Mobilization and transport of coarse woody debris to the oceans triggered by an extreme tropical storm

Abstract

A significant consequence of Typhoon Morakot in August 2009 was the production of vast volumes of driftwood in Pacific Asia. We have quantified the flux of this coarse woody debris (CWD) to the oceans from typhoontriggered landslides in Taiwan, where Morakot made landfall, by combining remote sensing (using FORMOSAT-2 imagery and aerial photography), analysis of forest biomass, and field observations. A total of 3.8-8.4 Tg CWD was transported to the oceans, carrying 1.8-4.0 Tg of organic carbon. In addition to the local effects on the marine and coastal environment from such a highly concentrated flux of carbon and nutrients, storm-driven mobilization of CWD may represent a significant, if infrequent, transfer of terrestrial biomass to the oceans. If the frequency of relatively rare, extreme storms such as Morakot increases in a changing climate, this transport mechanism may play an important role in feedbacks between global climate, storm intensity, and carbon cycling.

Mechanisms of carbon storage in mountainous headwater rivers

“…Although individual headwater floodplains are much narrower and shallower than the extensive floodplains that characterize downstream portions of large river networks, the cumulative length of the many small tributaries in a river network implies that organic carbon storage along these smaller rivers can be important. Further study of mechanisms and patterns of carbon storage in diverse geographic settings is needed to determine regional differences and the relative abundance of headwater rivers characterized by large downstream carbon fluxes 6,[8][9][10][11] versus headwater rivers characterized by the storage mechanisms described here. However, widespread reduction of geomorphic complexity along headwater channels likely has long-term and cumulative global effects on the carbon cycle.…”

“…Research in the mountainous tropics demonstrates that headwater rivers respond to disturbances, such as cyclones, landslides and large floods, by rapidly exporting terrestrial carbon downstream 6,[9][10][11] . Headwater rivers in the temperate zone and at higher latitudes, which typically have less frequent and intense disturbances than tropical rivers 12,13 , may not transmit organic carbon downstream as rapidly.…”

The mass distribution of coarse particulate organic matter exported from an Alpine headwater stream

“…However, if the scaling exponent of the mass distribution is known, and if for a given event a certain size fraction has been sampled representatively, the complete CPOM export can be calculated. Our study results suggest that CPOM export for all size fractions can be estimated from the volumes of LWD exported in a large event, for example by measuring piece sizes trapped in a reservoir or by video monitoring the passage of wood pieces (e.g., MacVicar and Piégay, 2012;MacVicar et al, 2009;Moulin and Pié-gay, 2004;Seo et al, 2008;West et al, 2011). In addition to scaling down from LWD deposits with the aim to estimate total CPOM export, the scaling relations also permit scaling up from measurements of small CPOM to estimate LWD transport.…”

Paleocene methane seep and wood-fall marine environments from Spitsbergen, Svalbard

“…Bienhold et al, 2013). We also speculate that in addition to wood, which is the main terrestrial plant material delivered to the sea (West et al, 2011), investigated sandstone bed could initially comprise bark, twigs and leaves which in modern seas can cover the seabed close to the areas rich in vegetation even in relatively deep waters (Wolff, 1979), but are less likely to become fossilized. Such material could also contribute to the overall substrate for the bacterial wood consumers during the Paleocene on Svalbard.…”