Forest carbon cycles and elevated CO[sub 2]: What can experiments on seedlings tell us
- Harvard Univ., Cambridge, MA (United States)
To understand how elevated CO[sub 2] may affect forests, we must link controlled environment experiments and field studies. We must also address ontogenetic differences in CO[sub 2] response. Our previous results show correspondence between species- and height-specific leaf-level gas exchange and ecosystem-level CO[sub 2] exchange, measured by eddy-correlation. We postulate that forest carbon exchange can be modeled as gas exchange of a population of leaf modules. But are all leaves alike We grew seedlings of 4 tree species in pots placed on platforms at the top (20 m) and mid-point (12 m) of Canopy Access Towers, corresponding to canopy heights of the domant trees (red oak, red maple, white and yellow birch). We grew a similar set of seedlings in the glasshouse with light levels, temperature and wind simulating 2 canopy heights, at ambient and elevated CO[sub 2]. Photosynthetic light response curves, leaf chlorophyll and N, leaf-air temperature differentials, leaf [delta][sup 13]C and N-photosynthesis relationships were compared. For red maple and the birches, P[sub max] was higher for canopy-top than sub-canopy foliage, and was consistent for ontogenetic stages. The [open quotes]glasshouse effect[close quotes] was minimal. Elevated CO[sub 2] doubled the seedlings photosynthetic rate. Ontogenetic differences in oak were pronounced: mature tree P[sub max] was three-fold that of all seedlings. Thus the model of leaves as modulus is most useful for scaling leaf-level photosynthesis of early successional, indeterminate species, and should be used cautiously for late successional species.
- OSTI ID:
- 7264782
- Report Number(s):
- CONF-940894-; CODEN: BECLAG
- Journal Information:
- Bulletin of the Ecological Society of America; (United States), Vol. 75:2; Conference: Annual Ecological Society of America (ESA) meeting: science and public policy, Knoxville, TN (United States), 7-11 Aug 1994; ISSN 0012-9623
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
CARBON DIOXIDE
BIOLOGICAL EFFECTS
ECOLOGICAL CONCENTRATION
FORESTS
CARBON CYCLE
POPULATION DYNAMICS
SEEDLINGS
PHOTOSYNTHESIS
PLANT GROWTH
TREES
CARBON COMPOUNDS
CARBON OXIDES
CHALCOGENIDES
CHEMICAL REACTIONS
GROWTH
OXIDES
OXYGEN COMPOUNDS
PHOTOCHEMICAL REACTIONS
PLANTS
SYNTHESIS
560300* - Chemicals Metabolism & Toxicology