Will Subtropical Grasses Keep Spreading through New Zealand?

n this paper we briefly examine the effects that rising temperature and atmospheric CO2 concentrations may have on the spread of subtropical grasses in New Zealand. Data are presented from controlled-environment experiments measuring the growth and competitive suppression of white clover by a variety of local temperate and subtropical grasses at CO2 concentrations of 3S0 ppm and 700 ppm. These data support the prediction that some subtropical grasses may decline in aggressiveness relative to temperate species in New Zealand in the future as atmospheric CO2 levels rise. Some of the factors likely to modify the expression of temperature and CO2 effects on the spread of subtropical grasses are identified. It is concluded that the rate of spread of subtropical grasses in pastures may be slowed in future by an increasing competitiveness of some temperate species.