Effects of leaf litter aqueous extract on seed germination and seedling growth of Elymus nutans in Eastern Qilian Mountains

To understand the potential allelopathy of shrub litter in the maintenance of shrub-grass community structure, three dominant shrub species and the dominant herbaceous species Elymus nutans in Eastern Qilian Mountains were used as experimental materials. This paper analyzed the effects of Potentilla fruticosa, Salix rehderiana, and Rhododendron capitatum with different concentrations（0.01 g/L, 0.025 g/L, 0.05 g/L, 0.075 g/L, 0.1 g/L） of water extracts from the shrub leaf litter and herbs litter between shrubs on seed germination, seedling morphology and physiological indexes of E. nutans. The results are as follows:（1） The germination rate and germination potential of E. nutans seeds showed a concentration effect of "low promotion and high inhibition" under the treatment of leaf litter extract of P. fruticosa and S. rehderiana. Under the treatment of litter extract of herbaceous, the germination rate and germination potential were firstly increased and then decreased. Under the treatment of leaf litter extract of R. capitatum, the germination rate and germination potential were decreased, and the seeds did not germinate when the concentration exceeded 0.075 g/L.（2） The leaf litter extract of shrub species inhibited both the root length and dry weight of E. nutans seedlings, and it increased with the increase of concentration. The concentration effects of P. fruticose, S. rehderiana and herbaceous under leaf litter extracts on E. nutans seedling height showed "low promotion and high inhibition". R. capitatum litter extract inhibited the fresh weight and seedling height of E. nutans seedlings.（3） The activities of catalase and superoxide dismutase of E. nutans seedlings showed a trend of first increasing and then decreasing with the increase of the concentration of the extract. The contents of soluble sugar and soluble protein were higher when the concentration of litter extract was lower than 0.075 g/L. The content of malondiadehyde continued to increase with the increase of the concentration under P. fruticose leaf litter extract treatment, while it showed a trend of first increasing and then decreasing under S. rehderiana and herbaceous under leaf litter extract treatments. On the whole, the allelopathic effect of leaf litter extract from shrub on E.nutans in descending order: R. capitatum, S. rehderiana, herbaceous plants and P. fruticose, among which R. capitatum had a greater impact on the herbaceous plants under shrub canopy, and allelopathy of leaf l