Physiological Studies on Temperate Lichen Species I. A Mathematical Model to Predict Assimilation in the Field, Based on Laboratory Responses

Abstract

SUMMARYA model has been constructed to predict assimilation in four lichen species using climatological data. Gas exchange of the lichens has been measured in the laboratory in response to seasonal, light, temperature and moisture changes. By fitting polynomial equations to the response curves, the model predicts assimilation on the basis of these variables. A comparison of weight changes measured in the field with assimilation values predicted by the model using climatological data measured in the field, shows that the model gives realistic predictions over periods of 1 month. The model also permits the importance of the various environmental parameters to be examined, singly and in combination. Predicted assimilation values on climatically different days suggest that moisture is the single most important factor governing lichen growth -the assimilation gains during one rainy summer day can counteract the losses of five dry days. The model can now be extended to examine possible reasons for lichen distribution.

Water and vapor transport in algal‐fungal lichen: Modeling constrained by laboratory experiments, an application forFlavoparmelia caperata

“…The uniform potential profiles confirm the assumption made in our inverse‐modeling of model parameters from observations (water retention and capacitance) and suggest that vertical resistances are negligible within the thallus (between cortices, photobiont layer, and medulla), while the sharp gradient in potentials near the surface of the cortices suggest that the vertical resistance to water flow are concentrated at the sites of vapor transport between lichen and the atmosphere, supporting our first hypothesis. These results also support earlier models that simulate lichen bulk moisture dynamics and model vapor dynamics at the cortices as the dominant control on hydration and desiccation (Jonsson et al, ; Paterson et al, ; Péch, ). However, these earlier models cannot describe the internal gradients between symbionts and external water.…”

Predicting lichen hydration using biophysical models

“…However, the aim of these other studies was not to explicitly predict the length and occurrence of wet active periods of lichens in field conditions. On the other hand, previous models were also able to predict the uptake of various water sources (Paterson et al 1983;Pech 1989) and/or the mechanistic loss of water (Kershaw and Harris 1971;Lloyd 2001) and/or prediction by meteorological variables (Kershaw and Harris 1971;Paterson et al 1983;Pech 1989;Lloyd 2001). Therefore, the major advantage of the models presented A. sarmentosa P. glauca C. rangiferina C. rangiferina A. sarmentosa, P. glauca and C. rangiferina (exposed and embedded thalli separately).…”

Growth of foliose lichens: a review

“…Seasonal fluctuations in growth measured as RaGR per month, often correlate best with average or total rainfall (Karenlampi 1971;Armstrong 1973;Golm et al 1993), but linear regressions fitted to radial growth increments measured per month against total rainfall often account for relatively small amounts of the total variance (usually <40%) (Armstrong 1988). In a study of Cetraria, Paterson et al (1983) found that moisture was the most important factor governing growth. In addition, assimilation gains during rainy days were sufficient to offset carbon losses over five dry days.…”