Fernandez and Norton say the original models predicted a particular equilibrium concentration for sulfate would be reached in stream runoff, but that plateau was never attained.
“For the first 10 years, the model predicted well, so had we only done a three- to five-year study, we would have been really happy with the model’s performance,” Fernandez says. “But after about a decade, we found sulfate concentration in the stream started to plateau earlier than it should have and we still don’t really know why. It does indicate the model was wrong as comprised if applied to this ecosystem.”
However, Bear Brook has turned out to be a near-perfect demonstration of model predictions for the effects of acidification on calcium loss in watersheds to date. Researchers found calcium concentrations increased in the West Bear stream because calcium was being stripped out of the soil for the first 10 years. At that point, the ecosystem switched from a calcium-buffering system to an aluminum-buffering system, and calcium concentrations in the treated watershed decreased.
“In fact, we joke that we should stop the study soon because we’ll find out that it doesn’t behave as perfectly over the long term,” Fernandez says. “Yet, if that is true, it is exactly that type of discovery that can only be achieved through long-term research programs like Bear Brook, where we can learn about ecosystem sustainability on time scales of the 21st century.”