Description: Old and Ancient Forests
Based on VRI data with changes to approximately 30 polygons whose age has been corrected (to much older) based on coring data (Brett and Ruddy 2019; Brett unpublished data). Note that the VRI is a timber-based inventory that often under-reports the age of unlogged stands. See notes under the descriptions of age groups below.
Logged (<100 years):
- Industrial logging did not start in Whistler until the 1920s, with most logging from the 1930s through mid 1970s. Stands (polygons) with VRI <100 years therefore assumed to be previously logged.
- While age data for logged stands is generally accurate, the VRI data does not accurately differentiate between logged and unlogged stands younger than 100 years (the latter could include burned areas, treeline stands, etc.). This class could therefore include young stands that have not been logged.
Unlogged Mature Forest (100-249 years)
- At least some (and probably most) polygons shown in the VRI within this age range are actually older, unlogged stands, i.e., >250 years. This statement is based on coring data (Brett and Ruddy 2019; Brett unpubl. data). Further would be needed to clarify the actual ages of these and other stands.
- To complicate classification, many low-elevation stands were high-graded (partially cut), especially for western redcedar.
Old = 250-399 years
- The accuracy of age data in the VRI for older unlogged stands is variable. For low-elevation stands with shade-tolerant canopy trees (mainly Douglas-fir in our region), ages are fairly accurate in most cases. (There are, however, some Douglas-fir stands >500 years old that are not shown in the VRI).
- The ages of stands with shade-tolerant species in the canopy layer are meanwhile typically underestimated in the VRI, often by many centuries. This is due to the methodology used to produce age data in the VRI: mainly air photo interpretation, with higher-resolution data from helicopter-based analysis, and some coring in the field. Accurate ages of trees in these very old/ancient stands cannot be determined without multiple cores analyzed under a microscope -- a process which was rare if ever applied to local stands in the VRI.
Ancient = 400+ years (including Yellow Cedar forests)
- Notes above apply here also.
- Based on Brett's coring data, ancient forests are far more common than shown in the VRI, especially in north-south valleys such as Brandywine, Callaghan, Twenty-one Mile, Nineteen Mile, and Cheakamus. There are also extensive ancient forests on Whistler and Blackcomb Mountains.
- Yellow cedar is slow-growing, shade-tolerant, and exceptionally long-lived, e.g., numerous coring locations included trees>800 years and even >1300 years.
- In the absence of coring data for each polygon, the presence of yellow cedar in the canopy layer is therefore the best indicator that a forest stand is ancient. Polygons with yellow cedar in the canopy layer (656 polygons in the study area) are therefore classed as Ancient within this map. For transparency, they are duplicated in the “Yellow Cedar Ancient Forest” layer. See additional notes in that map.
- Further coring work is needed to improve the accuracy of age data in all stands, but especially ones dominated by shade-intolerant species that include western hemlock, western redcedar, mountain hemlock, and amabilis fir. These stands are most likely to be in "climax" or ancient stage, that is, uneven-aged, multi-generational forests.