无芒雀麦和紫花苜蓿在(1:1)混播中的竞争与共存

摘要

[Objective] The relationship between intraspecific competition and interspecific competition simultaneously exists in mixture of legume and grass, the results of the competition led to the phenomenon that one species will be fade, the other will be a dominant gradually due to difference of the competitiveness of different plants. It is of great significance to study the mechanism of competition and coexistence between legume and grass to maintain stable and high yield in mixture grassland.[Method]A pot experiment was conducted to examine the effects of variable rates of nitrogen application (0, 75, 150 kg N·hm-2), hereafter referred as N0, N75, N150, on competition of alfalfa (Medicago sativa L.), Smooth brome (Bromus inermisLayss.) in monoculture, alfalfa and smooth brome in mixture (1:1), with indicators including the relative biomass (RY), relative density (RD), competitive ratio (CR), relative yield total (RYT), percentage of atmospheric N2 fixation (%Ndfa) and percentage of N transferred (%N Trans), to study the mechanism of competition and coexistence in mixcure of smooth brome and alfalfa.[Result] The results showed that with increasing of N application (from 0 to 150 kg·hm-2), the above-ground and below-ground biomass and tiller number of smooth brome significantly increased (P0.05). The above-ground and below-ground biomass and tiller number of smooth brome increased, which in a certain extent inhibited biomass and branch number of alfalfa in mixture (P0.05). In addition, application of N fertilizer significantly inhibited the proportion of N2 fixation of alfalfa and N transfer from smooth to alfalfa, forcing alfalfa compete for soil N and fertilizer N with smooth brome.[Conclusion] Applied N fertilizer at 75 and 150 kg N·hm-2 enhanced the competitiveness of smooth brome, and inhibited the proportion of biological nitrogen fixation of alfalfa and nitrogen transfer form alfalfa to smooth brome, diminished the promotion effect and enhanced competition effect of the two.%[目的]在豆科与禾本科牧草混播草地中不仅存在种内竞争也存在种间竞争,由于不同植物之间竞争力强弱不同,竞争的结果将出现一方逐渐消退,另一方逐渐占据优势的现象,因此研究豆科与禾本科牧草之间竞争与共存机制对于维持混播草地稳定高产具有重要意义.[方法]在温室栽培条件下设置3个氮肥水平(0, 75, 150 kg N·hm-2,记作N0, N75, N150)以及单播和混播两种种植模式(无芒雀麦单播,紫花苜蓿单播,无芒雀麦和紫花苜蓿1﹕1混播),采用相对生物量(RY)、相对密度(RD)、竞争率(CR)和相对产量总值(RYT)以及紫花苜蓿的固氮比例(%Ndfa)和转氮比例(%N Trans)等指标研究无芒雀麦和紫花苜蓿在1﹕1混播中的竞争关系与共存机制.[结果]施氮量从0增加到150 kg N·hm-2,单播中无芒雀麦的地上和地下生物量和分蘖数显著增加(P0.05).在混播中无芒雀麦的地上和地下生物量和分蘖数也显著增加(P0.05).另外,施入氮肥明显抑制了紫花苜蓿的生物固氮比例和对无芒雀麦的氮素转移的比例,导致混播中无芒雀麦和紫花苜蓿同时竞争土壤氮素和肥料氮.[结论]施入75和150 kg N·hm-2的氮肥增强了无芒雀麦的竞争力,而抑制了紫花苜蓿的生物固氮和对无芒雀麦氮素的转移,二者促进作用减弱,竞争效应增强.