Based on the investigating undergrowth vegetation in the forests with different densities in semi-arid region on the loess plateaus

the niche of undergrowth vegetation are described and analyzed

with different densities as the resource state and with the important value as the resource state descriptor of the niche.The results indicate that most of undergrowth vegetation have lower niche breadth values

but Heteropasppus altaicus and Arremisia sacrorum have higher niche breadth values

59.7% of the herbage species have niche overlaps

but which are lower.All the above reveal that the bad condition of undergrowth vegetations.