Linking tree-rooting profiles to leaf phenology : a first attempt on Tectona grandis Linn F.

2019

Article référencé dans le Web of Science WOS:000491468100018

Clement C., Pierret Alain, Maeght Jean-Luc, Hartmann Christian, Xayyathip K., Soulileuth B., Sounyafong P., Latsachack K., Thammahacksa C., Sengtaheuanghoung O.

Trees : Structure and Function, 2019, 33 (5), p. 1491-1504 ISSN 0931-1890

Key message In this study, deep roots of teak tree seem to have acted as a "safety net", allowing trees to maintain their canopy cover longer, thus coping with inter- and intra-seasonal drought. Abstract Most deciduous species of dry monsoon forest, such as teak tree (Tectona grandis Linn F.), establish new foliage slightly before, or at the onset of the rainy season, when the upper soil layers are the driest. This phenomenon suggests that trees rely upon deep water storage to cover their need for the new canopy development. Therefore, we hypothesized that deeper rooted trees may display phenological patterns that confer them physiological advantages with regard to access to water. At an upland location in Northern Laos, we characterized 10 mono-specific teak tree plantations corresponding to micro-environments that differed with regard to soil, slope, elevation, and orientation. We compared the leaf phenology of trees, taking into account their age, diameter at breast height (DBH), and rooting pattern down to 3.5 m depth. With at least 5% of its total fine roots below 2 m, teak trees were found to be deep rooted. There was no correlation between the timing of leaf flushing and rooting depth nor with primary production (assessed on the basis of tree girth increase). Leaf flushing was strongly synchronous with rainfall rather pointing out that its primary determinant is the water status of topsoil and near-surface soil horizons that results from seasonal rainfall, even though the mechanism(s) underlying such a process remain to be clarified. However, deeper rooted teak trees tended to maintain a denser canopy cover over longer periods than trees with shallower rooting systems. This suggests that, deep roots may play a role as a "safety net", i.e., providing improved resilience to inter- and intra-seasonal drought events, but do not influence the timing of the leaf flushing.

Sciences du monde végétal [076] ; Etudes, transformation, conservation du milieu naturel [082]

LAOS

Fonds IRD [F B010077166]

fdi:010077166