Dam Construction as an Important Anthropogenic Activity Disturbing Soil Organic Carbon in Affected Watersheds

Abstract

To explore whether and how anthropogenic activities related to surface water regulation (i.e., dam construction) disturb soil ecosystems in the surrounding uplands, a long-term monitoring program was conducted from 1998 to 2017 in the Three Gorges Reservoir Region, China. The Three Gorges Dam (TGD) is the largest hydraulic engineering project in the world. We present a direct, ecosystem-scale demonstration of changes in the soil organic carbon (SOC) content in the TGD watershed before and after the surface water was reshaped. The average SOC content decreased from 12.9 to 9.5 g/kg between 2004 and 2012 and then recovered to 13.8 g/kg in 2017. Dynamics of SOC were partly attributed to shifts in the composition of soil microbial communities responsible for carbon biogeochemistry. The shifts in microbial taxa were associated with the changed microclimate affected by the TGD as well as global and regional climate variability. The microclimate, soil microorganisms, and plant organic carbon input explained 40.2% of the variation in the SOC content. This study revealed that dam construction was an important and indirect driver for the SOC turnover, and the subsequent effects on the upland soil ecosystem must be considered when large-scale disturbance activities (such as dam construction) are conducted in the future.

Driver–response relationships in a large shallow lake since the Anthropocene: Short‐term abrupt perturbations versus long‐term sustainable pressures

“…First, they promoted vegetation fixation and dam retention, which hindered the movement of many land materials (Feng et al, 2013;Yang et al, 2022). Second, they affected the photosynthesis and mineralization of organic matter within the lake by influencing various biogeochemical processes through water-level changes and vegetation growth, including the microclimate, plants, and microorganisms (Wang et al, 2020;Zhao et al, 2023). Both large reservoir/ dam buildings and regional land-use changes at the global scale have an impact on the source-sink processes of material transport (Best, 2018;Loewen, 2023).…”

The Three Gorges Dam accelerates acidification of upland soils

“…The Three Gorges Dam (TGD) on the Yangtze River is the largest hydraulic engineering project in the world [1][2][3] , and its impact on the health of ecosystems has been a subject of intense debate at all levels, including climate, eco-environment and social economy [4][5][6][7] . No matter what the results of these debates are, it is commonly accepted that large dams (height >15 m or volume > 3 million m 3 ) in different areas and climatic zones often affect the microclimate during their building and service life span [8][9][10][11] . However, the environmental impacts of large dams (e.g.…”

“…One viewpoint underscores that the presence of TGD causes negative environmental impacts such as ampli cation of pollutant (e.g. methyl mercury) transport into tributaries [12][13][14] , and disturbances to soil organic matter 11,15 due to the changes in hydrological regime and inundation 16 , as well as resettlement and construction of the dam 7 . Another viewpoint argues that natural variation in the environment is more signi cant than the dam effects 17 .…”