Theoretical limits of belowground production by Spartina alterniflora: an analysis through modelling
1984
Morris, J.T. | Houghton, R.A. | Botkin, D.B.
Emperical measurements of standing leaf biomass in tall-form stands of Spartina alterniflora and climatic data were used to solve a growth model in order to place upper limits on belowground production. The model was solved using data from Great Sippewissett Marsh in Massachusetts, Flax Pond in New York, and a Sapelo Island marsh in Georgia. The upper limits of belowgroung production were calculated for these marshes, 1.1, 3.2, and 6.5 kg C m−2 yr−1, respectively, when a zero rate of belowground respiration was assumed. Best estimates of net belowground production were calculated, 0.6, 0.6, and 1.4 kg C m−2 yr−1, respectively, when the respiration of roots and rhizomes was subtracted from the gross rate of belowground production and when we assumed that the loss of belowground biomass from death or exudation of organics was great enough to maintain the average annual belowground biomass in steady state. Best estimates of belowground production gave predicted CO2 exchange rates that were consistent with all of the independent measurements of gas exchange, but suggested that CO2 from sources belowground, probably from respiration, may be lost through the leaves. Photosynthetic efficiencies predicted by the model were similar to those reported for a number of other highly productive species.
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