-Yes. If you do not have reentry permit and stay outside U.S. for more than one year, your GC will be cancelled.
平时赴美短暂逗留,可以在入境时不出示绿卡, 使用外国人通道吗?多谢
-If you just use your 澳洲护照 to enter U.S. without showing the GC to the CBP (that equals to getting a B2 visa), USCIS will consider you have abandoned your GC. So, you need to show your GC to the CBP every time you enter U.S.