Nitrogen productivity of some conifers

Abstract

Nitrogen productivity, expressed as annual yield of foliage per unit of nitrogen in the foliage, is recommended for interpreting responses to changes in nitrogen availability. This index can be directly coupled to growth and is well suited for application in mathematical analyses of tree or forest growth dynamics. This paper demonstrates that the nitrogen productivity decreases predictably as biomass increases probably as a result of the reduction in irradiance as the canopy becomes more dense. For five species of conifers from northern latitudes (Piceaabies Karst., Pseudotsugamenziesii Mirb. Franco, Pinusnigra var. maritima (Ait.) Melv., Pinusresinosa Ait., and Pinussylvestris L.) nitrogen productivity is shown to decrease linearly with increasing needle biomass. For a particular species, these regressions allow for estimation of maximum needle biomass.