Free-ranging livestock cause forest understory degradation in giant panda (Ailuropoda melanoleuca) habitat

•Disturbance by free-ranging livestock dramatically degraded the understory layer in giant panda habitat.•Livestock grazing on bamboo lessened its competitive effect on moss.•Moss height rapidly declined under livestock trampling, but not significantly inside bamboo clumps, suggesting shelter effects of bamboo on moss from livestock disturbance.•No recovery of bamboo and moss layer after two years of livestock exclusion.•Artificial bamboo and moss planting were necessary in severely degraded areas to restore giant panda habitat.