山丘区中小河流边滩植被分布驱动因子及响应关系

河岸带滩地植被是维持河流系统健康的重要屏障.以浙江省龙游县灵山港边滩为研究对象,运用聚类分析和RDA约束性冗余分析等方法,分析中小河流边滩植被分布特征及其主要驱动因子,并建立各驱动因子对植被分布的响应关系.结果表明:灵山港滩地植被种类丰富多样,共有62种植被(被子植物61种,蕨类植物1种),其植被群落结构包括9种类型;滩地相对水面高差因子、滩地形态系数和水文特性是植被分布空间差异性的主要影响因子,各因子贡献率分别为37.50％、27.50％和16.82％,各因子对植被分布的驱动响应机制不同.其中:在滩地相对水平面高差因子作用下,植被从滩地外缘到滩地内部,耐水性由强到弱,丰富性由低到高,生物量由小到大;当边缘线发育系数SDI值处于2.0～4.0之间,且滩地狭长指数Pe/Pa值在0.12 ～0.3之间时,至少有60％的保证率使得滩地植被多样性维持在1.03 ～1.96的高水平;水文特性能够影响植被的形态特征和滩地的生境条件,水文作用下,滩地外围砂粒质量分数随着离水距离增大而逐渐减小,植被类型也会随着离水距离的增加,从喜湿耐冲型到中生型过渡.掌握滩地植被的分布特征及其影响因子,以期为河道生态修复,提供理论依据.

Vegetation distribution and its driven-forces on the floodplains of small and medium rivers in hilly area

Background] Vegetation in riparian zone is an important buffer to sustain the health of a river system.It is a typical ecotone characterized as edge effect,and plays a significant role in the conservation of river system health.Therefore,it is vital to know how the vegetation in floodplain distributes and what the driven-forces of the distribution are.Methods] Taking the Lingshan River,in Longyou County,Zhejiang Province,as a typical example of small and medium rivers in hilly area,the characteristics of the vegetation distribution and its driven-forces were studied.After investigating the vegetation species in the quadrat sampling,the data was calculated and analyzed using the Clustering Analysis (CA) in SPSS software,and the Redundancy Analysis (RDA) in Canoco5 software and through which the composition and cluster numbers of vegetation species,the cosine of the angle at the origin of the two vectors,the contribution rate of driven-forces were calculated.On the basis of GPS site survey and the maps downloaded from Google Earth,the elevation and shape coefficient were analyzed by Digital Elevation Model (DEM) in Surfer software.Then combined with the regression analysis,the relationship between the vegetation and driven-forces were obtained.Results] In the floodplain of Lingshan River,there were 62 vegetation species (61 kinds of Angiospermaes and one kind of Pteridophyta) and the vegetation community structure was mainly divided into 9 classes.The major three driven-forces of the vegetation distribution were elevation factor (ButtElev),shape coefficient (Shapindx) and hydrological characteristics (HydrChar),and their contribution rates were 37.50％,27.50％,16.82％,respectively.Particularly,under the influence of ButtElev,from outer to inner edge of floodplain,the moisture capacity varied from strong to weak,the diversity varied from low to high,and the biomass varied from small to large.There was at least 60 percent of the guarantee rate making the vegetation diversity between 1.03 and 1.96 when the SDI coefficient was between 2.0 and 4.0,and the Pe/Pa was between 0.12 and 0.3.The hydrological characteristics affected the morphological plasticity of vegetation and the habitat conditions of the floodplain.The sand content in the outer zone of the floodplain decreased with the increase of the distance from the water,and the anti-scour ability and moisture capacity of the vegetation decreased from strong to weak.Conclusions] The elevation factor,shape coefficient and hydrological characteristics are the key driven-forces of vegetation distribution in small and medium rivers in hilly area.When we design ecological restoration projects,the three factors should be focused on,and the suitable measures should be employed in order to control and optimize the three factors.