Wang XiaoXiao, Huang Ping, Ma Maohua, Shan Kun, Wen Zhaofei, Wu Shengjun
Key Laboratory of Reservoir Aquatic Environment, Chongqing Institute of Green and Intelligent Technology, Chinese Academy of Sciences, ChongQing, China.
University of Chinese Academy of Sciences, Beijing, China.
PeerJ. 2020 Feb 18;8:e8503. doi: 10.7717/peerj.8503. eCollection 2020.
A huge reservoir was formed by the Three Gorges Dam in China, which also formed a riparian zone along the bank of the reservoir. In the period of low water-level, the riparian zone in tributary bays of the Three Gorges Reservoir (TGR) was always unordered cultivated, owing to its gentle slope and high soil fertility. This land-use practice creates high potential of generating greenhouse gas (GHG) emissions with periodic water level fluctuation.
To evaluate potential GHG emissions from the soil-air interface, the static opaque chamber method was adopted to evaluate the effect of elevations (180 m, 175 m, 170 m and 165 m) and land use types (dry lands, paddy fields and grass fields) from April to September in 2015 and 2016.
The results showed that carbon dioxide (CO) was the main contributor of GHG emission in riparian zone most likely because of high organic carbon from residues. Furthermore, high soil water content in paddy fields resulted in significantly higher methane (CH) flux than that in dry lands and grass fields. Compared to grass fields, anthropogenic activities in croplands were attributed with a decrease of soil total carbon and GHG emissions. However, inundation duration of different elevations was found to have no significant effect on CH and CO emissions in the riparian zone, and the mean nitrous oxide (NO) flux from dry lands at an elevation of 165 m was significantly higher than that of other elevations likely because of tillage and manure application. The high NO fluxes produced from tillage and fertilizer suggested that, in order to potentially mitigate GHG emissions from the riparian zone, more attention must be paid to the farming practices in dry lands at low elevations (below 165 m) in the riparian zone. Understanding factors that contribute to GHG emissions will help guide ecological restoration of riparian zones in the TGR.
中国三峡大坝形成了一个巨大的水库，同时也在水库岸边形成了一个河岸带。在低水位时期，三峡水库支流河湾处的河岸带由于坡度平缓且土壤肥力高，一直处于无序耕种状态。这种土地利用方式在水位周期性波动时产生温室气体排放的潜力很大。
为了评估土壤 - 空气界面的潜在温室气体排放，采用静态不透明箱法评估了2015年和2016年4月至9月不同海拔（180米、175米、170米和165米）和土地利用类型（旱地、水田和草地）的影响。
结果表明，二氧化碳（CO）是河岸带温室气体排放的主要贡献者，这很可能是由于残留物中的有机碳含量高。此外，水田中较高的土壤含水量导致甲烷（CH）通量显著高于旱地和草地。与草地相比，农田中的人为活动导致土壤总碳和温室气体排放减少。然而，发现不同海拔的淹没持续时间对河岸带的CH和CO排放没有显著影响，海拔165米处旱地的平均氧化亚氮（NO）通量显著高于其他海拔，这可能是由于耕作和施肥。耕作和施肥产生的高NO通量表明，为了潜在地减少河岸带的温室气体排放，必须更加关注河岸带低海拔（低于165米）旱地的耕作方式。了解导致温室气体排放的因素将有助于指导三峡水库河岸带的生态恢复。
