Landscape asymmetry of soil organic matter as a source of agro-ecosystem resilience

In agricultural landscapes, drivers at different spatial and temporal scales result in a non-random spatio-temporal variability of landscape characteristics. Patterns of soil organic matter (SOM) are for example controlled by both pedological and climatic factors as well as historic and current land use. The observed patterns linked to their generating processes can be referred to as the landscape asymmetry of SOM.In this paper we identify and evaluate landscape asymmetry of SOM in an agricultural landscape in the Netherlands. Subsequently we infer implications of applying the concept of landscape asymmetry for understanding agro-ecosystem resilience.We modeled SOM dynamics of grassland soils to identify dominant long-term drivers and combined and analyzed land use history and landscape characteristics to explain the spatial variability of SOM contents. Sensitivity analyses show that the dominant parameter for attainable SOM content is the mineralization rate of SOM. Results furthermore indicate, that SOM content is related to temporal variability in land use and to spatial variability of groundwater hydrology and soil texture. The landscape asymmetry of SOM provides windows of opportunities for farmers who wish to reduce fertilizer input. However, connecting landscape asymmetry to other scales reveals potential cascades of events that might undermine agro-ecosystem resilience.

Research highlights
► SOM decomposition rate determines attainable SOM content.
► Hydrology, soil texture and land use history affect the spatial distribution of SOM.
► Landscape asymmetry is a promising concept to study agro-ecosystem resilience.