Modeling bio-engineering traits of Jatropha curcas L.

• We measured root distribution and strength of Jatropha curcas L. age 6–36 months.
• We calibrated a root density model and the Root Bundle Model using above data.
• Root density and reinforcement increase with age but decrease rapidly from stem.
• Significant root reinforcement requires plant spacing of 1 m for 3 year-old plants.

The wide distribution of Jatropha curcas L. in tropical areas provides the opportunity to use this plant for improving slope stability and controlling erosion. To determine the effectiveness of Jatropha curcas L. as a bio-engineering plant we measured stem diameter and height of 1, 3, 5, 6, 18, and 36 month-old plants, and root distribution at 6, 18, and 36 months by full excavation of the root system. We also measured in the laboratory the elastic modulus and maximum tensile force of 50 roots. These data were used to calibrate a weighted log-likelihood root distribution model and a root reinforcement model. Models were coupled to estimate root reinforcement at stand scale over a three year period as a function of the plantation's tree density. Our results of root distribution indicate a rapid decrease of root diameter along the root length leading to rapidly decreasing root reinforcement with distance from the stem. Minimal root reinforcements at 0.5 m from the stem is about 1 and 11 kPa for 18 and 36-month old plants, respectively. At 1 m from the stem only 36-month old plants provide any significant root reinforcement.Despite its relatively low root reinforcement relative to other larger tree species Jatropha curcas L. is a suitable bio-engineering plant because it easily propagates, grows fast, and is resilient. Root reinforcement in the first stage of growth needs high density plantation of up to 40,000 plants per hectare. This should then be followed by thinning down to 10,000 plants per hectare to optimize root reinforcement at 3 years age.