Leaf litter breakdown in a Mediterranean stream characterised by travertine precipitation

1. Breakdown of four leaf species (Platanus orientalis, Populus nigra, Sali x atrocinerea, Rubus ulmifolius) was studied in a Mediterranean second-orde r stream characterised by abundant travertine precipitation, a history of f ire in its catchment, and a recently revegetated alluvial corridor. 2. Compared to breakdown rates reported in the literature for congeneric sp ecies, breakdown of the four species was slow (k = 0.0024-0.0069 day(-1) fo r the tree species, and 0.0103 and 0.0111 day(-1) for Rubus), in spite of h igh water temperatures, indicating that the travertine layer that quickly c overed submerged leaves impeded decomposer activity and physical fragmentat ion losses. 3. Breakdown rates nevertheless differed between leaf species in a predicta ble manner, suggesting that the observed mass loss was largely due to biolo gical processes. 4. The observed tendency towards increasing leaf nitrogen and phosphorus co ncentrations during breakdown suggests that microorganisms were actively in volved in leaf breakdown; however, this interpretation must be viewed with caution because of potentially confounding effects by nutrients contained i n the travertine layer. 5. Leaf breakdown of the three indigenous species was faster than that of t he exotic species P. orientalis. Due to the recalcitrance of its leaves, th e frequent use of Platanus in revegetation schemes following the destructio n of indigenous vegetation by fire, exacerbates the negative effect of trav ertine precipitation on leaf breakdown and, by extension, energy flow in Me diterranean karst streams.