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Simulation Studies of the Influence of Understory Location on Transpiration and Photosynthesis of Arnica Cordifolia on Clear Days
Author(s) -
Young Donald R.,
Smith William K.
Publication year - 1982
Publication title -
ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.144
H-Index - 294
eISSN - 1939-9170
pISSN - 0012-9658
DOI - 10.2307/1940118
Subject(s) - understory , transpiration , botany , photosynthesis , ecology , environmental science , biology , canopy
A computer model incorporating field microclimatic and ecophysiological measurements was developed to study the effects of understory location and leaf phenotype on the water and photosynthetic relations of the understory herb, Arnica cordifolia (Compositae). Three representative, understory locations were simulated: a microhabitat shaded throughout the day (SH), a location receiving direct sunlight only in the early morning and late afternoon (EL), and a microhabitat receiving long intervals of direct sunlight at midday (LM). Photosynthesis and transpiration for three morphological and physiological phenotypes (represented by plants with small—, average—, and large—size leaves, which occurred naturally in the LM, EL, and SH locations, respectively) were simulated at all three locations. For all simulations, predicted photosynthesis and transpiration were greatest during periods of high insolation and varied substantially according to location. Daily carbon gain for all three phenotypes was greater at the EL location, followed by the LM and SH microhabitats. Although predicted daily water loss was similar at a given location, substantial differences occurred for each phenotype among the locations (0.83 vs. 2.7 kg.m — 2 °d — 1 for small leaves at the SH and LM locations, respectively). All three phenotypoes were also predicted to have the greatest water use efficiency (WUE) at the EL location, with the average leaf having the highest (0.0079), followed by the large (0.0056) and small leaves (0.0045). The simulations suggest that both location and phenotype may strongly influence understory plant ecopohysiology. Moreover, only the most common phenotype (plants with average—size leaves) had a maximum daily carbon gain and WUE in its natural microhabitat (EL) compared to the SH and LM locations. The results of the simulations are discussed in terms of the apparent adaptive fitness of the observed phenotypic variations in A. cordifolia.