Data from: Divergence of vessel diameter explains interspecific variation in hydraulic safety to salinity in the Sundarbans mangrove ecosystem

Sundarbans (~10000 sq km), the world’s largest single-block mangrove
ecosystem, provides important ecosystem goods and services to > 7.5
million coastal people in two neighboring countries, Bangladesh (~60%) and
India (~40%). It has extensive variability in environmental variables,
including siltation and salinity, which are influenced by freshwater
damming in the north and changing seawater levels from the south. Based on
spatial salinity gradients, this ecosystem is divided into three
contrasting salinity zones: the low salinity zone (LSZ, eastern and
northeastern part), the medium salinity zone (MSZ, central and southern
part), and the high salinity zone (HSZ, western and southwestern part).
Forest growth, such as tree height, increases from the HSZ to the LSZ and
varies between salinity zones. However, human disruptions and rapid
environmental changes, such as sea level rise (SLR), pose a threat to this
sensitive ecosystem. Increasing salinity creates challenges for hydraulic
transport in mangrove species. Therefore, studies on variation in intra-
and interspecific hydraulic traits, and associated xylem anatomy may allow
us to understand the adaptation of mangrove species to changing
environmental conditions. in this study, we examined how xylem and
hydraulic traits vary among dominant tree species such
as Exocecaria agallocha, Xylocarpus moluccensis, and Heritiera
fomes growing under climatically identical but heterogeneous environmental
conditions in the Sundarbans. Although potential conductivity (KP) and
leaf-specific conductivity (KL) showed species-specific variation, a
notably greater conductivity was found in the low salinity zone (LSZ),
which had lower vessel wall reinforcement (t/b)2. Xylem and hydraulic
traits exhibited mostly strong phylogenetic signals, whereas pairwise
relationships between traits were phylogenetically independent. The study
species had distinct hydraulic characteristics, where vessel diameter was
strongly related to the variation in KP and KL. Furthermore, the study
species exhibited a weak trade-off between hydraulic efficiency and
safety. A higher frequency of smaller vessel diameters in light-demanding
E. agallocha indicates greater hydraulic safety under stressful conditions
than in shade-tolerant H. fomes, followed by X. moluccensis. Although
species characteristics place broad bounds on xylem traits, the combined
effects of salinity, nutrient availability, and tree size modulate vessel
diameter, which leads to hydraulic conductivity variation. The contrasting
safety in terms of vessel diameter in mangroves suggests an important role
in adaptation to salinity and reveals an underlying mechanism of tree
growth and species distribution in the Sundarbans.