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At least two different effects were used to create that image.
1. The first thing I notice are the curly, bright edges. This was most likely done using a plugin called "Fractalius":
http://www.redfieldplugins.com/filterFractalius.htm
However, it can also be done using multiple applications of the Topaz "Clean" plugin:
http://www.topazlabs.com/clean_static/_images/forest.jpg
http://www.topazlabs.com/clean
2. It is possible that a vignette effect was used to darken the edges of the image, but I strongly suspect the darkened edges came about as part of applying an "Orton effect" to the image:
http://www.practicalphotoshopmag.co...ct-try-this-quick-soft-focus-photoshop-trick/
http://www.photo-kako.com/en/orton.cgi
http://digital-photography-school.com/the-orton-effect-mimicking-darkroom-processes-in-photoshop/
There are quite a few different variants of the Orton effect. I call the one being used here "spreading the blacks".
HTH,
Tom M