Hydraulic conductivity and xylem structure of partially buried mangrove tree species

Abstract

Natural sedimentation rates may not affect mangrove trees adversely, but large and sometimes episodic delivery of sediment may result in decreased growth, dieback or mortality. In this study, we aim to assess the effects of different levels of partial sediment burial on mangrove tree structure and function. Trees of Avicennia marina, Ceriops tagal and Rhizophora mucronata were experimentally buried with terrestrial sediment to simulate different sedimentation levels (15, 30 and 45 cm). After 14 months, branch hydraulic conductivity, xylem structure and stomatal properties were assessed. Sedimentation resulted in general increase in hydraulic conductivity following intermediate levels of burial. The process is also associated with varied anatomical modification in vessel grouping, vessel lumen size and potential conductive area in the three investigated mangrove tree species. Additionally, stomatal adjustment was observed in C. tagal with up to 37% reduction of total stomata area in leaves of buried trees. Although sedimentation may stimulate modification in vessel and stomatal properties of buried mangrove trees after a relatively short period of exposure, these traits may not necessarily be important in ensuring hydraulic conductivity which either increases or remains the same as in control following burial.