Identifying Nutrient Export Hotspots Using a Spatially Distributed Model in Boreal-Forested Catchments

The implementation of the Water Framework Directive (WFD) aimed to reduce nutrient export from catchments to water courses. Forest operations cause diffuse loading, which challenges the efficient targeting of water protection measures. We formed 100 equally probable clear-cut scenarios, to investigate how the location of the clear-cuts influenced the total nitrogen (TN) and phosphorous (TP) export on different scales. The nutrient export was calculated by using a distributed nutrient export model (NutSpaFHy). The clear-cut-induced excess TN and TP exports varied by 4.2%-5.5% and 5.0%-6.5%, respectively, between the clear-cut scenarios. We analyzed how the sub-catchment characteristics regulated the background export. The results also suggested that there was no single sub-catchment feature, which explained the variation in the TN and TP exports. There were clear differences in the background export and in the clear-cut-induced export between the sub-catchments. We also found that only 5% of the forest area could contribute up to half of the total nutrient export. Based on our results, we presented a conceptual planning framework, which applied the model results to finding areas where the nutrient export was high. Application of this information could improve the overall effectiveness of the water protection measures used in forestry.

Automated summary

This study investigated the impact of forest clear-cutting on nitrogen and phosphorous export in water systems, finding that the location of clear-cuts had different effects on nutrient export and only 5% of the forest area could contribute to half of the total export. A conceptual planning framework was proposed based on the findings to identify areas with high nutrient export, aiming to improve the effectiveness of water protection measures in forestry.