While leaf litter decay rates are considered a function of litter biochemistry and microclimate, we poorly understand if interannual variation in climate is sufficient to significantly alter decomposition rates. To determine the effect of interannual variation in climate on decomposition, we placed mesh bags containing either Quercus spp. or Acer rubrum leaves after leaf drop every year for 3 years. Litter bags were collected every 90 days for 2.5 years, allowing us to compare directly 0.5 y and 1.5 y decay times over three and two year periods, respectively. Mass loss and litter biochemistry were quantified for each sample as well as temperature & precipitation. We observed a significant interannual variation in mass loss after 90 days that only became more different with time with Quercus spp. For example, at 90 days mass loss went from a significant 4% to a 13% increase after 1.5 years when comparing the first and second years. However, we observed no significant difference in A. rubrum mass loss rates. Faster decay rates are consistent with warmer winter temperatures in years two and three. Declines in cellulose and lignin were similar to the mass loss results. Our results suggest that the decay of Quercus leaves is sensitive to interannual climate variation, whereas A. rubrum is relatively unaffected. The difference between Quercus and A. rubrum leaf decay may be explained by Quercus leaves having a higher proportion of lignin that requires more thermal energy to degrade by the microbial community.
