Print PageLong-term elemental budgets for watersheds at the Hubbard Brook Experimental Forest (HBEF) have provided new insights into the integration of biogeochemistry and ecology. These budgets have shown how forest disturbance from timber harvest, acid deposition, and climate disturbance (e.g., ice storms) alters the elemental dynamics of forested ecosystems. The element budgets have been analyzed, knowing that inherent uncertainties exist and their approximate magnitudes, however detailed propagation of uncertainty through the inputs, outputs, and net hydrologic flux has not been attempted. We have analyzed uncertainty in multiple element budgets at HBEF in order to identify the major sources of uncertainty in each input-output budget and how those sources of uncertainty have changed. Through uncertainty analysis we can gain a greater understanding of the ecosystem change over time and how to optimally monitor the ecosystem to reduce uncertainty in the future.
The uncertainty analysis combined Monte Carlo estimation of some sources of error and bootstrap resampling of others to propagate uncertainty through to the inputs, outputs, and net hydrologic flux. The approach was applied to data from Watershed 6 (the biogeochemical reference watershed) between 1965 and 2004.
Results/Conclusions
Preliminary results for nitrate fluxes show consistent uncertainty throughout the record, arising from consistent monitoring practices. The main source of uncertainty in the nitrate budget was statistical estimate of the daily streamwater concentration, suggesting that higher frequency concentration data, which could be produced by an optical nitrate sensor, would reduce the annual flux uncertainty
