COS 38-10 - Multi-element limitation:  Simulation and measurements suggest that P is more limiting than n in young northern hardwood ecosystems

Tuesday, August 9, 2011: 4:40 PM
6A, Austin Convention Center
Ruth D. Yanai, Forest and Natural Resources Management, SUNY College of Environmental Science and Forestry, Syracuse, NY, Edward B. Rastetter, Ecosystem Center, Marine Biological Lab, Woods Hole, MA, Melany C. Fisk, Biology, Miami University of Ohio, Oxford, OH, Timothy J. Fahey, Department of Natural Resources, Cornell University, Ithaca, NY, R. Quinn Thomas, Department of Ecology and Evolutionary Biology, Cornell University, Ithaca, NY and Matthew A. Vadeboncoeur, Earth Systems Research Center, University of New Hampshire, Durham, NH
Background/Question/Methods

Although temperate forests have long been thought to be primarily nitrogen limited, resource optimization theory suggests that ecosystem productivity should be co-limited by multiple nutrients.  In northeastern North America, air pollution and forest harvesting disturbance elevate N availability and contribute to the likelihood of P limitation. 

Results/Conclusions

The Multi-Element Limitation (MEL), which now includes P, light, and water as well as N and carbon, predicted a greater response of aboveground productivity to N+P than N or P alone.  In older stands, MEL predicted a greater response to N than to P addition, but in younger stands, the supply of N from detritus was predicted to be sufficient to create P limitation.  Field observations in replicate young (26-30 years) and mature (>100 years) stands in the Bartlett Experimental Forest, New Hampshire, support these predictions.  Fine roots foraged preferentially for P in young stands and for N in mature stands, according to ingrowth into nutrient-amended cores.  Foliar retranslocation of P exceeded that of N in yellow birch and sugar maple, especially in young stands.   Experimental nutrient manipulations are planned to test the prediction that young stands are commonly more P limited and mature stands are more N limited in this widespread forest type.

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