Graminoids vary in functional traits, carbon dioxide and methane fluxes in a restored peatland: Implications for modelling carbon storage

Abstract

1. One metric of peatland restoration success is the re-establishment of a carbon sink, yet considerable uncertainty remains around the time-scale of carbon sink trajectories. Conditions post-restoration may promote the establishment of vascular plants such as graminoids, often at greater density than would be found in undisturbed peatlands, with consequences for carbon storage. Although graminoid species are often considered as a single plant functional type (PFT) in landatmosphere models, our understanding of functional variation among graminoid species is limited, particularly in a restoration context.2. We used a traits-based approach to evaluate graminoid functional variation and to assess whether different graminoid species should be considered a single PFT or multiple types. We tested hypotheses that greenhouse gas fluxes (CO 2 , CH 4 ) would vary due to differences in plant traits among five graminoid species in a restored peatland in central Alberta, Canada. We further hypothesized that species would form two functionally distinct groupings based on taxonomy (grass, sedge).3. Differences in gas fluxes among species primarily reflected variation in leaf physiology related to photosynthetic efficiency and resource-use, and secondarily by plant size. Multivariate analyses did not reveal distinct functional groupings based on taxonomy or environmental preferences. Rather, we identified functional groups defined by plant traits and carbon fluxes that are consistent with ecological strategies related to differences in growth rate, resource-acquisition and leaf economics, representing plants with either a strategy to grow quickly and invest in resource capture or to prioritize structural investment and resource conservation. These functional groups displayed larger average carbon fluxes compared to graminoid PFTs currently used in modelling. Synthesis.Existing PFT designations in peatland models may be more appropriate for pristine or high-latitude systems than those under restoration. Although replacing PFTs with plant traits remains a challenge in peatlands, traits related to leaf physiology and growth rate strategies offer a promising avenue for future applications.

A direct comparison of ecological theories for predicting the relationship between plant traits and growth

“…Specifically, two strategies with similar growth and leaf area differed in height, suggesting that leaf area may be most predictive for plants that invest primarily in photosynthesizing leaf biomass, while plant height may be most effective for plants investing in more structural stem biomass. These results are consistent with previously observed positive associations between ecosystem productivity and leaf area (Goud et al, 2017;Litton et al, 2008) and height (Goud, Touchette, et al, 2022;Westoby, 1998).…”

“…Both leaf N and P are predicted to positively correlate with growth due to the functional need for N and P in photosynthesis (Walker et al, 2014; Wright et al, 2004). However, nonlinear or insignificant relationships are frequently reported (Feng & Dietze, 2013; Goud, Touchette, et al, 2022; Midgley et al, 2004). Here, growth was negatively associated with leaf N and P (Figure 1G–I; Table 2), which has been observed for other herbaceous species grown under common conditions (Poorter et al, 1990).…”

Blanket bog CO2 flux driven by plant functional type during summer drought

“…and other mosses (Berger et al, 2018; Laine et al, 2016). Previous long‐term studies using a PFT approach have demonstrated that peatland vascular PFTs (graminoids and shrubs) control gaseous methane emissions (Armstrong et al, 2015; Goud et al, 2021; Robroek et al, 2015), while increased Sphagnum moss coverage reduces fluvial dissolved organic carbon (DOC) effluxes (Dunn et al, 2016). Furthermore, peatland carbon cycling may be constrained by ericoid shrubs presence, as increased gross CO 2 fluxes from graminoids were observed during selective removal experiments of key PFTs, that is, ericoid shrubs (Ward et al, 2009).…”

The hidden roots of wetland methane emissions

“…‐ Couple measurements of above‐ and belowground traits : Investigating the relationship between above‐ and belowground traits may help in determining the best aboveground proxies for belowground wetland CH 4 dynamics. Relevant aboveground traits to be connected to root traits could include vascular plant green area (Goud et al., 2017; Malhotra & Roulet, 2015), plant height (Chen et al., 2009; Goud et al., 2022), stem diameter and number per plot (Noyce et al., 2023; Pangala et al., 2013, 2015), and photosynthetic rate (Sutton‐Grier & Megonigal, 2011), as well as aboveground biomass (e.g., Joabsson & Christensen, 2001; Sutton‐Grier & Megonigal, 2011). Trees add to the complexity of ecosystem CH 4 emissions, as their stems can emit CH 4 , even when the soil consumes CH 4 (Covey & Megonigal, 2018).…”