扭黄茅竞争对金沙江干热河谷区滇榄仁幼苗早期生长的影响

滇榄仁为金沙江干热河谷特有的一级标志种,常与乡土草本植物扭黄茅形成"稀树草丛"景观。长期以来,滇榄仁幼苗极少能在自然群落中成功建植。为了探讨扭黄茅竞争对滇榄仁幼苗早期生长和存活的影响,通过室内盆栽实验人为控制滇榄仁幼苗与扭黄茅之间的竞争强度,研究了扭黄茅竞争对滇榄仁幼苗形态、生物量积累与分配以及叶片数量与大小等特征的影响。结果表明,扭黄茅竞争严重限制了滇榄仁幼苗的早期生长。当存在扭黄茅竞争时,滇榄仁幼苗的生物量分配格局发生了较大变化,根冠比变化范围为0.42 0.62之间。无论滇榄仁幼苗延后定居、同时定居或提前定居,其根系长度以及生物量干质量均会因为受到限制而缩短或减少。然而,定居时间在滇榄仁幼苗存活与生长状况中扮演了一个极为重要的角色。提前定居时,滇榄仁幼苗根冠比远高于同时定居和延后定居时,且其根冠比不受扭黄茅竞争强度的显著影响,表现出了较强的竞争力。

Effects of Heteropogon contortus Competition on the Early Growth of Terminalia franchetii Seedlings in the Dry-Hot Valley of Jinshajiang River

Terminalia franchetii is an endemic species, often form "savanna grass" landscape with native grasses Heteropogon contortus. But for a long time, T. franchetii seedlings are rarely successful establishment in the natural community. In order to investigate the effects of H. contortus on the early growth and survival of T. franchetii seedlings, through the indoor pot experiment and artificially controlling the intensity of competition between T. franchetii seedlings and H. contortus, the effects of H. contortus competition on T. franchetii seedlings' morphology, biomass accumulation and distribution as well as the number and size of leaves were studied. The results showed that, T. franchetii seedlings' morphology, biomass accumulation and distribution as well as the number and size of leaves were significantly affected by H. contortus competition and the early growth of T. franchetii seedlings were severely restricted. When competed by H. contortus, the biomass allocation pattern of T. franchetii seedlings could not be changed significantly, and the R/S ratios changed from 0.42 to 0.62. No matter when the T. franchetii seedlings settle down, their roots length and dry biomass would be limited because of shortened or reduced resources. However, the settlement time and survival status of T. franchetii seedlings play very important roles. The R/S ratios of the early settlers were higher than that of the later settlers and delayed settlers, and not affected by the competitive intensity of H. contortus. So the T. franchetii showed a strong competitiveness.