Plant-soil feedback is a process where plants alter the biotic and abiotic qualities of soil they grow in, which then alters the ability of plants to grow in that soil in the future. Negative plant-soil feedback occurs when plants are less able to grow in soil that was previously occupied by a member of the same species, and positive plant-soil feedback occurs when plants are more able to grow in soil that was previously occupied by a member of the same species. Although it was originally assumed that negative plant-soil feedback was caused by plants depleting the soil of nutrients, recent work has suggested that a major cause of plant-soil feedback is a buildup of soil-borne pathogens. Mutualism and allelopathy are also thought to cause plant-soil feedback. Studies have shown that, on ave