Contrasting growth responses of dominant peatland plants to warming and vegetation composition

Walker, T. K.; Ward, Susan E.; Ostle, Nicholas J.; Bardgett, Richard D.

doi:10.1007/s00442-015-3254-1

Cited by 39 publications

(30 citation statements)

References 57 publications

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“…The microenvironmental drivers examined in the present study (i.e., water level and shading) mediate the effect of macroclimate on Sphagnum processes on a local scale. There are experiments that indicate that warming may indirectly promote Sphagnum growth by increasing the growth of dwarf shrubs in the bog‐fen complex, which promote Sphagnum growth via a shading effect cooling the peat surface (Walker, Ward, Ostle, & Bardgett, ). Indeed, we found that growth and mass loss would be higher in shaded conditions.…”

Section: Discussionmentioning

confidence: 99%

Scaling functional traits to ecosystem processes: Towards a mechanistic understanding in peat mosses

et al. 2018

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The role of trait trade‐offs and environmental filtering in explaining the variability in functional traits and ecosystem processes has received considerable attention for vascular plants but less so for bryophytes. Thus, we do not know whether the same forces also shape the phenotypic variability of bryophytes. Here, we assess how environmental gradients and trade‐offs shape functional traits and subsequently ecosystem processes for peat mosses (Sphagnum), a globally important plant genus for carbon accumulation. We used piecewise Structural Equation Modeling (SEM) to understand how environmental gradients influence vital processes across levels of biological organization. We gathered data on functional traits for 15 globally important Sphagnum species covering a wide range of ecological preferences. Phenotypes lie along well‐established axes of the plant economic spectrum characterizing trade‐offs between vital physiological functions. Using SEM, we clarified the mechanisms of trait covariation and scaling to ecosystem processes. We tested whether peat mosses, like vascular plants, constrain trait variability between a fast turnover strategy based on resource acquisition via fast traits and processes, and a strategy of resource conservation, via slow traits and processes. We parameterized a process‐based model estimating ecosystem processes linking environmental drivers with architectural and functional traits. In our SEM approach the amount of variance explained varied substantially (0.29 ≤ R2 ≤ 0.82) among traits and processes in Sphagnum, and the model could predict some of them with high to intermediate accuracy for an independent dataset. R2 variability was mainly explained by traits and species identity, and poorly by environmental filtering. Some Sphagnum species avoid the stress caused by periodic desiccation in hollows via resource acquisition based on fast photosynthesis and growth, while other species are adapted to grow high above the water‐table on hummocks by slow physiological traits and processes to conserve resources. Synthesis.We contribute to a unified theory generating individual fitness, canopy dynamics and ecosystem processes from trait variation. As for vascular plants, the functional traits in the Sphagnum economic spectrum are linked into an integrated phenotypic network partly filtered by the environment and shaped by trade‐offs in resource acquisition and conservation.

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Section: Discussionmentioning

confidence: 99%

Scaling functional traits to ecosystem processes: Towards a mechanistic understanding in peat mosses

et al. 2018

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“…However, the bias was similar in each plot, thus making species frequencies comparable among treatments, and did not further influence the response of plant species to treatments. We especially distinguished the graminoid cover from the ericoid cover as these two plant types differ in productivity, litter, root inputs and plant–fungal associations, and as such may have different effects on ecosystem C dynamic (Robroek et al., , ; Walker, Ward, Ostle, & Bardgett, ; Walker et al., ).…”

Section: Methodsmentioning

confidence: 99%

Tipping point in plant–fungal interactions under severe drought causes abrupt rise in peatland ecosystem respiration

