The erosion of mountain belts controls their topographic and structural evolution and is the main source of sediment delivered to the oceans. Mountain erosion rates have been estimated from current relief and precipitation, but a more complete evaluation of the controls on erosion rates requires detailed measurements across a range of timescales. Here we report erosion rates in the Taiwan mountains estimated from modern river sediment loads, Holocene river incision and thermochronometry on a million-year scale. Estimated erosion rates within the actively deforming mountains are high (3-6 mm yr(-1)) on all timescales, but the pattern of erosion has changed over time in response to the migration of localized tectonic deformation. Modern, decadal-scale erosion rates correlate with historical seismicity and storm-driven runoff variability. The highest erosion rates are found where rapid deformation, high storm frequency and weak substrates coincide, despite low topographic relief.

Email alerting servicescite this article to receive free e-mail alerts when new articles www.gsapubs.org/cgi/alerts click Subscribeto subscribe to Geology www.gsapubs.org/subscriptions/ click Permission requestto contact GSA http://www.geosociety.org/pubs/copyrt.htm#gsa click viewpoint. Opinions presented in this publication do not reflect official positions of the Society.positions by scientists worldwide, regardless of their race, citizenship, gender, religion, or political article's full citation. GSA provides this and other forums for the presentation of diverse opinions and articles on their own or their organization's Web site providing the posting includes a reference to the science. This file may not be posted to any Web site, but authors may post the abstracts only of their unlimited copies of items in GSA's journals for noncommercial use in classrooms to further education and to use a single figure, a single table, and/or a brief paragraph of text in subsequent works and to make GSA, employment. Individual scientists are hereby granted permission, without fees or further requests to

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Tropical-cyclone-driven erosion of the terrestrial biosphere from mountains.', Nature geoscience., 1 (11). pp. 759-762.Further information on publisher's website:The full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. 10 11 The transfer of organic carbon from the terrestrial biosphere to the oceans via 12 erosion and riverine transport constitutes an important component of the global 13 carbon cycle 1-4 . More than one third of this organic carbon flux comes from 14 sediment-laden rivers that drain the mountains in the western Pacific region 3,5 . This 15 region is prone to tropical cyclones, but their role in sourcing and transferring 16 vegetation and soil is not well constrained. Here we measure particulate organic 17 carbon load and composition in the LiWu River, Taiwan, during cyclone-triggered 18floods. We correct for fossil particulate organic carbon using radiocarbon, and find 19 that the concentration of particulate organic carbon fromvegetation and soils is 20 positively correlatedwith water discharge. Floods have been shown to carry large 21 amounts of clastic sediment 6 .Non-fossil particulate organic carbon transported at 22

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(2010) 'The isotopic composition of particulate organic carbon in mountain rivers of Taiwan.', Geochimica et cosmochimica acta., 74 (11). pp. 3164-3181.Further information on publisher's website:http://dx.doi.org/10. 1016/j.gca.2010.03.004 Publisher's copyright statement: NOTICE: this is the author's version of a work that was accepted for publication in Geochimica et cosmochimica acta. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reected in this document. Changes may have been made to this work since it was submitted for publication. A denitive version was subsequently published in Geochimica et cosmochimica acta, 74/11, 2010, 10.1016/ j.gca.2010.03.004 Additional information: Use policyThe full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. AbstractSmall rivers draining mountain islands are important in the transfer of terrestrial particulate organic carbon (POC) to the oceans. This input has implications for the geochemical stratigraphic record. We have investigated the stable isotopic composition of POC (δ 13 Corg) in rivers draining the mountains of Taiwan. In 15 rivers, the suspended load has a mean δ 13 Corg that ranges from -28.1 ± 0.8 to -22.0 ± 0.2 (on average 37 samples per river) over the interval of our study. To investigate this variability we have supplemented suspended load data with measurements of POC in bedrock and river bed materials, and constraints on the composition of the terrestrial biomass. Fossil POC in bedrock has a range in δ 13 Corg from -25.4 ± 1.5 to -19.7 ± 2.3 between the major geological formations. Using coupled δ 13 Corg and N/C we have found evidence in the suspended load for mixing of fossil POC with non-fossil POC from the biosphere. In two rivers outside the Taiwan Central Range anthropogenic land use appears to influence δ 13 Corg, resulting in more variable and lower values than elsewhere. In all other catchments, we have found that 5 variability in δ 13 Corg is not controlled by the variable composition of the biomass, but instead by heterogeneous fossil POC.In order to quantify the fraction of suspended load POC derived from non-fossil sources (F nf ) as well as the isotopic composition of fossil POC (δ 13 C fossil ) carried by rivers, we adapt an end-member mixing model. River suspended sediments and bed sediments indicate that mixing of fossil POC results in a negative trend between N/C and δ 13 Corg that is distinct from the addition of non-fossil POC, collapsing multipl...

