You are here:
MODELING MINERAL NITROGEN EXPORT FROM A FOREST TERRESTRIAL ECOSYSTEM TO STREAMS
Citation:
Li, X., R B. Ambrose Jr., AND R Araujo. MODELING MINERAL NITROGEN EXPORT FROM A FOREST TERRESTRIAL ECOSYSTEM TO STREAMS. TRANSACTIONS OF THE ASAE 47(3):727-739, (2004).
Impact/Purpose:
Improve the scientific understanding of the processes controlling nutrient distributions in surface waters. Produce a suite of enhanced models for characterizing nutrient distributions in surface waters by incorporating improved process understanding in existing models (e.g., WASP), by developing new models (e.g., WHAM, reactive transport), and improving linkages between model components.
Description:
Terrestrial ecosystems are major sources of N pollution to aquatic ecosystems. Predicting N export to streams is a critical goal of non-point source modeling. This study was conducted to assess the effect of terrestrial N cycling on stream N export using long-term monitoring data from Hubbard Brook Experimental Forest (HBEF) in New Hampshire. The field-scale DAYCENT model was used to quantify N pools and long-term annual streamflow and mineral N export for 6 subwatersheds at the HBEF. By combining DAYCENT with the watershed model the Soil and Water Assessment Tool (SWAT), mineral N export simulations were extended to the watershed scale. Our study indicated that only 13% of external N input was exported to streams during 1951-2000 at HBEF. Most inputted N (4763kg/ha of N) was stored in forest litter, soil organic matter (SOM) and living plant biomass. Net N mineralization of SOM and forest litter contributed 93% of total available N for export within HBEF ecosystem. The Nash-Sutcliffe coefficient evaluating model performance of DAYCENT at 6 subwatersheds ranged from 0.72 to 0.82 for simulating annual streamflow (1964-2000) and from 0.48 to 0.67 for annual mineral N export (1971-1995), indicating reasonable simulated values. DAYCENT successfully predicted the effect of ecosystem disturbance such as forest cut and insect invasion on stream mineral N export. The watershed-scale simulation suggested that soil spatial variability affects stream N export in addition to the accepted controls of land cover, external N input, climate and ecosystem disturbance.