New Zealand Journal of Agricultural Research abstracts
The place of C4 grasses in temperate pastures in Australia
W. H. JOHNSTON
NSW Department of Land and
Water Conservation
Wagga Wagga Soil Conservation Research Centre
P.O. Box 146, South Wagga Wagga
NSW 2650, Australia
Abstract This paper explores the potential role of
summer-active C4 grasses in temperate areas in Australia from an ecological
perspective. The main functional differences between C3 and C4 plants are
briefly outlined. Taken together, the characteristics and environmental
requirements of introduced C3 perennial pasture cultivars lessen their natural
competitive ability except in well-watered and cool habitats. C4 plants are
more competitive under conditions of high temperature and solar radiation.
Within the C4 group, grasses belonging to the sub-family Panicoideae usually
prefer humid, wet environments and generally decline in importance with
increasing grazing pressure and increased soil nitrogen (N) levels. Genera of
Eragrostoideae generally prefer hot, dry habitats; they increase in dominance
with increased grazing pressure and N availability. These responses give the C4
group as a whole a wider adaptive range and at the community level provide
versatility in responses to changed conditions such as grazing. Based on their
preferred zones of natural distribution, it appears that introduced C3 pasture
species are sown widely outside the area where they would be favoured to
persist. The ecological impacts of grazing by domestic livestock and pasture
improvement are briefly outlined with particular emphasis on changes in
botanical composition. There are similarities between changes in Australian
grasslands and those reported in South Africa. It is concluded that species
which naturally increase in abundance in grazed pastures (such as some genera
of Eragrostoideae) would offer considerable advantages for the development of
naturally sustainable pastures. Such pasture species would offer a number of
side-benefits including reduced rates of pH decline and deep drainage of excess
water to water tables. These two problems represent major threats to
agricultural sustainability in the temperate zone and both result from the
inability of C3 grass-based pastures to grow actively in summer.
Keywords C4 grasses; C3 grasses; native grasslands; pasture
ecology; grazing
New Zealand Journal of Agricultural Research, 1996, Vol. 39: 527-540
0028-8233/96/3904-0527 $2.50/0 (c) The Royal Society of New Zealand
1996
PDF file of entire paper: medium quality (1311K); (scanned from paper original: notes about this process)
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