Abstract:

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.

Key words: Crofton weed (Eupatorium adenophorum), moisture, bioinvasion, light, soil seed banks, seedling fate