Global patterns in root decomposition: comparisons of climate and litter quality effects

Root decomposition represents a significant C flux in terrestrial ecosystem s. Roots are exposed to a different decomposition environment than abovegro und tissues, and few general principles exist regarding the factors control ling rates of root decay. We use a global dataset to explore the relative i mportance of climate, environmental variables, and litter quality in regula ting rates of root decomposition. The parameters that explained the largest amount of variability in root decay were root Ca concentrations and C:N ra tios, with a smaller Proportion explained by latitude, mean annual temperat ure, mean annual precipitation, and actual evapotranspiration (AET). Root c hemistry and decay rates varied by plant life form (conifer, broadleaf, or graminoid). Conifer roots had the lowest levels of Ca and N, the highest C: N and lignin:N ratios, and decomposed at the slowest rates. In a stepwise m ultiple linear regression, AET, root Ca, and C:N ratio accounted for approx imately 90% of the variability in root decay rates. Root chemistry appeared to be the primary controller of root decomposition, while climate and envi ronmental factors played secondary roles, in contrast to previously establi shed leaf litter decomposition models.