Measuring the Complexity of Fine Root Systems at the Population and Community Levels in a Temperate Forest.

Fine roots are responsible for most nutrient and water acquisition in plants and key in belowground ecological processes such as soil carbon accrual, soil microbial dynamics and soil respiration. Recent evidence highlighted that root systems in temperate trees vary drastically in their morphology and the way roots respond to changes in soil conditions. Nonetheless, few studies have considered community-level patterns in root morphology. In order to understand how the structure of fine root systems changes with topography in a temperate forest in Northeastern Ohio, we analyzed 130+ soil cores and the morphology of > 1000 root systems identified by molecular typing. The study area included forest dominated by sugar maple (Acer saccharum) and American beech (Fagus grandifolia) from well-drained uplands to poorly drained bottomlands and riparian floodplains. Preliminary results indicated contrasting patterns in root distribution. All sites showed higher densities of fine roots in the uppermost layer of soil and similar root biomass of fine roots (1-3 mm in diameter), ranging from 91-105 g m^-2. However, upland forest had higher root mass of absorptive roots (< 1 mm in diameter) in the upper layer (210 g m^-2) than that of bottomland or riparian forests (161 and 154 gm^-2 respectively)  suggesting higher branched root systems in the uplands. Additional analysis will show if the fractal dimension of root systems (a surrogate of root system structure) is correlated with surface area, topological index and specific root length. We will analyze the variations of these parameters along changes in soil conditions and topography. Moreover, we will analyze changes in root structure of individual species represented in different soil types in order to understand root plasticity dynamics of temperate tree species in natural conditions.