Network Analysis and Comparative Studies on Baiyangdian and Okefenokee Wetland Systems in China and US

Abstract

Many individual wetlands are interconnected by complex hydrological processes, acting as a large wetland system (WS) with specific structure and function in certain temporal and spatial scale. An understanding of the holistic attributes of a WS is especially critical for the long-term persistence and biodiversity maintenance of various wetlands. In this study, we developed a framework to use ecological network analysis (ENA) in a holistic assessment to WSs. The Baiyangdian WS in China and the Okefenokee WS in USA were presented as two examples. Network models of two WSs were developed to facilitate the application of network analysis, in which network nodes represent river segments, lakes and reservoirs, and network links are directional representations of water flow between nodes. Using 25 network indicators, we compared two WSs to show how ENA can be used to provide a unified benchmark for holistic comparisons. Results show there is a large difference, such as system activity, inner organization and so on, between two WSs. The Baiyangdian WS is a sparsely connected system with a connectance of 0.13 while the Okefenokee WS is a well connected system with a connectance of 1.08. Comparing with the Okefenokee WS, the Baiyangdian WS has higher inner organization (2.25 bits versus 1.27 bits) but lower system activities (0.19 m3y-1 per m2 versus 0.34 m3y-1 per m2). System ascendency of the Baiyangdian WS is slightly lower than that of the Okefenokee WS (0.43 m3y-1 per m2 versus 0.42 m3y-1 per m2). On the basis of the current results, we proposed the network-based indicators for assessing the holistic attributes of WSs. This study could provide a novel prospective and methodology for evaluating system attributes at the system level and contributes to the basin-wide wetland protection and water resources management.

Keywords: wetland system, ecological network analysis, system attributes, Baiyangdian basin, Okefenokee watershed