Allelopathy Of The Planted Forest In Loess Plateau

The singularity of biological characteristic,selectivity of nutrient absorption and utilization and particularity of environmental effectunder the artificial pure forests usually result in the polarization of soil properties,which is one of the basic reasons leading to soil degradation.The land capacity decline and continuous cropping obstacle is a problem in the sustainable management of plantation, to which has been payed attention in the Forest and Eco Schools. In the past, plantation research put high emphasis on the competition, species distribution patterns and aspects of niche theory advances to analyze and explore the relationship between species, but little research on biochemical allelopathy is carried out from a biochemical allelopathy view. This paper analyzed influences of the R.. Pseudoacia; P.tabulaeformis, P. Orientalis, P. sylvesris var. Mongolica, P. Simonii, S. Matsudana, C. Microphylla, H. Rhamnoides litter extract on seed germination and Seedling growth of R. Pseudoacia ,P.tabulaeformis, P. Orientalis and P. sylvesris var. Mongolica. Test could be explored by different conifer species and between Tree and Shrub Species in allelopathy. To address barriers to plantation Replanting problems, reduced productivity and even the planting of tree species for the plantation of mixed tree species selected to provide updated and valuable reference. The results show that:(1)The extract of R. Pseudoacia, P.tabulaeformis and P. Orientalis can inhibit seed germination and seedling growth at lower content.With the increasing of extract content, the inhibition increased and gradually reached a significant level.In each extract concentration, the three trees leaf litter extract has toxic effects to seed germination, enzyme activity, root activity and other physiological index, and height, root length and other morphological index. R. Pseudoacia, P.tabulaeformis and P. Orientalis from the toxic effect may exist, but also its chemical composition in the leaf litter were determined.(2)P.tabulaeformis and P. Orientalislitter extract can promote the other tree seed germination and seedling growth.The germination rate of the three species, enzyme activity, root activity increased with the decrease of the concentration, Extract concentration is 0.005g.ml^-1, the maximum value of the index, reached a significant level, When the concentration is 0.1g.ml^-1, all indices were less than the control, either for germination or seedling growth are inhibited. P. sylvesris var. Mongolica leaf litter extract can promote the four species, and has a certain concentration effect, With the lower concentration of water extract of four tree seed germination and seedling growth increased role in promoting. P. sylvesris var. Mongolica trend indicators were similar to R. Pseudoacia, P.tabulaeformis, P. Orientalis. Concentration 0.1g.ml^-1, basically completely inhibited the seed germination and seedling growth, when the concentration of 0.005g.ml^-1, the root activity, enzyme activity and other physiological indicators of the highest.(3) R. Pseudoacia on the other Allelopathy and P.tabulaeformis, P. Orientalis on the other species of allelopathy is the same trend.(4) S. Matsudana,P. Simonii,H. Rhamnoides,C. Microphylla litter extract on seed germination of four trees to promote the role of overall performance (except 0.1gml^-1 ), but either promote or inhibit, not obvious; Litter extracts of four tree species, whether physiological or morphological indicators of overall performance in promoting the role of the indicators of different concentrations of the sensitivity of the different extracts, but there is a maximum concentration.