Carbon Export from the Pacific Northwest Coastal Rainforest Margin
Abstract
The Pacific Coastal Temperate Rainforest Region (PCTR) extends from northern California to southeast Alaska and is characterized by steep coastal mountains, robust fisheries, and abundant icefields in the northern part of the domain. The region also contains the largest stores of recently fixed biological carbon on Earth. The coastal margin of the PCTR has extremely high rates of precipitation (exceeding 6m yr-1 at high elevation) due to steep topography and the high frequency of frontal storms from the northern Pacific. As a result, the PCTR discharges roughly 1,300 km3 of freshwater each year. This volume of run-off is 2.5 times greater than the Mississippi River. Such large volumes of water across the PCTR landscape allows for the rapid transfer of carbon from terrestrial ecosystems to the coastal zone. Several large continental rivers contribute to the flux of carbon and water, but the majority of runoff and carbon is derived from the thousands of small, ungauged watersheds along the coastal margin of the PCTR. Here we present results from the NSF-Coastal Margins Research Coordination Network synthesis of the exports of dissolved organic carbon (DOC) across the terrestrial-marine interface. With a newly compiled database encompassing over 10,000 measurements, we show that the PCTR exports 3.5 Tg-C yr-1 as DOC with over half of this flux derived from individual small watersheds that comprise only 22% of the total drainage area. We also identify hot-spots of DOC flux, with organic carbon yields in excess of 60-g-C m2 yr-1 driven by a balance of both temperature, precipitation and, the unique forest and soil matrix with high soil organic carbon content from Northern Vancouver Island and southeast Alaska. These fluxes and their potential support for coastal heterotrophic production are assessed in the context of a changing climate.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2020
- Bibcode:
- 2020AGUFMB015...03B
- Keywords:
-
- 0414 Biogeochemical cycles;
- processes;
- and modeling;
- BIOGEOSCIENCES;
- 0439 Ecosystems;
- structure and dynamics;
- BIOGEOSCIENCES;
- 1630 Impacts of global change;
- GLOBAL CHANGE;
- 1833 Hydroclimatology;
- HYDROLOGY