Ecology of Cladonia lichens. II. Comparative physiological ecology of C. mitis, C. rangiferina , and C. uncialis

• Published in: Canadian Journal of Botany
• Main Authors: Lechowicz, Martin J., Adams, Michael S.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Canadian Science Publishing 1974
• Subjects: Plant Science; Cladonia rangiferina
• Online Access: http://dx.doi.org/10.1139/b74-052; http://www.nrcresearchpress.com/doi/pdf/10.1139/b74-052

The net CO 2 exchange responses of Cladonia mitis, C. rangiferina, and C. uncialis from the Wisconsin Pine Barrens to irradiance, thallus temperature, and thallus relative water content were statistically compared for fall, spring, and summer. The absolute net photosynthetic rate of C. rangiferina exceeded that of C. uncialis under essentially all conditions and in all seasons; C. mitis's absolute net photosynthesis fluctuated with the seasons between these two contrasting species. Cladonia mitis showed significant intraspecific seasonal variation in net photosynthetic responses to temperature and irradiance. Cladonia rangiferina showed significant seasonal variation in dark respiratory response to temperature. Cladonia uncialis showed no significant intraspecific seasonal variation in net CO 2 exchange responses. Significant interspecific differences in net CO 2 exchange responses centered on the net photosynthetic responses to thallus temperature and relative water content.Despite its low net photosynthetic rates, C. uncialis is the most prevalent lichen in the Wisconsin Pine Barren ground-layer community. We attribute this not to broad physiological tolerance, but to its significantly slower drying rate. Lichens photosynthesize only when wetted. Cladonia uncialis photosynthesizes at generally lower rates than C. mitis or C. rangiferina, but it photosynthesizes longer under comparable environmental drying regimes. This and other aspects of the physiological ecology of the three species are discussed in relation to microdistribution and microhabitats within the Wisconsin Pine Barrens.