It has always been appealing to attempt to estimate site index by observing the height growth rate in young trees at early ages (Bull, 1931). Various methods have been proposed with varying starting heights and numbers of years to observe (Wakeley, 1954).
With the development of the 10m Site Index classification methodology (Arney, 2010) there is now the opportunity to take very useful field methods and separate the best use of their application between a) macro-site classification of natural forest growth capacity or b) micro-site effects of silvicultural treatments.
There is a very definite and specific need to be able to characterize improvements in early stand growth, due to silvicultural investment, in a quantitative and repeatable way. This characterization is most useful if conducted as early after stand establishment as may be measureable, repeatable and defensible.
The timing of this characterization of silvicultural gain is constrained by two delaying factors:
- sufficient time must elapse to realize any gains from the silvicultural investment (planting stock, container size, site preparation, brush control, pest control, nutrient management, etc.); and,
- sufficient dimensional differences must occur to observe significant differences from baseline expectations within the practical limitation of field measurement devices and methods.