年轮

shǔ nián lún

数年轮

count the rings

tōng guò guān chá shù de nián lún kě yǐ tuī cè chū sēn lín xíng chéng de nián dài

通过观察树的年轮可以推测出森林形成的年代。

The forest can be dated by studying tree rings.