Effects of certain burning and cutting treatments and fluctuating annual rainfall on seasonal variation in grassland basal cover.

Abstract

The variation in total basal cover from one time of year to another was investigated by means of the bridge and wheel-point methods over a period of seven years. Treatments were: a control plot, one cut annually in winter and one in spring; a fourth plot was burnt and a fifth burnt and cut alternately, in spring. Statistically significant increases and decreases in total basal cover were found between a number of consecutive surveys. Maximum basal cover was usually recorded between April and July and the minimum basal cover between July and October, although exceptions to both ranges were found. Winter and spring basal covers were significantly correlated (P = 0,001 and 0,01 respectively) with the rainfall of the preceding season on the control plot, but no correlation with rainfall was found on the treated plots. The cover of Trachypogon spicatus and Eragrostis curvula increased and decreased, respectively, with or without cutting and burning treatments, over the period of study. Themeda triandra increased in basal cover with treatments, while cover of Setaria perennis decreased. The cover of Heteropogon contortus remained fairly constant, but decreased when no treatments were applied. The various treatments gave similar results, but usually differed from those of the control. It was concluded that the best time for making an annual survey of basal cover by means of a point method is between May and June. At this time the plants may be easily identified and basal cover is at its highest.

Keywords: basal cover; burning; cover; cutting; effects; eragrostis curvula; grassland; heteropogon contortus; national botanic garden; pretoria; rainfall; seasonal variation; setaria perennis; south africa; themeda triandra; trachypogon spicatus; treatments; wheel-point method