C, N, and P stoichiometric characteristics of plant communities and dominant plants from different vegetation restoration periods in typical Ningxia grasslands

Plant C, N, and P stoichiometric characteristics are directly related to the normal functioning of grassland ecosystems. To determine changes in the stoichiometric characteristics of plant communities and dominant plants from different vegetation restoration periods in the Ningxia typical steppe area, grassland from different restoration periods (21, 16, 11, 9, 5, 3, and 2 years) in southern Ningxia were analysed and the C, N, and P stoichiometric characteristics of plant communities and dominant plants, including Elymus dahuricus, Stipa bungeana, Leymus secalinus, and Poa annua were examined. The results showed that with an increase in the restoration period, the C content of the aboveground part of the plant communities had an overall upward trend, total N content fluctuated, and total P content decreased. C∶N, C∶P, and N∶P were the highest in 1995 and the lowest in 2007. The C content of the aboveground part of the dominant plants was higher than that of the underground part, whereas the total P content of the underground part was larger than that of the aboveground part. There was a positive correlation between N꞉P and total N of plant communities N∶P, total N of dominant plants showed a positive correlation, and N∶P was less than 14. The plant communities and dominant plants in the Ningxia typical steppe area were restricted by N content, and the characteristics of the plant eco-stoichiometry showed some indication of the degradation and restoration of grasslands.