Stem water storage dynamics of Vochysia divergens in a seasonally flooded environment

- We investigated stem radius variations of V. divergens for 2 year in the Pantanal.
- Environmental factors affecting tree water deficit and stem cycle were identified.
- Variations in actual vapor pressure modulated stem cycles on a monthly basis.
- Onset of growth season were triggered by soil water content.

Stem radius measurements can vary over the short and medium-term in relation to changes in certain environmental parameters, providing useful information about the impacts of climate variation on tree physiology and growth processes. Here, use a variety of approaches to identify the main environmental variables that influence annual stem water dynamics in the tree Vochysia divergens in a seasonally flooded forest in Northwest Pantanal, Brazil. The circadian stem cycle and diel phases of stem radius (contraction, recovery and increment) was quantified over two growth seasons (2013-2015) using high resolution dendrometer measurements. Our results demonstrate that stem radial variation is strongly linked to water availability which, in turn, is significantly associated with soil water content (SWC) and actual vapor pressure (ea). Our data suggest that the duration of contraction and recovery phases are related to SWC, whereas the increment phase is more influenced by the phenological cycle of the tree. The contraction phase has a limiting association with high vapor pressure deficit (VPD) (decoupled from SWC), indicating stomatal regulation. The circadian stem cycle was characterized by monthly fluctuations reflecting atmospheric water demand status. Monthly mean actual vapor pressure (eamean) was strongly associated with annual variation in the amplitude of the circadian stem cycle.