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

Abstract

Detailed information on post-logging sediment dynamics in tropical catchments is required for modelling downstream impacts on communities and ecosystems. Sediment tracing methods, which are potentially useful in extending to the large catchment scale and longer time scales, are tested in primary and selectively logged rainforest catchments of Sabah, Borneo. Selected nutrient (P and N) and trace metal (Ni and Zn) concentrations are shown to discriminate surface, shallow subsurface and deep subsurface sediment sources. Analysis of channel-stored fine-sediment samples and use of an unmixing model allow the relative importance of these vertical sediment sources to be estimated and erosion processes to be inferred for catchments of contrasting size.

Identifying subsoil sediment sources with carbon and nitrogen stable isotope ratios

“…Additional source sampling would likely reduce the bias of these three samples resulting in significant discrimination between channel and grazing sources. In two of the three catchments, TOC and/or TN significantly discriminated between surface and subsoil sources, one catchment less than anticipated based on the general analysis of TOC and TN in sediment tracing research (Carter et al ., ; Blake et al ., ; Owens et al ., ; Collins et al ., ).…”

“…TOC and TN have potential to discriminate between surface and subsoil sources as their concentration decreases with depth in the soil profile (Blake et al ., ; Owens et al ., ). Further, there is less TOC in cultivated soils than surface soils because of tillage and harvesting (Walling et al ., ; Walling and Woodward, ; Juracek and Ziegler, ).…”

The challenges and opportunities of addressing particle size effects in sediment source fingerprinting: A review

“…Although they are not as extensively analyzed in sediment tracing research as fallout radionuclides, carbon and nitrogen parameters provide an interesting example into tracer property relationships with particle size. Total organic carbon (TOC) and total nitrogen (TN) often discriminate between sediment derived from surface and subsoil erosion processes as their concentration decreases with depth in the soil profile (Blake et al, 2006;Owens et al, 2006). Carbon stable isotopes (δ 13 C) may potentially discriminate between sediment derived from soils with C3 vegetation (majority of tree or temperate grass species) compared to those covered with C4 vegetation (grass and cropping species typically under warmer climates) (Fry, 2006;Schimel, 1993).…”

Fingerprinting and tracing the sources of soils and sediments: Earth and ocean science, geoarchaeological, forensic, and human health applications

“…This reflects the potential for density-related differences in the transport behaviour of ash and mineral soil, resulting in the modification of surface soil tracer signatures during downstream transfer. Magnetic properties show the greatest potential for burnt soil spatial source discrimination because burn-related changes are associated with the mineral component of surface soils (Blake et al, 2006b).…”