Jassey

Reczuga

Zielińska

et al. 2017

Global Change Biology

108

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Ecosystems are increasingly prone to climate extremes, such as drought, with long-lasting effects on both plant and soil communities and, subsequently, on carbon (C) cycling. However, recent studies underlined the strong variability in ecosystem's response to droughts, raising the issue of nonlinear responses in plant and soil communities. The conundrum is what causes ecosystems to shift in response to drought. Here, we investigated the response of plant and soil fungi to drought of different intensities using a water table gradient in peatlands-a major C sink ecosystem. Using moving window structural equation models, we show that substantial changes in ecosystem respiration, plant and soil fungal communities occurred when the water level fell below a tipping point of -24 cm. As a corollary, ecosystem respiration was the greatest when graminoids and saprotrophic fungi became prevalent as a response to the extreme drought. Graminoids indirectly influenced fungal functional composition and soil enzyme activities through their direct effect on dissolved organic matter quality, while saprotrophic fungi directly influenced soil enzyme activities. In turn, increasing enzyme activities promoted ecosystem respiration. We show that functional transitions in ecosystem respiration critically depend on the degree of response of graminoids and saprotrophic fungi to drought. Our results represent a major advance in understanding the nonlinear nature of ecosystem properties to drought and pave the way towards a truly mechanistic understanding of the effects of drought on ecosystem processes.

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“…Northern peatlands are dominated by four vegetation types, namely bryophytes, graminoids, dwarf‐shrubs and trees (not naturally present in UK peatlands) (Rodwell, ), which differ considerably in their ecophysiological traits. For example, Sphagnum moss species produce decay‐resistant litter that promotes low rates of soil respiration (Dorrepaal et al ., ), but are expected to have limited influence at the ecosystem level due to their low productivity relative to dwarf‐shrubs and graminoids (Walker et al ., ). By comparison, the ubiquitous graminoid Eriophorum vaginatum grows rapidly and generates litter that is decomposable (Trinder et al ., ), leading to greater rates of decomposition and short‐term carbon turnover (Ward et al ., , ).…”

Section: Introductionmentioning

confidence: 99%

Vascular plants promote ancient peatland carbon loss with climate warming

Walker

Garnett

Ward

et al. 2016

Global Change Biology

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Northern peatlands have accumulated one third of the Earth's soil carbon stock since the last Ice Age. Rapid warming across northern biomes threatens to accelerate rates of peatland ecosystem respiration. Despite compensatory increases in net primary production, greater ecosystem respiration could signal the release of ancient, century‐ to millennia‐old carbon from the peatland organic matter stock. Warming has already been shown to promote ancient peatland carbon release, but, despite the key role of vegetation in carbon dynamics, little is known about how plants influence the source of peatland ecosystem respiration. Here, we address this issue using in situ 14C measurements of ecosystem respiration on an established peatland warming and vegetation manipulation experiment. Results show that warming of approximately 1 °C promotes respiration of ancient peatland carbon (up to 2100 years old) when dwarf‐shrubs or graminoids are present, an effect not observed when only bryophytes are present. We demonstrate that warming likely promotes ancient peatland carbon release via its control over organic inputs from vascular plants. Our findings suggest that dwarf‐shrubs and graminoids prime microbial decomposition of previously ‘locked‐up’ organic matter from potentially deep in the peat profile, facilitating liberation of ancient carbon as CO2. Furthermore, such plant‐induced peat respiration could contribute up to 40% of ecosystem CO2 emissions. If consistent across other subarctic and arctic ecosystems, this represents a considerable fraction of ecosystem respiration that is currently not acknowledged by global carbon cycle models. Ultimately, greater contribution of ancient carbon to ecosystem respiration may signal the loss of a previously stable peatland carbon pool, creating potential feedbacks to future climate change.

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Contrasting growth responses of dominant peatland plants to warming and vegetation composition

Cited by 39 publications

References 57 publications

Scaling functional traits to ecosystem processes: Towards a mechanistic understanding in peat mosses

Scaling functional traits to ecosystem processes: Towards a mechanistic understanding in peat mosses

Tipping point in plant–fungal interactions under severe drought causes abrupt rise in peatland ecosystem respiration

Vascular plants promote ancient peatland carbon loss with climate warming

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