Road impacts on spatial patterns of land use and landscape fragmentation in three parallel rivers region, Yunnan Province, China

The structure and function of network is a central issue in landscape ecology. Road networks with hierarchical structure are crucial for understanding landscape dynamics. In this study, we compared the distribution of national road, provincial road, county road and rural road in the Three Parallel Rivers Region (TPRR) in Yunnan Province of China, and estimated the effect of roads (and other factors) on the spatial patterns of land use and land cover with logistic regression. In addition, we analyzed the land use and land cover change (LUCC) and landscape fragmentation in 1989–2005 along a buffer zone of the primary traffic corridor, national road G214. The results showed that, county and rural roads had much higher percentage of length extending into more natural habitats at higher elevation and steeper slope, compared with the higher level roads in this region. While the distributions of natural land cover types were dominated by environmental factors, human land use types i.e., building land and farmland types were significantly related with roads, linking more closely with lower level roads. The LUCC dynamics (1989–2005) of the G214 buffer zone showed a general trend of land transformation from conifer forests and valley arid shrubs to building land and farmland, and from ice and snow to alpine shrubs and forests. With the length of G214 unchanged during the time, the overall landscape pattern changed little in the buffer zone, but habitat fragmentation and area decrease had occurred for the natural vegetation types, in contrast to patch mergence and expansion of human land use types, and landscape fragmentation was intensified above 2500 m a.s.l. but declined below the elevation. The results indicated the dynamics of landscape composition and patch type level distribution in spite of the stability of the overall landscape pattern, and implied the potential role of roads, especially the low level roads on landscape changes.