Wood distribution in neotropical forested headwater streams of La Selva, Costa Rica

Surveys of wood along 30 forested headwater stream reaches in La Selva Biological Station in north-eastern Costa Rica represent the first systematic data reported on wood loads in neotropical streams. For streams with drainage areas of 0.1-8-5 km(2) and gradients of 0.2-8%, wood load ranged from 3 to 34-7 m(3) wood/100 m channel and 41-612 m(3) wood/ha channel. These values are within the range reported for temperate streams. The variables wood diameter/flow depth, stream power, the presence of backflooding, and channel width/depth are consistently selected as significant predictors by statistical models for wood load. These variables explain half to two-thirds of the variability in wood load. These results, along with the spatial distribution of wood with respect to the thalweg, suggest that transport processes exert a greater influence on wood loads than recruitment processes. Wood appears to be more geomorphically effective in altering bed elevations in gravel-bed reaches than in reaches with coarser or finer substrate. Copyright (c) 2009 John Wiley & Sons, Ltd.