Arrow IFPA Series: Note 6 of 8: Criterion 2: Ecosystem productivity

Abstract

This extension note is the sixth in a series of eight that describes a set of tools and processes developed to support sustainable forest management (SFM) planning and its pilot application in the Arrow Timber Supply Area (TSA). It describes the criterion and two of the indicators selected to set thresholds and evaluate potential impacts on ecosystem productivity for an SFM scenario for the Lemon Landscape Unit. The note also summarizes the analysis results obtained when an ecosystem-based simulation model (FORECAST) was used to examine the effects of varying rotation length on measures of selected indicators of long-term ecosystem productivity for representative site types.

The analysis considered changes in site index, soil organic matter (SOM), and site nitrogen (N) capital on poor-, medium-, and good-quality sites, and evaluated the utility of these measures in assessing and monitoring the effects of different intensities of stand management (as reflected in harvest rotation length) on ecosystem productivity.

Shortening the rotation lengths increased losses of SOM and site N. The poor site showed smaller relative changes in both of these measures when compared to the good and medium sites. This suggests that different sustainability thresholds may be warranted for locations with different site qualities. Shortened rotation lengths had little effect on stemwood production (a proxy for site index), but the reduction in SOM and site N capital would likely translate into a decrease in ecosystem resiliency. Both SOM and N capital are important indicators for evaluating the sustainability of site productivity under alternative management practices. The model results highlight the value of using a multi-indicator approach when evaluating the sustainability of site productivity under alternative management practices.