Channel storage; Coarse particulate organic matter; Large wood; Nonperennial stream; Semiarid;

Coarse particulate organic matter (CPOM) and large instream wood (LW) belong to elements transported by stream flows, but their pattern of storage in nonperennial streams remains unclear, especially in the relationship with living trees and shrubs living in the active channels. This study evaluates the role of woody plants that occupy relatively wide active channels of nonperennial streams on the storage of CPOM and LW. All CPOM, LW and woody plants were inventoried along 18 transects in three mutually distinct reaches of intermittent streams in Peloponnese, Greece. We observed high variations of the CPOM (4.85 m3/ha - 15.65 m3/ha) and LW volumes (1.95 m3/ha - 13.35 m3/ha) deposited in the studied reaches with their highest abundance in the confined reach upstream of a landslide-related knickpoint. Woody plants were recognised as an important trapping element for CPOM in the case of a sufficient frequency of shrubs and trees in the active channel, which was not the case for the lowland reach with the far lowest measured basal area of the stems (1.84 m2/ha) in contrast to the other reaches (9.80 m2/ha and 6.32 m2/ha). A positive association was found between the basal area of the stems and the volume of CPOM deposits. However, the importance of woody plants in LW storage was confirmed only for the transects with abundant large trees with diameters greater than 0.1 m occupying the channel. The function of trees and shrubs not only as sources, but also as retention elements, should be carefully considered in the establishment of CPOM and LW budgets in nonperennial fluvial systems