By Paul Carrel and Noah Barkin KARLSRUHE, Germany (Reuters) - German Chancellor Angela Merkel defended her refugee policies at a congress of her conservative party on Monday, fending off a challenge from critics with a pledge to reduce the influx of migrants and a repeat of her optimistic mantra "we can do this". In a rousing speech, Merkel recounted a remarkable year that has seen Germany stand up to Russia over the Ukraine crisis, broker a deal to keep Greece in the euro zone, and welcome hundreds of thousands of refugees fleeing war and deprivation in the Middle East. "We want to, and we will, noticeably reduce the number of refugees," she said to applause at the congress in Karlsruhe, in the southwestern state of Baden-Wuerttemberg, which holds a state election next March.