Interactive plant functional group and water table effects on decomposition and extracellular enzyme activity in Sphagnum peatlands

Wiedermann, Magdalena M.; Kane, Evan S.; Potvin, Lynette R.; Lilleskov, Erik A.

doi:10.1016/j.soilbio.2017.01.008

Cited by 52 publications

(28 citation statements)

References 66 publications

(51 reference statements)

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“…This is supported by the significant but weak regression between GEP and DOC concentration, E2/E3 and SUVA, particularly across sites experiencing drainage (Figure 4). The results of the RDA analysis suggest that the changing DOC dynamics were specifically linked to the shift from a largely Sphagnum- (Wiedermann, Kane, Potvin, & Lilleskov, 2017). Although this was not specifically investigated in the present study, suppression of decomposition could also result in the observed shift in the DOC pool towards smaller, less aromatic molecules generally associated with fresh plant inputs.…”

Section: Links Between Vegetation Productivity and Doc Concentratiomentioning

confidence: 66%

“…These shifts appear to be linked not only to higher deposition of DOC into the rhizosphere, but also changes in belowground carbon and nitrogen cycling related to higher polyphenol concentration and fungal abundance at sites with greater shrub cover. The decomposition of complex organic molecules may also be slowed in the presence of Ericaceous shrubs, likely linked to the abundance of ectomycorrhizal fungus (Wiedermann, Kane, Potvin, & Lilleskov, ). Although this was not specifically investigated in the present study, suppression of decomposition could also result in the observed shift in the DOC pool towards smaller, less aromatic molecules generally associated with fresh plant inputs.…”

Section: Discussionmentioning

confidence: 99%

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Shrub abundance contributes to shifts in dissolved organic carbon concentration and chemistry in a continental bog exposed to drainage and warming

2019

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Northern peatlands are globally significant soil carbon sinks but contribute a significant amount of dissolved organic carbon (DOC) to streams. Climate change driven warming and drying will likely alter peatland DOC dynamics; however, few field studies have quantified the individual and interactive effects of temperature and moisture changes. Using a full factorial water table (control, drained 2 years [experimental], drained 12 years [drained]) × warming (ambient, open‐top chamber warming) × microform (hummock, hollow) study design, we monitored DOC concentration and spectrophotometric properties (specific ultraviolet absorbance [SUVA], E2/E3, E4/E6) in a wooded boreal bog in Alberta, Canada. Ecohydrological conditions including water table (WT), soil temperature, plant cover, biomass, and productivity were also measured at each plot. We observed a significant interaction between WT treatment, warming and microform for explaining variation in DOC concentrations, with the highest values at drained, warmed hummocks. Overall, drainage resulted in higher DOC concentration. DOC concentration and E2/E3 increased, whereas SUVA decreased, in response to greater plant productivity (i.e., more negative values of gross ecosystem photosynthesis). For DOC concentration and SUVA, this correlation was largely driven by drained, warmed hummocks where shrub growth increased. Moreover, redundancy analysis indicated that shrub and lichen cover, along with WT and soil temperature, were important for explaining variation in DOC concentration and quality. The results indicate that, although DOC concentrations in peatlands are likely to increase under climate change, much of this increase may be from recent carbon fixation, suggesting more rapid carbon cycling as opposed to destabilization of existing carbon stocks.

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Section: Links Between Vegetation Productivity and Doc Concentratiomentioning

confidence: 66%

Section: Discussionmentioning

confidence: 99%

Shrub abundance contributes to shifts in dissolved organic carbon concentration and chemistry in a continental bog exposed to drainage and warming

2019

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“…In bog ecosystems, decomposition of recalcitrant compounds associated with the breakdown of Sphagnum could be analogous to prior models of aromatic lignin decomposition (Straková et al, ; cf. Wiedermann, Kane, Potvin, et al, ; Worrall et al, ). 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.…”

Section: Discussionmentioning

confidence: 99%

“…The Ericaceae produce recalcitrant litter (Cornelissen, 1996) and have mycorrhizal fungi, which possess some oxidative extracellular enzymes but lack peroxidase enzyme activity (Cairney & Burke, 1998;Cairney & Meharg, 2003); these factors have an inhibitory effect on peat decomposition (Read et al, 2004) thus promoting hummock formation and creation of microsites that are more likely to be above the WT (Belyea & Malmer, 2004;Ohlson & Dahlberg, 1991). As such, there are interactive effects between altered hydrology and plant functional groups, which have been shown to influence decomposition dynamics in peat (Wiedermann, Kane, Potvin, et al, 2017). However, the interactive effects of changes in peat saturation or vegetation community on oxygen supply and redox environment remain to be elucidated.…”

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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“…Moisture also has the potential to affect litter decomposition and nutrient cycling rates. Decomposition is usually slow under very wet (Wiedermann, Kane, Potvin, & Lilleskov, ) or dry conditions (Vogel, Eisenhauer, Weigelt, & Scherer‐Lorenzen, ), which could result in lower soil nutrient availability to plants and hence the production of lower‐quality root and shoot litter at the extreme ends of the moisture gradient (Reich, ). This could result in more negative plant–litter feedbacks for fast‐growing plants that are more dependent on high nutrient inputs and less able to tolerate harsh conditions (Figure b).…”

Section: Abiotic Driversmentioning

confidence: 99%

Why are plant–soil feedbacks so unpredictable, and what to do about it?

et al. 2018

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The study of feedbacks between plants and soils (plant–soil feedbacks; PSFs) is receiving increased attention. However, PSFs have been mostly studied in isolation of abiotic and biotic drivers that could affect their strength and direction. This is problematic because it has led to limited predictive power of PSFs in “the real world,” leaving large knowledge gaps in our ability to predict how PSFs contribute to ecosystem processes and functions. Here, we present a synthetic framework to elucidate how abiotic and biotic drivers affect PSFs. We focus on two key abiotic drivers (temperature and soil moisture) and two key biotic drivers (above‐ground plant consumers and below‐ground top‐down control of pathogens and mutualists). We focus on these factors because they are known drivers of plants and soil organisms and the ecosystem processes they control, and hence would be expected to strongly influence PSFs. Our framework describes the proposed mechanisms behind these drivers and explores their effects on PSFs. We demonstrate the impacts of these drivers using the fast‐ to slow‐growing plant economics spectrum. We use this well‐established paradigm because plants on opposite ends of this spectrum differ in their relationships with soil biota and have developed contrasting strategies to cope with abiotic and biotic environmental conditions. Finally, we present suggestions for improved experimental designs and scientific inference that will capture and elucidate the influence of above‐ and belowground drivers on PSFs. By establishing the role of abiotic and biotic drivers of PSFs, we will be able to make more robust predictions of how PSFs impact on ecosystem function. http://onlinelibrary.wiley.com/doi/10.1111/1365-2435.13232/suppinfo is available for this article.

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Interactive plant functional group and water table effects on decomposition and extracellular enzyme activity in Sphagnum peatlands

Cited by 52 publications

References 66 publications

Shrub abundance contributes to shifts in dissolved organic carbon concentration and chemistry in a continental bog exposed to drainage and warming

Shrub abundance contributes to shifts in dissolved organic carbon concentration and chemistry in a continental bog exposed to drainage and warming

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

Why are plant–soil feedbacks so unpredictable, and what to do about it?

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