Scene has been rendered with mentalray and 'Physical Sun and Sky' based lighting. That's why shader in Maya has 'gamma correct' node pluged-in between colormap and colorshader. If model will be rendered with different lighting, 'gamma correct' should be excluded and color value should go directly to main shader.
To open mb file, Maya2014 or higher is needed. To open FBX file, FBX2009 or higher is needed (gamma corect node has been removed from FBX file) OBJ contains two separate meshes - one for bark's surface (st_bark.obj) and another one (st_branch.obj) for branches. There is also another file with merged mesh stored as 'spruce_tree.obj'