CANBERRA (Reuters) - Australia’s prime minister appointed Gary Gray, a former adviser to the country’s largest oil and gas firm Woodside Petroleum, as resources minister on Monday in a cabinet reshuffle forced by a string of ministerial resignations. Gray, a senior Labor party figure in the resource-rich Western Australia state, should ensure an advocate for the resources industry remains in place at a time when investment in the sector is slowing amid signs the mining boom has peaked. PM Julia Gillard also said the Climate Change Dept, which has overseen the introduction of a controversial carbon tax, would now be merged with the Industry Dept, and would be overseen by Climate Change Minister Greg Combet.