The sun was actually only visible for a few minutes before disappearing once again into the low cloud just above the horizon. Luckily, I had arrived early enough that I was already prepared to get the shot, and managed a few more in the moments whilst the sun was visible. The quality of light you get at sunrise can be seen in the tree. It's easy to see how much more delicate it is than would be the case during the rest of the day. It's next to impossible to see these kinds of colours at any other time than sunrise or sunset, although even at sunset the colours tend to be a lot warmer and lack that crispness you get on early mornings.
This photo is a good example of when you have to mask sky back in to an HDR. In this case, the clouds had moved between exposures, so large parts of the sky looked a bit odd. Blending back these areas of cloud allowed a much more natural finish.