Plant response to solar ultraviolet‐B radiation in a southern South American Sphagnum peatland

Abstract

Summary1 Plant growth and pigmentation of the moss Sphagnum magellanicum and the vascular plants Empetrum rubrum , Nothofagus antarctica and Tetroncium magellanicum were measured under near-ambient (90% of ambient) and reduced (20%) ultraviolet-B (UV-B) radiation for three growing seasons in a Sphagnum peatland in Tierra del Fuego, Argentina (55 ° S). 2 Reduction of solar UV-B increased height growth but decreased volumetric density in S. magellanicum so that biomass production was not influenced during the 3 years. The morphology of vascular plants tended not to respond to UV-B reduction. 3 A 10-20% decrease in UV-B-absorbing compounds occurred in T. magellanicum under solar UV-B reduction. No effects were seen on chlorophyll or carotenoids in S. magellanicum , although, for UV-B-absorbing compounds, a significant interaction between UV-B and year suggests some response to solar UV-B reduction. 4 The climate-related growth of the dwarf shrub E. rubrum was assessed retrospectively by correlating an 8-year record of annual stem elongation with macroclimatic factors including solar UV-B and visible radiation, precipitation and temperature. 5 No significant negative correlations were found between annual E. rubrum stem elongation and ambient solar UV-B, the ratio of UV-B : visible radiation, or the 305-nm : 340-nm irradiance ratio for an 8-year record (1990 -91 to 1997-98), nor was stem elongation affected by solar UV-B reduction in our experimental field plots after 3 years. 6 The role of solar UV-B radiation on plant growth in Sphagnum peatlands in Tierra del Fuego, Argentina, is likely to depend on the severity of stratospheric ozone depletion over the next several decades. The increases in ambient solar UV-B associated with ozone depletion over the last 20 years are less than the difference between our radiation treatments. Therefore, providing that the ozone layer substantially recovers by the middle of this century, only modest effects of increased solar UV-B on plant growth may be expected.

Growth responses of Sphagnum hollows to a growing season lengthening manipulation in Alaskan Arctic tundra

“…These values are within the range of annual height increments reported on S. angustifolium in Québec (Moore 1989) and other Sphagnum species measured in high latitude locations Aerts et al 1992;Gehrke 1998; Abbreviations for climatic variables defined in Table 2 Standard deviations are indicated in parentheses a The CS615 was not calibrated for this soil type, and thus, reported values are relative estimates of volumetric water content Searles et al 2002;Sonesson et al 2002;Dorrepaal et al 2004;Gunnarsson 2005).…”

Effect of UV-B radiations on the pigments of two Antarctic lichens of Schirmacher Oasis, East Antarctica

“…Changes in chlorophyll have been observed in some species but are not a consistent response to natural variations in UV−B expo− sure, although they have previously been observed in Arctic bryophytes in response to enhanced UV−B radiation (Gehrke 1999;Searles et al 2001;Caldwell et al 2003). No change in chlorophyll concentration was observed as a result of seasonal changes in UV−B radiation in either the South American Sphagnum magellanicum (Searles et al 2002) or two Antarctic bryophytes studied by Newsham et al (2002). Carotenoid synthesis is known to be induced by exposure to UV−B radiation (Cockell and Knowland 1999).…”

Photoprotection, photosynthesis and growth of tropical tree seedlings under near-ambient and strongly reduced solar ultraviolet-B radiation

“…the daily period of high PAR and UV exposure (Krause et al, 2001). In several reports (Liu et al, 2005;Lovelock et at., 1992;Lud et al, 2001;Rousseaux et al, 2004;Searles et at., 2002), not all tested plant species responded with a reduction in the level of UV-B absorbing compounds, when solar UV-B was attenuated by means of filters. The significance of these different responses among species is unclear at present.…”

“…on the moss Sphagnum magellanicum (Searles et al, 2002) and crop plants such as oat (Avena sativa L.) and lettuce (Lactuca sativa L.) (Rousseaux et al, 2004), cannot be generalized among species. Substantial inhibition of dry matter productivity by solar UV-B has been shown in a number of reports (see Day and Neale, 2002, for review;Liu et al, 2005;Zavala and Ravetta, 2002).…”