Use of root-ingrowth cores to assess nutrient limitations in forest ecosystems

We tested the suitability of using root-ingrowth cores to identify nutrient limitations in a Metrosideros-dominated forest in Hawaii that previously was demonstrated to be nitrogen limited. Plastic mesh cylinders filled with a calcined-clay growing medium were treated with nitrogen, phosphorus, calcium and potassium, or distilled water, and were inserted into the surface soil of the forest. After 6 months in situ, significantly more roots grew into the cores dosed with nitrogen. Fertilization trials provide the best means of identifying nutrient limitations to forest growth, but our results indicate that root-ingrowth cores can provide a reliable, alternative method of assessing nutrient limitations in forest ecosystems.