Growth, Production, and Decomposition Dynamics of Sphagnum under Natural and Experimentally Acidified Conditions

Abstract

Annual linear growth, net primary production, and decomposition of Sphagnum fuscum, Sphagnum magellanicum, and Sphagnum angustifolium were measured under experimental acidification and natural conditions in a poor fen at the Experimental Lakes Area (ELA), Ontario, Canada. Acidification increased growth and production of most species (2 out of 3 in the oligotrophic zone, and 2 out of 3 in the minerotrophic zone) in the first 2 yr. After 2—3 yr of artificial acidification, growth and production were not stimulated to the same extent in experimental areas as in earlier years. After 4 yr, growth and production in the experimental area declined so that they were the same as controls for 4 of the 6 treatments. Therefore, the effect of the acid treatment changed over the years. With 4 yr of simulated “acid rain,” decomposition was unaffected. Our results suggest that the fertilizing effect of SO42— and NO3— in North American acid precipitation as suggested previously in the literature is a very short—term one, at least for this type of peatland. Under natural conditions, in the oligotrophic central zone of mire 239, production for hollow species was somewhat greater than for hummock species for the 4 yr studied. Since the decomposition rate ratio between hummock—top, mid—hummock, and hollow species is roughly in the ratio 7:9:13, the rate of peat accumulation should be higher in hummocks. Hence hummocks appear to be maintained in this poor fen due to low decomposition rates rather than relatively high production. For 3 of the 4 yr studied (1985—1987) in the minerotrophic edge zone, hummock production (303, 175, and 156 g°m—2°yr—1, respectively) was greater than hollow (198, 100, and 97 g°M—2°yr—1) and mid—hummock production (103, 59, and 52 g°m—2°yr—1). The relative decomposition rates of the species had the same ratio as in the oligotrophic zone. Thus hummocks appear to be expanding in this minerotrophic edge zone at a faster rate than in the oligotrophic zone.

Plant Litter Decomposition and Nutrient Release in Peatlands

“…Increased decomposition rates of vascular plant litter in peatlands with increasing temperature were also reported by other authors [Hobbie, 1996;Thormann et al, 2004;Moore et al, 2005;Breeuwer et al, 2008]. Furthermore, many laboratory and field experiments have shown that higher temperature resulted in increasing decomposition of vascular plant and Latter and Cragg [1967], Rochefort et al [1990], Johnson and Damman [1991], Gallardo and Merino [1993], Aerts and De Caluwe [1997], Foote and Reynolds [1997], Wrubleski et al [1997], Latter et al [1998] …”

Does prolonged flooding prevent or enhance regeneration and growth of Sphagnum?

“…Increases in length measured after the 3.5 months field experiment (Table 2) varied between species, but were in the range of growth rates recorded for the same Sphagnum species under natural conditions (see Lindholm and Vasander, 1990;Rochefort et al, 1990). Comparisons of biomass increase with values reported in other North American studies (Table 3), including data recorded on the same peatland as our study (Waddington et al, in press), suggest that for certain species the increase in biomass was not as high as might be expected from the increase in length.…”

Seasonal patterns and controls on net ecosystem CO2 exchange in a boreal peatland complex

“…The biomass samples were dried at 60øC for 24-48 hours and weighed. Bryophyte productivity was measured by a cranked wire technique [Rochefort et al, 1990] for Sphagnum mosses and other mosses with a vertical growth pattern and by velcro markers for prostrate growth forms, such as "brown" mosses (e.g., Scorpidium scorpioides) and feather mosses (e.g., Pleurozium schreberi). For each technique, linear increments in growth were measured and converted into mass per unit area using the average bulk density of three replicate 103 cm samples for each species.…”