© 2000 Heron Publishing—Victoria, Canada
Comparative water relations of mature mahogany (Swietenia macrophylla) trees with and without lianas in a subhumid, seasonally dry forest in Bolivia
Martin G. Barker (1) and Diego Pérez-Salicrup (2)
1. Department of Plant and Soil Science, University of Aberdeen, Cruickshank Building, Aberdeen AB24 3UU, U.K. / 2. Harvard Forest, P.O. Box 68, Petersham, MA 01366-0068, USA / Received September 30, 1999
Summary
Many evergreen mahogany (Swietenia macrophylla King) trees in the seasonally dry Bajo Paragua forest in northeast Bolivia carry substantial liana loads. Evergreen lianas
may impede the growth of their host trees in various ways, including competition for water. Hypotheses tested were that water
relations status differs (a) between lianas and their host trees, and (b) between trees infested with lianas that were cut
3.5 months previously (treated trees) and control trees with intact lianas. Diurnal measurements of stomatal conductance (gs) and leaf water potential (Ψ) were made on canopy leaves of treated and control trees and lianas at the start and end of
the dry season. Lianas had higher (less negative) Ψ values (mean and predawn) and higher diurnal gs (expressed as mean or sum of diurnal values) than mahogany trees, indicating that lianas had a higher demand for, and ability
to obtain, water than their host trees. Control and treated trees had a similar water relations status, suggesting that removal
of lianas had no effect on the water relations of the trees, even at the end of the dry season. We conclude that either both
life forms have conservative water relations that were unaffected by water availability in our study, or that the trees and
lianas have access to sufficient and different sources of water because of differences in their rooting depths. Our data are
consistent with studies of temperate species, indicating that lianas do not interfere with water availability to their host
trees.
Keywords:
diurnal, interspecific competition, liana cutting, stomatal conductance, water potential.
