Simulated climate warming increases plant community heterogeneity in two types of boreal peatlands in north-central Canada

摘要

Questions Climate warming has been demonstrated to shift peatland plant community composition fromSphagnummosses to vascular plants inSphagnum-dominated peatlands. However, fewer studies have determined how increasing temperature affects vegetation patterns inCarex-dominated peatlands. As plants are important determinants of carbon storage potential in peatlands, we aim to determine how climate warming alters plant community composition in peatlands of two different vegetation types. Location Boreal peatlands in north-central Ontario, Canada. Methods In aSphagnum- and aCarex-dominated peatland over two growing seasons, we instigated passive warming using clear open-topped chambers, providing a modest increase (1-2 degrees C) in temperature. In replicated plots we examined shifts in plant community composition using the point intercept method, and total above-ground biomass using Leaf Area Index (LAI) against non-warmed control plots. Results While there was no difference in species diversity between control and warmed plots in either fen site, warming significantly increased above-ground biomass in theCarex-dominated fen and decreased moss abundance in theSphagnum-dominated fen. Both fens also displayed significantly different plant community composition between warming and control plots, and increased heterogeneity under warming. Conclusion Peatlands are important global carbon stores and the plant community contributes to their carbon storage;Sphagnummosses, in particular, are linked to high peatland carbon storage potential. Previous studies inSphagnum-dominated peatlands have shown concomitant declines inSphagnumbiomass and increases in vascular plant biomass, and in the short term, we show only a decline inSphagnum. At both sites the increase in plant community heterogeneity suggests that climate warming effects on plant community composition in boreal peatlands may be more unpredictable than the literature suggests. Furthermore, this study demonstrates that plant community shifts occur even under modest warming scenarios.