THE OCCUPATION AND FRAGMENTATION OF SPACE - CONSEQUENCES OF NEIGHBORING ROOTS

1. Physical space provides access to light, soil water and nutrients. In crowded neighbourhoods, these resources are quickly depleted. At the same time, physical space may become less available and increasingly fragmented. The present study examines whether constraining the deployment of roots through the occupation of below-ground space by neighbouring plants can affect plant growth. The below-ground spatial environment was fragmented with increasing densities of artificial root systems. The artificial root systems provided physical obstruction, fragmenting the below-ground spatial environment, but were not physiologically active, thus decoupling the availability of space from the resources contained therein. 2. Fragmenting the below-ground physical space available to roots resulted in reduced plant growth. 3. The reduction in growth of plants constrained in the deployment of their roots was not affected by water availability. 4. The reduction in growth of plants constrained in the deployment of their roots was not detected at higher nutrient levels, suggesting that growth reductions may have been mediated through reduced plant nutrition. 5. There were differences among species in sensitivity to fragmented below-ground spatial environment. 6. Although we did not directly assess patterns of root deployment, our results suggest that flexibility in the deployment of roots in response to a fragmented below-ground spatial environment may be a potential mechanism by which plants might maximize resource capture in competitive environments.