Some tropical rainforests have distinct dry seasons where rainfall is greatly reduced for several months and consequently, intermittent stream flows occur only in the wet season.  In contrast, the non-seasonal rainforests, such as those in Puerto Rico’s Luquillo Experimental Forest, usually have relatively high rainfall every month.  However, flows in intermittent stream channels are highly variable from year to year.  Predicted changes in the intensities and frequencies of both droughts and hurricanes in the Caribbean region will likely further increase variability in intermittency.  Reduced rainfall in 1994 and 2007 dried out riffles and pools in some headwater streams in the wettest rainforests of Puerto Rico.  These dry channels, along with zero-order gullies, serve as storage reaches for the accumulation of leaf litter.  Species-specific differences in rates of leaf-litterfall and litter breakdown during these dry periods indicate the importance of Basidiomycetes white-rot fungi.   When the first large rainfalls begin, accumulated litter can be transported downslope in both channels and surrounding riparian zones into active channels where aquatic fungi and detritivores breakdown the pulsed input of litter. This pulse of terrestrially accumulated litter can form debris dams, especially at confluences of zero-order and first-order streams within the drainage network.