高羊茅与黑麦草混播种间相互作用对密度效应的响应

以人工草地生态系统为对象,分析在各生长发育阶段,随密度水平变化植物间正、负相互作用的转化,采用复合De Wit取代试验设计,研究了高羊茅与黑麦草生长前期、中期、后期,不同种植密度(低(32株/钵)、中(64株/钵)、高(128株/钵))水平上的叶片长和宽、根长、生物量及根冠比变化。结果表明:单播时,两种草叶片宽度在各个时期都受到密度制约; 叶片长度、根长、干质量及根冠比在生长前、中期没有严格受密度效应制约,而后期均随密度增大而减小。混播的植株形态与生物量在后期显著高于单播方式,并且种植密度越大该现象出现越早,此外生物量随密度增加下降的程度也小于单播; 中、后期混播根冠比显著小于单播。混播时正、负相互作用的表现依赖于生长时期和密度梯度,特别在生长后期,混播有助于该生态系统的稳定。同一时期内高密度使正作用削弱,但有利于正作用在较早时期产生。混播可能引起两个草种对潜在生态位的利用,出现生态位分化。因此,在生长后期,同一密度下混播草种间表现出正相互作用,而不同密度又表现出负相互作用,说明混播草坪生态系统比单播的草坪更加稳定。

The interactions between Festuca elta Keng and Lolium perenne L. relate to density effect under mixture sowing

The positive interaction between plants of the artificial grassland ecosystem was analyzed in order to test the transforms between positive and negative interactions during the plant growth and the density changes. The composite De Wit instead of the experimental design was used to determine the length and width of leaf, root length, biomass and the root/shoot ratio of Festuca elta Keng and Lolium perenne L. at growth prophase, metaphase, anaphase, and the under different planting densities(low(32 plants/pot), middle(64 plants/pot), high(128 plants/pot)). In single population, leaf width was restricted by density in each period. Leaf length, root length, dry weight and root/shoot ratio were not controlled by density effect strictly at the prophase and metaphase. Whereas, the value decreased with the density raised at the anaphase. In mixed population, the morphology and in the mix-population were higher than those in single population at the anaphase period. This appeared earlier in greater planting density. Moreover, the decreasing biomass that resulted from density was lower than that in a single population. Mixture produced a significant decrease in the ratio of root to shoot compared with mono. The presence of the positive and negative interactions between F. elta Keng and L. perenne L. depended on the life history and the planting density. Particularly mixture improved the managed ecosystem stability in the anaphase. The higher density showed the negative effect, which decreased the positive plant interactions, but it would present earlier. The ratio of root to shoot decreased statistically significantly. It indictated that the plants showed potential niche and niche differentiation. Thus, mixture showed positive interactions under the same density, whereas the negative interaction was observed while the density increased. Mixture artificial grassland ecosystem was steadier than the single one.