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Peatlands play a critical role in terrestrial carbon (C) storage, containing an estimated 30% of global soil C, despite occupying only 3% of global land area. Historic management of peatlands has led to widespread degradation and loss of important ecosystem services, including C sequestration. Legacy drainage features in the peatlands of northern Minnesota, USA were studied to assess the volume of peat and the amount of C lost in the ~100 years since drainage. Using high-resolution Light Detection and Ranging (LiDAR) data, we measured elevation changes adjacent to legacy ditches to model pre-ditch surface elevations, which were used to calculate peat volume loss. We established relationships between volume loss and site characteristics from existing geographic information systems datasets and used those relationships to scale volume loss to all mapped peatland ditches in northern Minnesota (USA). We estimated that 0.165 ± 0.009 km3 of peat have been lost along almost 4000 km of peatland ditches. Peat loss upslope of ditches was significantly less than downslope (P < 0.001). Mean width of the entire ditch-effect zone was 333 ± 8.32 m. Using our volume loss estimates, literature estimates of oxidation, and mean bulk density and peat C% values from Minnesota peatlands, we calculate a total historic loss 3.847 ± 0.364 Tg C. Assuming a constant oxidation rate during the 100 years since drainage, euic and dysic peatlands within the ditch effect zone have lost 0.26 ± 0.08 and 0.40 ± 0.13 Mg C ha-1 yr-1, respectively, comparable to IPCC estimates. Our spatially-explicit peat loss estimates could be incorporated into decision support tools to inform management decisions regarding peatland C and other ecosystem services.

Tropical peatlands are a major, but understudied, biophysical feedback factor on the atmospheric greenhouse effect. The largest expanses of tropical peatlands are located in lowland areas of Southeast Asia and the Amazon basin. The Loreto Region of Amazonian Peru contains ~63,000 km2 of peatlands. However, little is known about the biogeochemistry of these peatlands, and in particular, the cycling of carbon dioxide (CO2) and methane (CH4), and their responses to hydrometeorological forcings. To address these knowledge gaps, we established an eddy covariance (EC) flux tower in a natural palm (Mauritia flexuosa L.f.) swamp peatland near Iquitos, Peru. Here, we report ecosystem-scale CO2 and CH4 flux observations for this Amazonian palm swamp peatland over a two-year period in relation to hydrometeorological forcings. Seasonal and short-term variations in hydrometeorological forcing had a strong effect on CO2 and CH4 fluxes. High air temperature and vapor pressure deficit (VPD) exerted an important limitation on photosynthesis during the dry season, while latent heat flux appeared to be insensitive to these climate drivers. Evidence from light-response analyses and flux partitioning support that photosynthetic activity was downregulated during dry conditions, while ecosystem respiration (RE) was either inhibited or enhanced depending on water table position. The cumulative net ecosystem CO2 exchange indicated that the peatland was a significant CO2 sink ranging from −465 (−279 to −651) g C m−2 y−1 in 2018 to −462 (−277 to −647) g C m−2 y−1 in 2019. The forest was a CH4 source of 22 (20 to 24) g C m−2 y−1, similar in magnitude to other tropical peatlands and larger than boreal and arctic peatlands. Thus, the annual carbon budget of this Amazonian palm swamp peatland appears to be a major carbon sink under current hydrometeorological conditions.

Wet meadows are seasonally saturated wetlands that can develop in arid and semi-arid areas. In the semi-arid region of North Patagonia, Argentina wet meadows are islands of high net primary productivity surrounded by low productivity steppe vegetation. Because of this, Patagonian wet meadows have been heavily grazed by livestock for more than a century. It has been shown that overgrazed wet meadows have lower soil carbon, however, little is known about how overgrazing impacts N dynamics. To this end, we measured ammonium (NH4+), nitrate (NO3−), and total nitrogen (Nt) in paired wet meadows that varied in long-term grazing intensity (heavy vs. light). Results indicate that heavily grazed sites had on average 43% less Nt and 57% less NH4+ than lightly grazed sites. Soil NH4+ concentrations were always significantly greater than NO3− concentrations, being the later often below detection levels. In addition, NH4+ concentrations were correlated with soil moisture in lightly grazed sites, but not in heavily grazed sites. These findings indicate that implementation of better management practices are currently needed to promote more sustainable grazing in semi-arid wet meadows of North Patagonia.

We quantified the relationship between water table position and CO 2 emissions by manipulating water table levels for two summers in microcosms installed in a Colorado subalpine fen. Water levels were manipulated in the microcosms by either adding water or removing water and ranged from +10 cm above the soil surface to 40 cm below the soil surface, with ambient water levels in the fen averaging +3 and +2 cm above the soil surface during 1998 and 1999, respectively. Microcosm installation had no significant effect on CO 2 efflux; the 2 year means of natural and reference CO 2 efflux were 205.4 and 213.9 mg CO 2 -C m −2 h −1 , respectively ( p =0.80). Mean CO 2 emissions were lowest at the highest water tables (water +6 to +10 cm above the soil surface), averaging 133.8 mg CO 2 -C m −2 h −1 , increased to 231.3 mg CO 2 -C m −2 h −1 when the water table was +1 to +5 cm above the soil surface and doubled to 453.7 mg CO 2 -C m −2 h −1 , when the water table was 0–5 cm below the soil surface. However, further lowering of the water table had little additional effect on CO 2 emissions, which averaged 470.3 and 401.1 mg CO 2 -C m −2 h −1 when the water table was 6–10 cm, and 11–40 cm beneath the soil surface, respectively. The large increase in CO 2 emissions as we experimentally lowered the water table beneath the soil surface, coupled with no increase in CO 2 emissions as we furthered lowered water tables beneath the soil surface, suggest the presence of an easily oxidized labile carbon pool near the soil surface.