Quassia amara L. diameter and total height under different light conditions: implications for the management of agroecosystems.

Quassia amara L. is a semi-sciophyte species that can be found growing as a large shrub or a small tree in Neotropical rainforests. It is traditionally harvested as a non-wood forest product for culinary, medicinal and insecticidal uses. Lack of knowledge on the ecological conditions that support tree growth limits the development of sustainable forest management plans of natural forests and the development of new agroecological cultivation models. The overall objectives of the present work are to (1) compare the Quassia amara L. growth in different forest structures; (2) evaluate the impact of light conditions on Quassia amara L. diameter growth, total height growth and height–diameter relationship and (3) discuss implications for the sustainable management of the species in agroecosystems. Light conditions are characterized at the tree level by the crown illumination index (cii), which is a visual and ordinal index. Results show that tree growth varies between plots with different forest structures and light conditions. The cii was able to characterize light conditions. Best light conditions were different for diameter and total height growth: cii value of 5.0 (tree crown completely exposed to overhead and lateral direct light) and cii value of 3.5 (tree crown exposed to some vertical/overhead direct light and low direct light), respectively. The cii did not affect the height–diameter relationship. A value of cii equal to 4 was found as an intermediate condition and recommended for the establishment of new agroecosystems including the Quassia amara L.