Most likely avalanche, knocks the trees down then melts for no sign of the source.
Well isn't that a decisive statement for the limited amount of information offered. Gary, a few more questions about the situation:
How many trees?
Which kind of trees (differences in root/branch structures)?
Proximity to other trees?
Where is the field located? Near a slope that might hold snow?
What side of the lake?
...and so on.
Wind could also be a likely culprit, as Tioga definitely gets hit hard and can regularly see zephyrs of 100-150kts in the winter. A localized downdraft could definitely uproot a few things, as it does on the westside to the sequoias fairly regularly.
The slopes under the north of Dana might cause some damage if they let go. But that basin is fairly wide and flat...
