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Optimal co‐allocation of carbon and nitrogen in a forest stand at steady state
Author(s) -
Mäkelä Annikki,
Valentine Harry T.,
Helmisaari HeljäSisko
Publication year - 2008
Publication title -
new phytologist
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.742
H-Index - 244
eISSN - 1469-8137
pISSN - 0028-646X
DOI - 10.1111/j.1469-8137.2008.02558.x
Subject(s) - photosynthesis , primary production , nitrogen , productivity , biomass (ecology) , respiration , carbon fibers , environmental science , steady state (chemistry) , optimal allocation , agronomy , botany , ecosystem , ecology , mathematics , biology , chemistry , economics , mathematical optimization , macroeconomics , organic chemistry , algorithm , composite number
Summary• Nitrogen (N) is essential for plant production, but N uptake imposes carbon (C) costs through maintenance respiration and fine‐root construction, suggesting that an optimal C:N balance can be found. Previous studies have elaborated this optimum under exponential growth; work on closed canopies has focused on foliage only. Here, the optimal co‐allocation of C and N to foliage, fine roots and live wood is examined in a closed forest stand. • Optimal co‐allocation maximizes net primary productivity (NPP) as constrained by stand‐level C and N balances and the pipe model. Photosynthesis and maintenance respiration increase with foliar nitrogen concentration ([N]), and stand‐level photosynthesis and N uptake saturate at high foliage and fine‐root density. • Optimal NPP increases almost linearly from low to moderate N availability, saturating at high N. Where N availability is very low or very high, the system resembles a functional balance with a steady foliage [N]; in between, [N] increases with N availability. Carbon allocation to fine roots decreases, allocation to wood increases, and allocation to foliage remains stable with increasing N availability. • The predicted relationships between biomass density and foliage [N] are in reasonable agreement with data from coniferous stands across Finland. All predictions agree with our qualitative understanding of N effects on growth.