三峡水库消落带土壤侵蚀与生态重建研究进展

Research advances on soil erosion and ecological restoration in the riparian zone of the Three Gorges Reservoir

三峡水库消落带对库岸稳定性、入库泥沙和水库水质有重要意义,但土壤侵蚀等过程复杂,治理与保护难度大,缺乏高效简便的治理技术。作者基于水文资料、调查数据和长期野外土壤侵蚀观测数据,结合相关研究文献,分析三峡水库消落带土壤侵蚀现状及其时空分异规律,侵蚀模数高达9万4 887 t/(km^2·a),比周围环境高出16倍,但土壤侵蚀强度在近年来减弱。研究影响消落带土壤侵蚀主要因素为波浪冲蚀。梳理陡坡固土挡护、坡面植生护坡、平缓坡地快速排水等土壤基质稳固与整治途径,概述抗旱耐淹且具护坡效应的乔灌草等适宜植物选育进展和品种组配模式,提出不同生态型植被的海拔分区配置模式,凝练自然恢复、景观植被生态恢复、分区固土护岸、生态湿地拦沙截污、季节性环境友好利用、生态渔业饲草种植等6种三峡水库土质消落带生态治理综合模式,并展望消落带急需开展的研究内容。

[Background]Compared to the riparian zones of unregulated rivers,the riparian zone of the Three Gorges Reservoir(TGR)experiences relatively longer-duration artificial flooding and with high dynamic morphological changes.Reservoir riparian zone represents a hydrogeomorphological and biogeochemical ecotone between aquatic and terrestrial ecosystems and have been well recognized as a key area for maintaining ecosystem goods and services.However,this zone is ecologically fragile due to issues caused by frequent water level fluctuations.Little knowledge of successful management of environmental problems related to reservoirs riparian zone is currently available.Furthermore,there is lack of low-cost,high-benefit and easy-to-implement management technology.[Methods]Soil erosion intensities along 12 transects in the reservoir riparian zone were continuously measured between 2008 and 2016 using erosion pins.The factors mainly influencing soil erosion were assessed using hydrological data,survey data,and long-term in situ soil erosion observation data.Based on authors’sci-tech achievements,combined with literatures,various ecological restoration technologies and site-specific modes were summarized.[Results]Soil erosion modulus on riparian-zone slope was up to 94 887 t/(km^2·a),16 times on the counterpart of upland slope.Soil erosion intensity fortunately has been decreasing in recent years.The dominant driving force was wave erosion which was generated by wind and ship transportation,especially in mainstream riparian zone.The main measures for controlling soil erosion,stabilizing slope and restoring eco-system was to rebuild vegetation.Species selection for planting should be emphasized on the mechanisms attributing to adaptation of species to the extreme submergence stress,the growth recovery ability of species following release from submergence.In addition to focusing on improving the survival rate of plants and vegetation coverage,the effects of vegetation restoration on the bank stability,surface runoff regulation,sediment trapping,pollutant absorption,and plant diversity conservation should be considered.Six modes of ecological restoration at the TGR riparian zone were suggested:natural restoration,landscape vegetation ecological restoration,zonal soil consolidation and bank protection,ecological wetland,seasonal environment-friendly land utilization,and forage planting of ecological fishery.[Conclusions]The TGR riparian zone is a new geomorphological unit,and its structure and function are still unstable.Soil erosion,landscape changing and ecological degrading have been all remarkable during the study period.Long-term monitoring and studies are needed to figure out the landscape processes and the ecosystem evolution.