Tropical tree species show a wide range of light requirements, which determine species occurrence from canopy gap to understory and along larger-scale disturbance gradients such as those caused by ground fires or direct human disturbance. The life history strategies and plant traits associated with differential light requirements are well established. Strong correlations amongst such traits provide useful scalars of species responses to irradiance.

© S. Gourlet-Fleury - Cirad

Tropical tree species also show a wide range of drought tolerance, which can lead to reduced growth and increased mortality even in plants in TMFs. Traits conferring drought tolerance remain largely unknown, although deciduousness, wood density (or hydraulic architecture) and rooting depth are strong candidates. The few studies to date that have directly linked species drought tolerance to their distribution across rainfall gradients emphasized this tolerance importance for shaping distribution patterns in tropical forests. A trade-off between species shade and drought tolerance has been widely assumed but it has not been comprehensively tested yet.