Controls on litter decomposition in the Mojave Desert under current and future levels of atmospheric carbon dioxide

To quantify whether production of litter under elevated CO₂ results in altered decomposition, chemical quality (C:N ratio) or species/tissue composition, we collected litter over two years (1998 - 306mm precipitation and 1999 - 94mm) and allowed it to decompose where it was collected for 12 months in 2001 at the Nevada Desert Free Air CO₂ Enrichment Facility. Elevated CO₂ increased the C:N ratio of litter in both years, but did not affect decomposition. 1998 litter had more Larrea (%) and decomposed slower and 1999 litter had more Lycium (%) and decomposed faster. To determine how microclimate effects decomposition, standardized materials (cotton and sticks) were decomposed in 9 microsites; 3 below ground and 6 above ground. Decomposition increased with increasing mean microsite temperature, but was not related to mean microsite humidity. Decomposition is unlikely to change due to elevated CO₂, but may change if the intensity or frequency of wet years changes.