Soil seed bank dynamics in Tithonia diversifolia dominated fallowland at Ile- Ife, South-western Nigeria
The soil seed bank of Tithonia diversifolia, an invasive species which dominates open waste fallowland vegetation was studied. Two different roadside sites which vary in extent of open waste land were selected. The species composition of the established vegetation was assessed in the two different sites. Twenty top soil samples were collected at 0-15 cm five different distances (15 m, 30 m, 45 m, 60 m, and 75 m) inwards away from each main road in dry and rainy seasons and the seed bank composition was determined by greenhouse germination over a 6 month period. The similarity between the composition of the seed bank flora and that of the established vegetation was low. The least and the highest emerged seedlings density were recorded in the 15 m and 75 m respectively inwards away from the main road in both seasons. The results of the seedlings emergence are a reflection of the extent of open waste land dominated by the invasive species due to human disturbance (road construction) on both sites. Overall results suggest that the emergence of the species from the soil seed bank may be due to the impact of the invasive species – Tithonia diversifolia on other plant species in the study environment.
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Keywords: Fallowland, invasive species, seedling emergence, seed bank.