Peatland vegetation composition and phenology drive the seasonal trajectory of maximum gross primary production

Abstract

Gross primary production (GPP) is a key driver of the peatland carbon cycle. Although many studies have explored the apparent GPP under natural light conditions, knowledge of the maximum GPP at light-saturation (GPPmax) and its spatio-temporal variation is limited. This information, however, is crucial since GPPmax essentially constrains the upper boundary for apparent GPP. Using chamber measurements combined with an external light source across experimental plots where vegetation composition was altered through long-term (20-year) nitrogen addition and artificial warming, we could quantify GPPmax in-situ and disentangle its biotic and abiotic controls in a boreal peatland. We found large spatial and temporal variations in the magnitudes of GPPmax which were related to vegetation species composition and phenology rather than abiotic factors. Specifically, we identified vegetation phenology as the main driver of the seasonal GPPmax trajectory. Abiotic anomalies (i.e. in air temperature and water table level), however, caused species-specific divergence between the trajectories of GPPmax and plant development. Our study demonstrates that photosynthetically active biomass constrains the potential peatland photosynthesis while abiotic factors act as secondary modifiers. This further calls for a better representation of species-specific vegetation phenology in process-based peatland models to improve predictions of global change impacts on the peatland carbon cycle.

Refining the role of phenology in regulating gross ecosystem productivity across European peatlands

“…Our results support the importance of plant phenology as a regulator of seasonal GEP dynamics in peatlands (Järveoja et al, ; Linkosalmi et al, ; Peichl et al, , ). While the previous studies provided site‐specific insights, here we demonstrate that the observed relations hold across a range of different peatlands in various climate regions.…”

Contrasting Temperature Sensitivity of CO2 Exchange in Peatlands of the Hudson Bay Lowlands, Canada

“…The importance of peatland vegetation species composition and plant‐specific phenology on GPP has been highlighted in a number of studies (e.g., Korrensalo et al, , Peichl et al, ). Here we find that the growing season started two weeks earlier at the evergreen plant‐dominated bog versus the deciduous plant‐dominated fen (where the growing season start was evaluated as the date daily GPP exceeded 10% of maximum daily GPP; Wu et al, ).…”

Effects of climate warming on Sphagnum photosynthesis in peatlands depend on peat moisture and species‐specific anatomical traits

“…As major soil C stock (Yu et al, 2011), peatlands are expected to contribute to the majority of warming-induced soil C loss over the next century (Crowther et al, 2016). Plant photosynthesis strongly affects C balance of peatlands (Frolking et al, 1998), which in turn influence regional and global climates (Booth et al, 2012;Peichl et al, 2018). More particularly, photosynthesis of peatforming mosses (Sphagnum spp.)…”