Speaker
Description
Introduction.
Biodiversity-based cropping systems are a promising option for agriculture to meet socio-environmental issues under climate change. Yet, the levers that could be employed to establish a system based on biodiversity, such as crop diversification, require a degree of coordination with the underlying agroecosystem processes and the specific requirements of farmers. The long-term impacts of diversified systems are particularly challenging because design and assessment methods are not yet adapted. We hypothesized that crop models, combined with other tools, can be used to assess the impacts of biodiversity-based cropping systems on the provision and stability of ecosystem services over time. In this way, we implemented a disruptive crop succession with the STICS model (Brisson et al., 2003) version 10.0.0)and estimated the long-term (50-year) trade-offs between the ecosystems services of this biodiversity-based cropping system in a temperate oceanic region.
Materials and Methods.
The STICS model was used to simulate the long-term effects of a biodiversity-based cropping system on three variables: (i) the annual quantity of nitrates resulting from mineralisation in the topsoil (0-60 cm), (ii) the annual quantity of nitrates leached (beyond the sol depth measuring 110cm) and (iii) the annual soil organic carbon stock. These variables represent two regulating ecosystem services: regulation of soil quality and regulation of water quality.
The topsoil characteristics were as follows: 18.8% of clay; pH of 5.9; organic matter content of 2.8%. Historical climate data (1973-2023) from SAFRAN model and DRIAS projection data (2023-2073) were used for two IPCC climate scenarios (representative concentration pathways (RCP) 4.5 and 8.5).
The biodiversity-based cropping system was co-designed through two participatory workshops with local experts (two farmers, two technicians and one researcher). The resulting cropping system comprised 16 crop species (eight cash crops and eight service plants) over a six-year period. In order to facilitate comparison, two additional cropping systems were virtually implemented: a conventional two-species rotation (corn-wheat) that is commonly found in western France, and an agroecological diversified rotation that was recently tested in western France. The simulations were conducted over a 50-year period, with three different climate scenarios considered: the past climate (1973-2023), and scenarios RCP 4.5 and 8.5 (both 2023 to 2073). The evolution of variables was then analysed through time series statistics, using the R software (version 4.3.3). A functional principal component analysis was conducted to characterise each series and to identify temporal patterns. Subsequently, a linear regression model with time interaction was employed to compare the consequences of the biodiversity-based cropping system vs. the two additional systems, for each period.
Results.
The results are still being compiled and statistically analysed. Nevertheless, preliminary findings indicate that the annual quantity of nitrates resulting from mineralisation is higher in the soil where the biodiversity-based cropping system is implemented compared to the two additional systems. One possible explanation for this phenomenon is the supply of N-rich residues by leguminous plants introduced through the biodiversity-based cropping system. However, the higher quantity of nitrates resulting from mineralisation in the biodiversity-based cropping systems is also accompanied by more frequent nitrates leaching events. The soil organic carbon stock decreases in all three situations, but the biodiversity-based cropping system reaches balance earlier than both additional systems, with a higher balance value. These results indicate a positive evolution of the regulation of soil quality service over time for the biodiversity-based cropping system, while the regulation of water quality service deteriorates due to increased nitrate leaching compared to the other systems. The subsequent phase of this research will involve the study of additional variables to assess the contribution of biodiversity-based cropping systems on the provision of other ecosystem services and their stability over time (e.g. crop yields for the provisioning service, greenhouse gas emissions for climate regulation).
Reference.
Brisson, N., Gary, C., Justes, E., Roche, R., Mary, B., Ripoche, D., Zimmer, D., Sierra, J., Bertuzzi, P., Burger, P., 2003. An overview of the crop model STICS. European Journal of agronomy 18, 309-332.
| Keywords | Biodiversity-Based cropping system; Long term; Crop Diversification; Nature Based Solution, Agroecosystem; Ecosystem Services; Agroceology |
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