Plant litter decomposition in a semi-arid ecosystem controlled by photodegradation

Biological processes are thought to be the primary cause of decomposition of organic matter in terrestrial ecosystems, with abiotic processes such as degradation by UV-B radiation playing a minor role. Not so, according to a study in the semi-arid Patagonian steppe. Here solar radiation has been identified as a major influence on carbon turnover. Blocking full sunlight or UV-B radiation dramatically reduced the rate of decomposition of plant litter, yet, reduction of soil organisms or addition of limiting soil resources had no effect. These results suggest a short-circuit in the carbon cycle; a substantial fraction of primary production could be lost to the atmosphere via photodegradation without cycling through soil organic matter pools. As nearly 40% of Earth's land surface is desert, global change affecting levels of radiation such as ozone depletion or cloud cover could have major impacts on carbon storage.