Effects of climate warming on the distribution of C4 grasses in New Zealand

Abstract

Data from pasture and roadside surveys and from an appeal to the public were used to assess whether recent climate warming has increased the spread of C4 grasses. Because of differences in date of introduction, saturation of existing range, ability to spread by seed, frost tolerance, and soil and moisture requirements, each species studied had a different potential increase in response to higher temperatures. Also spread could be exhibited as greater abundance within existing range as well as increase in geographical range. The strongest evidence that could be construed as an effect of climate warming was an increase of about 1.5" latitude in the area of 40% pasture occurrence of paspalum in the last 10-12 years. In the same period both carpet grass and knot-root bristle grass also greatly increased their impact. Most of the species studied (including the annual summer grass) underwent an explosive increase in the last 2-3 years after several particularly mild winters and warm summers. C4 species will probably be an increasing feature of pastures and lawns in future, and this should be accommodated by appropriate management and the introduction of improved pasture and amenity cultivars of this type. Keywords C4 grasses, climate change, paspalum, pasture survey