An investigation to assess the spatial structure and severity of Pseudocercospora leaf and fruit spot disease (PLFSD) on citrus trees in cocoa-based agroforests was carried out in three contrasting ecological zones in southern Cameroon, viz: 1) the humid forest zone, 2) the degraded forest zone, and 3) the forest-savannah transition zone. Two main parameters were investigated viz: 1) the spatial structure of cocoa based agroforests, and 2) the disease severity. In total, the spatial structure of 19 cocoa-based agroforests was analysed using the Ripley K(r) function, meanwhile the collection of epidemiological data that consisted of noting the presence of PLFSD spots on leaves and fruits on 438 citrus trees was used to characterise the severity of the disease. Results showed that, the spatial structure of citrus trees in these agroforests investigated were regular in seven plots, random in nine, and aggregated in three. Aggregated plots presented a significantly higher mean of disease severity on leaves and fruits (28.55 and 30.37 respectively), as compared to randomised (20.91 and 16.32 respectively) and regular plots (16.28 and 14.97 respectively), at P-value < 0.05. These results suggest that the spatial structure of citrus trees in the cocoa-based agroforests studied influences the severity of PFLSD. Proper integrated control measures can therefore be initiated, leading to a considerable reduction of the use of manufactured inputs, and thereby, the cost of production of citrus fruits.
Diachronic analysis of satellite images was used to assess the spatiotemporal dynamics of land use and land cover change in the coffee production basins of Cameroon, located in the forest agroecological zones (Moungo and Haut-Nyong) and the highland humid savannah (Noun). A survey of farmers was carried out to identify land use and changes in the area of coffee agroforests over time. While the period 1980 to 2001 was marked by an increase in the area of the forest/agroforest land-use unit, the period 2001 to 2019 shows significant regressions ranging from 14 to 22% of the total area of each basin. Significant changes in the land use units have repercussions on the areas dedicated to coffee growing, which have decreased significantly; today, the largest areas under cultivation are in Haut-Nyong (1.51±1.27 ha), the medium areas in Moungo (1.14±1.13 ha) and the smallest in Noun (0.67±0.72 ha). Coffee abandonment coupled with anthropogenic factors such as agriculture and housing expansion are mainly responsible for the degradation of coffee agroforests, with notable repercussions on land cover changes. The cocoa-coffee revival encouraged by sectoral Ministries in recent years seems to have encouraged cocoa production, since in agro-ecological regions; the increase in forest/agroforest area is mainly attributable to Theobroma cacao and Elaies guineensis.
Investigations to assess farmer’s perceptions on the fertilizing potential of associated trees species in cocoa agroforest of degraded forest ecology were carried out in southern Cameroon. The perception of the farmers was based on the ability of the trees to maintain or improve soil fertility of their farms. The verification of these perceptions was done through an evaluation of litter fall biomass nutrient content (N, P, K, Ca and Mg) of selected trees. The top 5 associates trees ranked by farmers was: Milicia excelsa, Ceiba pentandra, Ficus mucuso, Asltonia boonei, Terminalia superba. The chemical analysis of the leaf litter from the different tree species revealed a significant different between their chemical components. N appeared to have the highest concentrations varying from 2.82 to 5.57% with a mean value of 4.25 ± 1.065%, P had the lowest concentrations typically around 0.001%. The top 5 tree species based on the chemical analysis ranking were: C. pentandra, M. excelsa, Eribroma oblungum, Alstonia boonei, Zanthoxylum heitzi. Farmer’s perceptions thou holistic, are not completely different from scientific finding. Therefore, they should be taken in consideration in management plans for cocoa- based systems in order to enhance their ecological and economic performance.
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