Ligno-tubers, obligate or facultative?

To overcome the challenge of frequently occurring fires in savannas, some woody
species have evolved the ability to resprout from underground lignotubers. This
study set out to determine if the formation of these tubers is an obligate or facultative
adaptation to disturbance. This was done by comparing root to shoot ratios of three
savanna broad-leafed species, Sclerocarya birrea, Terminalia sericea and Euclea
natalensis growing in annually burnt, no burn and no disturbance (control)
treatments. Significant differences were found between the root/shoot ratios of E.
natalensis annual burn and no burn treatments (P=.028) and between S. birrea annual
burn and control treatments (P=.028). No significant difference was found between
root/shoot ratios for T. sericea from annual and no burn treatments. The outcomes of
this study suggest that S. birrea and E. natalensis are facultative tuber forming
species and T. sericea is an obligate tuber forming species. This suggests that some
savanna species are influenced by disturbance in terms of tuber formation and invest
in carbohydrate storage accordingly.
Second language abstract: Houtagtige spesies in savannas het deur evolusie die vermoë
ontwikkel om vanuit ondergrondse storingsorgane te herstel na
vuur. Die doel van hierdie studie was om vas te stel of die vorming
van storingsorgane in reaksie op versteuring gedoen word en of dit
voorkom in alle individue van ‘n spesie onafhanklik van die
versteurings waaraan dit onderwerp is. Dit is gedoen deur die
wortel tot groeipunt verhoudings van drie savanna spesies,
Sclerocarya birrea, Terminalia sericea en Euclea natalensis te
vergelyk. Individue wat in areas van drie verskillende vuur
frekwensies groei is vergelyk. Die drie verskillende
vuurfrekwensies wat ondersoek is, is jaarlikse vuur, geen vuur en
kontrole (geen versteuring). Betekenisvolle verskille is gevind in
die wortel tot groeipunt verhoudings van E. natalensis wat tussen
jaarlikse brand en geen vuur areas vergelyk is (P=.028).
Sclerocarya birrea in jaarlikse brand areas het betekenisvol verskil
van dieselfde spesie in die kontrole studie area (P=.028). Geen
betekinsvolle verskille is gevind in T. sericea nie. Die studie
verskaf bewyse vir die moontlikheid dat S. birrea en E. natalensis
slegs ondergrondse storinsorgane ontwikkel wanneer benodig bv.
wanner dit in areas wat gereeld versteur word deur vuur groei. In
teenstelling hiermee word dit gestel word dat T. sericea
storingsorgane ontwikkel onder enige groei versteurings
omstandighede. Sekere savanna species reageer dus op versterings
op verskillende maniere deur bv. ondergrondse storingsorgane vir
voedingstowwe te ontwikkel.