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Abstract Tree stems exchange CO2, CH4and N2O with the atmosphere but the magnitudes, patterns and drivers of these greenhouse gas (GHG) fluxes remain poorly understood. Our understanding mainly comes from static-manual measurements, which provide limited information on the temporal variability and magnitude of these fluxes. We measured hourly CO2, CH4and N2O fluxes at two stem heights and adjacent soils within an upland temperate forest. We analyzed diurnal and seasonal variability of fluxes and biophysical drivers (i.e., temperature, soil moisture, sap flux). Tree stems were a net source of CO2(3.80 ± 0.18 µmol m−2s−1; mean ± 95% CI) and CH4(0.37 ± 0.18 nmol m−2s−1), but a sink for N2O (−0.016 ± 0.008 nmol m−2s−1). Time series analysis showed diurnal temporal correlations between these gases with temperature or sap flux for certain days. CO2and CH4showed a clear seasonal pattern explained by temperature, soil water content and sap flux. Relationships between stem, soil fluxes and their drivers suggest that CH4for stem emissions could be partially produced belowground. High-frequency measurements demonstrate that: a) tree stems exchange GHGs with the atmosphere at multiple time scales; and b) are needed to better estimate fluxes magnitudes and understand underlying mechanisms of GHG stem emissions.
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This content will become publicly available on September 11, 2026
Responding to rising waters and temperatures: greenhouse gas flux from a high-latitude coastal wetland
Abstract Climate change is exposing coastal landscapes to more flooding, in addition to rapidly rising temperatures. These changes are critical in the Arctic where the effects of sea level rise are exacerbated by the loss of sea ice protecting coasts, subsidence as permafrost thaws, and a projected increase in storms. Such changes will likely alter the land-atmosphere gas exchange of high-latitude coastal ecosystems, but the effects of flooding with warming remain unexplored. In this work we use a field experiment to examine the interacting effects of increased tidal flooding and warming on land-atmosphere CO2and CH4exchange in the coastal Yukon–Kuskokwim Delta, a large sub-Arctic wetland and tundra complex in western Alaska. We inundated dammed plots to simulate two levels of future flooding: low-intensity flooding represented by one day of flooding per summer-month (June, July and August), and high-intensity flooding represented by three-consecutive days of flooding per summer-month, crossed with a warming treatment of 1.4 °C. We found that both flooding and warming influenced greenhouse gas (GHG) exchange. Low-intensity flooding reduced net CO2uptake by 20% (0.78µmol m−2s−1) regardless of temperature, and marginally increased CH4emissions 0.83 nmol m−2s−1(33%) under ambient temperature, while decreasing CH4emissions by −1.96 nmol m−2s−1(40%) under warming. In contrast, high-intensity flooding restored net CO2uptake to control levels due to enhanced primary productivity under both temperature treatments. High-intensity flooding decreased CH4emissions under ambient temperature by 0.76 nmol m−2s−1(30%), but greatly increased emissions under warming by 4.68 nmol m−2s−1(265%), presumably driven by increased plant-mediated CH4transport. These findings reveal that GHG exchange responds rapidly and non-linearly to intensifying flooding, and highlight the importance of short-term flooding dynamics and warming in shaping future carbon cycling in this Arctic coastal wetland.
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- Award ID(s):
- 2113641
- PAR ID:
- 10647377
- Publisher / Repository:
- IOP Publishing
- Date Published:
- Journal Name:
- Environmental Research Letters
- Volume:
- 20
- Issue:
- 10
- ISSN:
- 1748-9326
- Page Range / eLocation ID:
- 104040
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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