NutSpaFHy—A Distributed Nutrient Balance Model to Predict Nutrient Export from Managed Boreal Headwater Catchments

Abstract

Responsible forest management requires accounting for adverse environmental effects, such as increased nutrient export to water courses. We constructed a spatially-distributed nutrient balance model NutSpaFHy that extends the hydrological model SpaFHy by introducing a grid-based nutrient balance sub-model and a conceptual solute transport routine to approximate total nitrogen (N) and phosphorus (P) export to streams. NutSpaFHy uses openly-available Multi-Source National Forest Inventory data, soil maps, topographic databases, location of water bodies, and meteorological variables as input, and computes nutrient processes in monthly time-steps. NutSpaFHy contains two calibrated parameters both for N and P, which were optimized against measured N and P concentrations in runoff from twelve forested catchments distributed across Finland. NutSpaFHy was independently tested against six catchments. The model produced realistic nutrient exports. For one catchment, we simulated 25 scenarios, where clear-cuts were located differently with respect to distance to water body, location on mineral or peat soil, and on sites with different fertility. Results indicate that NutSpaFHy can be used to identify current and future nutrient export hot spots, allowing comparison of logging scenarios with variable harvesting area, location and harvest techniques, and to identify acceptable scenarios that preserve the wood supply whilst maintaining acceptable level of nutrient export.

Water Retention Characteristics of Mineral Forest Soils in Finland: Impacts for Modeling Soil Moisture

“…The SpaFHy is described in detail by [42], who tested it across over twenty boreal forest catchments and several eddy-covariance flux sites. The model has been lately extended to include nutrient balance and leaching to predict water quality impacts of forest management [27]. In the parameterization, we follow [42], with the exception of the humus layer and soil, where the soil map-based parameterization of hydrological properties (TP, FC, WP) was replaced by forest site-type-based parameters and humus layer properties obtained in this study.…”

“…Accurate knowledge on soil moisture and its spatiotemporal variability is thus needed to sustainable manage forest soil functions, forest ecosystems and environmental quality [1,2]. Hydrological, biogeochemical and forest ecosystem models are essential for planning sustainable forest management (e.g., plant selection, management chains, nutrient and carbon sink management), assessing risks for abiotic stresses (droughts, waterlogging) and forecasting operating conditions for forestry practitioners [25][26][27][28].…”

“…The proliferation of open high-resolution geospatial (GIS) and weather data is now starting to enable distributed process-based models to emerge as planning tools in forestry [23,27,41,42]. The use of such models, however, would require that soil hydraulic properties can be predicted from geospatial data.…”

Exploring the Role of Weather and Forest Management on Nutrient Export in Boreal Forested Catchments Using Spatially Distributed Model

“…Various spatially varying factors influence the magnitude of nutrient export from forests [11][12][13][14][15]. These include soil type (peat/mineral), site fertility, distance to water body, slope, tree species composition, and implemented forest management practices [11,12,14].…”

“…Various spatially varying factors influence the magnitude of nutrient export from forests [11][12][13][14][15]. These include soil type (peat/mineral), site fertility, distance to water body, slope, tree species composition, and implemented forest management practices [11,12,14]. Temporal variability in nutrient export is mainly related to intra-and inter-annual variability in runoff and changes in the nutrient demand -supply balance [14,[16][17][18].…”