Stable carbon isotope composition (δ13C) ofAcacia tortilissubsp.spirocarpa(A. Rich.) Brenan growing at three semi-arid sites in Kenya

Carbon isotope ratios (δ13C) were obtained from foliage and branch wood samples ofAcacia tortilisgrown with and without microbial inoculation, on three semi-arid sites in Kenya. δ13C ratios were higher in trees grown on the two drier sites than on the wetter site. In addition, δ13C ratios of seedlings inoculated with a mixed microbial inoculum (VA mycorrhiza with rhizobia) were higher than uninoculated controls at the wetter site. These preliminary results suggest thatAcacia tortilistrees growing on drier sites display relatively high water-use efficiencies, and that in some situations microbial inoculation may increase water-use efficiency of outplanted trees