Abstract:Longitudinal Range\|Gorge Region (LRGR) of YUN Nan Province is characterized with its complex mountain ecosystem and the globally important biodiversity. However, this unique mountain ecosystem is experiencing extensively increased degradation largely due to the human activities, especially the road network development and associated land\|use changes. To analyze the ecological impacts of road network on the ecosystem in LRGR, the impact threshold of road network on the ecosystem in LRGR was quantitatively evaluated through spatial correlation between road network density and ecosystem (i.e. landcover types) transformation from 1980-2000 at multi scales. The results showed that road network density functioned as the major anthropogenic factors to the transformations of some ecosystems. The transformation of forested land to sparse woodland was spatially correlated with overall road network density ranging from 0.8381-0.8800 km/km2. The road network density ranging from 0.6984-0.8124 km/km2 had triggered transformation of the ecosystem from forested land to medium\|covered grassland. The transformation from brush land to sparse woodland can be driven by the road network density from 1.2770-3.6426 km/km2. In addition, the results revealed that those ecological threshold of road network density mostly occurred at the sites where the elevation ranged from 1500-2000m, the slope was below 10 degrees and the aspects were on south and southeast.