But when Swetnam enrolled in graduate school at the University of Arizona's Laboratory of Tree-Ring Research, he was surprised to find a record of repeated blazes dating back hundreds of years before European colonists arrived on the continent.
但当斯威特纳姆进入亚利桑那大学的树木年轮研究实验室读研究生时，他惊讶地发现，早在欧洲殖民者到达大陆数百年之前，就有重复的火灾记录。
Their North American tree-ring fire-scar network (NAFSN) provided the basis for a study published last month.
他们的北美树木年轮火疤网络（NAFSN）为上个月发表的一项研究提供了基础。
the scarcity of tree-ring research in the U.S.
美国树轮研究的不足
例句取自历年考研英语真题，翻译为机器生成，仅供学习参考。