Carbon and nitrogen exports with hurricanes and other extreme storms: Implications for coupled effects of climate and landuse change (Invited)
Abstract
Climate and landuse changes and their interactions can have significant impacts on water quality and other ecosystem services. Future climate-change projections for the northeast USA indicate that the intensity of north Atlantic hurricanes and other large storms is likely to increase with a simultaneous increase in the duration and intensity of intervening droughts. Such shifts in climate and storm events can alter the export patterns of carbon (C) and nitrogen (N) and their cycling in watersheds. These changes are likely to differ for forested, agricultural and urban catchments. We determined the stream exports of particulate and dissolved C and N for multiple storms in a 12 ha forested watershed located in the mid-Atlantic Piedmont region of the USA. These storms included remnants of hurricanes - Nicole (2010), Irene (2011) and Sandy (2012). While particulate C and N forms in runoff were comparable to the dissolved species for the small storms (precipitation < 50 mm), particulate exports increased dramatically and were five to eight times the dissolved values for the largest storms (precipitation > 100 mm). Particulate and dissolved organic C concentrations for storm events ranged from 0-252 mg/L and 0.6-18 mg/L respectively, whereas particulate N and total dissolved N (TDN) concentrations varied between 0-16 mg/L and 0-2.1 mg/L, respectively. Nitrate-N was the dominant dissolved N form in runoff (0-2 mg/L). Particulate C and N exports from Hurricane Irene alone (over a 59 hour period) constituted 37% (22 kg/ha) and 27% (1.7 kg/ha) of the annual C (59 kgC/ha) and N (6.4 kgN/ha) exports for 2011. Within-event patterns for the largest storms indicated that while particulate concentrations continued to increase with streamflow discharge, dissolved concentrations declined at peak discharge indicating an exhaustion of supply of these constituents. Our observations suggest that these extreme storms can mobilize large amounts of particulate C and N, some of which may be directly exported to downstream aquatic ecosystems, while the remainder may be deposited in the catchment drainage network. This deposited material, both in aquatic ecosystems and the fluvial network, could then serve as a continuous, long-term source of C and N. Understanding how these large events impact the immediate and long-term cycling of C and N in watersheds is important. While this study was conducted in a forested watershed, we speculate that agricultural landscapes subject to similar storms could produce similar or even larger exports of particulate C and N. The response of urban catchments to these storms is uncertain and will be dictated by the amounts and forms of C and N that can be mobilized during the events.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2013
- Bibcode:
- 2013AGUFM.B32B..03I
- Keywords:
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- 0496 BIOGEOSCIENCES Water quality;
- 0428 BIOGEOSCIENCES Carbon cycling;
- 1807 HYDROLOGY Climate impacts;
- 1804 HYDROLOGY Catchment