Lessons from Lysimeters: Soil N Release from Disturbance Compromises Controlled Environment Study

Abstract

A controlled environment study of the effects of carbon dioxide (CO2) and nitrogen (N) on growth of ponderosa pine seedlings produced results contradictory to those obtained in the field with the same species, soil, and treatments. In the controlled environment study, there was a significant negative growth response to N fertilization, whereas in the field there was a significant positive response to N. The difference was due to high rates of native N mineralization after soil disturbance during potting. This was evident from soil solution NO3‐ concentrations that peaked at 5000 μmol/L in the unfertilized pots and 20 000 μmol/L in the fertilized pots. These concentrations are orders of magnitude greater than those typically observed in the field. The effects of soil disturbance on N mineralization and nitrification need to be carefully considered before initiating controlled environment studies. The results of this study show that excessive N mineralization caused by soil disturbance can seriously compromise the results of controlled environment studies