The study aimed to provide quantitative information on the ecology of short fallow systems in southern Cameroon, and their socio-economic value to farming communities of that area. Results from this study will lead to recommendations for the design of appropriate conservation and management decisions and plans that will improve the productivity and guarantee the sustainability of shortened fallows in the area. The specific objectives of the present research were to assess species diversity as impacted by fallow age and fallow type, both during the fallow phase as well as during the subsequent cropping period, and to evaluate the productivity of some key fallow trees identified by local farmers that could be components of productive agroforests. To address these objectives, field activities included ethnobotanical surveys throughout 15 villages of the study area, vegetation surveys of fallows and
food crop fields at Mengomo (over two years), and monitoring of about 100 fruit trees at Kaya (during 19 months). Analyses of the results showed that local farmers of the study area do have an extensive knowledge of their environment. Using a common criterion - the fallow duration - they were able to distinguish short, medium and longfallow systems (of respectively, <6, 7-10, and >10 years old) as well as the characteristics and constraints associated with their agricultural management. The effect of the resource use intensity was particularly evident on the availability and distribution of short and long fallows across the three study resource domains. About 174 useful plant species were identified, from which nearly 58 % were collected in fallows of less than 10 years old. Most frequently mentioned useful species that farmers collect from all fallow classes included 'wild' fruit trees and forest species. The present study revealed that species and functional diversity were significantly associated with vegetation structure and plant community composition in 5-7 years old fallows under different land use intensity regimes. The ordination analyses showed a clear pattern of distribution of species along a gradient of resource use
intensity: recurrent Chromolaena odorata-dominated fallows (reflecting high land use intensity) were clearly separated from fallow sites that had been forests in the previous cropping cycle (corresponding to relatively lower land use intensity). The pattern of the responses of maize, groundnut and cassava to the three fallow types did not differ over the two years of the study, all crops producing higher yield in fields established after clearing C. odorata-dominated fallows than in fields following bush fallows. Coula edulis, Dacryodes edulis, Irvingia gabonensis and Ricinodendron heudelotii were recorded at very low density values in fallow lands of the study area (< 10 individuals of more than 10 cm dbh ha^-1), suggesting the need to develop preferential management of regeneration for these species. Apart from leaf flushing, flowering and fruiting phenology of these species was seasonal, with irregular flowering/fruiting observed for some D. edulis and I. gabonensis individuals over the two years of monitoring. Fruiting was concentrated between July and October (and up to January for R. heudelotii), coinciding with the rainy season. An individual of C.
edulis, D. edulis, I. gabonensis and R. heudelotii produced, on average, 236±48 fruits (9.6±2.1 kg fresh weight in 2001, 335±94 fruits and 10.9 ±2.9 kg in 2002), 235±94 fruits (12.5±5.1 kg in 2001 and 801±246 fruits, 51.4±16.0 kg in 2002), 547±212 fruits (71.8±24.9 kg in 2001 and more than 2002 fruits, 133.3±30.0 kg in 2002), 2018±467 fruits (72.2±16.4 kg in 2001), respectively. Regression analyses showed that tree size parameters were correlated with fruit production for some species, but generally, do not explain an important pat of the production data of the study species (r² < 60%).