Species Composition and Species Richness in the Hetao Irrigation Region Drainage Ditches, Northern China

Abstract

Drainage ditches play an important role in maintenance of plant species diversity. We investigated plant species composition and diversity, and soil and water chemical properties in drainage ditches in the Hetao Irrigation Region of northern China. We compared species composition similarity within the same and among different drainage areas, and compared diversity of plant species, among different ditch sizes and slope positions. We identified a total of 70 plant species, which belonged to 64 genera and 30 families in the drainage ditch. The most frequent family was Compositae representing 15.7% of the total flora; Phragmites australis (Cav.) Trin. ex Steud was the most widespread species with a frequency of more than 60% in all plots. The highest similarity values occurred in lateral ditches within the same drainage areas, and in main ditches among different drainage areas. The coefficient of variation of total salt in soil was closely related to species similarity in all ditches. Ditch size and position were significantly correlated with the indexes of species diversity. Higher plant α-diversity occurred in smaller ditches and tended to be the highest at the transition zone and on the slope of the ditches. The response of species composition and diversity to environmental factors was significant for saline concentrations. Reducing the current water and soil saline contents, while maintaining current slope soil nitrogen content was suggested as an optimal way of maintaining high species diversity.

Keywords:

• ditch size
• nutrient
• saline concentrations
• slope effect
• species composition similarity
• species diversity

Acknowledgments

The authors gratefully acknowledge two anonymous reviewers for valuable comments that greatly improved the presentation of this manuscript. We would also like to thank Anne Bjorkman at the University of British Columbia for her assistance with English language and grammatical editing of the manuscript. This research was funded by the Innovation Project from the Chinese Academy of Sciences (KZCX2-EW-301-3) and the National Natural Scientific Foundation of China (40971033 and 31170385).

Notes

Note: TN: total nitrogen, TP: total phosphorus, TSS: Total salt in soil, TDS: Total dissolved solids in water.

Note: R² values mean the variations explained using two-way ANOVA model. a. R² = 0.878 (Adjusted R² = 0.813), b. R² = 0.789 (Adjusted R² = 0.642), c. R² = 0.656 (Adjusted R² = 0.433), d. R² = 0.579 (Adjusted R² = 0.313).

*Correlation is significant at the 0.05 level (2-tailed).

**Correlation is significant at the 0.01 level (2-tailed).