During, H.J., B. Verduyn & A.K. Jägerbrand. Biomechanical
properties of the terrestrial mosses Pleurozium schreberi (Brid.) Mitt.
and Pogonatum japonicum Sull. & Lesq. along altitudinal gradients in
northern Japan
Arctoa (2015) 24: 375-381
doi: 10.15298/arctoa.24.30
Altitudinal
gradients along mountain slopes provide valuable opportunities to study
variation in plant traits in response to changes in environmental conditions
along such gradients. This study focused
on biomechanical traits of two moss species, the more or less horizontally
growing Pleurozium schreberi and the erect-growing Pogonatum
japonicum, along altitudinal gradients on two mountains in Hokkaido,
northern Japan. We measured stem diameter in two directions to determine the
second moment of area I, used three-point bending tests with free stem ends to
determine the slope of the force-deflection curve dF/dx, and used these data to
calculate Young’s modulus and flexural rigidity of the stems. Both species showed much variation in all traits among
replicates in the samples at each altitude. Environmental variation associated
with altitude had more effect on the biomechanical traits of P. japonicum
than on those of P. schreberi. Stems of P. japonicum were thicker
(larger I) than those of P. schreberi and had a larger Young’s modulus
and flexural rigidity. Stems tended to become thinner (lower second moment of
area) and less rigid (lower flexural rigidity) at increasing altitude in both
species.