Abstract
Mango tree is a tropical evergreen tree whose leaves live for several years and gradually fall over time. It is important to understand the pattern of leaf fall because foliage distribution affects tree functioning. The objective of this work was to identify the growth unit (GU) characteristics and the environmental factors affecting leaf fall at the GU scale during one year. In January 2021, 240 GUs were sampled on five adult mango trees of the cultivar 'Cogshall' at three depths, expressed as the number of GUs from the terminal GU (1, 2 and 4 GUs) along the branches. GU depth was used as a proxy for GU age. The numbers of nodes and remaining leaves were counted for each GU. Their light environment was estimated from hemispherical photographs. The number of leaves per GU was then counted monthly during one year. The number of nodes per GU increased with GU length and was higher for GUs in apical position than for GUs in lateral position. The number of leaves remaining on the GUs in January 2021 was negatively related to GU depth. From February 2021 to January 2022, the occurrence of leaf fall was 10 times higher during the rainy season than during the dry season, and it increased with GU depth. Light environment did not affect leaf fall, except when analysis was restricted to December 2021. During that month, light environment had a negative effect on leaf fall for GUs in depths 1 and 2, but no effect for GUs at depth 4. This work highlighted the seasonal pattern of leaf fall and the major effect of GU depth, i.e., GU age, on leaf fall in the evergreen mango tree.