Effects of road construction on landscape pattern in Southwest China

To reveal the impact of road construction on landscape patterns in Southwest China, the kernel density and landscape index of roads were calculated based on land cover and road data in 2015. On this basis, the direct, indirect and comprehensive impacts of road construction were analysed, the spatial heterogeneity and characteristics of the impacts on different land cover types were discussed, and the applicability of each landscape index was pointed out. The results showed that（1） the road construction increased patch density and intensified patch discretization, leading to an obvious fragmentation trend. The road kernel density index（KD） was positively correlated with the patch density index（PD）, Shannon′s diversity index（SHDI）, and splitting index（SPLIT） and was negatively correlated with the patch cohesion index（COHESION）, contagion index（CONTAG）, landscape division index（DIVISION）, and perimeter-area fractal dimension index（PAFRAC）.（2） The impact of road construction on the landscape index was mostly due to fragmentation, followed by the patch spatial distribution form and aggregation connectivity. The PD could well represent the degree of road construction effect on landscape fragmentation. SPLIT was more advantageous for identifying areas with a high degree of fragmentation.（3） The different landscape indices had different applications. PAFRAC was suitable for the underdeveloped regions of roads. CONTAG was suitable for regions with a highly heterogeneous road distribution. DIVISION was suitable for regions with a low intensity of human activities. COHESION and SPLIT were suitable for exploring regions where roads and accompanying human activities interacted together, and PD and SHDI were widely applicable for exploring roads directly.（4） For exploring the effects of road construction on different land cover types, the PD and DIVISION indices were preferable for forests; DIVISION and SPLIT for grasslands; PD, PAFRAC, COHESION, SPLIT and DIVISION for farmlands; PAFRAC, COHESION and SPLIT for wetlands; PD, PAFRAC, and COHESION for construction lands; and DIVISION, SPLIT and COHESION for other land cover types. Exploring the effects of road construction on landscape patterns is of great practical significance for understanding landscape pattern changes and guiding environmental protection in Southwest China.