Does geographic origin dictate ecological strategies in Acacia senegal (L.) Willd.?: evidence from carbon and nitrogen stable isotopes

Background and aims: Acacia senegal, a leguminous
dryland tree, is economically and ecologically important
to sub-Saharan Africa.Water-use efficiency (WUE) and
biological nitrogen fixation (BNF) are fundamental to plant productivity and survival.We quantify provenance
differences in WUE, BNF, photosynthesis, biomass and
gum arabic production from A. senegal assessing genetic
improvement potential.
Methods: Using stable isotope ratios, we determined
WUE (δ13C) and BNF (δ15N) from provenances of
mature A. senegal in field-trials (Senegal), sampling
leaves at the beginning (wet) and end (dry) of the rainy
season. Seedling provenance trials (UK) determined
photosynthesis, and biomass and δ13C in relation to
water table. Environmental data were characterised for
all provenances at their sites of origin.
Results: Provenances differed in both δ13C and δ15N.
Gum yield declined with increasing WUE. Virtually no
BNF was detected during the dry season and seedlings
and mature trees may have different WUE strategies.
Wind speed and soil characteristics at provenance origin
were correlated with isotope composition and gum
production.
Conclusion: Provenance differences suggest that selection
for desirable traits, e.g., increased gum production,
may be possible. As ecological strategies relate to
native locality, the environmental conditions at plantation
site and provenance origin are important in
assessing selection criteria.