Several generations of soil microbiologists and plant
pathologists have attempted to unravel the microbial
composition, population dynamics and various life-sustaining
processes in the soil. However, until recently, this
basic resource for plant growth and nutrient recycling has
to a large extent remained a black box. Studies have been
made of the behavior of individual microorganisms or
their population dynamics, but the relationship between
the growth of individual organisms or parts of organisms
(such as fungal hyphae) and that of populations and
communities has been largely unknown. In particular, the
spread of fungal colonies in soil has been an enigma, but
now Bailey et al. (pp. 000–000 in this issue) have clearly
demonstrated that spatial behavior of Rhizoctonia colonies
can switch from finite to invasive expansion dependent on
the non-linear relationship between the distance among
substrate particles and the probability of colonization.