Effects of tillage regime, cropping duration and fallow age on diversity and structure of secondary vegetation in Madagascar

The objective of this paper is to determine the effects of tillage regime, cropping duration and fallow age on the diversity, structure and floristic composition of secondary vegetation in a tropical forest of eastern Madagascar. Tillage regime was divided into three categories: (1) no tillage, (2) light tillage (local shallow tillage <10 cm deep) and (3) heavy tillage (tillage of the whole plot, 10–20 cm deep). Cropping duration was divided into three classes: (i) short (1–2 years), (ii) medium (3–4 years) and (iii) long (5–15 years). Eighty-nine fallows subdivided in three regrowth age classes (1–5; 6–10 and 11–29 years) were surveyed. We found that heavy tillage regime was associated with a long cropping duration favouring the establishment of herbaceous and wind-dispersed species and reducing species richness, basal area and maximal height. The recovery of species richness and maximum height was faster under no till compared to heavy tillage. Heavy tillage regime favours proliferation of herbaceous species in the middle age regrowths (6–10 years). Long cropping duration (5–15 years) slowed down the recovery rate of maximal height in the old regrowths (11–29 years). A blockage of secondary succession was never found but a total forest recovery takes a longer time when heavy tillage and long cropping duration were observed.

► Heavy tillage and long cropping duration reducing species richness and basal area. ► Heavy tillage and long cropping duration favour herbaceous, wind-dispersed species. ► Recovery of species richness, basal area and maximum height was faster under no till. ► No blockage of secondary succession when heavy tillage and long cropping duration.