Introduction

The ecosystem paradigm is reviewed as the basis for introducing a discussion of ecosystem processes and in particular revision of the concept of net primary productivity of a forest. Here we revise the ecosystem processes of forest carbon and nutrient cycling as essential background to understanding limitations to forest productivity.

Objectives

The first objective of this module is to equip students with a first principles approach to understanding the flow of energy and nutrients through a forest system. This knowledge is generic and can be applied to any forest restoration or plantation development project where nutrient conservation, carbon sequestration and growth optimization are part of the goals of management. The second objective is to explain the role of different groups of organisms in maintaining ecosystem function and net primary productivity. The final objective is to review the plant and soil factors that determine the main cycling pathways of five important macronutrients (N, P, K, Ca and Mg).

Upon completion of this module, you should be able to:

• Explain the ecosystem paradigm and describe the key ecosystem processes of carbon and nutrient cycling;
• Identify and explain the four main groups of biota in terms of their mode of energy and nutrient acquisition;
• Define and describe the concept of net primary productivity; and
• Describe in detail nutrient cycling in forests and explain how these cycles contribute to maintaining forest productivity.