Crop production under different rainfall and management conditions in agroforestry parkland systems in Burkina Faso: observations and simulation with WaNuLCAS model

Abstract

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.

Climate Change Sensitivity of Multi-Species Afforestation in Semi-Arid Benin

“…In accordance with previous studies [41,57,69,70], the range of the GOF statistics and the high correlation between the simulated and observed growth parameters for both the calibration (Figure 3) and the validation (Table 4) are indicative of the ability of the WaNuLCAS model to reproduce the early growth dynamics of the tested afforestation species with an acceptable accuracy and precision. A R 2 value of 0.5, CD value of 0.5-2, and EF value above 0.5 represent a good predicted-to-observed relationship [69].…”

“…The relative increase in AGB, induced by the deep rooting depth, was greater under severe water stress compared to mild water stress, suggesting that deep-rooted saplings are less sensitive to extreme drought than shallow-rooted saplings. Similarly, Coulibaly et al [41] has reported that tree species with deep rooting systems are less vulnerable to water deficits. These results can be attributed to the fact that during extreme drought conditions, deep rooted saplings take advantage of their access to deeper soil horizons, which could result in increased photosynthetic activity and continued biomass production, as reported by Hartl-Meier et al [22] for beech (Fagus sylvatica L.) and larch (Larix decidua Mill.)…”

“…and Vitellaria paradoxa C.F. Gaertn) growth in agroforestry parklands in West Africa [39][40][41]. The aim of our research was to assess the climate sensitivity of two afforestation species-Jatropha curcas L. and Moringa oleifera Lam.-in the early stages of their development (i.e., the first two years of growth), decisive for the future growth [42] and also when plants are most sensitive to changes in water availability [43][44][45].…”

Between land sharing and land sparing – what role remains for forest management and conservation?

“…Achieving this goal will, however, require extensive understanding of agro-ecological interrelationships and intensive efforts to transfer this knowledge to farmers. 13 See, for example, models by Coulibaly et al (2014) Knoke et al (2014) compared three restoration pathways -afforestation, repasturization with low-input management and high-input management -for a tropical mountain region using 23 ecological, economic and social indicators. Among these options, afforestation showed the highest and low-input pasture management the lowest increase in the socioeconomic and ecological value of these abandoned farmlands.…”

Sustainable intensification of smallholder farming systems in Ethiopia : what roles can scattered trees play?

“…Their interactions with crops involve complex management decisions in order to maximize total farm level benefits. Regardless of established ecological and provisioning contribution of trees (Bayala et al, 2002), their direct contribution to increased crop yield is often contested (Coulibaly et al, 2014) and context specific (Brandt et al, 2012). For example, on-farm trees and crops compete for resources such as soil moisture and nutrients depending on soil type, climate and tree-crop management (Huth et al, 2010).…”