The impact of different introduced artificial grassland species combinations on community biomass and species diversity in temperate steppe of the Qinghai-Tibetan Plateau.
The temperate steppe ecosystem on the Qinghai-Tibet Plateau has degenerated greatly in recent decades. Cultivating artificial grassland can alleviate the degradation of natural grassland and result in higher biomass yield. However, the influence and suitability of different species combinations when used to establish artificial grassland in this region remain unclear. Therefore, we selected one natural pasture (NP) as a comparison and three different adjacent artificial seeding regimes [Elymus nutans monoculture (A1), oat monoculture (A2) and oat-highland barley-oilseed rape mixed-culture (A3)] to establish artificial grasslands for experimental comparison in temperate steppe of Guinan county, Qinghai Province. The research aim was to evaluate the influence that different forages (oat and E. nutans; A1 and A2) and sowing methods (monoculture or mixed-culture; A2 and A3) would have on herbage yield and vegetation community stability. Results were obtained by community investigation and sampling in each plot. In this study, the three artificial grasslands under agricultural management significantly decreased the biomass of poisonous plants (P<0.05), and also significantly improved the proportion of high-quality forage (P<0.05). A2 provided the highest aboveground biomass (1263.21 g.m-2) and was 9.77 times more productive than NP and significantly higher than the other three grasslands (P<0.05). The three artificial grasslands did not significantly change the belowground biomass or the total biomass, and no significant difference of these two indices was found among artificial grasslands. Artificial grasslands in this study changed the species composition, especially A2 and A3, which were quite different from NP. The Pielou evenness index of A2 was significantly lower than NP and A3 (P<0.05), while the Shannon-Wiener index of A3 was significantly lower than NP (P<0.05). In contrast, A1 had a high species diversity index, by various measures, including Gleason index, Shannon-Wiener index and Pielou evenness index, was similar to NP. Our results demonstrate that the oat monoculture grassland (A2) changed the species composition of the NP temperate steppe vegetation community more strongly than other treatments and produced higher aboveground biomass in comparison to E. nutans grassland. By contrast, E. nutans grassland did not greatly improve aboveground biomass, but maintained community species diversity and evenness, which was conducive to retention of a relatively stable community productivity under harsh conditions.