Purpose

Soil bulk density and hydraulic conductivity are two of many key factors for vegetation establishment and the other way around. Variations in them may cause patchy vegetation distribution in arid and semiarid areas. Characterizing their spatial variations in relation to quasi-circular vegetation patches (QVPs) is important for the effective revegetation of wetlands in the Yellow River Delta (YRD), China.

Materials and methods

This study investigated the variations of soil bulk density and hydraulic conductivity based on 86 soil bulk density and 63 hydraulic conductivity samples within a quasi-circular vegetation patch area in the YRD. The nonparametric Mann-Whitney U and Kruskal-Wallis H tests, respectively, were used to evaluate the differences in soil bulk density and hydraulic conductivity between the QVPs and bare soil areas.

Results and discussions

There were significant differences in soil bulk density and hydraulic conductivity between QVPs and bare soil areas. Conversely, there were no significant differences in the two parameters among different QVPs. The average QVP bulk density and hydraulic conductivity (2.0 cm suction) were 12.4% lower and 191.8% higher, respectively, than those of bare soil areas. Plant species communities within QVPs did not significantly differ in terms of their influences on hydraulic conductivity but did differ in terms of their impacts on soil bulk density. Soil bulk density increased from the QVP centers to their edges whereas the opposite was observed for hydraulic conductivity. This finding indicated that QVPs drastically increase soil hydraulic conductivity, and soil bulk density influenced the spatial distribution of plant species communities within QVPs.

Conclusions

This study expanded our understanding of occurrence and encroachment of QVPs in the YRD, may help understand spontaneous plant colonization and succession mechanism and lay the foundation for developing adaptive wetland restoration strategies in the YRD.