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- Title
Event Scale Relationships of DOC and TDN Fluxes in Throughfall and Stemflow Diverge From Stream Exports in a Forested Catchment.
- Authors
Ryan, Kevin A.; Adler, Thomas; Chalmers, Ann; Perdrial, Julia; Shanley, James B.; Stubbins, Aron
- Abstract
Aquatic fluxes of carbon and nutrients link terrestrial and aquatic ecosystems. Within forests, storm events drive both the delivery of carbon and nitrogen to the forest floor and the export of these solutes from the land via streams. To increase understanding of the relationships between hydrologic event character and the relative fluxes of carbon and nitrogen in throughfall, stemflow and streams, we measured dissolved organic carbon (DOC) and total dissolved nitrogen (TDN) concentrations in each flow path for 23 events in a forested watershed in Vermont, USA. DOC and TDN concentrations increased with streamflow, indicating their export was limited by water transport of catchment stores. DOC and TDN concentrations in throughfall and stemflow decreased exponentially with increasing precipitation, suggesting that precipitation removed a portion of available sources from tree surfaces during the events. DOC and TDN fluxes were estimated for 76 events across a 2‐year period. For most events, throughfall and stemflow fluxes greatly exceeded stream fluxes, but the imbalance narrowed for larger storms (>30 mm). The largest 10 stream events exported 40% of all stream event DOC whereas those same 10 events contributed 14% of all throughfall export. Approximately 2–5 times more DOC and TDN was exported from trees during rain events than left the catchment via streams annually. The diverging influence of event size on tree versus stream fluxes has important implications for forested ecosystems as hydrological events increase in intensity and frequency due to climate change. Plain Language Summary: Rainfall over forests links carbon and nutrients on tree surfaces to the forest floor and streams. Rain falling through the canopy is called throughfall while water running down the tree trunk is called stemflow. The ultimate fate of throughfall and stemflow is uncertain. We measured carbon and nitrogen dissolved in throughfall, stemflow, and stream water during rain events in Vermont. We then used rain event size to estimate how much carbon and nitrogen were transported by throughfall and stemflow during a 2‐year period, which we then compared with the amount of carbon and nitrogen leaving the forest in streams. The results indicated that the carbon and nitrogen in throughfall and stemflow were washed from tree surfaces and diluted by bigger storms whereas carbon and nitrogen in the streams became more concentrated. Climate change could alter the amount of carbon and nutrients in the forest that is carried away by water by changing the frequency and timing of small and large storms occurring throughout the year. Key Points: Most throughfall event dissolved organic carbon (DOC) fluxes were ∼10–100 times larger than stream fluxes, but the imbalance narrowed for larger storms (>30 mm)Approximately 2–5 times more DOC and total dissolved nitrogen (TDN) was removed from trees than exported from the catchment in streams annuallyThe influence of event size on tree and stream fluxes has important implications for forested ecosystems experiencing climate change
- Subjects
MARINE ecology; NITROGEN supersaturation; FORESTS &; forestry; CARBON compounds; CHEMICALS
- Publication
Journal of Geophysical Research. Biogeosciences, 2021, Vol 126, Issue 7, p1
- ISSN
2169-8953
- Publication type
Article
- DOI
10.1029/2021JG006281