Sprouting by semi‐arid plants: testing a dichotomy and predictive traits

Abstract

M. 2004. Sprouting by semi-arid plants: testing a dichotomy and predictive traits. Á/ Oikos 107: 72 Á/89.A widely-used description of vegetation response to fire is that species can be clearly classified as sprouters or non-sprouters. We aimed to assess: (1) how well this dichotomous classification (sprouter/non-sprouter) described the responses of a semiarid flora to experimental disturbance; (2) how similar were sprouting responses to treatments mimicking intense herbivory and fire; (3) how well easily-measured traits could predict sprouting. Sprouting was assessed for 45 species from a range of growth forms (grasses, forbs, sub-shrubs, woody shrubs and trees) from semi-arid southeastern Australia. We used two treatments: clipping at stem base, and clipping followed by burning with a blowtorch.A dichotomy accounted for !/60% of deviance explained by species identity. Models with three or four groups were not substantially better. The dichotomy was not between 0% and 100% sprouting, rather between 'weak' and 'strong' sprouters. Probabilities of sprouting for weak sprouters were 23% after clipping and 6% after burning, while strong sprouters had sprouting probabilities of 90% after clipping and 79% after burning. While sprouting varied in space and time, the dichotomy was robust to this variation. Sprouting ability increased with size in most of the species with variable sprouting.Sprouting was partially related to growth form; grasses sprouted strongly, chenopods weakly, and forb and woody species covered the range of sprouting. Strong sprouters were likely to have more stems per plant, greater basal area, shorter potential height and deeper buds than weak sprouters. A hierarchical model that used growth form and then stems-per-plant provided a simple, robust predictor of sprouting.Four-fifths of species responded consistently to clipping and burning while one-fifth of species were strong sprouters after clipping but weak sprouters after burning. Burning reduced sprouting most in intermediate sprouters. Differences between sprouting after clipping and burning reflected increased intensity and were related to the depth of buds below ground.

Population and clonal level responses of a perennial grass following fire in the northern Chihuahuan Desert

“…Examples include Table 2 Sources of variation and P values for Wxed eVects following ANCOVA, Tukey-Kramer comparisons, and contrasts (n/a not applicable). These tests were used to examine Wre and livestock grazing eVects on survivorship, collective basal cover, and clone basal area for three size classes of B. eriopoda clones: small (0-10 cm 2 basal area), medium (10-30 cm 2 ), and large ( >30 cm 2 ) a F, Fire; N, no Wre; S, small clones; M, medium clones; L, large clones southeastern longleaf pine savannas (Grace and Platt 1995;Mulligan and Kirkman 2002) and savannas and shrublands of Belize (Miyanishi and Kellman 1986) and Australia (Radford et al 2001;Vesk et al 2004). Perennial grass clones of smaller size classes may be more susceptible to complete kill after Wre because their root systems are less developed than larger clones and thus they lack the necessary resources for resprouting (Grace and Platt 1995).…”

“…Third, past research has evaluated perennial grass responses to Wre by measuring general, population level changes in aerial and basal cover. However, perennial grasses are comprised of clones or clumps of diVerent basal area sizes that can be aVected diVerently by Wre (Vesk et al 2004). It is not understood if such reductions in cover, as reported in past research, were attributed to clones that survived or did not survive Wre.…”

“…Examples include tallgrass prairies of the American Midwest (Collins 1987;Briggs and Knapp 1995), savannas of the southeastern and southwestern USA (Platt et al 1991;Sparks et al 1998;McFarland and Mitchell 2000), South African grasslands (Uys et al 2004), and mallee shrublands of Australia (Vesk et al 2004). In grasslands, the resprouting of perennial grasses tends to occur rapidly within one or two growing seasons following Wre such that cover, aboveground productivity, and tiller density can equal or exceed levels in Wreexcluded areas (Knapp and Hulbert 1986;McFarland and Mitchell 2000;De Luis et al 2004).…”

Fitness and evolution of resprouters in relation to fire

“…Manual removal of the crown has been used as an alternative approach to test for the ability to resprout (Negreros-Castillo and Hall 2000;Parrotta et al 2002) but, critically in the context of this review, it lacks the heat component. Burrows (2002) has shown how the stored buds in some rainforest trees are near the stem surface compared with their fireprone counterparts, whereas burnt plants are more likely to die than pruned ones (Lloret et al 1999;Vesk et al 2004). Nevertheless, some systems burn strongly under special circumstances and this does enable fireresprouters to be detected; e.g., large desert fires in central Australia have been recorded following occasional heavy rainfall events that provide temporary grassy fuel continuity (Luke and McArthur 1978;Nano and Clarke 2011).…”

“…Resprouters, other than those with apical bud survival, have a large bud 'bank' often associated with many short stems, possibly as a 'failsafe' system following damage. Even so, their production may sometimes be spontaneous (Mesléard and Lepart 1989;López-Soria and Castell 1992;Vesk et al 2004; Banksia attenuata, B. Lamont pers. obs.)…”