Browsing by Subject "peatland"

Now showing 1 - 5 of 5
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    Carbon and Phosphorus Dynamics in Restored Minnesota Peatlands
    (2022-04) Wille, Emilie
    While many peatlands have been drained for anthropogenic purposes across the world, there is currently high interest in restoring peatlands for carbon and nutrient cycling benefits. Peat holds a disproportionate amount of the world’s soil carbon, making peatlands promising ecosystems for mitigating greenhouse gas emissions and climate change. Additionally, peatlands can sequester phosphorus (P) and prevent it from causing eutrophication in downstream waters, but they can also act as a P source under high runoff conditions. This study aimed to investigate the factors impacting 1) peat carbon dioxide (CO2) flux and 2) mobilization of peat P to porewater in a restored bog and fen in Minnesota. Peat CO2 flux was monitored in-situ throughout the growing season in conjunction with peat type, water table depth, and temperature. Peat columns from each site were saturated and subjected to controlled laboratory incubations to relate porewater ortho-P content to temperature and porewater aluminum (Al), calcium (Ca), and iron (Fe) content. A higher water table was significantly related to lower peat CO2 flux in the fen, and peat CO2 flux across both sites was higher in regions with more decomposed peat. During the peak of the growing season, CO2 flux was much higher in the fen than the bog, but both sites had similarly low CO2 flux at the end of the growing season. It is important that restoration ecologists consider a peatland’s water table when restoring a site’s hydrological, ecological, and biogeochemical functioning in order to achieve the greatest carbon benefit. Higher porewater ortho-P corresponded to higher dissolved porewater Al, Ca, and Fe. Additionally, higher initial peat Ca was significantly related to lower porewater P. These ions play a role in binding and mobilizing P, and their dynamics can help researchers predict and mitigate P release and subsequent export.
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    The Effect of Annual and Seasonal Variation in Precipitation on Temporal Water Storage Dynamics in Six Headwater Peatland Catchments: Marcell Experimental Forest, Minnesota
    (2023-06) Adams, David
    Using data collected from six headwater peatland catchments at the Marcell Experimental Forest in northern Minnesota, I assessed the relationship between variability in annual precipitation and annual changes in catchment water storage. Three hypotheses are addressed; (1) annual variability in precipitation is a primary driver of catchment storage change, (2) years of below average precipitation drive the relationship between precipitation and catchment water storage change, and (3) winter and fall precipitation variability are significant seasonal drivers of the annual catchment water storage change. The above relationships were analyzed via cross-correlation lag analysis and linear regression analysis of long-term precipitation, peatland water table elevation (WTE), and upland soil moisture (SM) time series, where WTE and SM served to quantify catchment water storage. Results indicate strong correlations between annual water storage change and annual precipitation variability, both in contemporaneous and antecedent years. Concurrent fall precipitation and antecedent winter precipitation were found to have the most influence on a given year’s water storage change. Years in which precipitation fell below the catchment average (dry years) exhibited a moderately significant linear relationship with annual catchment water storage change. Results of the above analysis were used to create a series of multivariate linear regression models, both with and without moving-average (MA) errors; these models were able to explain between approximately 50% and 70% of the variance found in the annual water storage change time series. Boreal peatlands play a vital role in the planet’s carbon cycle; developing a better understanding of the hydrologic function of these environments will likely prove important to future climate management practices.
