Multi-scale analysis of hydrological connectivity and plant response in the Yellow River Delta

The Yellow River Delta is one of the International Important Wetlands on the west coastline of the Pacific Ocean in China. Despite its importance for regional and global ecological security, it is vulnerable because of human activities and climate change. Local government is trying to identify a more efficient way to conserve the delta thereby reducing a potential environmental crisis. The framework of hydrological connectivity provides a new perspective to study hydrological related ecological processes, while the method is highly exclusive because of environment and scale heterogeneity. This study collaborated with managers to develop a new algorithm to parameterize the hydrological connectivity on plot, point and landscape scales. Then the interspecific and conspecific structures of two dominate species (Phragmites communis and Suaeda salsa) are linked to these indices. The results show: (1) According to the point and plot scale results, AP (semi-artificial pond) and IF (intertidal flat) has the strongest hydrological connectivity followed by TM (tidal marsh). The average positive point-scale index values in AP, IF RS (river side wetland) and TM are 0.610, 0.495, 1.162 and 1.217 and the average plot-scale index values in AP, IF RS and TM are 1.53, 0.87, 0.48 0.55. At the landscape scale, index values show high collinearity with plot density and lack of hydrological significance because of low data resolution and scale effects. (2) At the individual level, P. communis and S. salsa showed a higher interspecific and conspecific competitive strength to respond to environmental stress in the weak hydrological connectivity area. (3) At the community level, in higher salinity wetland classes, biomass, plant coverage and biodiversity showed a positive linear correlation with plot-scale indices. Future study will improve the current parametrization method at the landscape scale and reveal the response of other important plant species to hydrological connectivity in this area.