Changes in the spatial distribution of erosion within a selectively logged rainforest catchment in Borneo 1988-2003.

Abstract

This paper synthesizes the results of a 15-year study (1988-2003) assessing the changes in slope and catchment erosion and sediment sources within the Segama catchment in Sabah, Malaysia, that was selectively-logged using a combination of tractor and high-lead logging techniques between December 1988 and June 1989 and then left to regenerate naturally. Comparisons are drawn with date on slope erosion rates and sediment sources in adjacent primary forest catchments.

Quantifying Fine-Sediment Sources in Primary and Selectively Logged Rainforest Catchments Using Geochemical Tracers

“…This would accord with Baru monthly sediment yields in 2003 being of a similar order to those of West Stream (Walsh et al, 2006). On the other hand, the 50% lower nutrient levels in Baru than in West Stream sediment suggests that Baru has not fully recovered from selective logging, but is actively reworking deeper-sourced material from landslide and logging road inputs of the late 1990s (Douglas et al, 1999) that have been stored in debris dams (Walsh et al, 2006). An alternative explanation of the similarity between Baru and West source contributions is that a recent natural landslide less than 200 m upstream of the sampled reach has temporarily elevated deeper subsurface inputs to West stream.…”

“…This would accord with Baru monthly sediment yields in 2003 being of a similar order to those of West Stream (Walsh et al, 2006). On the other hand, the 50% lower nutrient levels in Baru than in West Stream sediment suggests that Baru has not fully recovered from selective logging, but is actively reworking deeper-sourced material from landslide and logging road inputs of the late 1990s (Douglas et al, 1999) that have been stored in debris dams (Walsh et al, 2006).…”

“…Long-term monitoring within the selectively logged Baru catchment in Sabah suggests a four-phase impact model (Douglas et al, 1999;Walsh et al, 2006). Phase 1 (during and years 1-2 post-logging) has high sediment loads related to erosion of disturbed surface soil.…”

Characteristics of rain events at an inland locality in northeastern Borneo, Malaysia

“…unequal variance), shows that the number of days with some gauges measuring rainfall whilst others recorded none increased as the distance between gauges increased (r 2 D 0Ð6649, P < 0Ð001). The observed spottiness of daily rainfall incidence within an area of only 5 km 2 has significant implications for our ability to extrapolate plot-based estimates of wet-canopy evaporation (Chappell et al, 2001;Bidin and Chappell, 2004), hillslope hydrological experiments (Chappell et al, 1998;Chappell and Sherlock, 2005) or erosion Walsh et al, 2006) across the local region.…”

“…The 5 km 2 study region selected (5°01 0 N and 117°48Ð75 0 E) is 50 km inland from the eastern coast of Sabah, and contains the core study areas of the rainforest research station called the Danum Valley Field Centre (DVFC; Figure 1). The DVFC locality forms the focus of ongoing hydrological research on rainfall, throughfall and wet-canopy evaporation (Chappell et al, 2001;Chappell and Tych, 2002;Bidin andChappell, 2003, 2004), soil-water regulation of landscape ecology (Gibbons and Newbery, 2003), streamflow generation mechanisms (Chappell et al, 1998;Chappell and Sherlock, 2005), rainfall-runoff modelling (Chappell et al, 1998(Chappell et al, , 2004b and erosion Chappell et al, 2004a;Walsh et al, 2006). All of this work could be advanced with a better understanding of the temporal characteristics of rainfall within experimental catchments.…”