Responses of Acer saccharum canopy trees and saplings to P, K and lime additions under high N deposition
Tomasz Gradowski (1) and Sean C. Thomas (2, 3)
1. Department of Renewable Resources, University of Alberta, Edmonton, AB T6G 2M7, Canada / 2. Faculty of Forestry, University of Toronto, Toronto, ON M5S 3B3, Canada / 3. Corresponding author () / Received May 1, 2007; accepted August 1, 2007; published online December 3, 2007
Summary
Heavy atmospheric nitrogen (N) deposition has been associated with altered nutrient cycling, and even N saturation, in forest
ecosystems previously thought to be N-limited. This observation has prompted application to such forests of non-N mineral
nutrients as a mitigation measure. We examined leaf gas-exchange, leaf chemistry and leaf and shoot morphological responses
of Acer saccharum Marsh. saplings and mature trees to experimental additions of non-nitrogenous mineral nutrients (dolomitic lime, phosphorus
+ potassium (P + K) and lime plus P + K) over 2 years in the Haliburton region of central Ontario, which receives some of
the largest annual N inputs in North America. Nutrients were adsorbed in the mineral soil and taken up by A. saccharum trees within 1 year of fertilizer application; however, contrary to expectation, liming had no effect on soil P availability.
Saplings and canopy trees showed significant responses to both P + K fertilization and liming, including increased foliar
nutrient concentration, leaf size and shoot extension growth; however, no treatment effects on leaf gas-exchange parameters
were detected. Increases in shoot extension preceded increases in diameter growth in saplings and canopy trees. Vector analysis
of shoot extension growth and nutrient content was consistent with sufficiency of N but marked limitation of P, with co-limitation
by calcium (Ca) in saplings and by Ca, Mg and K in canopy trees.
Keywords:
canopy development, fertilization, liming, N saturation, photosynthesis, P limitation, resource allocation, sugar maple, vector
analysis.
