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

1. One metric of peatland restoration success is the re-establishment of a
carbon sink, yet considerable uncertainty remains around the timescale 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 land-atmosphere 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 (CO2, CH4) 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 were primarily driven
by 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 modeling. 4.
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.