The role of soil (a)biotic properties on performance of urban plant species

The vegetation of urban areas provides many essential benefits. However, urban environments can be challenging for plant growth, with limited space, poor soil quality and low water availability. In addition, many cities are becoming hotter and drier with climate change. This research aimed to test (1) how abiotic properties of urban compared with non-urban soil affect plant performance, and (2) the effect of microbial communities in urban soil compared with non-urban soil on plant resilience to drought stress. To investigate this, I grew three native horticultural tree species (Angophora costata, Callistemon citrinus and Syncarpia glomulifera) in a fully factorial glasshouse experiment. The factors were site (urban streetscape and bushland), soil treatment (sterilised and unsterilised) and water treatment (well-watered and drought). I measured plant stress (Fv/Fm), biomass and allocation. Surprisingly, plants grown in the high nutrient urban soils had greater total biomass than their counterparts grown in non-urban soil, irrespective of the water treatment. Plant biomass was significantly reduced in all three species under water stress treatment. This decline in growth was not negated by the presence of a soil microbiome, irrespective of soil type. These results suggest that soil abiotic properties have a greater effect on plant performance compared to the biotic properties.