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

Annamari (Ari) Lauren,Antti Leinonen,Aura Salmivaara,Samuli Launiainen,Marjo Palviainen,Mingfu Guan

doi:10.3390/f12060808

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.

Highlights

Introduction iationsResponsible forest management requires balancing between the economic gains and adverse environmental effects of the production [1]
From a water quality perspective, a catchment forms the basic unit to quantify the impacts of forestry as water and nutrients released from a site are transported to the downstream watercourse. To bridge these two scales, we developed a distributed nutrient balance and transport model, NutSpaFHy
NutSpaFHy is aimed as a robust and practically applicable tool to assist forest management planning, and the model development was guided to meet the following requirements: (1) Modular structure to allow future development; (2) Use only open data for model calibration and applications; (3) Produce realistic nutrient exports in a versatile stand, site and soil combinations; (4) Describe how nutrient export depends on spatial harvesting patterns in the catchment; (5) Respond to climate gradient across Finland, as well as on seasonal and inter-annual variability of meteorological conditions; (6) Have a low number of calibrated parameters to be applicable outside specific research catchments

Summary

Introduction

Responsible forest management requires balancing between the economic gains and adverse environmental effects of the production [1]. In Nordic and Baltic countries, forestry has a significant role in national and regional economies and risks adverse environmental effects. Forest management operations increase nutrient exports to water courses deteriorating water quality especially in headwater streams and lakes [2,3,4,5], but forestry is a significant source of nutrient load to the Baltic sea [2]. Forest harvesting increases nutrient export through combined hydrological and biogeochemical responses. Numerous experimental studies have quantified the effects of forest management on the water quality and nutrient export in headwater catchments [2,4,7,8].

Methods

Results

Conclusion