Root and leaf production, mortality and longevity in response to soil heterogeneity

Abstract

Summary Patches of fertile soil support concentrations of roots, but whether this reflects increased production or increased longevity is not known. We examined the production and longevity of roots of the grass Festuca rubra in response to soil heterogeneity. We also explored the extent to which root dynamics reflect shoot responses to heterogeneous soils. Root and leaf dynamics were followed in pots of heterogeneous or homogeneous soils containing the same total amount of nutrients. Digital minirhizotron images of roots and leaves were collected weekly. Root length was significantly greater in homogeneous than heterogeneous soils. This was caused by significantly larger root production but shorter life span. In contrast, soil heterogeneity had no effect on leaf production or longevity. Within heterogeneous pots, root and leaf production were strongly concordant, both being significantly greater in fertilized patches. More roots died in fertilized patches, but leaf mortality was not affected. Longevity of neither roots nor leaves was affected by the location of a fertile patch. Spatial variation in production of roots and shoots in response to nutrient patches was concordant. Roots and shoots, however, showed independent responses to the presence of within‐pot heterogeneity. A decrease in total root length in heterogeneous soils was a counterintuitive result of decreased production and increased longevity.