| Sumario: | Boreal peatlands are important in the global carbon cycle. Despite covering
only 3% of the global land area, peatlands store approximately one third of all soil
carbon. Temperature is one of the major drivers in peatland carbon cycling as it
affects both plant production and CO2 fluxes from soils. However, it is relatively
unknown how boreal peatland plant photosynthesis is affected by higher
temperatures. Therefore, we measured plant photosynthetic rates under two different
warming treatments in a poor fen in Northern Michigan. Eighteen plots were
established that were divided into three treatments: control, open-top chamber (OTC)
warming and infrared (IR) lamp warming. Previous work at this site has shown that
there was a significant increase in canopy and peat temperature with IR warming (5°C
and 1.4°C respectively), while the OTC’s had mixed overall warming. Plots were
divided equally into lawns and hummocks. We measured mid-day carbon dioxide
(CO2) uptake on sedges (Carex utriculata), shrubs (Chamaedaphne calyculata) and
Sphagnum mosses. Sphagnum moss net primary production (NPP) was also measured
with cranked wires and compared with CO2 uptake.
Our results indicate that there was no significant difference in sedge CO2
uptake, while shrub CO2 uptake significantly decreased with warming. A significant
increase occurred in Sphagnum moss gross ecosystem production (GEP), ecosystem
respiration (ER) and net ecosystem exchange (NEE). Contrary to the positive CO2
exchange of Sphagnum, overall NPP decreased significantly in hummocks with both
warming treatments. The results of the study indicate that temperature partly limits
the photosynthetic capacity of plants in sub-boreal peatlands, but not all species
respond similarly to higher temperatures.
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