Ecophysiological studies of the arid grasses Digitaria coenicola (F. Muell.) Hughes and Enteropogon acicularis (Lindl.) Lazarides

Abstract

Autecological information of key plant species is considered an essential prerequisite for sound grazing management strategies of arid grasslands. Such information is meagre for even the preferred grasses found in central Australian ecosystems. This work presents quantitative information on specific requirements for the germination and growth of two preferred perennial grasses found in central Australia. Fresh seed of D. ooenioolr. was inherently dormant due to some property of the pericarp. Maximum germination of E. acicularis occurred over a wider range of temperature (25 to 41°C), compared with D. coenicola (29 - 37°C). The speed of germination and total germination percentage of both species declined as water potential decreased below -4 b. There were little differences in relative growth rates during the seedling stage, values recorded were 0.28 and 0.33 gg * day”'*' for D. coenicola and E. acicularis, respectively. During vegetative growth, values recorded for relative growth rate were 0.27 and 0.28 gg~* day-*, respectively. Under non-limiting external conditions the dry weight achieved after 42 d by D. coenicola was over three times greater than E. acicularis. This superiority was attributed to the higher leaf area ratio during the vegetative stage as well as a greater value for net assimilation rate during the reproductive stage of D. coenicola compared with E. acicularis. The agronomic and ecological implications of these results are discussed in relation to the management of these arid grasslands. Particular emphasis is placed on the central role of germination in the recruitment of these species in central Australia. Show more