水电开发影响下河岸带植被结构和生物量分布

Study on riparian vegetation structure and biomass distribution under the influence of hydropower development

为了解水电开发不同阶段对河岸带植被的影响差异,在澜沧江中下游小湾电站、漫湾库区、漫湾坝下、大朝山库区、大朝山坝下、景洪电站河岸带设置6个样带进行植被结构指标和生物量空间分布特征调查分析。结果表明:澜沧江中下游河岸带植被以乔木为主体,乔木层结构指标以已建库区和坝下样带较高,灌木层和草本层结构指标以在建电站和坝下样带较高;已建库区、坝下和在建电站样带乔木层和群落生物量的最高值分别出现在距离河岸100,50 m和200 m处;乔木层生物量以库区样带最高,灌木层生物量以坝下样带最高,草本层生物量以在建电站样带最高;库区和坝下样带群落生物量大致相当,高于在建电站样带;漫湾库区及其坝下乔木层结构指标以及群落生物量相对变化幅度小于大朝山库区及其坝下样带,小湾样带小于景洪样带。研究区植被结构和生物量的分布格局反映了库区植被恢复程度的差异和电站施工影响强度的差异。

In order to understand the impacts of hydropower development on riparian vegetation at different stages, six riparian areas were selected from Manwan and Dachaoshan reservoir areas, downstream of Manwan and Dachaoshan dams, Xiaowan and Jinghong dam site areas in middle and lower reaches of Lancang River to investigate vegetation structure and the spatial distribu- tion of biomass. The results show that the arbor species dominate the riparian vegetation in the study areas. The higher structure indexes of arborous layer are found in the sampling sites of reservoir areas and downstream of the dams. The higher structure in- dexes of shrub layer and herbaceous layer are found in the sampling sites of dams under construction and downstream of the dams. The maximum of arborous layer biomass and community biomass are observed at 100m - to - bank in the reservoir areas, 50m - to - bank in the downstream of the dams and 200m - to - bank in the dams under construction respectively. And the greatest bio- mass of arborous, shrub and herbaceous layers appear in the reservoir areas, the downstream of the dams and the dams under construction, separately. In the whole, the community biomass in the reservoir areas is comparable to that in the downstream of dam sites, greater than the sampling area of the dams under construction. The relative variation rates of structure index of arbor- ous layer and the community biomass in Manwan Reservoir and its downstream section are lower than those in Dachaoshan Reser- voir and its downstream section, and the relative variation rates in Xiaowan Dam are lower than those in Jinghong Dam. The vege- tation structure and biomass distribution in the study area reflect the difference of vegetation restoration in reservoir areas and the extents of the impacts by dam constructions.