Abstract: Aims Invasive plants commonly occupy disturbed soils, thereby providing a stage for understanding the role of disturbance-enhanced resources in plant invasions. Here, we addressed how soil space and soil nutrients affect the growth and competitive effect of invasive plants and whether this effect varies with different invaders.
Methods We conducted an experiment in which two invasive plants (Bromus tectorum and Centaurea maculosa) and one native species (Poa pratensis) were grown alone or together in four habitats consisting of two levels of soil space and nutrients. At the end of the experiment, we determined the total biomass, biomass allocation and relative interaction intensity of B. tectorum, C. maculosa and P. pratensis .
Important findings Across two invaders, B. tectorum and C. maculosa, increased soil nutrients had greater positive effects on their growth than increased soil space, the effects of soil space on root weight ratio were greater than those of soil nutrients, and their competitive effect decreased with soil space but increased with soil nutrients. These findings suggest that changing soil space and nutrients differentially influence the growth and competitive advantages of two invaders. Bromus tectorum benefited more from increased soil resources than C. maculosa. Soil space and nutrients affected the biomass allocation of C. maculosa but not B. tectorum. The competitive effect of B. tectorum was unaffected by soil space and soil nutrients, but the opposite was the case for C. maculosa. Thus, the effects of soil space and nutrients on growth and competitive ability depend on invasive species identity.

Key words: biomass, Bromus tectorum, Centaurea maculosa, competitive ability, Poa pratensis, soil nutrients, soil space