Maintaining ecosystem productivity is fundamental to the principles of sustainable forest management (SFM); yet, there is still no effective method for measuring and monitoring the impacts of management activities on ecosystem productivity. The concept of ecological rotation (see Kimmins 1974) provides a viable framework for assessing such impacts but its application within a system of SFM Criteria and Indicators presents two principal difficulties. First, if the anticipated economic rotation for a particular site is shorter than the associated ecological rotation a decline in ecosystem productivity will result. However, because of the buffering capacity provided by the nutrient capital stored within soil organic matter (SOM), the decline may be subtle and not easily detected after a single rotation. Evidence from ecosystems subject to long-term harvesting (plantations in the southern US, New Zealand, Australia, China, and South Africa) supports this contention but also indicates that the decline in productivity will be cumulative and increase non-linearly across multiple rotations. Secondly, the efficacy of the approach requires the identification of near-term measures that can be used as practical and reliable indicators of long-term productivity trends. Total SOM (or SOM carbon (C)) has been developed for use as a measure of indicator 2-1 of CanFor's Framework for Sustainability (http://www.sfmportal.com/). As part of a related project conducted with the Fort Nelson TSA, Seely (2005) found, through a joint field and modelling analysis, that ecosystem productivity was strongly related to changes (declines) in relative total site SOM C. However, questions still remain regarding the development of total SOM C as a measure of the maintenance of ecosystem productivity that can be effectively employed as part of a sustainable forest management (SFM) monitoring program. Specifically, information regarding the development of thresholds for different ecosystem types is required as well as information regarding the sampling intensity required to detect meaningful declines in SOM C.
Brad Seely and Clive Welham.
Seely, Brad A., Welham, Clive. 2006. Towards the application of SOM as a measure of ecosystem productivity in the Quesnel Forest District: deriving thresholds, determining effective sampling regimes, and evaluating practices. Forest Investment Account (FIA) - Forest Science Program. Forest Investment Account Report