Field Simulation of Global Change: Transplanting Northern Bog Mesocosms Southward

Abstract

A large proportion of northern peatlands consists of Sphagnum-dominated ombrotrophic bogs. In these bogs, peat mosses (Sphagnum) and vascular plants occur in an apparent stable equilibrium, thereby sustaining the carbon sink function of the bog ecosystem. How global warming and increased nitrogen (N) deposition will affect the species composition in bog vegetation is still unclear. We performed a transplantation experiment in which mesocosms with intact vegetation were transplanted southward from north Sweden to northeast Germany along a transect of four bog sites, in which both temperature and N deposition increased. In addition, we monitored undisturbed vegetation in control plots at the four sites of the latitudinal gradient. Four growing seasons after transplantation, ericaceous dwarf shrubs had become much more abundant when transplanted to the warmest site which also had highest N deposition. As a result ericoid aboveground biomass in the transplanted mesocosms increased most at the southernmost site, this site also had highest ericoid biomass in the undisturbed vegetation. The two dominant Sphagnum species showed opposing responses when transplanted southward; Sphagnum balticum height increment decreased, whereas S. fuscum height increment increased when transplanted southward. Sphagnum production did not differ significantly among the transplanted mesocosms, but was lowest in the southernmost control plots. The dwarf shrub expansion and increased N concentrations in plant tissues we observed, point in the direction of a positive feedback toward vascular plant-dominance suppressing peat-forming Sphagnum in the long term. However, our data also indicate that precipitation and phosphorus availability influence the competitive balance between Sphagnum, dwarf shrubs and graminoids.

Microbial mediation of biogeochemical cycles revealed by simulation of global changes with soil transplant and cropping

“…The use of soil transplant as a proxy to study the effects of global changes has been successfully demonstrated in both plant biology and microbiology (Balser and Firestone, 2005;Breeuwer et al, 2010;De Frenne et al, 2011;Lazzaro et al, 2011;Vanhala et al, 2011). It was reported that soil microbial community structure and community functions were altered when soil was transplanted into warmer regions to simulate global warming (Vanhala et al, 2011), which was consistent with a number of studies showing that warming altered microbial community (Petchey et al, 1999;Rinnan et al, 2007;Zhou et al, 2012).…”

Different effects of warming and cooling on the decomposition of soil organic matter in warm–temperate oak forests: a reciprocal translocation experiment

“…Several field experimental approaches have been used to investigate potential effects of global warming on the ecosystem, for example field warming using external heat inputs (Luo et al 2001;Melillo et al 2002), observing differences in ecosystems along natural climatic gradients (Conant et al 2000;Rodeghiero and Cescatti 2005), or transferring ecosystem components to a new site with different climatic conditions (Breeuwer et al 2010;Hart 2006;Link et al 2003;Rey et al 2007). Especially, reciprocal treatment (simulating climate cooling) to that of warming can strengthen the conclusions drawn from warming treatment in which temperature has a dominant effect on soil-plant processes (Hart and Perry 1999).…”

Fine‐scale dynamics and community stability in boreal peatlands: revisiting a fen and a bog in Sweden after 50 years

“…The main environmental gradients are pH and height above the water table, the latter often dichotomized as hollows (peat surface closer to the water table) and hummocks (peat surface farther above the water table). Not surprisingly, vegetation changes have also been attributed to changes in precipitation and temperature (Belyea and Clymo 2001, Weltzin et al 2003, Gunnarsson and Flodin 2007, Breeuwer et al 2010) and long-term exposure to atmospheric deposition (Gunnarsson et al 2000, Limpens et al 2011. The impact of atmosphere deposition is likely most evident in bogs, as they more heavily rely upon atmospheric fluxes than fens.…”