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Limitations within “The Limits to Tree Height” 1
Author(s) -
Netting Andrew G.
Publication year - 2009
Publication title -
american journal of botany
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.218
H-Index - 151
eISSN - 1537-2197
pISSN - 0002-9122
DOI - 10.3732/ajb.0800144
Subject(s) - biology , sequoia , xylem , photosynthesis , turgor pressure , botany , transpiration , biomass (ecology) , range (aeronautics) , horticulture , agronomy , materials science , composite material
Koch et al. ( Nature 428: 851–854) measured various parameters that were thought to limit the height of Sequoia sempervirens from northern California and concluded that the maximum height for this species is 122–130 m because within this range: (1) Irreversible embolism formation was proposed to occur when the xylem pressure was less than −1.9 MPa. (2) The leaf mass to area ratio exponentially approached 833 g×m −2 . (3) The discrimination against 13 CO 2 exponentially approached −20. (4) Light‐saturated photosynthesis per unit leaf mass decreased to zero, indicating no net gain in leaf biomass. These conclusions are questioned here by reassessing the assumed limits to the biophysical parameters and by reexamining the proposed linear and exponential relationships between these parameters and tree height. It is concluded that: (1) Embolism repair mechanisms could have occurred at −2.7 MPa. (2) The leaf mass to area ratio could be a result of, rather than a determinant of, the large differential between cellular turgor and the xylem pressure. (3) The discrimination against 13 CO 2 may show two populations of foliage with apparent linear relationships with height rather than one exponential relationship. (4) The light‐saturated photosynthesis per unit leaf mass as a measure of biomass investment in leaf expansion excludes investment in branch and trunk wood. As a result, tree height may be limited by a long‐term balance between dieback and continued growth.