Effect of mixture sowing on biomass allocation in the artificially-planted pastures, Southeastern Tibetan

Artificial planting is an important measure to promote the restoration of degraded grassland and protect the ecological environment. The objectives of the current study were to investigate the allocation pattern between aboveground biomass (AGB) and belowground biomass (BGB) in different seeding types of artificially-planted pastures. We explored the variation in biomass and the relationship between above- and belowground biomass in four artificially-planted pastures with one species from Elymus nutans Griseb (EN, perennial), Elymus sibiricus Linn (ES, perennial), Medicago sativa Linn (MS, perennial), and Avena sativa Linn (AS, annual) and in six artificially-planted communities with mixtures of two species by seeding ratio 1:1 from the abovementioned grasses (EN + AS, MS + AS, EN + ES, MS + EN, MS + ES, AS + ES) in 2015 and 2016. The results showed that E. nutans is the most productive species with the highest biomass production among the single crops. MS + ES was the most productive group in 2015, while the group with the highest biomass production changed to AS + ES in 2016. AGB was positively correlated to BGB in the surface soil layer in the first year, but positively related to BGB in the subsoil layer in the second year. In the early stage of artificial grassland succession, plants allocated more biomass to aboveground parts, with a root to shoot (R/S) ratio of 1.98. The slope of the log-log relationship between AGB and BGB was 1.07 in 2016, which is consistent with the isometric theory. Different sowing patterns strongly affected the accumulation and allocation of biomass in artificiallyplanted grassland, E.sibiricus was the suitable plant in the alpine regions, which will be conducive to understanding vegetation restoration and plant interactions in the future.