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    The Effect of Atmospheric Sulfate Deposition on Mercury Biogeochemistry in an Experimental Peatland: Impacts, Recovery, and Natural Variability
    (2014-07) Coleman Wasik, Jill
    Elevated mercury deposition resulting from human activities has caused wide-spread mercury contamination of aquatic systems around the world. Peatlands are generally considered to be sinks for mercury deposited to the landscape, but also act as biogeochemical reactors wherein inorganic mercury is transformed into bioaccumulative, organic methylmercury (MeHg). Recent, short-term investigations have demonstrated that sulfate deposition alone can increase MeHg production in, and flux from, peatlands through the stimulation of sulfate-reducing bacteria, a group of known mercury methylators. However, over longer periods of time the interaction between the biogeochemical cycles of mercury and sulfur is complicated by variability in climate, hydrology, and sulfur and mercury deposition rates. These complexities were addressed by experimentally altering sulfate-loading to a 2.5-ha peatland in northern Minnesota over eight years. The peatland was initially divided into control and experimental treatments and sulfate was added to the latter three times each field season in simulated rainfall events. Porewaters were sampled before and after each sulfate addition and peat samples were collected five times from sites located within the raised central bog and along the peatland margins. The lagg margin is generally considered to be the primary site of mercury methylation in peatlands. However, sulfate addition caused more pronounced and persistent increases in MeHg in the central bog sites, relative to the margin sites, demonstrating that sulfate delivery to the central bog can greatly expand the areal extent of mercury methylation in peatlands. MeHg production also responded to sulfate release following severe summer drought. The increase was much higher in experimental-treatment sites than in control sites suggesting that the experimental treatment was "primed" to quickly respond to new sulfate inputs. In early 2006 sulfate addition was halted to the upgradient one-third of the original experimental treatment in order to monitor how MeHg production changed as sulfate deposition declined. Although drought appeared to slow the recovery process by increasing sulfate availability and mobilizing MeHg, three years after sulfate additions ceased MeHg in the recovery treatment was significantly lower than in the experimental treatment. This indicates that MeHg production in peatlands formerly affected by elevated sulfate deposition may return to background conditions and highlights the potential benefits that further controls on atmospheric sulfur emissions may have on MeHg production in peatlands and consequent mercury burdens in aquatic foodwebs. The long-term nature of this study allowed for an in-depth exploration of the effects that hydrologic flucutations on mercury cycling in peatlands and calls attention to the potential negative consequences that changing precipitation patterns and evapotranspirative demands may have on MeHg production in these systems.
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    An investigation of mercury dynamics in the pore water of peat columns during experimental warming, freezing, and thawing
    (2016-12) Sirota, Jennie
    Biogeochemical processes in northern peatland ecosystems are influenced by seasonal temperature fluctuations that are becoming altered with changes in climate. Since mercury is commonly found in peatlands, it is important to understand how temperature impacts mercury dynamics. This study investigates how changes in temperature influences belowground concentrations of total mercury (THg), methylmercury (MeHg), and dissolved organic carbon (DOC) in peat pore waters. Four large peat columns were removed from an ombrotrophic peat bog and exposed to experimental warming, freezing, and thawing. Pore water was sampled across seven depths in the peat columns during the different temperature treatments and analyzed for THg, MeHg, and DOC concentrations. Results indicated that a 2 degree Celsius air temperature increase during warming was not great enough to change the THg and MeHg concentrations in the peat pore water. Freezing resulted in significant decreases in THg and MeHg concentrations and showed evidence of THg exclusion from the ice structure. During thawing, THg concentrations significantly increased while MeHg concentrations remained low. Depth results showed increased bulk density and decreased THg, MeHg, and DOC after 15 cm, which may be indication of the mesotelm layer in the peat columns. These findings fill a gap in peatland research by providing data related to how the freeze-thaw cycle impacts mercury dynamics in peat pore water.
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    Peatland Hydrological Dynamics in Northern Minnesota
    (2015-09) Roush, Benjamin
    I investigated peatland water table elevation responses to large precipitation events and long precipitation-free periods for a fen, poor fen, and bog, and pore water chemistry trends in a fen boundary zone, in northern Minnesota. Water table change compared to both precipitation and dry periods was slower in the fen than the poor fen or bog, a response attributed to connections between the fen and the regional groundwater aquifer. Water table change compared to larger dry periods remained consistent over a 51-year period and among peatlands. Calcium-silicon ratios in fen pore water were collected along transects perpendicular to the fen boundary. Larger calcium-silicon ratios at edge of the fen were interpreted as originating from a regional aquifer source, with minimal influence from vegetative calcium uptake and upland subsurface runoff. The extent of the fen-upland boundary zone was demarcated where calcium-silicon ratios matched average fen and stream outlet calcium-silicon ratios.