Ring-forming species of spinifex grasses (Triodia spp.) are a dominant feature across much of Australia’s arid and semi-arid zone. Researchers have long been curious about the mechanisms underpinning their striking growth form. However, none of the factors investigated to date provide a convincing explanation for ring formation. Here, we asked whether an accumulation of pathogenic soil microbes might impede seedling emergence and subsequent growth in the centre of Triodia basedowii rings. We collected soil from inside and outside naturally occurring spinifex rings and compared plants grown in soil with live microbes to plants grown in sterilised soil. Consistent with our hypothesis, we found that emergence of T. basedowii seedlings was lower in live soil from inside the rings than in live soil from outside the rings. Further, seedling emergence in soil from inside the rings increased significantly in response to soil sterilisation. We found no significant difference in growth between sterile and live soils. However, this might be due to a lack of power caused by high rates of seedling mortality in all treatments. Overall, our study provides evidence for the role of soil pathogens in shaping this iconic Australian grass.

在澳大利亚大部分的干旱和半干旱地区，菠菜草（Triodia spp。）的成环物种是主要特征。长期以来，研究人员一直对支撑其惊人增长形式的机制感到好奇。但是，迄今为止研究的所有因素均未提供令人信服的成环解释。在这里，我们询问病原性土壤微生物的积累是否会阻止幼苗在Triodiabasedowii环中心的出现和随后的生长。我们从天然存在的棘形环的内部和外部收集土壤，并将在土壤中生长的具有活微生物的植物与在无菌土壤中生长的植物进行了比较。与我们的假设相一致，我们发现基于T.basedowii的出现圆环内部的活土中的幼苗比圆环外部的活土中的幼苗低。此外，响应于土壤灭菌，从环内部的土壤中出现的幼苗显着增加。我们发现无菌土壤和活土壤之间的生长没有显着差异。但是，这可能是由于在所有处理中因幼苗死亡率高而造成的动力不足。总体而言，我们的研究提供了土壤病原体在塑造这种标志性澳大利亚草丛中的作用的证据。