Dear Rosanna, uprooting of the trees depend on many parameters specially water condition of soil and texture as well as tree species. As I see in your picture i think its a big red oak uprooted. How can an oak tree uprooted is a surprising question, because Quercus species have deep and strong root systems even on fine textured soils. Check if the tree roots are not affected by any pest and/or fungi.

Refer to these article for more info:

http://www.amjbot.org/content/93/10/1501.full

Thank's you for all the interesting links!

It might be wind gusts that worked on the tree set it to swaying with the wind.

This generates a lot more force ( the cyclical forces which have momentum ).

It is even more pronounced if that tree was not surrounded by other trees.

Dear Rosanna,

do you know reports by Gardinder et al. (2010) and Schelhaas et al. (2003)? You should find there some useful information. Please, see attached copies of them.

Good luck,

Lukasz

and Gardiner et al. (2010)...

Thank's Lukasz

In the Canary Islands we had a similar experience in November 2005 with tropical storm "Delta", which affected also Madeira Island. I remember to see many big trees (Pinus canariensis and some laurel forest species) fallen to the floor by strong winds of more than 200 km/h. This created some important gaps in several forest areas, mainly in Tenerife and La Palma islands. There is an interesting article on this event, published in Spanish; see: http://www.ub.edu/geocrit/sn/sn-267.htm.