The fire uses these smaller trees as a step ladder to reach the higher canopy of old lodgepole pines.

火焰通过这些作为阶梯的小树蔓延到更高的黑松树冠。

Flames ravage the thick understory provided by species like douglas fir, a shade-tolerant tree that's able to thrive under the canopy of lodgepole pines.

火焰燃烧着底层茂密灌木，如花旗松，这是一种能在树荫下茁壮成长的树，它们长在黑松树的树荫下。