The dynamics of agricultural production and riverine carbon and nitrogen fluxes in the Mississippi River Basin as influenced by climate change and land use: 1901-2010

Background/Question/Methods

The Mississippi River Basin (MRB), one of the most productive and intensive agricultural regions in the world, has experienced profound changes in climate and land use over the past century, fueled by food demand and growing population, and is likely to undergo further rapid development in the coming decades. Farming in MRB has produced the majority of agricultural products in the Unitized States (e.g. corn, soybeans, wheat), and meanwhile altered the hydrology and chemistry of the Mississippi river with significantly enhanced fertilizer input, which is threatening the coastal ecosystem health. How to work with agriculture to meet the food requirement and improve river health in the MRB is an urgent question to be addressed. However, the magnitude, temporal and spatial patterns of agricultural production and riverine nutrient fluxes in response to climate and land use changes, and the underlying mechanisms are still far from certain. Here, we applied the process-based ecosystem model DLEM (Dynamic Land Ecosystem Model) driven by regional database including historical changes in climate, land use/land cover, agronomic practices (e.g. fertilizer, irrigation), and other factors (e.g. CO₂, ozone, nitrogen deposition etc.). We investigated the variations of crop production and yield and riverine carbon and nitrogen fluxes in response to environmental changes in climate variability/extremes, land cover and land management practices during 1901-2010. 

Results/Conclusions

The preliminary results show that, in MRB region, historical climate variability/change controlled the annual variations of crop production/yield and riverine carbon and nitrogen fluxes. Climate extreme disturbances such as flooding events significantly reduced crop production and yield, and meanwhile enhancing the export rates of carbon and nitrogen (dissolved vs. particulate; organic vs. inorganic). Land management practices such as nitrogen fertilizer application continuously increased crop production and yield, and also led to a significant increase in nitrogen export. The results suggest that optimized land management (i.e. enhancing fertilizer use efficiency rather than fertilizer input, and bettering fertilizer timing with considering irrigation and climate extreme events) could be an effective strategy for ensuring regional food security and for improving river health.