Response of reactive N gas emissions to soil heating. McCalley and Sparks, 2009

Laboratory measurements of the response of reactive N gas emissions and soil respiration to changes in soil temperature in (A) dry soil from beneath L. tridentata, (B) dry soil from plant interspaces, and (C) wetted soil from beneath L. tridentata. In arid environments such as deserts, nitrogen is often the most limiting nutrient for biological activity. The majority of the ecosystem nitrogen flux is typically thought to be driven by production and loss of reactive nitrogen species by microorganisms in the soil. We found that high soil-surface temperatures (greater than 50°C), driven by solar radiation, are the primary cause of nitrogen loss in Mojave Desert soils. This abiotic pathway not only enables the balancing of arid ecosystem nitrogen budgets, but also changes our view of global nitrogen cycling and the predicted impact of climate change and increased temperatures on nitrogen bioavailability. … Our study not only identifies N cycling as being equally sensitive to solar radiation as carbon, but also as highly temperature-dependent. Ultimately, rates of N export from arid ecosystems will be determined by summer surface soil temperatures and the frequency of summer precipitation events, both of which are predicted to change under most scenarios of future global climate (30). The conditions that promote abiotic N gas loss from desert soils also inhibit N fixation (31), the dominant N input to arid regions. Future environmental shifts will therefore probably disrupt natural N dynamics by unbalancing rates of N inputs and losses, gradually reinforcing N limitations in arid environments.

Carmody K. McCalley and Jed P. Sparks, Abiotic Gas Formation Drives Nitrogen Loss from a Desert Ecosystem, Science 6 November 2009: Vol. 326. no. 5954, pp. 837 – 840 DOI: 10.1126/science.1178984