Climatic and geomorphic controls on the erosion of terrestrial biomass from subtropical mountain forest
Journal
Global Biogeochemical Cycles
Journal Volume
26
Journal Issue
3
Date Issued
2012
Author(s)
Abstract
Erosion of particulate organic carbon (POC) occurs at very high rates in mountain river catchments, yet the proportion derived recently from atmospheric CO2 in the terrestrial biosphere (POCnon-fossil) remains poorly constrained. Here we examine the transport of POCnon-fossil in mountain rivers of Taiwan and its climatic and geomorphic controls. In 11 catchments we have combined previous geochemical quantification of POC source (accounting for fossil POC from bedrock), with measurements of water discharge (Qw) and suspended sediment concentration over 2 years. In these catchments, POCnon-fossil concentration (mg L-1) was positively correlated with Qw, with enhanced loads at high flow attributed to rainfall driven supply of POCnon-fossil from forested hillslopes. This climatic control on POCnon-fossil transport was moderated by catchment geomorphology: the gradient of a linear relation of POCnon-fossil concentration and Qw increased as the proportion of steep hillslopes (>35) in the catchment increased. The data suggest enhanced supply of POCnon-fossil by erosion processes which act most efficiently on the steepest sections of forest. Across Taiwan, POC non-fossil yield was correlated with suspended sediment yield, with a mean of 21 10 tC km-2 yr-1. At this rate, export of POCnon-fossil imparts an upper bound on the time available for biospheric growth, of ∼800 yr. Over longer time periods, POC non-fossil transferred with large amounts of clastic sediment can contribute to sequestration of atmospheric CO2 if buried in marine sediments. Our results show that this carbon transfer should be enhanced in a wetter and stormier climate, and the rates moderated on geological timescales by the regional tectonic setting. © 2012. American Geophysical Union. All Rights Reserved.
Other Subjects
Atmospheric CO; Carbon transfer; Clastic sediments; Climatic controls; Erosion process; Forested hillslopes; Geological timescales; Geomorphic controls; High flow; High rate; Hillslopes; Linear relation; Marine sediments; Mountain forests; Mountain rivers; Particulate organic carbon; Regional tectonics; Suspended sediment concentrations; Terrestrial biosphere; Time-periods; Upper Bound; Water discharges; Biospherics; Carbon dioxide; Erosion; Forestry; Runoff; Submarine geology; Suspended sediments; Catchments; bioerosion; biogeochemistry; carbon dioxide; carbon sequestration; catchment; climate effect; concentration (composition); fluvial geomorphology; marine sediment; montane forest; particulate organic carbon; rainfall; river discharge; sediment yield; subtropical region; suspended sediment; tectonic setting; Taiwan
Type
journal article