东祁连山灌丛凋落叶水浸提液对垂穗披碱草种子萌发和幼苗生长的影响

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

为了解灌丛凋落叶在灌草群落结构维持中可能存在的潜在化感作用,以东祁连山3种优势灌木和灌下优势草种垂穗披碱草(Elymus nutans)为供试材料,分析了不同浓度(0.01 g/L、0.025 g/L、0.05 g/L、0.075 g/L、0.1 g/L)的金露梅(Potentilla fruticosa)、川滇柳(Salix rehderiana)、头花杜鹃(Rhododendron capitatum)及灌间草本的凋落叶水浸提液,对垂穗披碱草种子萌发、幼苗形态和生理指标的影响。结果表明:(1)垂穗披碱草种子发芽率与发芽势在金露梅与川滇柳凋落叶浸提液处理下呈“低促高抑”的浓度效应,在灌间草本凋落叶浸提液处理时表现为先升后降,而头花杜鹃凋落叶浸提液处理时均下降,并在浓度超过0.075 g/L时种子不发芽。(2)灌丛凋落叶浸提液对垂穗披碱草幼苗根长与干重均表现出抑制作用,且随浓度增大而增强;金露梅、川滇柳与灌间草本凋落叶浸提液对垂穗披碱草幼苗苗高表现出“低促高抑”的浓度效应;而头花杜鹃凋落叶浸提液处理对垂穗披碱草幼苗鲜重与苗高均呈抑制作用。(3)垂穗披碱草幼苗CAT、SOD活性随着浸提液浓度升高均表现出先升后降的变化趋势;可溶性糖与可溶性蛋白在灌丛凋落叶浸提液浓度低于0.075 g/L时含量较高;MOD含量在金露梅凋落叶浸提液处理下随浓度升高而持续升高,而在川滇柳与灌间草本凋落叶浸提液处理下呈先升高后降低的趋势。综合来看,灌丛凋落叶浸提液对垂穗披碱草的化感作用由大到小依次为:头花杜鹃、川滇柳、灌间草本、金露梅,其中头花杜鹃对灌下草本植物影响较大,凋落叶化感作用是影响该地区灌草系统群落分布及灌草结构的重要因素。

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 litter had a greater impact on the distribution of shrub-grass system and the structure of shrub-grass community.