Diffusion of constructed resources and specialism promote facilitation in spatial systems

Sessile organisms, such as plants, contend with locally limiting nutrients and neighbours. By consuming nutrients or increasing local concentration by niche construction, they alter the conditions of growth in their local environment. Diffusion of resources alters the interaction sign between two neighbours usually thought to compete for resources. We investigate conditions under which the positive effect of niche construction outweighs the negative effect of competition. Following the experimental design of facilitation experiments, we model patches connected by a flow of resources and ask whether the presence of a niche constructor in one patch eases the colonisation of the other by a conspecific or heterospecific organism. The net interaction sign between a constructor and a coloniser depends on the niches of the two organisms, the diffusion of resources, and the type of niche construction. Niche constructors have a positive effect on neighbouring organisms when niches are sufficiently differentiated, and when the constructed resource diffuses more than the non‐constructed resource. Our work proposes mechanisms for the emergence of facilitation, which is increasingly recognised as a key process structuring plant communities. We discuss the implications for the spatial structure of plant communities and their functioning, including in an agricultural context.