Many’s the tree that…是什么句型（怎么样剖析和理解）

Many’s the tree that has been cut down. 已砍了不少树。

请问这是一种什么句式？怎么样理解？谢谢！

▲依据《牛津高阶英汉双解词典》：many’s the sb / sth who / that...是一个句式，意思是there are many people / things that...有不少的……人[事物]。如：

Many’s the promise that has been broken. 违反诺言的事常常有。

Many’s the time that I heard him use those words. 有不少次我听到他用那些词汇。

▲比较有关表达 many a … 的使用方法（两者意思基本相同）：

Many a promise has been broken. 违反诺言的事常常有。

I heard him use those words many a time. 有不少次我听到他用那些词汇。