Low Nitrous Oxide Emissions in a Boreal Spruce Forest Soil, Despite Long-Term Fertilization

Tobias Rütting,Anna-Karin Björsne,Åsa Kasimir,Per Weslien,Leif Klemedtsson

doi:10.3389/ffgc.2021.710574

Tobias Rütting, Anna-Karin Björsne + Show 3 more

Open Access

https://doi.org/10.3389/ffgc.2021.710574

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Abstract

Nitrogen (N) fertilization can increase stem wood production by several hundred percent in boreal forests. At the same time, there are concerns about the environmental consequences of N fertilization, especially considering losses of the greenhouse gas nitrous oxide (N2O) to the atmosphere. Soils are a large contributor to N2O emissions on a global scale. The aim of this study was to investigate the consequences of long-term nutrient optimization fertilization on N2O emissions in a boreal forest in Northern Sweden. Field N2O flux measurements were conducted during 2 years with manual and automatic chambers, as well as gas probes in the snow. The N2O emissions were generally low during the whole period of measurements, both from the control and fertilized plots. The emissions were generally highest during the winters, as well as the variability in the observed values. Overall, N2O emissions from fertilized plots were about twice the control, which could be explained by changes in the soil carbon-to-nitrogen ratio.

Highlights

Nitrogen (N) is the main limiting nutrient for growth in many boreal forests (Tamm, 1991; Högberg et al, 2017) and fertilization is an effective way to increase the net primary production in this slow growing ecosystem (Axelsson and Axelsson, 1986; Linder, 1987)
During the first year of measurements (March 2009–February 2010) there was no statistical significant difference between control and fertilized plots, but during summer and fall 2010, when fluxes were measured with automatic chambers, the emissions from the fertilized plot were significantly higher compared to the control plot (p < 0.001, see Figure 2)
During the rest of the period measured with automatic chambers (October–December) the emissions were low and there was no significant difference between control and fertilized plots (Figure 2)

Summary

Introduction

Nitrogen (N) is the main limiting nutrient for growth in many boreal forests (Tamm, 1991; Högberg et al, 2017) and fertilization is an effective way to increase the net primary production in this slow growing ecosystem (Axelsson and Axelsson, 1986; Linder, 1987). Leaching of NO3− is often related to anthropogenic inputs, either N deposition or fertilization (Sponseller et al, 2014). In non-fertilized boreal forests with low N deposition, the majority of the leaching to streams and waters is in the form of dissolved organic nitrogen (Hedin et al, 1995; Stepanauskas et al, 2000)

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