Co-evolution of soil organic carbon and landscapes in intensively engineered landscapes
Abstract
Intensively engineered landscapes expand the availability of farmlands but significantly alter the hydro-bio-geochemical functionality of soils, the largest reservoir of carbon in the terrestrial system. Understanding how the biogeochemical transformation and erosion-induced SOC redistribution together influence the SOC dynamics is critical to our food security and adaptation to climate change. However, due to the complexity of the co-evolution of soil composition and landscape, quantifying such dynamics is still challenging. Here, we develop a process-based quasi 3-D model that couples surface water runoff, soil moisture dynamics, biogeochemical transformation, SOC transport, and landscape evolution with high spatial and temporal resolutions at a watershed scale.
We apply this model into two Critical Zone observatories: a sub-catchment in the Clear Creek Watershed in Iowa, U.S.; and the Gully Land Consolidation project in China's Loess Plateau. In the Clear Creek Watershed, our simulations show that in a fast transport landscape, SOC profiles have 'noses' below the surface at depositional sites, which are validated with the core samples. Generally, erosional sites are local net carbon sinks to the atmosphere, and depositional sites are net sources. Furthermore, the mechanical soil mixing from tillage practices affects the biogeochemical transformation by enhancing SOC stock at erosional sites and reducing it at depositional sites. In China's Loess Plateau, we focus on whether the consolidated gully lands have the resilience to provide sustainable SOC content for farming. We show that consolidated gullies serve as enhanced carbon sinks. Overall, the SOC biogeochemical transformation in consolidated gullies has little influence from surficial transport even though the fluxes of SOC transport is stronger than the ones of transformation over a long-term co-evolution (i.e., 50-yr). Furthermore, we find that extending the surface carbon residence time (i.e., applying biochar) would be a more efficient approach to sequestrate carbon into soils than adding more plant residues. These studies not only help us predicts the future behavior of the carbon cycle in engineered landscapes but can also serve as an instrument to develop long term sustainable agricultural practices.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFMEP33C2353Y
- Keywords:
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- 0428 Carbon cycling;
- BIOGEOSCIENCES;
- 1030 Geochemical cycles;
- GEOCHEMISTRY;
- 1815 Erosion;
- HYDROLOGY;
- 1862 Sediment transport;
- HYDROLOGY