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Harvard Forest Symposium Abstract 2005

• Title: Effects of nitrogen fertilization/deposition on the foliar nutrition and stress physiology of coniferous and broadleaf tree across Northeastern US.
• Primary Author: Rakesh Minocha (USDA Forest Service)
• Additional Authors: Stephanie Long (USDA Forest Service)
• Abstract:

  Atmospheric deposition of nitrogen (N) may cause forest decline or enhance its productivity depending on the initial N status of the soil, and the rate and duration of N deposition. Continuous input of N can move ecosystems towards nitrogen saturation. A major goal of our research is to develop a set of early physiological and biochemical markers that can assess the positive or negative impact of N deposition on forest productivity in an asymptomatic forest stands. The evaluation of apparently healthy trees is beneficial in developing risk assessment and stress remediation strategies for forest trees prior to the onset of obvious decline. Our objective is to determine the usefulness of polyamines (aliphatic organic amines), particularly putrescine, and amino acids (such as arginine), as foliar indicators of stress in visually asymptomatic trees and relate changes in these metabolites to forest productivity. Data collected thus far from several hardwood and conifer sites across Northern New England in collaboration with several scientists belonging to various state, federal, and academic institutions show a strong correlation between soil nutrient deficiencies and/or chronic N addition and increased foliar free putrescine levels, indicating that foliar putrescine can potentially be used as a reliable and easily quantifiable marker of general stress in visually healthy trees. Free amino acids, especially arginine, also increased in response to chronic N input at several hardwood and conifer sites. In some cases, such as Harvard Forest LTER study, these changes were also accompanied by lower site productivity in red pine stand (See the references below). In summary, foliar physiology response to N addition depended upon the initial N saturation stage of a site along with the amount and the duration of the N application. Also, hardwoods were more sensitive to N addition than red spruce growing at the same site in terms of foliar physiology. In most cases, foliar putrescine, arginine, and Ca changed significantly in response to N addition of higher than 25 Kg ha-1 y-1 for more than 5 years. Under chronic N deposition conditions over very long time (Harvard Forest study) most amino acids were found to be in significantly higher quantities. Putrescine was always found to be inversely proportional to foliar exchangeable Ca and soil Ca data.
  
  
  
  
  
  
  
  
  
  Minocha R, Aber JD, Long S, Magill AH, McDowell W. 2000. Foliar polyamine and inorganic ion content in relation to soil and soil solution chemistry in two fertilized forest stands at the Harvard forest, Massachusetts. Plant and Soil. 222:119-137.
  
  
  
  
  
  
  
  
  
  Bauer G.A., Bazzaz F.A., Minocha R., Long S., Magill A., Aber J. D., and Berntson, G.M. 2004. Effects of chronic N additions on tissue chemistry, photosynthetic capacity, and carbon sequestration potential of a red pine (Pinus resinosa Ait.) stand in the NE United States For. Ecol. Manage.196: 173-186.
  
  
  
  
  
  
  
  
  
  

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