%,and then shrub pollen with only 1%-9%.（2） The abundance of the pollen types is not clearly related to the recovery stage.（3） The list of taxa at each site is,however,indicative of the vegetation.It is therefore concluded that palynology can indicate the stages of recovery in the natural environment of the study area.