Sustainability assessment of restoration of abandoned soil excavation sites along the Gongyu Highway on the Qinghai-Tibetan Plateau

A large number of soil excavation and deposition sites which were produced during highway construction on the Qinghai-Tibet Plateau have been restored over time, however, there is still considerable uncertainty regarding whether the restored grassland ecosystem is sustainable. This study examined restored grassland at abandoned soil excavation sites along the Gonghe-Yushu Expressway (hereinafter referred to as Gongyu Road) and compared differences in vegetation community height, coverage, species richness, Shannon-Wiener index, Simpson diversity index, and grassland plant community structures between the abandoned soil excavation site grassland and corresponding natural grasslands. The results showed that vegetation community coverage, species richness, Shannon-Wiener index, Simpson diversity index, and community structure differed significantly between excavation sites and natural grassland (P < 0.05). The vegetation community height of excavation site grassland was significantly lower than that of natural grasslands ( P < 0.05), while height of the vegetation community in excavation site grassland of the high-altitude sample plot was not significantly different from that of natural grassland ( P > 0.05). In summary, grassland coverage has increased after four years of grass reseeding in abandoned excavation site grassland, however, the overall restoration effect did not restore used sites to natural grassland. Taken together, the grassland-restoration effect on abandoned excavation site grassland is not sufficient in this region.