[1] Erosion of particulate organic carbon (POC) occurs at very high rates in mountain river catchments, yet the proportion derived recently from atmospheric CO 2 in the terrestrial biosphere (POC non-fossil ) remains poorly constrained. Here we examine the transport of POC non-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 (Q w ) and suspended sediment concentration over 2 years. In these catchments, POC non-fossil concentration (mg L À1 ) was positively correlated with Q w , with enhanced loads at high flow attributed to rainfall driven supply of POC non-fossil from forested hillslopes. This climatic control on POC non-fossil transport was moderated by catchment geomorphology: the gradient of a linear relation of POC non-fossil concentration and Q w increased as the proportion of steep hillslopes (>35 ) in the catchment increased. The data suggest enhanced supply of POC non-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 AE 10 tC km À2 yr À1 . At this rate, export of POC non-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 CO 2 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.

Patterns and rates of landsliding and fluvial sediment transfer in mountain catchments are determined by the strength and location of rain storms and earthquakes, and by the sequence in which they occur. To explore this notion, landslides caused by three tropical cyclones and a very large earthquake have been mapped in the Chenyoulan catchment in the Taiwan Central Range, where water and sediment discharges and rock strengths are well known. Prior to the M W 7·6 Chi-Chi earthquake in 1999, storm-driven landslide rates were modest. Landslides occurred primarily low within the landscape in shallow slopes, reworking older colluvial material. The Chi-Chi earthquake caused wide-spread landsliding in the steepest bedrock slopes high within the catchment due to topographic focusing of incoming seismic waves. After the earthquake landslide rates remained elevated, landslide patterns closely tracking the distribution of coseismic landslides. These patterns have not been strongly affected by rock strength. Sediment loads of the Chenyoulan River have been limited by supply from hillslopes. Prior to the Chi-Chi earthquake, the erosion budget was dominated by one exceptionally large flood, with anomalously high sediment concentrations, caused by typhoon Herb in 1996. Sediment concentrations were much higher than normal in intermediate size floods during the first 5 years after the earthquake, giving high sediment yields. In 2005, sediment concentrations had decreased to values prevalent before 1999. The hillslope response to the Chi-Chi earthquake has been much stronger than the five-fold increase of fluvial sediment loads and concentrations, but since the earthquake, hillslope sediment sources have become increasingly disconnected from the channel system, with 90 per cent of landslides not reaching into channels. Downslope advection of landslide debris associated with the Chi-Chi earthquake is driven by the impact of tropical cyclones, but occurs on a time-scale longer than this study. . Here we report on landslide patterns and rates caused by this sequence of triggers, and the concomitant fluvial sediment transfer, in a mountain area drained by the Chenyoulan River, close to the epicentre of the Chi-Chi earthquake. Specifically, we have investigated the rate and location of landsliding as a function of topography, substrate properties and the nature of active and preceding triggers. We have also considered how hillslope mass wasting in the Chenyoulan catchment is reflected in the downstream transfer of sediment. Study AreaThe mountain island of Taiwan has formed from the rapid, oblique collision between the Luzon Arc on the Philippine Sea Plate, and the Eurasian continental margin. Its current mean annual precipitation is 2·5 m year −1 , about 80 per cent of which falls between May and October, and the island receives an average of four typhoon hits per year (Shieh, 2000). The combination of strong climatic and tectonic forcing results in rapid rates of geomorphological processes, with average erosion rates of 3 -7 mm year ...