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Abstract Peat mosses (Sphagnumspp.) are keystone species in boreal peatlands, where they dominate net primary productivity and facilitate the accumulation of carbon in thick peat deposits.Sphagnummosses harbor a diverse assemblage of microbial partners, including N2‐fixing (diazotrophic) and CH4‐oxidizing (methanotrophic) taxa that support ecosystem function by regulating transformations of carbon and nitrogen. Here, we investigate the response of theSphagnumphytobiome (plant + constituent microbiome + environment) to a gradient of experimental warming (+0°C to +9°C) and elevated CO2(+500 ppm) in an ombrotrophic peatland in northern Minnesota (USA). By tracking changes in carbon (CH4, CO2) and nitrogen (NH4‐N) cycling from the belowground environment up toSphagnumand its associated microbiome, we identified a series of cascading impacts to theSphagnumphytobiome triggered by warming and elevated CO2. Under ambient CO2, warming increased plant‐available NH4‐N in surface peat, excess N accumulated inSphagnumtissue, and N2fixation activity decreased. Elevated CO2offset the effects of warming, disrupting the accumulation of N in peat andSphagnumtissue. Methane concentrations in porewater increased with warming irrespective of CO2treatment, resulting in a ~10× rise in methanotrophic activity withinSphagnumfrom the +9°C enclosures. Warming's divergent impacts on diazotrophy and methanotrophy caused these processes to become decoupled at warmer temperatures, as evidenced by declining rates of methane‐induced N2fixation and significant losses of keystone microbial taxa. In addition to changes in theSphagnummicrobiome, we observed ~94% mortality ofSphagnumbetween the +0°C and +9°C treatments, possibly due to the interactive effects of warming on N‐availability and competition from vascular plant species. Collectively, these results highlight the vulnerability of theSphagnumphytobiome to rising temperatures and atmospheric CO2concentrations, with significant implications for carbon and nitrogen cycling in boreal peatlands.
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Spectral Indices of Vegetation Condition and Soil Water Content Reflect Controls on CH 4 and CO 2 Exchange in Sphagnum ‐Dominated Northern Peatlands
Abstract Northern peatlands play an important role in the global C cycle due to their large C stocks and high potential methane (CH4) emissions. The CH4and CO2cycles of these systems are closely linked to hydrology, with water table level regulating the balance of oxic and anoxic conditions and the water content ofSphagnummosses that dominate primary production. Previous work has demonstrated that hyperspectral indices well‐suited to the detection of altered hydrology inSphagnumpeatlands are also highly correlated with GPP. However, little work has been done to extend these findings to CH4effluxes. In this study, we evaluate the utility of four hyperspectral indices, two reflecting vegetation photosynthetic function (chlorophyll index (CI); normalized difference vegetation index) and two reflecting water content (wetness index (WI); floating water band index), for detecting effects of altered water table, precipitation, and vegetation community on CH4and CO2exchange in two peatland mesocosm studies. We found that CI is a good predictor of net CO2exchange, and that it captured both drought and vegetation effects consistently across a broad range of vegetation treatments. Further, we demonstrate for the first time that WI combined with CI explained a significant percentage of CH4efflux (R2 = 0.32–0.57). Our results indicate that CI and WI together may be effective tools for detecting effects of altered hydrology and vegetation on northernSphagnum‐peatland CH4and CO2emissions, with implications for detecting and modeling changes in emissions of greenhouse gases at scales ranging from the ecosystem to the Earth system.
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- PAR ID:
- 10369140
- Publisher / Repository:
- DOI PREFIX: 10.1029
- Date Published:
- Journal Name:
- Journal of Geophysical Research: Biogeosciences
- Volume:
- 127
- Issue:
- 7
- ISSN:
- 2169-8953
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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