[Construction and Optimization of Multi-scale Ecological Network of Urban Agglomeration Combined with Cross-scale...

Urban agglomeration ecosystems face dual challenges of habitat fragmentation and ecological function degradation under rapid urbanization， highlighting the urgent need to construct multi-scale ecological networks to enhance regional connectivity and ecological security. However， existing multi-scale ecological network optimization methods suffer from limitations such as overestimating the connectivity contribution of local patches， neglecting cross-scale mediating functions， and lacking systematic evaluation of global connectivity， which constrain network connectivity efficiency and long-term temporal stability. To address these issues， this study takes the Xi'an metropolitan area as a case and proposes a multi-scale ecological network optimization method based on the cross-scale connectivity contribution index （CCCI）， establishing a three-dimensional evaluation framework integrating "global connectivity-directional connectivity-cross-scale mediating connectivity" to identify key ecological source areas and construct ecological networks across metropolitan， municipal， and urban district scales. The results indicate that： ① This method significantly streamlines the number of source areas （retention rate of approximately 14%） while effectively preserving core ecological spaces， with the screened sources exhibiting differentiated characteristics-metropolitan-dominant sources trending toward large-scale consolidation， municipal-dominant sources serving as intermediary bridges， and urban district-dominant sources functioning as local stepping stones. ② Compared with existing methods （equal-weight integration method and maximum-value method）， the network constructed by this method demonstrated significant advantages in cross-scale intermediary connectivity （0.512 4 vs. 0.286 1/0.304 9）， network closure index （0.417 4 vs. 0.306 3/0.308 8）， and line-point ratio （0.827 8 vs. 0.612 1/0.617 1）. ③ During the urbanization process from 2000 to 2020， the network connectivity of existing methods plummeted by over 95%， whereas this method achieved a counter-trend increase of 89.7%， demonstrating superior long-term temporal stability. The findings suggest that the cross-scale connectivity contribution index can effectively identify key intermediary nodes with multi-scale hub functions， achieving synergy between network structural optimization and efficient resource allocation， thereby providing scientific basis for ecological security pattern construction and territorial ecological restoration in metropolitan areas.