Stem radial increment of forest and savanna ecotypes of a Neotropical tree: relationships with climate, phenology, and water potential

Abstract

The aim of the present study was to investigate differences in stem radial increment between the savanna and forest ecotypes of Plathymenia reticulata at an ecotonal site. It was hypothesised that even under similar climate conditions, the savanna and forest ecotypes exhibit differences in radial growth, phenology, and water status because of differences in wood density. Stem radial increment, phenology, and water potential were evaluated monthly. The radial increment was positively related to precipitation and displayed no increment (or decrement) in months with low rainfall. A negative relationship was observed between radial growth and wood density, with the forest ecotype exhibiting a higher radial increment than the savanna ecotype. Midday water potential (ΨMD) was also negatively related to wood density. Compared to the forest ecotype, the savanna ecotype displayed lower values of ΨMD during the dry season and started leaf senescence earlier at the beginning of the dry season. Leaf fall improved water status, resulting in leaf flushing even without a significant increase in rainfall. Radial growth significantly increased only after the crown leaf cover was completed. The results confirmed the importance of wood density in the differential responses of ecotypes in relation to growth, water status, and phenology.