Allometric relations in Jatropha curcas production systems of Burkina Faso

Abstract

Our study addressed biomass dynamics in traditional and newly introduced Jatropha curcas production systems in Burkina Faso, West Africa. Five prevailing J. curcas systems included interplanting with annual crops, intensely managed plantations, afforestation of abandoned land, plantings along contour stone walls, and traditional living fences. Measurements of stem diameter, tree height (n = 670) and above- and below-ground biomass (n = 157) enabled the development of generic allometric models relating shoot and root biomass with stem diameter. The relations showed very good fits (R2 > 0.9) for all studied systems, except afforestation sites which largely perished. Considering system-specific height-diameter (HD) relationship improved the model performance for living fences where trees allocated more biomass in the height rather than diameter growth. Self-propagation in living fences results in variable stand density, tree age, and consequently shifting HD relations. Therefore these models would benefit from local calibrations should they be applied elsewhere. We argue that for the other systems the developed generic equations are applicable subject to accounting for the tree ontogenetic stages deduced from HD relations. In this respect, the allometric models for juvenile trees are most robust whereas overall validity range of the equations can be improved with more observations of large-size trees.