Nutrient uptake in eastern deciduous tree seedlings |
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Authors: | K Lajtha |
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Institution: | (1) Department of Biology, Boston University, 02215 Boston, MA, USA |
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Abstract: | Tree seedlings that colonize large treefall gaps are generally shade-intolerant species with high potential relative growth
rates. Nutrient availability may be significantly elevated in disturbance-induced gaps, however, little is known about the
role of differences in nutrient uptake capacities of different species in structuring the community response to gap openings
in eastern North American deciduous forests. Seven tree species were grown from seed under both a high and a low nutrient
regime, and uptake kinetics of phosphate, ammonium, and nitrate were studied. Yellow birch, a species with intermediate shade
tolerance and relative growth rate, had the highest maximum rates of uptake of all ions, while tulip tree, a gap-colonizing
species with high relative growth rate, had the lowest rate of phosphate uptake and intermediate rates of ammonium and nitrate
uptake. Beech and hickory, which have low relative growth rates and are not gap-colonizing species, had intermediate levels
of nutrient uptake. There was no evidence that species with the highest maximum uptake rates measured at high supply concentrations
had relatively low uptake at low nutrient supply concentrations. Although birch increased phosphate absorption capacity when
grown under a low nutrient regime, this pattern did not hold for nitrate or ammonium uptake, and other species showed no change
in nutrient uptake capacity according to nutrient growth regime. Clearly, factors other than nutrient absorption capacity,
such as nutrient use efficiency or allocation to root vs. shoot biomass, underlie differences in species' capacities to colonize
and maintain a high relative growth rate in canopy gaps. |
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Keywords: | gaps ion uptake nitrogen nutrient acquisition phosphorus |
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