Solar UV‐B radiation affects below‐ground parameters in a fen ecosystem in Tierra del Fuego, Argentina: implications of stratospheric ozone depletion

Abstract

Stratospheric ozone depletion caused by the release of chlorofluorocarbons is most pronounced at high latitudes, especially in the Southern Hemisphere (including the so‐called ‘ozone hole’). The consequent increase in solar ultraviolet‐B radiation (UV‐B, 280–315 nm) reaching the earth's surface may cause a variety of alterations in terrestrial ecosystems. Most effects might be expected to occur above‐ground since sunlight does not penetrate effectively below‐ground. Here, we demonstrate that solar UV‐B radiation in a fen in Tierra del Fuego (Argentina), where the ozone hole passes overhead several times during the Austral spring, is causing large changes of below‐ground processes of this ecosystem. During the third and fourth year of a manipulative field experiment, we investigated root systems in these plots and found that when the ambient solar UV‐B radiation was substantially reduced, there was a 30% increase in summer root length production and as much as a threefold decrease in already low symbiotic mycorrhizal colonization frequency of the roots compared with plots receiving near‐ambient solar UV‐B. There was also an apparent shift toward older age classes of roots under reduced solar UV‐B. Such large changes in root system behaviour may have decided effects on competition and other ecological interactions in this ecosystem.

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