Assessing Impacts of Changes in 3D Urban Landscape Structures on Ecological Connectivity by Using Multitemporal Airborne Lidar Dataset

For achieving conservation of urban biodiversity, it is important to know the temporal changes of landscape connectivity. This study aimed to assess the impacts of changes in 3D-based urban landscape structures on connectivity using three-year LiDAR datasets. The study area was the neighborhood in Cheonan city, Republic of Korea. Large blocks in the study site developed from barren lands (2013) to residential and commercial areas (2018). The airborne LiDAR datasets were acquired on 16 May 2013, 30 October 2015, and 10 September 2018 using IGI LiteMapper 6800. Moreover, we acquired the terrestrial-based LiDAR dataset in 50 urban parks in April 2020. Bird species observation data were collected in two breeding seasons (April 2015 and April 2020). We classified the LiDAR data into the buildings, vegetation, and ground by overlapping and clipping by GIS files. Then, we generated 0.5 m resolution of the canopy height models (CHMs) by subtracting the digital elevation models (DEMs) from the digital surface models (DSMs). We calculated 3D urban landscape structures such as building/vegetation volume ratios, vegetation, building heights, and canopy complexity in a 10 m x 10 m x height (m) grid unit. Circuit-theory-based connectivity analysis was conducted for deriving structural and functional connectivity in the study site. Before processing the connectivity analysis, we generated resistance maps in each year by testing Spearman' rho correlation, principal component analysis (PCA), and linear regression analysis between the structural variables with bird species observation data. We found that canopy height and volume (rho > 0.63), building height and volume (rho < -0.61), and canopy complexity (rho = 0.58) showed significantly (p < 0.05) correlated with bird species richness per area. Then, we conducted linear regression using PCA components. The normalized Current Flow Betweenness Centrality (CFBC) was used for comparing temporal changes in connectivity between the years. The expected results would reveal the impact of the changes in urban landscape structures by the large developments on the entire connectivity. Moreover, the expected results would determine the importance of the newly landscaped small urban green spaces such as street trees, pocket gardens, or small parks on the connectivity.