Can intensively managed forest ecosystems be self-sufficient in nitrogen?

Abstract

A simple input-outpu model was constructed to evaluate the long-term net nitrogen (N) gain or loss or N self-sufficiency of several silvicultural systems. In general, short-rotation, whole-tree-harvest systems are not self-sufficient in N. If they include an active biological nitrogen fixation (N 2 fixation) component, however, they are highly N self-sufficient even when they sustain large losses of N in harvested biomass. Forestry systems, with or without substantial N 2 fixation, appear to be greatly superior in this respect to most annual agricultural crops with or without N 2 fixation. All N inputs and outputs must be measured in field experiments, however, before N self-sufficiency can be accurately evaluated. Better estimates of loss through harvest removal, and gain through N 2 fixation and atmospheric inputs, over more than one rotation are particularly needed.