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Allometric relations and growth in Pinus taeda : the effect of elevated CO 2 , and changing N availability
Author(s) -
GEBAUER RENATE L. E.,
REYNOLDS JAMES F.,
STRAIN BOYD R.
Publication year - 1996
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.1469-8137.1996.tb01148.x
Subject(s) - allometry , biomass (ecology) , loblolly pine , biomass partitioning , pinus <genus> , chemistry , botany , zoology , agronomy , biology , ecology
summary Loblolly pine (Pinus taeda L.) seedlings were grown for 138 d at two CO 2 partial pressures (35 and 70 Pa CO 2 ) and four N solution concentrations (0.5, 1.5, 3.5 and 6.5 mM NH 4 NO 3 ). Allometric regression analysis was used to determine whether patterns of biomass allocation among functionally distinct plant‐parts were directly controlled by CO 2 and N availability or whether differences between treatments were the result of size‐dependent changes in allocation. Both CO 2 and N availability affected growth of loblolly pine. Growth stimulation by CO 2 at nonlimiting N solution concentrations (3.5 and 6.5 mM NH 4 NO 3 ) was c. 90%. At the lowest N solution concentration (0.5 mM NH 4 NO 3 ), total plant biomass was still enhanced by 35% under elevated CO 2 . Relative growth rates were highly correlated with net assimilation rates, whereas leaf mass ratio remained unchanged under the wide range of CO 2 and N solution concentrations. When differences in plant size were adjusted apparent CO 2 effects on biomass allocation among different plant parts disappeared, indicating that CO 2 only indirectly affected allocation through accelerated growth. N availability, by contrast, had a direct effect on biomass allocation, but primarily at the lowest N solution concentration (0.5 mM NH 4 NO 3 ). Loblolly pine compensated for N limitation by increasing specific lateral root length and proportional biomass allocation to the lateral root system. The results emphasize the significance of distinguishing size‐dependent effects on biomass allocation from functional adjustments made in direct response to changing resource availability.