Seasonal and inter-annual variation in the chlorophyll content of three co-existing Sphagnum species exceeds the effect of solar UV reduction in a subarctic peatland.

Anna Hyyryläinen,Minna Turunen,Pasi Rautio,Satu Huttunen

doi:10.1186/s40064-015-1253-7

Anna Hyyryläinen, Minna Turunen + Show 2 more

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https://doi.org/10.1186/s40064-015-1253-7

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Abstract

We measured chlorophyll (chl) concentration and chl a/b ratio in Sphagnum balticum, S. jensenii, and S. lindbergii, sampled after 7 and 8 years of ultraviolet-B (UVB) and temperature manipulation in an open field experiment in Finnish Lapland (68°N). We used plastic filters with different transmittance of UVB radiation to manipulate the environmental conditions. The plants were exposed to (1) attenuated UVB and increased temperature, (2) ambient UVB and increased temperature and (3) ambient conditions. Chlorophyll was extracted from the capitula of the mosses and the content and a/b ratio were measured spectrophotometrically. Seasonal variation of chlorophyll concentration in the mosses was species specific. Temperature increase to 0.5–1 °C and/or attenuation of solar UVB radiation to ca. one fifth of the ambient (on average 12 vs. 59 uW/cm2) had little effect on the chlorophyll concentration or its seasonal variation. In the dominant S. lindbergii, UVB attenuation under increased temperature led to a transient decrease in chlorophyll concentration. Altogether, species-specific patterns of seasonal chlorophyll variation in the studied Sphagna were more pronounced than temperature and UVB treatment effects.Electronic supplementary materialThe online version of this article (doi:10.1186/s40064-015-1253-7) contains supplementary material, which is available to authorized users.

Highlights

Sphagna are crucial in forming and sustaining peatlands—specific ecosystems that maintain a unique diversity of habitats and species (Clymo and Hayward 1982; Vitt 2000; Rydin et al 2006; Rydin and Jeglum 2006) and function as a large store of organic carbon, in boreal and subarctic areas (Gorham 1991; Limpens et al 2008)
We aimed to study how changes in both UVB and temperature regime affect concentrations of chl a and b, and their ratio in three Sphagnum species: S. balticum, S. jensenii and S. lindbergii
This may explain why in S. lindbergii, both total chlorophyll concentration and chl a/b ratio were fairly stable in July–August 2008 (Figs. 5c, 6)

Summary

Introduction

Sphagna are crucial in forming and sustaining peatlands—specific ecosystems that maintain a unique diversity of habitats and species (Clymo and Hayward 1982; Vitt 2000; Rydin et al 2006; Rydin and Jeglum 2006) and function as a large store of organic carbon, in boreal and subarctic areas (Gorham 1991; Limpens et al 2008). As a key component of the ecosystem, they affect many processes within it; the changes triggered in Sphagna by a changing environment may be reflected in the entire ecosystem. This is important, as they are susceptible to changes in the environment, including shifts in UVB and temperature regime UV effects on mosses are speciesspecific, possibly reflecting differences in desiccation tolerance (Csintalan et al 2001). Changes in the intensity of different wavelengths of solar irradiance affect shape and size of chloroplasts (Glime 2007), as well as pigment concentration in bryophytes (Niemi et al 2002a, b)

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