It embodied the composition characteristics of bird communities in forest-stepped ecotone from forest zone to steppe zone gradually trastion.
体现了森林草原交错带鸟类群落的组成特点，即由森林鸟类逐渐向草原鸟类过渡。
2
In many semiarid areas there is also a lower timberline where the forest passes into steppe or desert at its lower edge, usually because of a lack of moisture.