摘要
三峡水库水位的反季节变化使流域水环境发生巨大改变。为探究水位变动背景下的水体新陈代谢过程对水环境变化的响应及相关水体碳吸收与碳排放情况,选取三峡库区干流上,受水库不同蓄水程度影响的两个库内断面(寸滩(受水库高水位影响,处于变动回水区)、晒网坝(常年受库区蓄水影响))及未受蓄水影响的库外断面(朱沱(自然河流))进行对比研究。根据各断面2023年相关水文水化学高频率监测数据,基于单站明渠法计算水体新陈代谢量,并利用分子扩散模型计算水体碳通量,同时使用随机森林模型对影响净初级生产力(NEP)的环境因子进行重要度排序。结果表明:①水体初级生产力(GPP)为寸滩>朱沱>晒网坝断面,而呼吸效率(ER)为晒网坝>朱沱>寸滩断面。受库区蓄水影响,晒网坝断面在三个断面中光合效率最小,而呼吸效率最大;②驱动各断面NEP变化的环境因子相似,其中溶解氧(DO)、水温、水体二氧化碳分压(pCO_(2))、光合有效辐射(PAR)和pH为主要贡献因子;③晒网坝断面水位与NEP变化无明显相关规律,朱沱断面水位与NEP变化为相反趋势,寸滩断面在汛期与蓄水初期水位与NEP变化为相反趋势,而在蓄水末期、高水位期及消落初期无明显规律;④寸滩断面在春季为自养系统,碳汇效应显著,在其余季节为异养系统;朱沱与晒网坝断面在各季节都为净异养生态系统,碳源效应显著。上述研究成果有助于揭示大型水库水位变动驱动的水环境和碳循环变化机制,对水库水环境保护和碳循环过程揭示具有重要的意义。
Anti-seasonal variations in water levels in the Three Gorges(TG)Reservoir have led to significant changes in the reservoir's hydrological environment.To explore the response of water metabolic processes in the reservoir under different water level fluctuation scenarios,their responses to environmental changes,and the carbon sequestration and emission in the water body,this study selected two transects(Cuntan transect and Shaiwangba transect)located within the TG reservoir,which are affected by different impounding degrees,and one transect(Zhutuo transect),located outside the TG reservoir,which is unaffected by impounding processes,along the main stream for comparison research.The Cuntan transect is located in a fluctuating backwater area and is affected by high water-level scenarios from the TG reservoir.The Shaiwangba transect is affected by water storage from the TG reservoir year-round.The Zhutuo transect is a natural river transect.Based on high-frequency monitoring of hydrological and hydrochemical data collected in 2023,water metabolism was calculated using the single-station open channel method.A molecular diffusion model was employed to estimate carbon flux in the water body.Additionally,a random forest model was applied to rank the environmental factors influencing net ecosystem production(NEP)according to their importance.The results showed:①Gross primary productivity(GPP)was the highest at Cuntan,followed by Zhutuo and Shaiwangba,while respiration(ER)was the highest at Shaiwangba,followed by Zhutuo and Cuntan.Due to reservoir impoundment,the Shaiwangba transect exhibited the lowest photosynthetic efficiency and the highest respiratory efficiency among the three transects.②The environmental factors driving NEP changes at each transect were similar,with dissolved oxygen(DO),water temperature,partial pressure of carbon dioxide(pCO_(2)),photosynthetically active radiation(PAR)and pH being the primary contributing factors.③There was no clear correlation between water level and NEP changes at the Shaiwangba transect.The Zhutuo transect showed an opposite trend between the water level and NEP.The Cuntan transect exhibited an inverse trend between water level and NEP during the flood season and the initial impoundment phase,while it was no clear pattern during the later stages of impoundment,high water levels,and drawdown periods.④The Cuntan transect was autotrophic system in the spring season,exhibiting a significant carbon sink effect,and was heterotrophic system in other seasons,showing a significant carbon source effect.Both Zhutuo and Shaiwangba transects were heterotrophic systems throughout all seasons,with a prominent carbon source effect.These findings contribute to understanding the mechanisms of the water environment and carbon cycle changes driven by water level fluctuations in large reservoirs and are of significant importance for water environment protection and carbon cycle process research in reservoirs.
作者
范家贞
张陶
蒲俊兵
FAN Jiazhen;ZHANG Tao;PU Junbing(Chongqing Key Laboratory of Carbon Cycle and Carbon Regulation of Mountain Ecosystems,Chongqing Normal University,Chongqing 401331,China;School of Geography and Tourism,Chongqing Normal University,Chongqing 401331,China)
出处
《生态学报》
北大核心
2025年第15期7202-7219,共18页
Acta Ecologica Sinica
基金
国家高层次人才特殊支持计划青年拔尖人才计划项目(2022)
重庆市自然科学基金(CSTB2022NSCQ-LZX0022,CSTB2022NSCQ-MSX0619)
国家自然科学基金项目(42377081)。
关键词
水体新陈代谢过程
水体CO_(2)
水位变动
环境影响
三峡水库
aquatic metabolism processes
water body CO_(2)
water level fluctuations
environmental drivers
Three Gorges Reservoir
