The hydrologic regime and zonation of riparian vegetation influenced the quantity and quality of coarse particulate organic matter (CPOM; >1 mm) stored in the channel and upper bank of a prairie stream. In a 5.4-km intermittent reach of the South Branch of Kings Creek on Konza Prairie, Kansas, total annual import was lowest in headwater reaches and increased downstream. Total storage of benthic CPOM in the dry channel and on the bank before the flow period was highest in the fourth- and fifth-order gallery forest zone (999 g ash-free dry mass∙m−2) and less in upstream reaches (320–341 g∙m−2). These longitudinal patterns of CPOM annual import and storage (before the flow period) were opposite those predicted by the river continuum concept for streams draining forested regions. Following flow, headwater channels had more CPOM (291 g∙m−2) than downstream reaches. On the bank, storage was always highest in downstream reaches. Composition of CPOM both in the channel and on the bank varied with changes in riparian vegetation; grass tissues dominated in headwater channels, while wood and leaves of trees and shrubs were more abundant downstream. During the flow period, storage of CPOM increased only in headwater channels, where retention was high despite the lack of woody debris. In this intermittent prairie stream, benthic CPOM may not contribute consistently to the terrestrial/aquatic linkages that are suggested in the river continuum concept because of (1) a paucity of large CPOM sources (e.g. trees, shrubs) in the upper reaches and (2) a hydrologic regime that reduces the amount, as well as the predictability, of stored CPOM. The biota of prairie streams must have opportunistic food gathering and reproductive strategies to take advantage of variable food resources in a flow environment that is itself very unpredictable.
Dynamics of allochthonous organic matter in a tropical Brazilian headstream