Disturbance type predicts Isoberlinia spp. regeneration modes across vegetation units in sudano-guinean woodlands of Benin

Abstract

The degradation of West African woodland ecosystems threatens the natural regeneration processes of Isoberlinia spp ., dominant tree species in sudano-guinean woodlands of Benin. This study analyzed its natural regeneration modes in the N'dali protected forest (Benin) across three vegetation units. Using stratified random sampling, we established 30 main plots (20 m × 20 m) and characterized 481 regenerating individuals as regeneration from seed, root suckers, and stump sprouts. Vegetative regeneration overwhelmingly dominated (82.5%), with stump sprouts accounting for 59%, root suckers 23.5%, and regeneration from seed for only 17.5%. Stump sprouts showed superior growth performance (median diameter: 0.8 cm, median height: 55 cm) compared to root suckers (0.5 cm, 45 cm) and regeneration from seed (0.2 cm, 15 cm). Regeneration modes varied significantly across vegetation units (p < 0.001). Stump sprouts decreased from 93.3% in fallow land to 55.6% in wooded savanna and 44.4% in woodland, whereas regeneration from seed rose from 6.7% to 17.8% and 23.5%. A multinomial mixed-effects logistic regression accounting for the nested spatial structure of the data (subplots within plots) identified disturbance type as the main driver of regeneration mode. Grazing alone suppressed stump sprouts (p < 0.001), whereas the combination of grazing and logging significantly increased the probability of root suckering (p = 0.018). These results reveal a dynamic shift between sexual and vegetative regeneration pathways in Isoberlinia spp. Woodland. Conserving sexual reproduction in less disturbed woodlands is recommended to maintain genetic diversity, while vegetative regeneration of Isoberlinia spp. can be harnessed for the rapid restoration of the degraded woodlands.