Quantifying biomass of secondary forest after slash-and-burn cultivation in Central Menabe, Madagascar

Biomass is the principal input of nutrients in slash-and-burn cultivation of tropical dry deciduous forest. In this paper, we report the aboveground biomass of ligneous and herbaceous vegetation as a function of the age of abandonment after cultivation in order to analyse the potential amount of nutrients released into the soil. To estimate the biomass of trees, we used dendrometric classes based on height and circumference at breast height of all individual plants inventoried in the plots in four growth types. For biomass measures, we harvested representative trees in each defined class. The quantity of total biomass increased with age of abandonment, reaching 72 t ha-1 after 40 years of abandonment. The species that contributed most to biomass were Fernandoa madagascariensis, Diospyros perrieri, Dalbergia sp., Poupartia silvatica, Tarenna sericea, Xeromphis sp., Phylloctenium decaryanum, Stereospermum euphorioides and Croton greveanum. Diospyros increased regularly already after 10 years of abandonment. The biomass of Dalbergia also increased with the age of abandonment, but after 30 years, this quantity decreased because of selective harvest by farmers. Fernandoa increased after 30 years, as did Poupartia, but the latter became a key player as it was, comparatively, the species with the highest biomass shortly after 30 years of abandonment.