PARENT SESSION
Oral Session #35: Nitrogen cycling: Response to inputs, variation in time and space. Presiding: M. Fenn.
Tuesday, August 7, 2001. 1:00 PM to 5:00 PM. Hall of Ideas G.
Interspecific divergence in foliar nutrient responses to excessive nitrogen deposition.
May, Jeffrey1, Burdette, Sarah1, Gilliam, Frank1, Adams, Mary2, 1 2
ABSTRACT- In regions impacted by elevated atmospheric nitrogen (N) deposition, plant nutrient dynamics may both modify and be modified by changes in ecosystem nutrient availability. For two years we studied effects of elevated nitrogen deposition on foliar nutrient dynamics in three important forest trees in a mixed deciduous forest. The study was conducted at the Fernow Experimental Forest, West Virginia, on two watersheds supporting stands of similar age: WS3 (fertilized with ammonium sulfate annually since 1989) and WS7 (untreated). Foliar nutrient dynamics were analyzed in Acer rubrum (ACRU), Liriodendron tulipifera (LITU), and Prunus serotina (PRSE) on each watershed. Between 1999 and 2000, N concentrations increased 28% in leaves of LITU and PRSE in WS3, but not significantly in ACRU. In WS7, all three species experienced N increases averaging 17%. Phosphorus (P) concentrations followed a similar trend in WS3, increasing 14% and 28% in LITU and PRSE, but again not significantly in ACRU. Nitrogen and P resorption efficiency in WS3 decreased 74% and 53%, respectively, in ACRU. At the same time, LITU in WS3 experienced a 10% increase in N resorption, and no change for P. Changes in PRSE were not significant for either nutrient. In WS7, there were no changes for either N or P resorption. Substantial interspecific divergence in nutrient responses to excessive N could lead to long-term changes in relative tree vigor and ultimately to shifts in species composition.
KEY WORDS: nutrient resorption, nitrogen deposition, nitrogen saturation, nutrient cycling