ROOT ARCHITECTURAL AND MORPHOLOGICAL RESPONSE OF PlNUS NIGRA ARN. AND QUERCUS ROBUR L. TO NUTRIENT SUPPLY AND ROOT DENSITY IN THE SOIL

Abstract

This study used seedlings of Quercus robur L. and Pinus nigra Arn. to investigate the respanse of root systems to nutrient supply and roat density in the sail. Variation in nutrient supply was tested by using two different concentrations of nitrate and phosphate. The influence of root density was tested by spacing seedlings to provide a density of 100, 67 and 25 plants m-2. At the end of the treatments the two species presented two different root topologies which apparently each derive from a proper ontogenic speciticity. Nevertheless, the data clearly indicate that competition for nutrients and root density have affected both root system topologies by inducing a considerable modification in root traits such as total fOot length and number of apices. These modifications were different when measured in first-or second-order root laterals. This study reveals that the response of these two species to heterogeneity in soil resource distribution and root competition is regulated by root turnover. A better understanding of the response of roots to environmental signals improves our knowledge of the interaction between plants and the soil ecosystem in forests.