river birch

river-birch的词性：
n.（名词）

1. A deciduous eastern North American tree (Betula nigra) having reddish-brown to silver-gray bark that peels off in papery flakes. Also called black birch
河桦：北美东部的一种落叶乔木（黑皮桦木） ，长有从红褐色到银灰色的树皮，它以轻薄如纸的薄片剥落 也作 black birch