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Environmental Control of Net Photosynthesis in Naturally Growing Pinus Ponderosa Laws
Author(s) -
Helms John A.
Publication year - 1972
Publication title -
ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.144
H-Index - 294
eISSN - 1939-9170
pISSN - 0012-9658
DOI - 10.2307/1935713
Subject(s) - photosynthesis , carbon dioxide , botany , ecology , environmental science , photosynthetic capacity , environmental stress , crown (dentistry) , biology , atmospheric sciences , geology , medicine , dentistry
Carbon dioxide exchange by intact foliage was monitored in the middle—crown region of 30—m tall ponderosa nine trees growing in their natural environment at 1,300 m in the Sierra Nevada of California. Characteristic diurnal patterns of net photosynthesis as a function of temperature are presented for summer conditions of low, medium, and high environmental stress. Changes in relationship between rates of net photosynthesis and factors of the environment were determined by examining the data within different time periods on days of markedly different stress conditions. Highest correlations were obtained under conditions of low stress when 80—90% of the variation in rates of net photosynthesis could be accounted for by changes in temperature and radiation alone. As general stress conditions increased, ability to predict rates of net photosynthesis decreased, with saturation vapor pressure deficit becoming the dominant factor accounting for variation. General prediction equations using data pooled from a wide range of summer conditions accounted for, at best, 65% of the variation in net photosynthesis.