Traditional agroforestry parkland systems in Burkina Faso are under threat due to human pressure and climate variability and change, requiring a better understanding for planning of adaptation. Field experiments were conducted in three climatic zones to assess Sorghum bicolor (L.) Moench (Sorghum) biomass, grain yield and harvest index in parklands under different rainfall pattern and compared to simulations of sorghum biomass and grain yield with the Water, Nutrient and Light Capture in Agroforestry Systems (WaNuLCAS) model for calibration and parametrisation. For planning adaptation, the model was then used to evaluate the effects of different management options under current and future climates on sorghum biomass and grain yield. Management options studied included tree densities, tree leaf pruning, mulching and changes in tree root patterns affecting hydraulic redistribution. The results revealed that sorghum biomass and grain yield was more negatively affected by Parkia biglobosa (Jacq.) Benth. (néré) compared to Vitellaria paradoxa C. F Gaertn (karité) and Adansonia digitata L. (baobab), the three main tree species of the agroforestry parkland system. Sorghum biomass and grain yield in different influence zones (sub-canopy, outside edge of canopy, open field) was affected by the amount of precipitation but also by tree canopy density, the latter depending itself on the ecological zone. The harvest index (grain as part of total biomass) was highest under the tree canopy and in the zone furthest from the tree, an effect that according to the model reflects relative absence of stress factors in the later part of the growing season. While simulating the effects of different management options under current and future climates still requires further empirical corroboration and model improvement, the options of tree canopy pruning to reduce shading while maintaining tree root functions probably is key to parkland adaptation to a changing climate.

Trees contribution in improving soil carbon is well established, but few works addressed how this was affected by a climatic gradient. This research investigated effects of Vitellaria paradoxa C. F Gaertn and Parkia biglobosa (Jacq.) Benth on total soil carbon in parklands along a rainfall gradient for recommendations of tree species which better improve soil carbon under specific climatic conditions for parklands adaptation to climate change. Total soil carbon at topsoil and subsoil layers measured using spectrophotometry infrared method, was higher when rainfall increased and were respectively (1.598 ± 0.040; 1.033 ± 0.022; 0.834 ± 0.014; 0.857 ± 0.016%). It was higher at topsoil (0.529 ± 0.015%) and subsoil (0.282 ± 0.019%) under V. paradoxa when rainfall decreased while it was higher under P. biglobosa and V. paradoxa when rainfall increased slightly. Its improvement was higher under V. paradoxa and P. biglobosa when rainfall respectively decreased and increased. A decrease trend of total soil carbon under both tree species from trunk to outside the canopy whatever rainfall levels and soil layers was observed. Tree species choice could play an important role in improving total soil carbon and crop productivity according to rainfall level for parklands adaptation to climate change.

This research assessed precipitation increase along a climactic gradient effect on tree and crop root length densities and belowground competition in parklands systems of Vitellaria paradoxa C. F Gaertn, Parkia biglobosa (Jacq.) Benth with Sorghum bicolor (L.) Moench for formulating parklands management options improving crop productivity. Field experiments were conducted at three sites along an increasing rainfall gradient. Soil samples were taken, roots were washed and sorted by categories and root length density was estimated using the method of Tennant. Belowground competition was assessed using the ratio method. Correlation between crop root and aboveground biomass was tested. For topsoil, higher crop root length density was at Sokouraba (0.087 ± 0.007 cm.cm-3). For subsoil, crop and tree average root length density was higher at Tougouri and were respectively 0.05 ± 0.009 and 0.117 ± 0.021 cm.cm-3. Trees reduce crop root length density with precipitation increase and more under P. biglobosa. Belowground competition along a climatic gradient and its interaction with zones and tree species was not significantly different. Higher crop root length density obtained at topsoil with precipitation increase did not reduce belowground competition. Tree management options reducing tree roots should be tested on belowground competition along a climatic gradient.

The objective of this review was to investigate the effects of drought on cashew and to identify options for cashew adaptation to drought in the aim to maintain and/or improve its productivity in plantation and in agroforestry under climate change in Burkina Faso. The methodology used was the review of the scientific literature through the analyse of the findings of 51 studies to explore the effects of drought on the cashew. Drought is a major factor causing land degradation and limiting crop productivity in the Sahel and particularly in Burkina Faso. The cashew contributes in creating jobs and generating revenues mainly for women employed in the cashew nuts processing units established in Burkina Faso. The cashew sensitivity to drought was reported through changes in some physiological parameters under water stress conditions. In order to maintain and/or improve cashew productivity in plantations and in agroforestry systems and the rural households socio-economic conditions under drought with climate change, it is urgent to develop and implement cashew adaptation options. This manuscript recommended adaptation actions to reduce the vulnerability of the effect of cashew to drought under climate change.