Understanding drivers of peatland extracellular enzyme activity in the PEATcosm experiment: mixed evidence for enzymic latch hypothesis

Romanowicz, Karl J.; Kane, Evan S.; Potvin, Lynette R.; Daniels, Aleta L.; Kolka, Randall K.; Lilleskov, Erik A.

doi:10.1007/s11104-015-2746-4

Cited by 40 publications

(40 citation statements)

References 88 publications

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“…Romanowicz et al . [] found a positive correlation between pore water total phenolics and peroxidase enzyme activity. Oxidative enzymes including peroxidase and phenol oxidase contribute to the degradation of lignin and polymeric complexes [ Romanowicz et al ., ].…”

Section: Resultsmentioning

confidence: 99%

“…[] found a positive correlation between pore water total phenolics and peroxidase enzyme activity. Oxidative enzymes including peroxidase and phenol oxidase contribute to the degradation of lignin and polymeric complexes [ Romanowicz et al ., ]. As pore water concentrations of THg and MeHg increased with total phenolics, which were positively correlated with peroxidase enzyme activity in the PEATcosm pore waters [ Romanowicz et al ., ], organic matter decomposition was likely the source of increased pore water Hg mobility (Figure S7).…”

Section: Resultsmentioning

confidence: 99%

“…Pore water collection and analysis for total phenolics by microplate technique (with tannic acid standard) were as previously described in Romanowicz et al . [].…”

Section: Methodsmentioning

confidence: 99%

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Mobility and transport of mercury and methylmercury in peat as a function of changes in water table regime and plant functional groups

Haynes

Kane

Potvin

et al. 2017

Global Biogeochemical Cycles

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Climate change is likely to significantly affect the hydrology, ecology, and ecosystem function of peatlands, with potentially important but unclear impacts on mercury mobility within and transport from peatlands. Using a full‐factorial mesocosm approach, we investigated the potential impacts on mercury mobility of water table regime changes (high and low) and vegetation community shifts (sedge‐dominated, Ericaceae‐dominated, or unmanipulated control) in peat monoliths at the PEATcosm mesocosm facility in Houghton, Michigan. Lower and more variable water table regimes and the loss of Ericaceae shrubs act significantly and independently to increase both total Hg and methylmercury concentrations in peat pore water and in spring snowmelt runoff. These differences are related to enhanced peat decomposition and internal regeneration of electron acceptors which are more strongly related to water table regime than to plant community changes. Loss of Ericaceae shrubs and an increase in sedge cover may also affect Hg concentrations and mobility via oxygen shuttling and/or the provision of labile root exudates. Altered hydrological regimes and shifting vegetation communities, as a result of global climate change, are likely to enhance Hg transport from peatlands to downstream aquatic ecosystems.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

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Mobility and transport of mercury and methylmercury in peat as a function of changes in water table regime and plant functional groups

Haynes

Kane

Potvin

et al. 2017

Global Biogeochemical Cycles

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“…The strong negative relationships between SUVA254 (an indicator of aromatic C) and Eh7, as well as between SUVA254 and E4:E6 presented herein (Figure ) are consistent with increased breakdown of aromatic biomolecules co‐occurring with the synthesis of larger macromolecules at higher Eh. Prior research in the mesocosms demonstrated that pore water phenol oxidase (a class of oxidative enzymes involved in oxidation of phenolic compounds) activities increased with Eh and ericaceous shrub root abundance but did not relate to the pool size of total phenolics (Romanowicz et al, ). This earlier interpretation of a lack of enzymatic controls over total phenolic concentrations, and therefore mixed support for the enzymic latch mechanism, was likely obscured because the phenolic character was greatly affected by the WT and PFG treatments (Table a; Figure ); the colorimetric methods for total phenolics likely cannot distinguish changes in quinone moieties.…”

Section: Discussionmentioning

confidence: 99%

“…In this conceptual model, the accumulation of phenolics further stabilizes peat by inhibiting hydrolytic enzyme activity. However, subsequent study has observed mixed evidence for this hypothesis and has shown higher phenolics with declines in WT position in peat mesocosm experiments controlling for plant functional groups and WT position (Dieleman et al, ; Romanowicz et al, ). In this same experimental framework, the highest phenolic concentrations were observed in treatments with lowered WT positions and sedge vegetation (Haynes et al, ).…”

Section: Introductionmentioning

confidence: 99%

Reduction‐Oxidation Potential and Dissolved Organic Matter Composition in Northern Peat Soil: Interactive Controls of Water Table Position and Plant Functional Groups

et al. 2019

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Globally important carbon (C) stores in northern peatlands are vulnerable to oxidation in a changing climate. A growing body of literature draws attention to the importance of dissolved organic matter (DOM) in governing anaerobic metabolism in organic soil, but exactly how the reduction-oxidation (redox) activities of DOM, and particularly the phenolic fraction, are likely to change in an altered climate remain unclear. We used large mesocosms in the PEATcosm experiment to assess changes in peatland DOM and redox potential in response to experimental manipulations of water table (WT) position and plant functional groups (PFGs). WT position and PFGs interacted in their effects on redox potential and quantity and quality of DOM. Phenolics were generally of higher molecular weight and more oxidized with sedges in lowered WTs. Altered DOM character included changes in dissolved nitrogen (N), with higher N:[phenolics] with higher E4:E6 (absorbance ratio λ = 465:665) DOM in the lowered WT and sedge PFG treatments. Conversely, biomolecular assignments to amino-sugars were largely absent from low-WT treatments. Low WT resulted in the creation of unique N compounds, which were more condensed (lower H:C), that changed with depth and PFG. The accumulation of oxidized compounds with low WT and in sedge rhizospheres could be very important pools of electron acceptors beneath the WT, and their mechanisms of formation are discussed. This work suggests the effects of changes in vegetation communities can be as great as WT position in directly and interactively mediating peat redox environment and the redox-activity of DOM. Plain Language Summary Peatlands are important ecosystems in both the global carbon (C)cycle and the Earth's climate system owing to their ability to store vast quantities of C taken from the atmosphere. Peat C stays locked up in these ecosystems largely owing to cool and wet conditions, and as such, these C stores are vulnerable to release back to the atmosphere if the climate or water levels change. Water table level and plant species composition have a combined effect on C and nitrogen (N) cycling in peatlands. We manipulated both factors in an experimental setting composed of 24 large bins into which we put intact peatland miniecosystems. Sedges play a big role in producing N compounds below the peat surface, and this work suggests these compounds can actually be synthesized into larger, less accessible compounds. In addition, activities of sedge roots and other dominant plant communities (such as shrubs in the heath family of plants) may interact in the synthesis of oxidized, larger molecules. These molecules can allow microbes to continue to decompose peat even in the absence of oxygen. This could increase the release of greenhouse gas carbon dioxide to the atmosphere, while reducing inputs of the stronger greenhouse gas methane.

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Plant functional group effects on peat carbon cycling in a boreal rich fen

et al. 2019

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Understanding drivers of peatland extracellular enzyme activity in the PEATcosm experiment: mixed evidence for enzymic latch hypothesis

Cited by 40 publications

References 88 publications

Mobility and transport of mercury and methylmercury in peat as a function of changes in water table regime and plant functional groups

Mobility and transport of mercury and methylmercury in peat as a function of changes in water table regime and plant functional groups

Reduction‐Oxidation Potential and Dissolved Organic Matter Composition in Northern Peat Soil: Interactive Controls of Water Table Position and Plant Functional Groups

Plant functional group effects on peat carbon cycling in a boreal rich fen

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