The Effects Of Spatial Patter And Species Combinations On The Plant Performance Of Three Species With Different Seed Mass

In order to test that the effects of spatial pattern and species combinations on the plant performances with different seed mass,the seeds of two annuals Galeopsis bifida Boenn and Botrydium schraderi Spach and a biennial Swertia tetraptera Maxim which occur commonly in the abandoned fields of the eastern Tibetan plateau,were sown by the treatment combinations,spatial pattern(aggregated vs.random)×density (low vs.high)×species combination(monocultures,two and three species combinations).The results indicated that:1> Spatial pattern and species combinations had no significant effects on the emergence rate of three species,but on the competition rank in a certain extent. Galeopsis bifida Boenn which has the large seed mass had the advantaged status in the interspecific competition;Botrydium schraderi Spach,having small seed mass,could benefit from aggregated pattern;Swertia tetraptera Maxim,which seed mass is in the middle rank,had the complex results of interspecific competition.2> Compared with random pattern,the death rate of small-seed species Botrydium schraderi Spach was lower in the aggregated pattern,and had the higher aboveground biomass;But the death rate of Galeopsis bifida Boenn was higher in the aggregated pattern.Compared with low density-aggregated pattern,the aboveground biomass of Botrydium schraderi Spach were lower in the high density-random pattern.3> Compared with other mixtureculture,Galeopsis bifida Boenn had the highest death rate and the lowest aboveground biomass in the monoculture treatment; Botrydium schraderi Spach had higher death rate when mixed with Swertia tetraptera Maxim comparing with monoculture treatment.Species combinations had no significant effects on the aboveground biomass of Botrydium schraderi Spach;Swertia tetraptera Maxim had the lowest death rate when mixed with Galeopsis bifida Boenn,and the highest when three species mixed together.4> Spatial pattern had no significant effects on the plant height and branch of Galeopsis bifida Boenn and Botrydium schraderi Spach(P＞0.05),but density-spatial pattern had significant difference on plant height of Galeopsis bifida Boenn,which had the highest plant height in high density-aggregated pattern,and the lowest branch,however,small-seeded species Botrydium schraderi Spach had the highest plant height in high density-random pattern,and the lowest branch.5> Species combinations had significant effects on the plant height and branch of Galeopsis bifida Boenn and Botrydium schraderi Spach.In monoculture, large-seeded species Galeopsis bifida Boenn had higher plant height but less branch;Small-seeded species Botrydium schraderi Spach had higher plant height, less branch when three species mixtureculture together,and the effects showed more obviously though density-species combination effects.6> Galeopsis bifida Boenn and Swertia tetraptera Maxim had higher root-shoot rate in monoculture comparing with mixtureculture;Small-seeded species Botrydium schraderi Spach had the highest root-shoot rate when mixed with two other species together.In random pattern,Botrydium schraderi Spach also had the highest root-shoot rate when mixed with two other species together.