As stated before, this isn't HDR, as HDR requires at least 3 images that are blended together, not just a pieced together image of good parts from different exposures.
The problem that arises from this image is an uneven mix of light that just looks peculiar, as you have very bright back lighting on the trees, but they are still completely visible, not silhouetted. Also, the edge of the hillside where you presumably separated the two exposures is getting a strange dark line that is resulting from your masking/erasing. The yellow color from the sunlight should be bleeding into the hillside, but since you've kept the hill from the exposure for the trees, it looks a little strange.
All in all, I'd say it looks far too unnatural for me.
Honestly, I think this would have made a great silhouette photograph as the sky is wonderful, but to each his own I suppose.
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