Disturbances during minirhizotron installation can affect root observation data

Use of minirhizotrons in forested ecosystems has produced considerable information on production, mortality, distribution, and the phenology of root growth, But installation of minirhizotrons severs roots and disturbs soil, which can cause root proliferation in perennial plants. We compared the magnitude and vertical distribution of root growth observations in a mature hardwood forest during the growing season immediately after minirhizotron installation with observations more than two years later. We also compared the vertical root growth distribution during these two different years with the preinstallation distribution of fine root biomass, Before minirhizotron installation and again two gears later, about 74% of fine root biomass was in the upper 30 cm of soil, but immediately after installation, 98% at the root elongation was in the upper 30 cm, Large differences in the quantity of root elongation were observed across different slope positions in the minirhizotron data from the first growing season (approximately four times greater on the upper slope as the lower slope). Such differences with slope position were not seen in the later minirhizotron data, nor in the preinstallation fine root biomass data. The evidence suggests that the minirhizotron data collected immediately after installation can be biased by disturbance of roots and soil during installation, which result in excessive root proliferation, particularly near the soil surface, Root proliferation appears to be the result of a response to both root pruning and to nutrient release in microsites near the newly installed minirhizotron.