Effects of goat grazing and woody charcoal production on xerophytic thickets of southwestern Madagascar

Abstract

The effects of goat grazing and woody charcoal production are analysed on the diversity, structure, production and regeneration of the xerophytic thickets in southwestern Madagascar. Twenty (20 × 20) m2 plots were sampled according to soil type (yellow sand and calcareous) and disturbance intensities (low: ungrazed and no woody charcoal production; high: grazed and with woody charcoal production). Woody charcoal production reduced shrub density and biomass and affected species composition on yellow sand soil. In contrast, goat grazing alone did not significantly affect the diversity, mean height, stem and leaf biomass or species composition of xerophytic thickets on calcareous soil. However, shrub regeneration rate was low on both grazed and ungrazed sites. Rainfall variability may be the reason for this low regeneration. Goat grazing at a moderate stocking rate (∼1 head per ha) does not affect xerophytic thickets communities (plant diversity, biomass, regeneration rate). This finding indicates a need to (i) emphasize individual case studies that help to manage shrub pasture in semi arid regions, and (ii) avoid broad generalisations about the negative effects of goats on dry vegetation. Furthermore, goat breeding may be a viable alternative to woody charcoal production in these xerophytic thickets.