AbstractYellow cedar (Chamaecyparis nootkatensis) is a valuable tree species that is experiencing an extensive forest decline on over 200000 ha of unmanaged forest in southeast Alaska. Biotic factors appear secondary and some abiotic factor is probably the primary cause of this naturally occurring decline. A warming climate, which coincided with the onset of extensive tree mortality about 100 years ago, may have triggered one of the possible abiotic causes such as freezing damage and/or soil toxicity.