Nitrous oxide emissions decrease with plant diversity but increase with grassland primary productivity.

Nitrous oxide (NO), a main greenhouse gas that contributes to ozone layer depletion, is released from soils. Even when it has been argued that agriculture is the main cause of its increase in the atmosphere, natural ecosystems are also an important source of NO. However, the impacts of human activities on NO emissions through biodiversity loss or primary productivity changes in natural ecosystems have rarely been assessed. Here, we analyzed the effects of vegetation attributes such as plant diversity and production, as drivers of NO emission rates, in addition to environmental factors. We measured NO emissions monthly during 1 year in 12 sites covering a large portion of the Rio de la Plata grasslands, Argentina, and related these emissions with climate, soil and vegetation attributes. We performed spatial and temporal models of NO emissions separately, to evaluate which drivers control NO in space and over time independently. Our results showed that in the spatial model, NO emissions decreased with increments in plant species richness, with concomitant reductions in soil [Formula: see text] whereas NO emissions increased with primary productivity. By contrast, in the temporal model, monthly precipitation and monthly temperature were the main drivers of NO emissions, with positive correlations, showing important differences with the spatial model. Overall, our results show that biological drivers may exert substantial control of NO emissions at large spatial scales, together with climate and soil variables. Our results suggest that biodiversity conservation of natural grasslands may reduce regional greenhouse gas emissions, besides maintaining other important ecosystem services.