Modeling denitrification in a changing climate

Abstract

Although uncertainty exists in the specifics of climate change, sufficient consensus has emerged regarding the scale and direction of changes that it is important for managers to consider the implications of these changes for essential ecosystem services such as denitrification. For the northeastern United States, it is expected that by the end of the 21st century, annual precipitation will increase by 10% and annual temperatures by 3 °C. Because denitrification rates are highly influenced by soil moisture and soil temperature, we expect the projected changes in temperature and precipitation to alter the rates and patterns of denitrification. We developed three future weather scenarios based on the B1, A2, and A1F1 emission scenarios and utilized them as inputs to a coupled hydrologic-denitrification model to analyze the effects of changing temperature and soil moisture on denitrification rates, assuming nitrate availability remains unchanged. Our results suggest denitrification rates will increase by 5.1–11.8 kg N ha⁻¹ yr⁻¹ across the watershed. The greatest projected increases are in the areas and seasons with the highest baseline rates, with smaller increases in those with lower baseline rates. We found that changing temperature is likely to be a much stronger driver of change to denitrification rates (7.7 kg N ha⁻¹ yr⁻¹) than changing precipitation (1.4 kg N ha⁻ yr⁻¹). This study utilizes scenario modeling and a field validated model to quantify the future benefits of the ecosystem service denitrification, addressing a lack of ecosystem service quantification studies and providing a model for quantification studies.