Here, we show that the attractive correlation between AET and decomposition does not necessarily apply to all vegetation types nor to severely disturbed sites. Decomposition is higher than predicted by the AET model in deserts where AET is low, and lower than predicted for a mesic clear-cut forest where AET values are higher than uncut forests. We suggest that the attractive simplicity of the AET decomposition relationship fails in these systems because it does not account for marked changes in microclimate produced by ecosystem perturbation like clear-cutting, or for biotic adaptations in desert ecosystems.