Characteristics of restorable plant communities on land used for engineering construction in different elevation belts in Qinghai-Tibet Plateau

Restoration of vegetation in a linear project is an important component of grassland ecosystem restoration in Qinghai-Tibet Plateau. In this study, variation of the plant community along the elevation gradient on the land used for engineering construction (approximately 30 cm deep) was analyzed from two levels of total plant population indicators and the economic value of plants indicators, which were based on the natural undegraded grassland plant community. The results showed that the aboveground biomass, height, and coverage of the natural undegraded grassland plant community decreased with the increase in elevation, whereas the aboveground biomass, height, and coverage in the restoration of regional plant communities first increased and then decreased with elevation. The height, coverage, and aboveground biomass of Leguminosae and Cyperaceae in the natural and restoration plant communities first increased and then decreased with increasing elevation. Although the height and coverage of weed families in the natural and restoration plant community first increased and then decreased with the increase of elevation, their aboveground biomass gradually decreased with increasing elevation. The coverage and aboveground biomass of Gramineae in the natural and restoration communities and the height of Gramineae in the natural undegraded grassland plant communities decreased with increasing elevation gradient; however, the height of Gramineae in the restoration of regional plant communities first increased and then decreased with increasing elevation gradient. The diversity index in both natural and restoration plant communities was first increased and then decreased with the elevation gradient, whereas the richness index and evenness index did not differ significantly with the elevation gradient. This indicates that the changes in height, coverage, biomass, and diversity index in the total communities were consistent with the increase in elevation of the restoration of regional plant communities and natural undegraded grassland plant communities. However, the height, coverage, and biomass values of each economic group were inconsistent.