Data from: Contribution of lianas to community-level canopy transpiration in a warm-temperate forest

1. Lianas (woody climbers) have a greater amount of leaves relative to
basal area or standing biomass than trees, and very wide vessels that
permit efficient water transport. These features suggest that lianas
possibly consume proportionally more water through transpiration than
trees. Despite their potential importance, researchers have made only
limited attempts to evaluate effects of lianas on forest water dynamics.
2. We conducted sap flow measurements for 1 year using a
thermal-dissipation method for four species each of lianas and trees in a
liana-rich, warm-temperate forest in Japan and estimated the contribution
of lianas to stand canopy transpiration. 3. Based on a calibration
measuring water uptake rates from cut-stem ends, the actual sap flux (Fd)
in liana stems was several times greater than those estimated from the
original calibration provided for the method. In the field, lianas showed
an average of 2–4 times greater Fd than trees throughout the year. Except
for this difference, diurnal and seasonal patterns of relative changes of
Fd were similar in both groups. The whole-plant transpiration (Qt) of
sample plants were exponentially related to basal diameter for both lianas
and trees; Qt of lianas increased more steeply with basal diameter than
that of trees. By extrapolating the relationships between Qt and basal
diameter to the inventory data of the study plot, we estimated that lianas
contributed 12.8% to the annual stand canopy transpiration while
comprising 2.3% of stand basal area, which probably reflected the
top-heavy architecture of lianas.4. Our results indicate that the
contribution of lianas to forest water dynamics may be several times
greater than their contribution to forest basal area. This implies that a
slight increase of liana abundance might have greater effects on water
dynamics and, through competitions with trees for limited water, the
carbon sequestration capacity of forests than expected from the increase
in basal area. This study underlines the necessity of evaluating the
relative importance of lianas to forest water dynamics in forests
worldwide.