Topic 2: Forest Productivity – Carbon Cycle


This topic aims to introduce students to the ecosystem concept as a way of understanding natural and managed forest landscapes. The ecosystem concept is a paradigm for understanding the underlying structure and function of nature by focusing on the flow of materials and energy through biological systems, or bio systems. Plants, animals, and microbes (bacteria, fungi, archaea) are grouped according to their major role in either the capture or transformation of energy, or their role in the reorganization of the materials that make up living and dead life forms. We know these major actions as photosynthesis and decomposition. Along with the biophysical resources of a forest site or landscape, they determine the productive capacity of a biological system whether it is natural or managed. In many artificial tree-based ecosystems, such as restored forests or plantations, we implement ecological concepts and principles to design and manage to maximize the sustainable productivity of the forest enterprise.

Video Lecture

Please view the following video lecture and video for this topic.

1.2 Lecture: Forest Productivity – Radiant Energy and the Carbon Cycle

Reflection Questions

Please answer the following self-reflection questions. After formulating your answers, you may post them online at the Knowledge Café for this course as a way to share your ideas and glean knowledge from other students’ responses.

  1. Outline in a diagram the flow of radiant energy through an ecosystem, and show the key functional groups of organisms involved in the capture of energy and the cycling of nutrients.
  2. Describe a practical method for estimating the aboveground net primary productivity of a forest.
  3. Go to the published literature to find the net primary productivity of a forest near where you are now (depending on your location this could be a long way from you!). Use the NPP value you find to calculate the efficiency of light capture by that forest. Calculate the “Energy conversion efficiency E (%)”, in terms of total short wave radiation received by the forest canopy and the plant matter produced. How does your calculated “ecological efficiency” compare with the values in the table below?
Forest Energy Conversion Efficiency (%)
Pinus radiata 1.2
Eucalyptus regnans 0.8
Tropical forest (1) 0.7
Tropical forest (2) 1.3

Supplementary Readings


Aber, J.D., & Melillo, J.M. (1991). Terrestrial Ecosystems. Philadelphia: Saunders College Publishing.

Attiwill, P., & Neales, T. (2006). Carbon flow, energy transformations, and productivity. In P. Attiwill, & B. Wilson (Eds.),Ecology: An Australian Perspective (pp 176-195) . Cambridge University Press.