Artemisia halodendron litters have strong negative allelopathic effects on earlier successional plants during vegetation restoration in a semi-arid sandy dune region in China

<p><em>Artemisia halodendron</em> Turcz. ex Besser occurs following the appearance of a pioneer species, <em>Agriophyllum squarrosum</em> (L.) Moq., and the former &#8220;killed&#8221; and replaced the latter during the naturally vegetation succession in sandy dune regions in China. A previous study revealed that the foliage litter of <em>A. halodendron</em> had strong negative allelopathic effects on germination of the soil seed bank and on the seedling growth. It is unclear whether an allelopathic effect of <em>A. halodendron</em> litters positively or negatively affects the seed germination, leading to a progressively replacement of the plant species in sandy dune regions.</p><p>We, therefore, carried out a seed germination experiment to determine the allelopathic effects of three litter types of <em>A. halodendron</em> (roots, foliage, and stems) on seed germination of six plant species that progressively occur along a successional gradient in the semi-arid grasslands of northeastern China.</p><p>In line with our expectation, we found that the early-successional species rather than the late-successional species were negatively affected by the allelopathic effects of <em>A. halodendron</em>, and that the allelopathic effects on seed germination increase with increasing concentration of litter extracts, irrespective of litter types.</p><p>Our study evidenced the negative allelopathic effects of <em>A. halodendron</em> on the species replacement and on the community composition during dune stabilization. Further studies are needed to better understand the successional process and thus to promote the vegetation restoration, as <em>A. halodendron</em> itself disappeared also during the process.</p>