Effects of roots systems on hydrological connectivity below the soil surface in the Yellow River Delta wetland

In this study, a new method based on field dye-tracing experiments was used to assess hydrological connectivity below the soil surface. In this method, Phragmites australis in the Yellow River Delta wetland was considered to characterize the interaction between roots systems and hydrological connectivity. The results showed that index of hydrological connectivity (IHC) declined non-linearly with depth below the soil surface. Roots systems of P. australis were mostly distributed in soils of 0-30 cm. Roots systems parameters (root length, root width, root surface area, root projected area, root volume and root biomass) were positively correlated with IHC. Coarse roots systems (3 < D < 5 mm) made the highest contribution to the changes of IHC. This study provided suggestions for wetland management in the study area: (1) Reeds should not be reaped every year to promote the litters decomposition for roots nutrition availability; and (2) freshwater inputs should be strengthened in the initial/middle growth stage of reeds to improve roots architecture. Knowledge about the interaction between roots systems and hydrological connectivity below the soil surface is crucial for large-scale wetland protection as wetland managers regulate the control and distribution of vegetation.

Automated summary

In this study, a new method using field dye-tracing experiments was utilized to assess hydrological connectivity below the soil surface, showing a non-linear decrease in the index of hydrological connectivity (IHC) with depth. The roots systems of Phragmites australis were found to be mainly distributed in soils of 0-30 cm and were positively correlated with IHC. Coarse roots systems significantly contributed to changes in IHC.