三峡库区消落带落羽杉与立柳林土壤微生物生物量碳氮磷动态变化

Dynamic changes in soil microbial miomass carbon, nitrogen and phosphorus of Taxodium distichum and Salix matsudana plantation in the hydro-fluctuation belt of the Three Gorges Reservoir Region

为探究库区消落带人工乔木植被恢复重建后土壤质量及肥力的变化特征,于2016年6月(T_1)、2016年9月(T_2)、2017年6月(T_3)及2017年9月(T_4)选择165—175 m高程落羽杉与立柳土壤为研究对象,并以裸地作为对照,测定土壤微生物生物量碳、氮、磷和相关理化性质。结果表明:(1)经历水淹(T_2—T_3)会使土壤微生物生物量处于较低水平,落干期(T_1—T_2、T_3—T_4)落羽杉与立柳人工植被恢复生长能显著提高土壤微生物生物量,对土壤微生物恢复具有重要意义。(2)落羽杉与立柳土壤微生物生物量碳、氮占土壤有机碳、全氮百分比在4个时期均显著高于裸地,表明落羽杉与立柳土壤微生物对土壤碳、氮库的贡献大于裸地;落羽杉土壤微生物生物量磷及其占全磷百分比在T_1和T_3处于极低水平,T_2和T_4处于较高水平,应注意磷元素的迁移。(3)土壤微生物生物量碳、氮、磷与土壤有机碳和全氮有极显著相关性,与土壤pH值呈不同程度的负相关。在三峡库区消落带进行落羽杉与立柳乔木植被恢复重建能显著提高土壤微生物生物量及土壤肥力,进一步证实开展科学的植被修复与重建值得提倡和肯定。

The operation of the Three Gorges Dam Reservoir (TGDR) on the Yangtze River, China, has formed a hydro-fluctuation belt with an annual water level change of 30 m, spanning an area of 350 km2. This has led to a decline in plant community within the hydro-fluctuation belt. Revegetation is an eco-friendly method that can be used to restore the ecological integrity of the hydro-fluctuation zone of the TGDR. This method also facilitates the proper maintenance of the functions and services of riparian ecosystem. Therefore, in this study, revegetation of the hydro-fluctuation belt of the Three Gorges Reservoir (TGR) of China was carried out in the Ruxi River basin in Gonghe Village of Shibao Township, Zhong County, Chongqing Municipality of China. The changes in soil fertility and quality were evaluated by assessing the content of soil microbial biomass carbon (SMBC), soil microbial biomass nitrogen (SMBN), and soil microbial biomass phosphorus (SMBP). Soil samples were collected from plots of previously planted T. distichum and S. matsudana woodland in Zhong County of the TGR in June 2016 (T1), September 2016 (T2), June 2017 (T3), and September 2017 (T4) at elevations between 165 and 175 m above sea level. The results showed the following.:(1) Under the conditions of flooding (T2-T3), the soil microbial biomass was low. The soil microbial biomass increased significantly after the restorative growth of T. distichum and S. matsudana during the period of drawdown (T1-T2 and T3-T4), indicating that artificial vegetation restoration has a positive effect on soil microbial recovery.(2) The SMBC/SOC and SMBN/TN of T. distichum and S. matsudana woodland were significantly higher than those of unplanted soil, indicating that the soil turnover rate was faster in the artificial vegetation restoration soil. However, the phosphorus level in the soil of T. distichum varied significantly, which necessitates further evaluation of phosphorus migration within soil.(3) The soil microbial biomass significantly correlated with the soil organic C and total N, but it negatively correlated with the soil pH. Overall, the revegetation of T. distichum and S. matsudana increased soil microbial biomass, and also enhanced the soil quality of the hydro-fluctuation belt. The results of this study further validate artificial revegetation as a suitable method for ecosystem restoration.