An Exploratory Study in Extending the Range of the Sitka Spruce Dynamic Yield Models to Highly Productive Stands

Dynamic yield models are a very useful tool to allow forest managers to make informed decisions regarding the management of their forests. In particular, they allow for the prediction of stand development and timber production based off just the current state of the stand. The first set of dynamic yield models in Ireland (Growfor) was produced for Sitka spruce in 2003. Sitka spruce is the dominate species in Irish forestry compromising of 51.1% of the total forested area. Due to recent developments in the forest estate, with afforestation of better land by private landowners now dominating, the dynamic models, especially for conifers such as Sitka spruce, have been found to inadequately cover the full range of yield classes now experienced in Irish forestry. For the first time Growfor’s performance in highly productive stands is assessed. Detailed measurements taken from felled sample trees enabled reconstruction methodologies to be employed. Recreating stand attributes three years previously; as well as obtaining detailed information on the current state. This allowed investigation of Growfor’s ability to model these stands’ growth over this period, as well as forming part of the developmental data of a new preliminary model. This study has shown that Growfor struggled to accurately predict the attributes of top height and basal area over the three-year period. While the new model created showed promise, it requires further work to improve its accuracy. It is recommended that Growfor’s developmental dataset for Sitka spruce be updated properly to reflect the ever-increasing proportion of stands now classified as high yield class.