Soil origin impacts Acacia longifolia above and belowground development: water and nutrition as players

Abstract

Context Acacia longifolia is an aggressive invader, disrupting habitats and communities worldwide. Understanding what drives its expansion is of paramount importance. Key functional traits include fast growth and the presence of bacterial symbionts performing nitrogen fixation. Aims To address early plant development of A. longifolia under different soils and growth conditions (water and nutrition availability), establishing the key factors that influence above and belowground responses. Methods Plants were grown in pots with soils collected from forest, agricultural and dune areas in relative proximity, in a controlled experiment designed to study water effect and nutrient availability on early growth. Growth parameters included shoot and root length, nodule number and weight. Bacteria were isolated from nodules for genetic diversity evaluation. Photosynthetic pigments and isotopic nitrogen and carbon analyses were performed to address nitrogen fixation and photosynthesis. Key results Soil origin influenced plant growth and bacterial diversity. Largest plant development was achieved in forest soils with added nutrition and water. Plants from agricultural soil displayed higher aboveground development; however, belowground nodule number and bacterial biodiversity decreased, possibly due to anthropogenic activities. Forest soil promoted belowground development and bacterial diversity. In dune soils overall growth was lower and nitrogen fixation was higher. Conclusion Abiotic factors influenced juvenile acacia development; nutrition acts as a growth enhancer, and soil origin, including its microbial communities, can be considered a development modulator. Bacterial diversity varied according to soil type. Implications Several above and belowground interactions showed the need for an integrative perspective to understand acacias invasive potential.