Plant-soil feedback of the invasive Sorghum halepense on Hainan island, China

Sorghum halepense is a perennial invasive weed causing great harm worldwide, including various regions on Hainan island. In this study, using two approaches, we examined plant-soil feedback of different S. halepense populations. In the first, rhizosphere soil of S. halepense from the field was either sterilized or not to study the role of soil biota on S. halepense growth. In the second, we first let S. halepense plants condition the soil, and then regrow plants on these conditioned soil to study the role of overall changes in soil properties in plant-soil feedback. Sterilization increased the growth of S. halepense, indicating that soil biota inhibited the growth of S. halepense. Soil biota from some populations inhibited the growth of S. halepense more than that from others. In most cases, the relative response of a S. halepense population when associated with its own soil vs. when associated with other soils was similar to the relative response of other populations across the same soils. In the second approach, the effect of conditioning on most soil chemical properties were not different among populations. The interactive effect of conditioning population and replanting population on plant biomass was not significant, indicating that the performance of different S. halepense populations did not depend on the population of S. halepense that conditioned the soil. These results indicate that on Hainan island, S. halepense can outburst and proliferate despite negative feedback with soil biota, and populations of S. halepense differ little in their interactions with soil.