Species-specific temporal variation in photosynthesis as a moderator of peatland carbon sequestration

Abstract

Abstract. In boreal bogs plant species are low in number, but they differ greatly in their growth forms and photosynthetic properties. We assessed how ecosystem carbon (C) sink dynamics were affected by seasonal variations in the photosynthetic rate and leaf area of different species. Photosynthetic properties (light response parameters), leaf area development and areal cover (abundance) of the species were used to quantify species-specific net and gross photosynthesis rates (P N and P G , respectively), which were summed to express ecosystem-level P N and P G . The ecosystem-level P G was compared with a gross primary production (GPP) estimate derived from eddy covariance (EC) measurements.Species areal cover, rather than differences in photosynthetic properties, determined the species with the highest P G of both vascular plants and Sphagna. Species-specific contributions to the ecosystem P G varied over the growing season, which, in turn, determined the seasonal variation in ecosystem P G . The upscaled growing season P G estimate, 230 g C m −2 , agreed well with the GPP estimated by the EC (243 g C m −2 ).Sphagna were superior to vascular plants in ecosystemlevel P G throughout the growing season but had a lower P N . P N results indicated that areal cover of the species, together with their differences in photosynthetic parameters, shape the ecosystem-level C balance. Species with low areal cover but high photosynthetic efficiency appear to be potentially important for the ecosystem C sink. Results imply that functional diversity, i.e., the presence of plant groups with different seasonal timing and efficiency of photosynthesis, may increase the stability of C sinks of boreal bogs.

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

“…The earlier growing season start and later senescence in the bog are likely caused by the dominance of Sphagnum spp. and evergreen shrubs and trees at this site, which have been found to be the most productive peatland species during the shoulder seasons (Korrensalo et al, ). However, by the middle of the summer, GPP at the fen was up to two times that of the bog.…”

“…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, ).…”

Net ecosystem exchange and energy fluxes measured with the eddy covariance technique in a western Siberian bog

“…However, one could speculate that this behaviour is due to the seasonality of plant functional group activity to an extent. A Finnish boreal fen study of Korrensalo et al (2017) found a wide seasonal variation in the contributions of moss and vascular species to the ecosystem-scale photosynthesis. The moss photosynthesis (gC m −2 d −1 ) declined steadily throughout summer, while various vascular species were most active in June, July, or August; it was also common for k of many species to have a peak in June and/or become reduced throughout the growing season, in line with the findings of the current study.…”

High‐resolution peat volume change in a northern peatland: Spatial variability, main drivers, and impact on ecohydrology

“…As a result, topographical differences became more pronounced and more patchy, and also the variance of water table depth relative to the peat surface (GWT R ) will increase ( Figure 9). Such increased habitat variability may increase species richness and thereby enhance peatland carbon sink stability and resilience to environmental extremes, such as droughts (Korrensalo et al, 2017;Loreau et al, 2001;Peterson, Allen, & Holling, 1998;Scherrer & Körner, 2011).…”