Plant diversity in different positions of gullies and valleys in the loess region of western Shanxi Province, northern China

Objective In order to provide more precise protection and restoration of small watershed gullies in loess hills and gullies, the natural restoration capacity of different geomorphic parts of gullies (gully floor, gully sunny slope and gully shady slope) was investigated in terms of plant diversity and ecological niche width.

Method Through field investigation at the National Field Scientific Observatory of Forest Ecosystems in Jixian County, Shanxi Province of northern China, we analyzed the growth characteristics of plant communities and their diversity in different parts of the landscape, and compared the similarities between plant communities in different parts of the landscape.

Result (1) There were 98 species of shrub and grass in 40 families and 76 genera in the study area, including 34 species of shrub in 17 families and 27 genera, and 64 species of herb in 29 families and 51 genera. Total number of family species in the shrub layer was showed as gully sunny slope > gully shady slope > gully floor, while in the herb layer, it was showed as gully floor > gully shady slope > gully sunny slope. (2) The dominant species in shrub layer was Rosa xanthina, Vitex negundo var. heterophylla, and Indigofera tinctoria. The dominant species in the herbaceous layer were Phragmites australis, Artemisia annua, and Carex lancifolia. In the shrub layer, Rosa xanthina and Periploca sepium in the gully floor had larger width of ecological niches, and Vitex negundo var. heterophylla and Indigofera tinctoria in the gully sunny slope and gully shady slope had larger width of ecological niches. In the herb layer, Phragmites australis and Artemisia stechmanniana in the gully floor had larger width of ecological niches, and Carex lancifolia in the gully sunny slope and gully shady slope had larger width of ecological niches. (3) Margalef index, Shannon-Wiener index, Simpson index and Pielou index were not significantly different (P > 0.05) among varied geomorphological parts (gully floor, gully sunny slope, gully shady slope). Jaccard’s coefficient between communities was 0.50 ≤ q < 0.75. The Jaccard coefficient reached a maximum of 0.630 between gully sunny slope and gully shady slope.

Conclusion Overall, the gully is found to be naturally resilient, with the gully sunny slope and gully shady slope among the geomorphological sites being more resilient to natural vegetation than the gully floor. The complexity of community composition at different landscape sites is shown as gully sunny slope > gully shady slope > gully floor. The dominant species varies in different geomorphological parts of the gully, from gully sunny slope, gully shady slope to gully floor, and the dominant species evolved from drought-tolerant sun-loving plants to shade-tolerant plants as light decreases and water increases.