Allelopathic Effects Of Dominant Shrub And Subshrub Species In The Southeast Of Mu Us Sandland

Artemisia ordosica, Hedysarum leave and Caragana intermedia are widely nativelydistributed in southestern Mu Us sandland. They are important constructive and dominantspecies of different communities, and they also are the main species of aerial seedlingafforestation. The research of allelopathy among these three species will promote theexploration of the interaction among dominant species in this area, and enrich the theory ofallelopathy. It also can provide another aspect except competition, at the same time, to reflecton varies of problems such as spatial distribution pattern, the mechanisms of interspecificcompetition, and community succession. In this research, bioassay methods were used tostudy the allelopathic effects of Artemisia ordosica, Hedysarum leave and Caraganaintermedia leaf and litter ultrasonic aqueous extracts on receptors’ seed germination andseedling growth. The main results are as follow:1. A. ordosica leaf aqueous extract caused inhibition on A. ordosica, H. leave and C.intermedia seed germination. The inhibitory effects on A. ordosica and C. intermedia seedgermination were increasing along with the concentration of the extracts. The inhibitoryeffects on C. intermedia seed germination showed the “Hormesis effect”. Seedlingsphysiology of the three species were inhibited, relative conductivity rate and MDA contentwere relatively sensitive indexes.2. A. ordosica litter aqueous extract caused light inhibition on self seed germination, butpromoted the growth of seedling. The inhibitory effects on H. leave were remarkably weakerthan the effects caused by leaf aqueous extract, and the inhibitory effects on C. intermediaseed germination were heightened, while on seedling growth were weakened.3. H. leave leaf aqueous extract caused inhibition on A. ordosica, H. leave and C.intermedia seed germination. The inhibitory effects were increasing along with theconcentration of the extracts. The leaf aqueous extract improved the growth of A. ordosicaoverground part, but inhibited the root. It showed the “hormesis effect” on seedlingphysiology. The inhibitory effects on H. leave were increasing along with the concentration ofthe extracts. The aqueous extract had a positive effect on the growth of C. intermediaoverground part, but nagtive effect on seedling physiology.4. H. leave litter aqueous extract had inhibitory effects on A. ordosica seed germination, and a positive effect on seedling growth. The inhibitory effects on seedling morphologyincreased, and on seedling physiology decreased. The aqueous extract had a positive effect onthe growth of C. intermedia, but had a nagtive effect on seedling physiology.5. C. intermedia leaf aqueous extract caused inhibition on A. ordosica, and H. leave seedgermination, the inhibitory effects were increasing along with the concentration, and itshowed the “hormesis effect”on C. intermedia seed germination. The aqueous extract hadstronger inhibitory effect on root than overground part, relative conductivity rate and MDAcontent were relatively sensitive indexes in seedling physiology. The aqueous extract had apositive effect on seedling root growth,and seedling physiology, but a nagtive one onoverground part. C. intermedia seedling dry weight, relative conductivity rate and MDAcontent were relatively sensitive indexes.6. C. intermedia litter aqueous extract had inhibitory effects on A. ordosica seedgermination, and had “hormesis effect” on seedling morphology, and had inhibitory effect onseedling physiology. The litter aqueous extract had lighter inhibitory effect than leaf aqueousextract, and there were positive effect on seedling physiology. The aqueous extract had“hormesis effect” on self seed germination, and had positive effect on root and seedling dryweight in seedling growth stage.By analysis the research results, and combined with the research results about populationdistribution pattern and community characteristics of Artemisia ordosica,Hedysarum leaveand Caragana intermedia, the writer suggest that planting density should be consideredduring the three species pure woods building, and besides density, species arrangement andproper proportion should be considered during mixed forest building.