大堤型湖滨带生态系统健康状态驱动因子——以太湖为例

Abstract

Dikes have been built in the littoral zones of many lakes in China,for the purpose of flood prevention.Lake Taihu is one of these lakes and its dikes occupy as much as about 73% of the length of the total lake bank.Therefore,a case study of Lake Taihu was conducted.Being different from the natural littoral zone,the littoral zone with dikes has unique properties because dikes block the natural material flow between the surrounding land area and the lake water,consequentially,the material exchange between them was reduced to a great extent.Dike-building has brought a lot of ecological and environmental problems,such as the reduction of littoral wetland area,the decrease of aquatic animals′ habitat,the damage of vegetation cover,and even the destruction of the ecological balance in littoral zones.The deterioration of its ecological health has caused more and more concerns and as a result,many ecological restoration measures have been adopted by local governments.However,not all of them had effect because the driving forces leading to ecological health deterioration in this kind of littoral zones were still unknown. According to the characteristic of Lake Taihu,4 main factors affecting its littoral zone ecosystem health were selected including the nutrient state of major lake area,the pollutant fluxes of inflow rivers,littoral zone type and wave strength.Then,two different methods,namely,'stepwise multiple linear regression' and 'partial correlation coefficient',were employed to determine the driving forces from the above 4 factors.Very similar results were obtained from these two methods,i.e.,3 factors were identified as driving forces and their driving forces from stronger to weaker,listed as the following sequence,the nutrient state of major lake area littoral zone type the pollutant fluxes of inflow rivers.All the 3 driving forces have negative effects on the ecosystem health of the littoral zone of Lake Taihu.The higher nutrient state of major lake area,the heavier pollutant fluxes of inflow rivers and the worse littoral zone type,the poorer the ecosystem health of littoral zone.The reason leading to the out of 'wave strength' as driving force was explained from the aspects of both statistical method and analysis results.Although it had significant correlation with ecosystem health of littoral zone,it showed non significant partial correlation with it when considering other 3 factors′ effects.This result is consistent with the real situations observed by other researchers.These results also suggest that human being activities played a significant driving role in ecosystem deterioration of the littoral zone with dikes,while the impact of natural force such as wave strength was quite uncertain.Therefore,it is possible to improve ecological health status of littoral zone through changing human being activities.Compared to driving force analysis in social,economic and medical fields,little study has been done on environmental and ecological sciences,so more work should be carried out.Some misunderstanding on the concept of 'driving force' and the abuse of statistical analysis are elaborated in this paper.This study may have some inspires on the future research about 'driving force'.Additionally,the present study provides a scientific theory foundation and decision support for ecological restoration of the lake littoral zone with dikes.