The Allelopathic Effects Of Humus Soil Of Coniferous Pureforest On Understory Plantsin The Loess Plateau

Pure forest soil polarization is an important influential factor of forestry sustainabledevelopment. Building tree-shrub-grass compound ecological system is an effective means toimprove and prevent pure forest soil polarization. Allelopathy is widespread in the ecosystem.It is one of the key factors of compound ecological system. Allelopathy between plants hasbecome a significant research subject. There are a lot of defects in the study of plantallelopathy on the Loess Plateau.Based onextensive investigations of the present Vegetation on the Loess Plateau, wesampled humus soil in Pinus tabelaeformis, Platycladus orientalis and Larix gmelini forestsfrom the hilly and gully areas of Loess Plateau for pot experiment with10common species ofplants (Robinia pseudoacacia, Amorpha fruticosa, Caragana korshinskii, Lespedeza bicolor,Hippophae rhamnoides, Vicia villosa, Medicago sativa, Coronilla varia, Astragalusadsurgens, Melilotus suaveolens). Seed germination, seedling growth and physiologicalindexes were measured during the whole experiment process. And then we studied whetherthese humus soil have allelopathic effects on the understory plant. Main results as follows:(1) In the hilly area of Loess Plateau, humus soil of pinus tabulaeformis pure forestshowed obvious comprehensive allelopathic inhibition effects on Amorpha fruticosa,Medicago sativa, Melilotus suaveolens, Vicia villosa, Robinia pseudoacaci and Astragalusadsurgens. For specific performance as follows: the soil reduced the germination rate andgermination index of Medicago sativa and Melilotus suaveolens, the leaf chlorophy content ofAmorpha fruticosa, Hippophae rhamnoides, Melilotus suaveolens and Vicia villosa, inhibitedcatalase actibity (CAT) of Robinia pseudoacacia, Amorpha fruticosa and Melilotussuaveolens，and significantly improved the malondialdehyde content (MDA) of Robiniapseudoacacia, Lespedeza bicolor, Vicia villosa andAstragalus adsurgens. The soil reducedseedling height, root length and biomass growth.(2) In the hilly area of Loess Plateau, humus soil of Platycladus orientalispureforest showed obvious comprehensive allelopathic inhibition effects on Medicago sativa,Melilotus suaveolens, Vicia villosa, and Astragalus adsurgens. For specific performance as follows: the soil reduced the germination rate and germination index of Medicago sativa,Melilotus suaveolens, inhibited catalase actibity (CAT) of Amorpha fruticosa, and Melilotussuaveolens，and significantly improved the malondialdehyde content (MDA) of Vicia villosaand Astragalus adsurgens. The soil reduced seedling height, root length and biomass growth.(3) In the hilly area of Loess Plateau, humus soil of Larix gmelini pureforest showed obviouscomprehensive allelopathic inhibition effects on Robinia pseudoacacia, Amorpha fruticosa,Medicago sativa and Melilotus suaveolens. For specific performance as follows: the soilreduced the germination rate and germination index of Medicago sativa and Melilotussuaveolens, the leaf chlorophy content of Amorpha fruticosa, Hippophae rhamnoides,Melilotus suaveolens and Vicia villosa, inhibited catalase actibity (CAT) of Robiniapseudoacacia, Amorpha fruticosa, Medicago sativa and Melilotus suaveolens, andsignificantly improved the malondialdehyde content (MDA) of Vicia villosa. The soil reducedseedling height, root length and biomass growth.(4) In the gully area of Loess Plateau, humus soil of pinus tabulaeformis pure forestshowed obvious comprehensive allelopathic inhibition effects on Hippophae rhamnoides,Coronilla varia and Medicago sativa. For specific performance as follows: the soil reducedthe germination rate and germination index of Hippophae rhamnoides and Medicago sativa，the leaf chlorophy content of Medicago sativa and Melilotus suaveolens, and significantlyimproved the malondialdehyde content (MDA) of Caragana korshinskii, Amorpha fruticosa,Lespedeza bicolor, Coronilla varia and Vicia villosa. The soil reduced the biomass growth ofCoronilla varia, Hippophae rhamnoides and Medicago sativa.(5) In the gully area of Loess Plateau, humus soil of Platycladus orientalis pure forest showedobvious comprehensive allelopathic effects inhibition on Coronilla varia, Melilotussuaveolens and Vicia villosa. Specific performance as follows: the soil reduced thegermination rate and germination index of Robinia pseudoacacia, Lespedeza bicolor,Coronilla varia, Medicago sativa, Melilotus suaveolens and Vicia villosa, the leaf chlorophycontent of all subjects except for Caragana korshinskii, and significantly improved themalondialdehyde content (MDA) of Coronilla varia and Vicia villosa. The soil reduced theseedling height and root length of Coronilla varia, Vicia villosa and Astragalus adsurgens,and biomass growth of Coronilla varia, Medicago sativa, Melilotus suaveolens and Viciavillosa.