干扰强度对群落中紫茎泽兰种子萌发、幼苗定居和生长的影响

Effects of disturbance intensity on seed germination， seedling establishment and growth of Ageratina adenophora

关键词:  紫茎泽兰  种子萌发  幼苗定居  生长  入侵性  干扰

Key words:  Ageratina adenophora or Eupatorium adenophorum  disturbance  growth  invasiveness  seed germination  seedling establishment

摘要:

干扰与外来植物入侵密切相关，种子萌发和幼苗定居是植物生活史中最脆弱、也是外来植物入侵最关键的阶段。为研究干扰在恶性外来入侵植物紫茎泽兰成功入侵过程中的作用，采用人工牧草群落代替自然群落，人为干扰（去除不同面积的牧草）模拟自然干扰的方式，研究了紫茎泽兰入侵初期种子萌发、幼苗定居和生长对不同干扰强度的响应与适应。结果表明：(1)随着干扰强度的增大，群落下层光强升高，在直径15、20、25、30 cm和35 cm的干扰强度下，群落下层相对光强分别为6%、9%、16%、20%和28%。在各干扰强度下，紫茎泽兰种子均能萌发（发芽率40%～50%）、幼苗均能成活（成活率26%～40%）和定居（定居率11%～15%），且差异均不显著（15 cm和35 cm干扰强度下幼苗定居率除外）；在100%光环境下，未发现成功定居的紫茎泽兰幼苗。(2)随着干扰强度的增大，紫茎泽兰株高、冠宽、叶片数、叶长、叶宽、单叶叶面积和总叶面积均有升高的趋势，100%光强下紫茎泽兰冠宽、叶片数和总叶面积最大。这说明紫茎泽兰耐阴性较强，较小的干扰就可能导致紫茎泽兰成功入侵；在不利环境下能缓慢生长，在环境改善后能充分利用资源加速生长，这可能是紫茎泽兰成功入侵的一个重要策略。

Abstract:

Alien plant invasions are tightly correlated with disturbance，and seed germination and seedling establishment are the most vulnerable plant life history stages，and also the key stages for alien plant invasions. To evaluate the roles of disturbance in success invasion of noxious Ageratina adenophora，responses to disturbance intensities of seed germination，seedling establishment and growth of this plant were studied by simulating natural invasion process into artificial pasture community after man made disturbances(remove different area of forage grass). Irradiance under canopy increased with increasing disturbance. Relative irradiance under canopy after 15 cm，20 cm，25 cm，30 cm，and 35 cm(diameter) disturbance were 6%，9%，16%，20%，and 28% respectively. At all disturbance intensities，Ageratina 〖WT6.〗〓〖ＷＴ9.5BＺ〗seeds were able to germinate，and seedlings were able to survive and colonize. The percentages of seed germination(40%-50%)，seedling survive(26%-40%) and establishment(11%-15%)were not significantly different between disturbances. Seedlings successfully established were not found at 100% irradiance. Plant height，crown width，leaf number，leaf length，leaf width，individual leaf area，and total leaf area increased with increasing disturbance. The crown width，leaf number，and total leaf area were the biggest at 100% irradiance. Our results indicated that Ageratina had a strong ability to tolerate shade，and small disturbance might lead to invasion success for this plant. The abilities to grow slowly at adverse environments and to grow fast after environments improved might be a key strategy for Ageratina invasion.