丹江口库区消落带植物群落生态修复模式及机制

The hydro-fluctuating belt of reservoir is a special aquatic-terrestrial ecotone wetland ecosystem which formed a huge ecological isolation zone between water body and land system. Danjiangkou Reservoir is the important water source region of Central Line Project of South-to-North Water Diversion. The new hydro-fluctuating belt had been formed in the previous agriculture area around this reservoir due to the rise of reservoir storage level after dam heightening. Long-term seasonal water level fluctuation leads to the release of nitrogen (N) and phosphorus (P) and other nutrient, it poses a serious threat to water quality of the reservoir. In order to ensure water quality and safety in Central Line Project of South-to-North Water Diversion, field experiments about different vegetation ecological restoration modes by using three dominant plant (Vetiveria zizanioides, Cynodon dactylon and Phragmites australis) would be carried out based on the bioremediation technique of plant extract and microbial decomposition and coupled relationship. In this study, the effect of different vegetation ecological restoration modes under mowing treatment on the absorption and transformation regular of N and P, rhizosphere soil microbial ecological effects and soil seed banks would be analyzed to explore the restoration mechanism of different ecological restoration modes. The optimal vegetation ecological restoration modes would be selected by considering the better removal rate of N and P, as well as improvement of soil environment. It is to provide reasonable vegetation ecological restoration strategy and the theoretical basis for water quality security of Danjiangkou Reservoir in the future.

水库消落带在库区水体与陆地之间形成的巨大环库生态隔离带，是一种特殊的水陆交错湿地生态系统。丹江口水库是南水北调中线工程的重要水源地，大坝加高后的库区蓄水位上升在周边原农业区域形成新的消落带，长期季节性水位涨落导致其中氮磷等营养盐释放，对水库水质构成了严重威胁。针对保障南水北调中线工程调水水质安全的重大战略需求，利用植物提取—微生物分解耦合关系的生物修复技术，本项目选取3种优势植物（香根草、狗牙根和芦苇）开展丹江口水库消落带不同植被生态修复模式原位试验，研究刈割处理下不同生态修复模式对氮磷吸收转化规律、根际土壤微生物生态效应和土壤种子库的影响，阐明植被不同生态修复模式的修复机制，筛选出对氮磷去除率高、能改善土壤生态环境的优良生态修复模式，为丹江口库区消落带植被的恢复和重建提供合理的生态修复策略，为库区水质安全保障提供理论依据。

本项目以库区新形成的消落带作为研究区域，选取3种消落带优势植物(香根草、狗牙根和芦苇)作为建群种，研究其不同生态修复模式中土壤有机碳及其组分的季节动态特征、根际微生物生态效应、氮磷的吸收转化规律及其土壤种子库的状况，揭示不同修复模式在生态修复过程中的贡献潜力大小，为恢复和重建受损的库区堤岸提供生态修复技术。研究结果如下：.（1）研究时段内土壤TOC、DOC和EOC含量随土层深度增加而降低。土壤TOC和DOC含量2018年和2019年分别是以9月和3月最高，复合修复模式均显著高于单一修复模式(p<0.05)。2018年土壤EOC和MBC季节变化与TOC相似，次年EOC含量6月份最高，以PV和VC较高，而MBC含量则是9月份最高，以复合模式较高。.（2）根际土壤蔗糖酶（除2018年3月外）和纤维素酶活性均随土层深度增加而降低。两个年份中蔗糖酶和纤维素酶活性分别以9月和6月最高，复合修复模式显著高于单一修复模式（p＜0.05）。过氧化氢酶活性2018年季节变化与蔗糖酶一致，2019年其酶活性以6月份最高，VZN和CDP的酶活性显著低于其它几种类型（p＜0.05）。.（3）根际土壤细菌、放线菌和真菌数量均随土层深度的增加而减少。土壤微生物数量季节变化为6月最高，3月最低，其中细菌数量最多，放线菌数量次之，真菌数量最少。3月份，各修复模式土壤微生物总数差异不显著；6月份，均以CDP土壤微生物总数最低；9月份均以复合修复模式的土壤微生物总数显著高于单一修复模式（p＜0.05）。.（4）根际土壤微生物呼吸速率均随土层深度增加而急剧降低。2018年以9月份最高，复合修复模式呼吸速率显著高于单一修复模式(p<0.05)；次年以6月份最高，PV的土壤微生物呼吸速率显著高于其它修复模式(p<0.05)。.（5）几种复合修复模式均具有较高的氮磷去除率，其中PV的氮去除率较高，PC的磷去除率较高。种子库平均密度以PV最高，CDP最低，上层土壤显著高于下层土壤。复合修复模式丰富度指数和多样性指数高于单一模式，随着植被恢复进程，物种多样性也随之上升。