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Experiments on Lichen Growth. I. Seasonal Patterns and Environmental Controls
James B. Benedict
Arctic and Alpine Research
Vol. 22, No. 3 (Aug., 1990), pp. 244-254
Published by: INSTAAR, University of Colorado
Stable URL: http://www.jstor.org/stable/1551587
Page Count: 12
You can always find the topics here!Topics: Thallus, Lichens, Plant growth, Precipitation, Photosynthesis, Snow, Snow cover, Species, Moisture content, Respiration
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Radial growth of mature Xanthoparmelia lineola and X. subdecipiens thalli (n = 10 thalli, 170 lobes) was measured bimonthly for 2 yr at a transplant locality on the East Slope of the Colorado Front Range (altitude 2565 m). Growth occurred during every measurement period, but was most rapid in May, June, July, and August. Ninety-three percent of seasonal growth-rate variation during the first year of the study, and 92% during the second year, are explained by differences in the duration of daytime, snow-free thallus moisture (moisture available for photosynthesis); the strength of the relationship suggests that a positive net carbon assimilation rate is translated almost immediately into lobe elongation. No negative correlation was found between radial growth and thallus moisture recorded at night or beneath snow. In the cool, continental environment of the study area, duration of photosynthetically significant thallus moisture is influenced more strongly by air temperature, day length, and snow cover than by total precipitation. At higher altitudes and latitudes, where lichenometry is used for dating, these factors will have even greater importance.