The Effects of Ultraviolet-B Radiation on Plant Competition in Terrestrial Ecosystems

Evidence regarding the interaction of ultraviolet-B radiation and plant competition in terrestrial ecosystems is examined. The competitive interactions of some species pairs were affected even by ambient solar UV-B radiation when compared to control pairs grown without UV-B. Also, the total shoot biomass of these species pairs was depressed under ambient UV-B. Relatively large increases in UV-B radiation altered the competitive interactions of some species pairs grown in pots under field conditions, but did not affect the total shoot biomass production of those pairs. Recent field experiments have examined the competitive interactions of wheat and wild oat under a simulated increased UV-B regime resulting from a 16% ozone layer reduction when weighted with the generalized plant action spectrum. This increase in UV-B altered the competitive interactions of these two species without affecting the total shoot biomass production for the species pair. The manner in which increased UV-B affected the relative competitive abilities of the two species was highly dependent upon the environmental conditions during the early life stages of the plants. The implications of these results for both agricultural and natural plant communities are discusses.