Ecosystem processes in semiarid grasslands. I. Primary production and water use of two communities possessing different photosynthetic pathways

Abstract

Above- and below-ground productivity and estimated evapotranspiration rates of a C₃ native grassland and a sown C₄ buffel grassland community growing on sandy red earth soils at Charleville were studied over a 12-month period. Resistance to water vapour transfer from leaves of both species was measured in the field and glasshouse.

Although buffel grass had the highest maximum above-ground growth rate in summer, the most striking difference between the two communities was the much greater standing root crop and root production of the C₄ community. Above-ground growth rates were very low in winter, and the differences in rates between communities were small. Over the summer growing period the water use efficiency of the C₃ community was about 60% the value for the C₄ community. Leaf resistance of the latter species was found to be greater under conditions of limiting and non-limiting water supply.

The role of external factors influencing the distribution of these grasslands, as well as the agronomic implications of the study, are discussed.