Measurements of hydrogen, oxygen and carbon isotope variability inSphagnummoss along a micro‐topographical gradient in a southern Patagonian peatland

Abstract

Peat archives offer a diverse range of physical and chemical proxies from which it is possible to study past environmental and ecological changes. Direct numerical calibration and verification is difficult so process-based and mechanistic studies are therefore required to establish and quantify links between environmental changes and their associated proxy-responses. Traditional 'space-for-time' calibrations provide a solution to this calibration problem, but are often unable to isolate a single environmental variable from other potentially confounding variables. In this study, we explored the potential of a site-specific 'space-for-time' approach applied to a hummock-hollow transect on an ombrotrophic raised bog in Patagonia, southern Chile. Coupled stable carbon, oxygen and hydrogen isotopic measurements were made on individual samples of Sphagnum moss cellulose and compared with plant-associated waters, local hydrology, temperature and relative humidity, sampled at the same points along the study transect. Results reveal a range of environmental responses, which were supported by plant-physiological models in the case of carbon and oxygen isotopes. For hydrogen isotopes, the results obtained from cellulose indicated a need for further research into hydrogen isotope fractionation in Sphagnum. We recommend conducting site-specific characterization of plant response to support the development of peat-based isotope records for palaeoenvironmental research, and where logistically possible, that monitoring is conducted over timescales appropriate to the time-integrative nature of the Sphagnum record.

Centennial-scale dynamics of the Southern Hemisphere Westerly Winds across the Drake Passage over the past two millennia

“…Likewise, this negative correlation was also found from another similar study at a Sphagnum-dominated peatland site in southernmost Patagonia ( Fig. DR5; Loader et al, 2016). Many studies on carbon isotope composition of mosses concluded that moisture availability exerts a critical influence (Rice and Giles, 1996;Price et al, 1997;Ménot and Burns, 2001;Loisel et al, 2009), although other studies indicated potential influence of temperature, probably due to intrinsic relation between temperature and moisture-related environmental factors (e.g., Ménot and Burns, 2001;Moschen et al, 2011).…”

Environmental and taxonomic controls of carbon and oxygen stable isotope composition in <i>Sphagnum</i> across broad climatic and geographic ranges

“…Loader et al (2016) reported a similar slope estimate for S. magellanicum in a single peatland and several studies have confirmed effects of contrasting microtopography (i.e. hummock-hollow differences) using multi-species comparisons (Price et al 1997, Loisel et al 2009, Markel et al 2010).…”

“…Because peat decomposes slowly and gradually accumulates, it preserves information on past peatland ecosystem dynamics and responses to allogenic and autogenic forcing. Palaeoenvironmental studies of peat may, therefore, help anticipate future response of these globally important ecosystems to climate change (Loader et al 2016). Past climate and local hydrology can be estimated using a variety of biotic and biogeochemical proxies, including the δ Royles et al 2016, Lamentowicz et al 2015.…”

“…Despite many detailed studies, there remains uncertainty about how the multiple controls on and how universal the proposed mechanisms are on a global scale. This uncertainty currently restricts the utility of C isotope signals as a palaeoclimatic/palaeoenvironmental indicator in peatlands (Loader et al 2016). …”

“…Paleoecological studies rely on such environment-isotope relationships for environmental reconstructions (Ellis andRochefort 2006, van der Knaap et al 2011). The underlying mechanisms are, however, rarely fully explored using known environmental gradients (but see Ménot and Burns 2001 for an example), or only tested across narrow bands of environmental variation, often with sets of correlated environmental factors (Loader et al 2016). Moreover, interactions with biotic factors such as species identity have received little attention despite the large variations in Sphagnum species dominance commonly observed down peat cores (e.g.…”