Fire and the dynamics of two unpalatable grass species (Cymbopogon pospischilii and Elionurus muticus) in a semi-arid climate

Abstract

Cymbopogon pospischilii and Elionurus muticus are unpalatable for most of the growing season and form a reasonably large component of the vegetation composition in semi-arid grassland areas. The influence of an accidental fire on the dynamics of these two grass species was quantified over a three-year period (2008/09 to 2010/11 growing seasons) in a semi-arid grassland. After burning, the production of C. pospischilii was 18% higher than that of the total production of the rest of the burned species for the third growing season. Production of E. muticus was lowered by fire by 82% for the first season. Three years after the fire, the density of C. pospischilii was 14.52 plants m⁻² versus an average for the unburned species of only 6.78 plants m⁻². Seedling emergence from the seed bank for C. pospischilii and E. muticus, at the end of the third growing season, was respectively 6.6 and 12.4 seedlings m⁻² more than that of unburned grassland – a reason for concern regarding plant composition stability of burnt semi-arid grasslands. This study provides a better understanding of the two unpalatable grass species Cymbopogon pospischilii and Elionurus muticus and the implications of this for the sustainable utilisation of semi-arid grassland.

Keywords: aboveground phytomass production, plant density, seedling density, soil seed bank, tuft basal area