Reed says the Oregon weather made the reshoots necessary.
Reed seemed to think they needed to keep this intel a secret, but Robert Pattinson (Edward), Peter Facinelli (Carlisle) and Kellan Lutz (Emmett) have already revealed that the new shoots included a scene establishing the history of the Cullens. To show when Carlisle and his family made a treaty with the Quileute Indian tribe, the actors dressed in pegged pants and old-timey caps. Facinelli even had to speak to the tribe leaders in their language.
The original shooting took place in Oregon. It's not clear where the reshoots took place. If they occurred in Oregon also, they couldn't have included the Quileute people, culture, or landscape (since the Quileutes live in Washington).
I wonder how they simulated the Quileute reservation. Perhaps they found a few dark-skinned people (Latinos?) and hung a dreamcatcher on the wall. It remains to be seen whether Twilight will have a single genuine Indian person, place, or thing in it.
For more on the subject, see Quileute Werewolves in Twilight.