Yellow cedar decline

Yellow-cedar decline has been identified as a problem in southeastern Alaska for several decades but, until 2005, its occurrence and impact was poorly documented in British Columbia. The decline can appear in small scattered patches or extend over a large area.

On this page

• Description
• Hazard and risk
• Management
• Priority and research

Description

Identification of dead or dying trees can be difficult due to the visual similarities to western redcedar and the tendency for the two species to commingle in coastal forests. The spike-top mortality common to western redcedar can hide the dead or symptomatic crowns of yellow-cedar, especially when the latter is infrequent in occurrence. 

Individual declining trees can die quickly, exhibiting red or brown crowns, or slowly with gradually thinning crowns. Regardless of the speed of death, root systems are always in an advanced stage of deterioration with the smallest roots dying first. Necrotic lesions are often found on the lower bole under the bark. Dead trees can remain standing for decades.

Recent assessments along the coast indicate about 95,000ha of yellow-cedar are exhibiting the effects of the decline and this may be affecting the future range of this species. The most noticeable areas are on the north and mid-coasts where landscape-level occurrence can be observed quite readily. The frequency of widespread decline decreases as one travels south and virtually disappears south of Kingcome Inlet. Individual or small group mortality may still occur south of this point but the infrequent distribution of yellow-cedar makes it difficult to detect.

Hazard and risk

Currently, yellow-cedar decline is considered to be a result of long term climate change. The current model is that declining snow levels and early snow melt lead to increased susceptibility of the shallow fine roots to sudden late season frost events where upper layer soil temperature falls below -5° C. If this is correct, then any yellow-cedar is potentially subject to decline if snow packs recede early due to a change in climate patterns.

We are currently working toward developing a predictive hazard model for coastal B.C. However, early results indicate decline seems to most strongly occur in the CWHvm2 variant of the north and mid-coast.

There is no current assessment of the extent or impact of yellow-cedar decline for the region.

Management

Since the decline appears to be climate driven and since we still do not understand fully the process that is unfolding, management options are limited. In time guidelines may be developed around the suitability of yellow-cedar for reforestation in areas where suitable conditions for occurrence of the decline could be predicted.

Priority and research

Assessing the impact of yellow-cedar decline is a high priority and currently consists of two projects:

1. Build on the landscape-level analysis completed in 2011 by expanding the physical attribute model beyond the test area across the range of yellow-cedar and testing its predictions
2. Build on recent dendrochronology work that attempts to explain the climatic variables controlling the growth and mortality of yellow-cedar