研究紫茎泽兰(Eupatorium adenophorum)土壤种子库特征及其对紫茎泽兰种子的萌发、幼苗命运的影响, 在综合治理紫茎泽兰入侵危害及防止紫茎泽兰的继续扩散等方面有着重要的意义。该文在攀枝花紫茎泽兰入侵严重的地区, 通过采集果园、放牧灌丛以及禁牧灌丛3种不同生境紫茎泽兰土壤种子库的样本, 以说明不同干扰程度下紫茎泽兰种子在土壤中的分布状况。通过野外调查并结合盆栽实验, 初步研究了紫茎泽兰土壤种子库基本特征以及光照和种子在土壤中的埋藏深度等对紫茎泽兰幼苗的影响。结果表明: 1)果园、放牧灌丛和禁牧灌丛等3种干扰程度不同生境的深层种子量占总种子量的比例分别为56.44%、46.96%和24.86% (p=0.006), 这说明土壤深层种子量大小与干扰成正比, 干扰越大, 深层次紫茎泽兰种子量占总种子量的比重越大。2)播种在0、1和5 cm深度的种子萌发率分别为64.67%、22.67%和13.33%, 即种子埋藏越深, 萌发率越低, 不同层次种子萌发率差异极显著(p=0.00); 幼苗死亡率分别为27.95%、0和0, 表层种子萌发的幼苗有较高的死亡率, 而由埋藏在深层的种子萌发的幼苗没有死亡, 土壤表层发芽的幼苗与不同埋藏深度种子萌发的幼苗之间死亡率差异极显著(p=0.00)。3)在无遮蔽、半遮蔽和全遮蔽3种不同情况下, 紫茎泽兰幼苗的死亡率分别为72.15%、30.38%和4.87%, 定居率分别为6.66%、33.99%和46.67%, 即遮蔽程度越高, 死亡率越低, 定居率越高, 不同处理之间死亡率和定居率差异均极显著(p=0.00)。研究结果暗示, 强光可能是导致紫茎泽兰幼苗死亡的重要原因, 人类活动的干扰可能导致更多的紫茎泽兰种子进入土壤深层, 从而改变了紫茎泽兰土壤种子库的结构。由于土壤深层种子比表层种子具有更强的抵抗强光照射等不良环境因子影响的能力, 所萌发的幼苗成活率高, 表明其具有更高的繁殖效率, 因此人类活动干扰是紫茎泽兰入侵后难以根除的原因之一。

Aims Our objective was to study the relationships between the distribution of Crofton weed (Eupatorium adenophorum) seeds in soil and the destiny of seedlings in order to help prevent the continued spread and to control the weed.

Methods We collected soil seed banks of Crofton weed in orchards and grazed and ungrazed shrublands (a gradient of decreased disturbance) in Panzhihua Prefecture, Sichuan Province, China, to determine seed distribution patterns in the soil. We also tested the effects of sowing depth and light intensity on seedling recruitment and establishment.

Important findings In orchard and grazed and ungrazed shrublands, the proportion of the seed bank in deeper layers of the soil was 56.44%, 46.96% and 24.86% (p=0.006), respectively. Therefore, the greater the disturbance, the higher the percentage of seeds deeper in the soil. Seeds of Crofton weed planted at 0, 1 and 5 cm depths of soil germinated at rates of 64.67%, 22.67% and 13.33%, respectively, revealing germination rates decrease with soil depth. The mortality of seedlings germinated from 0, 1 and 5 cm depths were 27.95%, 0 and 0, respectively, showing that seedlings germinated from the seeds on the surface have higher mortality. Mortality of seedlings that grew under three different light intensities (full light, half-shade and all shade) were 72.15%, 30.38% and 4.87%, respectively, indicating that shade can reduce mortality (p=0.00) and sunlight might be an important factor in seedling mortality. These results imply that disturbance from human activities could favor seeds lying in deeper layers of the soil seed bank by enabling these seeds to have higher efficiency of seedling establishment despite a lower germination rate. Therefore, human activities can promote the invasion of Crofton weed and limit control of the invasion.