Dynamics of resprouting in the lignotuberous shrub Banksia oblongifolia

Abstract

AbstractThe resprouting response of different sized Banksia oblongifolia lignotubers (genets) was followed in two field experiments. In the first, the density and speed of resprouting, and the growth in length of the leading shoot from each lignotuber in response to fire and to the time elapsed since the last fire was monitored for 18 months after fire and clipping treatments. In the second, sizes of bud banks were estimated by repeatedly clipping new shoots from individual lignotubers.Density of resprouting (shoots dm−2 lignotuber) decreased with increasing lignotuber size, and the length of the leading shoot increased. The direct effect of fire was to reduce shoot density by about 75%. The speed of resprouting (time taken by a cohort of shoots to reach 50% of their peak density) was similar after fire and clipping, but leading shoots grew significantly longer after fire. The elapsed time since lignotubers were last burnt did not influence their density of resprouting, but it did influence the speed of resprouting. Shoots from clipped lignotubers that had burnt 3 years earlier took about 90 days to each 50% of their peak density while shoots on lignotubers last burnt 5 and 17 years earlier took about 40 days. Death of shoots was unrelated to crowding in any stand. More lignotubers from the oldest unburnt stand were grazed by herbivores.The number of buds converted into shoots after successive clippings was surprisingly small; for most lignotubers this reserve was less than three times the size of their standing crop of shoots. In general, the smaller lignotubers carried a higher proportion of dormant buds in relation to their standing crop of shoots. About 30% of buds remained dormant after the first clipping and about 10% after the second and third clippings. Evidence suggests that buds are replaced within 6 months of fire. No lignotubers survived four clippings over 15 months.