三峡水库水位消退过程岸滩土壤呼吸特征

Soil Respiration of the Riverbank of Three Gorges Reservoir during Water Withdraw

为了研究三峡水库水位消退过程岸滩土壤呼吸及植被化护岸对土壤碳排放影响,以库区澎溪河段岸滩土壤为研究对象,利用Yaxin—1102便携式光合蒸腾仪系统对库区水退过程中岸滩土壤的呼吸速率进行了测定,并同时测定了土壤呼吸测点的土壤温度(土层深度0、5和10 cm)、土壤含水量、土壤有机碳和p H等土壤环境因子。结果表明:水位消退过程中岸滩近水层土壤呼吸速率表现出明显的时间变化,呈单峰曲线,2月份出现峰值;常年非淹水区土壤呼吸速率变动大于近水层,其峰值晚于近水层1个月。研究发现,长时间淹水可降低土壤呼吸强度即有利于岸滩土壤固持CO_2;但退水时间越长,岸滩土壤呼吸强度增加,接近或高于常年非淹没区。研究表明,岸滩现有植被在护岸同时是否亦能保持土壤碳的低水平排放亟待给予深入探讨。

In order to investigate soil respiration（ SR） and the effects of vegetation revetment on soil carbon emission from the riverbank of Three Gorges Reservoir area,using portable photosynthetic apparatus（ Yaxin—1102）,the riverbank soil of Pengxi River,a first-level branch of Changjiang River,was selected to monitor the SR rate,and concurrent monitoring was conducted for soil temperature（ soil depth 0,-5 and-10 cm）,soil water content,soil organic carbon and p H. The results showe a significant change of SR rate for soils adjoining the water surface,with a single peak occurred in February. The SR range of the perennial non-flooded area was higher than that adjoining water surface,and its peak value was 1 month later. Moreover,the prolonged flooding appeared reduced SR intensity,indicating a soil CO_2 sequestration. However,with the time of water withdraw,SR intensity of the riverbank can increase to or slightly higher than that of the perennial non-flooded area. Conclusively,some deep researches should be needed to establish suitable vegetation-based riparian protection with an effective maintenance of a low level of soil carbon emissions from the riverbank soils of the Three Gorges Reservoir area.