NONSTRUCTURAL CARBOHYDRATE ALLOCATION FOLLOWING DIFFERENT FREQUENCIESOF SIMULATED BROWSING IN 3 SEMIARID SHRUBS

Nonstructural carbohydrate allocation patterns in response to differen t frequencies of simulated browsing (leaf and twig removal) were studi ed in the following semi-arid shrubs: Osteospermum sinuatum, a dwarf d eciduous shrub, Pteronia pallens, a dwarf evergreen shrub, and Ruschia spinosa, a dwarf leaf-succulent shrub. Simulated browsing at all freq uencies resulted in the elevation, or had no effect, on total nonstruc tural carbohydrate (TNC) concentrations of O. sinuatum plant parts, an d resulted in the decrease in TNC concentrations of R. spinosa plant p arts. The responses of P. pallens were intermediate with elevations as well as declines in TNC concentrations of plant parts measured in res ponse to various clipping frequencies. At the low frequency of simulat ed browsing (every 26 weeks) elevations in plant TNC content were meas ured in the two non-succulent shrubs O. sinuatum and P. pallens. It wa s concluded that the overcompensation with respect to TNC accumulation observed in the two non-succulent species represents one of the ways in which excess photosynthate is utilized by browsed shrubs with a lim ited regrowth potential. Simulated browsing was the least detrimental with respect to biomass production to the non-succulent O. sinuatum an d P. pallens, and most injurious to the leaf-succulent shrub, R. spino sa. The observed TNC allocation patterns could not adequately explain the variation among species in the production of new growth and it was concluded that some factor(s) other than the carbon resource was limi ting regrowth.