Solar ultraviolet‐B radiation influence on Sphagnum bog and Carex fen ecosystems: first field season findings in Tierra del Fuego, Argentina

Abstract

Stratospheric ozone depletion occurs over Tierra del Fuego, southern Argentina and Chile, in the austral spring and summer due to the precession of the Antarctic ‘ozone hole’ and the general erosion of the ozone layer. Plots receiving either near‐ambient or reduced UV‐B radiation were established using different louvered plastic film filters over Sphagnum bog and Carex fen ecosystems in October 1996. In the Sphagnum bog system, growth measurements during the late spring and summer showed no significant differences in the moss Sphagnum magellanicum, or the vascular plants (Empetrum rubrum, Nothofagus antarctica, and Tetroncium magellanicum) between near‐ambient and attenuated UV‐B radiation treatments. In the Carex fen system, leaf length and spike height did not differ in the two dominant species, Carex decidua and C. curta, between UV‐B radiation treatments. The length of individual spikelets of C. curta under near‐ambient UV‐B radiation was less than under the reduced UV‐B radiation treatment, but this was not evident in C. decidua. No differences in seed number, seed mass, or viability were seen in either Carex species between the UV‐B treatments. Two important constituents of the microfauna that inhabit the Sphagnum bog are testate amoebae and rotifers. These both appeared to be more numerous under near‐ambient UV‐B radiation than under reduced UV‐B radiation. The subtle responses of the Sphagnum and Carex ecosystems may become more apparent in subsequent years as the treatments are continued. Trophic‐level changes, such as the differences in number of amoebae and rotifers, may be more sensitive to solar UV‐B radiation than growth and productivity of the vegetation.

Solar ultraviolet-B radiation affects plant-insect interactions in a natural ecosystem of Tierra del Fuego (southern Argentina)

“…During the experimental period (October 1996), the UV irradiance measured with the U.S. NSF scanning spectroradiometer at Ushuaia (weighted with the generalized plant action spectrum of Caldwell 1971) was near the minimum values of the last seven years on corresponding dates due to predominantly cloudy conditions. However, it outstripped the absolute maxima recorded during those years on several occasions later in the ®eld season (Searles et al 1998).…”

Effects of ultraviolet-B radiation on crop growth, development, yield and leaf pigment concentration of tartary buckwheat (Fagopyrum tataricum) under field conditions

“…In each experimental plot, there was an erected sheltered frame (3.5 m × 2.5 m × 1.5 m) made of light alloyed-metal. The frame was made up of four sticks (placed deep into soil) and a roof with parallel rails spaced 0.75 m as described by Searles et al (1999). The frame roof was covered with 0.038 mm thick Teflon plastic film (Chengguang Chem.…”

Late-Holocene climate dynamics recorded in the peat bogs of Tierra del Fuego, South America

“…One possibility is that the relative abundance of A. muscorum in the near-surface samples may have been enhanced by increased intensity of UV-B radiation because of stratospheric ozone depletion. Field experiments have shown that assemblages of living testate amoeba in Fuegian peatlands are sensitive to UV-B radiation, although 99% of light may be attenuated at 6-mm depth in the Sphagnum carpet (Searles et al, 1999(Searles et al, , 2001). In one experiment, Robson et al (2005) stretched two types of plastic film over a total of 20 sample plots which created either 'near-ambient' or 'reduced' UV-B conditions.…”