alder bark

例句：

1. 1. The alder treeis a symbol of strength and resilience.
   白杨树是力量和韧性的象征。
2. 2. The alder bark has been usedin traditional medicine for centuries.
   白杨树皮在传统医学中被使用了几个世纪。
3. 3. The alder bark was used totreat skin conditions by ancient civilizations.
   古代文明用白杨树皮治疗皮肤病。