喀斯特地区永久性禾草╋白三叶混播草地群落种间竞争与共存

永久性混播草地群落中,豆科牧草与禾草之间竞争不对等而实现竞争共存。在贵州灼圃示范牧场采用白三叶(Trifolium repens)分别与紫羊茅(Festuca rubra)、鸭茅(Dactylis glomerata)分两组建植并持续适度利用20年后的混播草地开展的去除试验表明,去除伴生禾草后,白三叶生物量、盖度和密度增加,禾草对白三叶有竞争关系,竞争强度随季节而不同,生长季节开始时小,后期增大。去除白三叶后初期,禾草产量变化不大,随后下降,白三叶对紫羊茅和鸭茅的竞争系数基本上为负数,范围在-0.023～-0.394,表明禾草由于依赖白三叶的固氮作用而形成的偏利关系大于白三叶对禾草的竞争影响。在适度放牧混播草地系统中,豆科、禾草之间的不对称竞争是白三叶长期维持合理比例和混播组分之间动态平衡的重要机制。

Interspecific competition and co-existence in permanent grasses+Trifolium repens mixed pasture in Karst region

Asymmetrical competitions play an actual role in population co-existence of permanent mixed pasture. Perturbation experiments was conducted on 20yr old binary mixed pasture, which composed of white clover with cocksfoot/red fescue, to study the mechanism of coexisted population. The net production of white clover increased after removal of company grass at both mixtures which suggested that company grass had a competitive effect on white clover. The competitive intensity varied in different seasons, with a low value at beginning of growing season and a high value at the late stage. However, company grass responded differently which decreased after the removal of white clover with the intensity values between -0.023～-0.394 and suggested that nutricism benefits exceeded competitive effects from white clover. In the current system with moderate grazing, asymmetrical competitions is very important for all components dynamically balanced over a long term.