Age is a major constraint when deciding on the ideal area for timber harvesting. Only mature trees are economically valuable and are harvestable according to regulations.

The mature age is dependent on species, weather and soil conditions. Biogeoclimatic Ecosystem Classification (BEC) is a system used by the British Columbia Ministry of Forests as a method to classify and manage sites on an ecosystem-specific basis. Each BEC zone is a geographical area with similar microclimates characterized by vegetation, soil and animal species reflecting the climate.

As seen from the Map 4 below, the two main BEC Zones within our area of interest are ESSF (Engelmann Spruce — Subalpine Fir) and ICH ( Interior Cedar — Hemlock). According to 100 Mile House TSR (100 Mile House TSA, 2012.), mature minimum mature age varies between 100 – 120 years old.

Map 4. Biogeoclimatic Ecosystem Classification (BEC) Zones

Old forests contain many unique habitat and ecosystem characteristics that are developed over a very long period which are not readily replaceable by second growth forests. Structural diversity and habitat features found in Old Growth forests provide unique habitats required by many species which are difficult to recover upon loss. Furthermore, old forests have significant and delicate hydrological features which are highly sensitive to disturbances such as logging. Since trees older than 250 years old are considered as old growth, we set the harvestable range between 120 and 249 years old, which is shown in the following Map:

Map 5. Age distribution

Age class 120 – 140 years old (2) is weighted higher than age class 141 – 249 years old (1). This is because trees between 141 – 249 years old are considered as “transitional old growth areas” (the age class immediately younger than old-growth which will assimilate into the old growth forests over time.