Allelopathic Effects Of Humus Soils From Several Coniferous And Broad-leaf Forest Species On Medicinal Plants Under Tree Layers In The Loess Plateau

Artificial forests, due to the simple tree species composition and generations planted,have appeared retained growth, soil degradation, and even difficult to update. Tree-herb ecosystem has obvious advantages not only in stability, resisting pests and diseases,utilization of solar energy, but also can make full use of land clearance from returning farmland to forest, improve the efficiency of the land utilization and land production and develop economic benefits, social benefits and ecological benefits. However, whether there are allelopathic effects between plantation species and some medicinal plants, especially whether decomposed leaf litters of trees that had a series of complex transformation process in the soil humus layer have inhibition allelopathic effects on seed germination and seedling growth of medicinal plants is not clear.Given this, humus soils of 3 types of coniferous trees and broad-leaved trees were chosen on the Loess Plateau as a cultivate medium, seed germination and seedling growth of11 species of local common medicinal plants were tested and the allelopathic effect of humus soil on medicinal plants and its strength were comprehensively evaluated, aiming to select appropriate forests and medicinal species for forming tree-herb complex system in the Loess Plateau. Main results as follows:(1) In the humus soil of Pinus tabulaeformis: Astragalus membranaceus, Glycyrrhiza uralensis and Achyranthes bidentata showed significant stimulation, which were the preferred species; while Angelica dahurica, Polygala tenuifolia, Arisaema heterophyllum and Bupleurum chinense showed significant inhibition, should be used less as far as possible or not.(2) In the humus soil of Platycladus orientalis: Angelica dahurica and Astragalus membranaceus showed significant stimulation, which were the preferred species; while Belamcanda chinensis, Platycodon grandiflorus, Arisaema heterophyllum, Isatis tinctoria and Glycyrrhiza uralensis showed significant inhibition, should be used less as far as possible or not.(3) In the humus soil of Larix Principis-rupprechtii: Platycodon grandiflorus,Saposhnikovia divaricata, Achyranthes bidentata, Bupleurum chinense and Astragalus membranaceus showed significant stimulation, which were the preferred species; while Arisaema heterophyllum, Belamcanda chinensis, Isatis tinctoria and Polygala tenuifolia showed significant inhibition, should be used less as far as possible or not.(4) In the humus soil of Hippophae rhamnoides: Angelica dahuirca, Polygala tenuifolia,Platycodon grandiflorus and Astragalus membranaceus showed significant stimulation,which were the preferred species; while Belamcanda chinensis, Arisaema heterophyllum,Saposhnikovia divaricata and Bupleurum chinense showed significant inhibition, should be used less as far as possible or not.(5) In the humus soil of Caragana korshinskii: Platycodon grandiflorus, Achyranthes bidentata and Angelica dahurica showed significant stimulation, which were the preferred species; while Bupleurum chinense, Glycyrrhiza uralensis, Astragalus membranaceus and Belamcanda chinensis showed significant inhibition, should be used less as far as possible or not.(6) In the humus soil of Amorpha fruticosa: Bupleurum chinense, Platycodon grandiflorus and Achyranthes bidentata showed significant stimulation, which were the preferred species; while Astragalus membranaceus, Arisaema heterophyllum and Isatis tinctoria showed significant inhibition, should be used less as far as possible or not.