A. Joabsson et al., Influence of vascular plant photosynthetic rate on CH4 emission from peat monoliths from southern boreal Sweden, POLAR RES, 18(2), 1999, pp. 215-220
Feat monoliths taken from a boreal peatland system were incubated at two di
fferent light intensities to investigate the effect of the photosynthetic r
ate of vascular plants (Eriophorum angustifolium) on net CH4 emission. The
experimental set-up consisted of six replicate monoliths as controls and si
x where the photosynthetic active radiation (PAR) was reduced by 60%. NEP a
nd total system respiration decreased significantly in response to reduced
PAR. No significant changes in CH4 emission were found, but two different t
rends were noted. Methane emissions from the shaded monoliths initially see
med to be higher than emissions from the controls. After approximately four
weeks the trend was reversed. The pattern may have been caused by "leakage
" of organic compounds from inactivated roots that fueled CH4 production. I
t is suggested that a new balanced exchange of potential substrate carbon b
etween the plants and the surrounding peat was established. Comparably less
easily degradable carbon compounds would then become available for CH4 pro
duction. The fact that there appeared to be an effect of decreased carbon f
low on CH4 emission is further supported by a tendency for lower concentrat
ions of organic acids in porewater in the shaded monoliths at the end of th
e experiment. These results indicate a possible lagtime on the order of wee
ks before changes in photosynthesis rates and NEP have an effect on CH4 emi
ssion rates. Nevertheless it confirms the linkage between CO2 and CH4 cycli
ng in wetland ecosystems.