National-scale connectivity analysis and construction of forest networks based on graph theory: A case study of China

Global forest cover has been shrinking at an accelerating rate over the past decade due to deforestation and forest degradation. Connecting fragmented forest patches can effectively promote ecosystem health and sustainability. However, previous studies have rarely conducted forest network analysis at the national scale. Therefore, we aim to provide a comprehensive solution for the establishment of large-scale forest networks. We focused on China and combined morphological spatial pattern analysis with connectivity indicators for recognizing forest ecological sources at different distance thresholds. Moreover, the linkage mapper was employed for determining practicable ecological corridors. We found 734 ecological sources and 1717 practicable corridors within the national forests at a distance threshold of 3000 m. At an increase threshold of 5000 m, the number of ecological sources reached 934, with 2176 practicable ecological corridors. Notably, smaller ecological sources dominated the country at both distance thresholds, but more small ecological sources acted as “stepping stones” when the distance threshold was 5000 m. The forest patches in Northeast China and the Eastern Himalayas had high centrality values because they are crucial for maintaining connections between ecological sources. Our findings underscore the importance of connecting dispersed and fragmented forest patches at large scales to promote ecosystem health and sustainability. These results not only contribute to the understanding of forest networks but also offer practical guidance for national-scale forest conservation endeavors. The construction of such forest networks could be a pivotal strategy for conserving biodiversity and ensuring the long-term well-being of ecosystems.