22 December 2014
The period of frozen ground has declined by an average of two or three weeks since 1948, research shows. During that time, wood harvests have shifted in years with more variability in freezing and thawing to red pine and jack pine — species that grow in sandy, well-drained soil that can support trucks and heavy equipment when not frozen.
http://feeds.sciencedaily.com/~r/sciencedaily/~3/llYbcPiHigo/141222165540.htm
