Ecological restoration of highly saline lands: studies and inspirations from natural processes in the Yellow River Delta

Background/Question/Methods

Ecological restoration is difficult in highly saline lands. The Yellow River Delta(YRD) was formed by continuous sediment accumulation from the river with interaction between land and sea, which made the YRD a typical saline land and it is very difficult to regenerate ecological service functions, especially in newly formed land. One typical characteristic of the YRD is the high human disturbance caused by oil exploitation since 1960s. For areas under both high salinity and oil exploitation effects, the regeneration and restoration is even more difficult. There are few reports of landscape ecological characteristics changes, ecological service function degeneration, vegetation structure, and succession patterns in these areas. The regeneration and restoration of these areas are also rarely mentioned. Special natural phenomena were observed in specific sites in the YRD in the ecological restoration process. Based on an investigation of areas under both high salinity and oil exploitation effects, we analyzed the landscape change pattern, vegetation characteristics, and oil salinity conditions. Based on the data of soil and vegetation properties, possible regeneration and restoration patterns in the study area were deduced and potential regeneration and restoration patterns and methods for areas under high salinity were proposed.

Results/Conclusions

Hundreds of research samples (patch) were distributed along the north-south and east-west directions, making the study area appear as a multi-rectangular shape. The elevation of the land increased from the center to the periphery of the samples. There were three species in the study area, Suaeda salsa, Salicornia herbacea, and Phragmites australis. The former two were dominant species, while the latter was only distributed in 19.35% of the samples, and the largest coverage degree was only 8% in the samples. The calculation of the vegetation density revealed the density of the vegetation increased from the center to the edge of the samples. No significant differences were found among the densities of different diameter circular rings. The largest density was 4.17/m² in the very edge of the samples, and the smallest density was 2.80/m² in the central part of the samples. The average height of the vegetation in the samples was 0.376m, and the average coverage degree was 32.7%. Pore Water Conductivity (PWC) results indicate soil was strongly saline, and the PWC increased from the center to the edge of the samples. There was no apparent tendency among the PWC outside the samples.