Yellow-cedar expansion much slower than expected

John's successfully defended (congrats again!), and manuscripts are in review.  It's time to start thinking about why he found so little expansion.  We're noting quite a bit of decline associated with lower snow conditions, of course, but it also appears that expansion may be associated with higher snow conditions.

The stands around Juneau, which John demonstrated are not currently expanding much at all (e.g., no seedlings outside of the established, mature group of trees), all seem to have started during colder, snowier periods in southeast Alaska.  There's currently no sign of decline around Juneau, at the northern range edge, and planted trees grow just fine.  In fact, they grow very well, as demonstrated by experimental plantings.  So climates not affecting their success, but perhaps their recruitment?  Might fecundity be higher in colder periods?  Or dispersal (perhaps seeds skating over snow)?  Or is it simply protection from herbivory for the young seedlings?  

John Krapek's thesis available from the UAF archives: