Climatic modifiers of the response to nitrogen deposition in peat‐forming Sphagnum mosses: a meta‐analysis

Abstract

Summary• Peatlands in the northern hemisphere have accumulated more atmospheric carbon (C) during the Holocene than any other terrestrial ecosystem, making peatlands long-term C sinks of global importance. Projected increases in nitrogen (N) deposition and temperature make future accumulation rates uncertain.• Here, we assessed the impact of N deposition on peatland C sequestration potential by investigating the effects of experimental N addition on Sphagnum moss. We employed meta-regressions to the results of 107 field experiments, accounting for sampling dependence in the data.• We found that high N loading (comprising N application rate, experiment duration, background N deposition) depressed Sphagnum production relative to untreated controls. The interactive effects of presence of competitive vascular plants and high tissue N concentrations indicated intensified biotic interactions and altered nutrient stochiometry as mechanisms underlying the detrimental N effects. Importantly, a higher summer temperature (mean for July) and increased *These authors contributed equally to this work.

Phylogenetic or environmental control on the elemental and organo-chemical composition of Sphagnum mosses?

“…Nitrogen deposition has been shown to alter Sphagnum nutrient stoichiometry (Bragazza et al 2004;Limpens et al 2011) and phenolic constituents (Bragazza and Freeman 2007). Likewise, drier surface conditions associated with water table drawdown enhanced both N and P concentrations in Sphagnum (Straková et al 2010).…”

Climatic conditions, soil fertility and atmospheric nitrogen deposition largely determine the structure and functioning of microbial communities in biocrust-dominated Mediterranean drylands

“…We hypothesized that chronic N deposition can significantly alter soil microbial c o m m u ni t i e s a n d th e N c y c l e i n s e m i a r i d Mediterranean ecosystems from Spain, although to a lesser extent than climate and local edaphic factors (Gaudnik et al 2011;Limpens et al 2011). We specifically predicted that N deposition would be negatively related to total soil bacterial and cyanobacterial abundance, as evidenced in multiple fertilization studies (Belnap et al 2008;Eisenlord and Zak 2010;Tian et al 2014;Treseder 2008;Wei et al 2013), and positively related to organic and inorganic N availability in soil (Fang et al 2009;Phoenix et al 2012;Waldrop and Zak 2006;Wei et al 2013).…”

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.…”