In the root-soil ecoboundary layers of black locust and slash pine growing under different soil conditions, there existed a concentration gradient of nutrient elements. The accumulation or deficit of Ca, Mg, K and P occurred in a distance of 25-400 μm from the root surface and was affected by soil types, fertilization and plant species. Mucilage layers found on the root surface were evidenced by low concentration of Si, Al and Fe within a range of 25-75 urn. It could be considered that the mucilage layer was an important part of the ecoboundary layer functioning as a passage of material exchange and energy flow between the root and soil.