Abstract
Nitrogen (N) cycle processes in terrestrial ecosystems are highly sensitive to temperature and soil moisture variations. Thus, future climate change may affect the degree to which N deposited from the atmosphere will be retained in forest ecosystems. We evaluated the effect of future changes in climate and N deposition on ecosystem N cycling using the model LandscapeDNDC forced with historical data from eight long-term forest ecosystem monitoring stations in Austria and downscaled future N deposition and climate scenarios. With every 1 °C of warming, annual N uptake in biomass increased by +0.03 to +0.54 kg N ha−1, total soil organic matter (SOM) increased annually by +0.003 to +0.08 kg N ha−1, and mean annual N leaching was between −0.09 and −2.03 kg N ha−1 lower. The magnitude of N deposition in the years from 1990 to 2010 was by far the most important determinant of the response of nitrogen cycling to future warming, including statistically significant relationships with humus N content and N leaching. We conclude that climate change will likely increase ecosystem N retention in temperate forest ecosystems, and even more so at forest sites with high past N deposition.
Highlights
Nitrogen deposition has led to changes in carbon and nitrogen dynamics in forest ecosystems (Butterbach-Bahl and Gundersen 2011), causing changes in C sequestration (Thomas et al 2010; Yue et al 2016), increased nitrate leaching (Gundersen et al 2006), increased gaseous N emissions (van Groenigen et al 2015) and the loss of plant species susceptible to high nutrient availability (Dirnböck et al 2014)
Nitrogen deposition has led to changes in carbon and nitrogen dynamics in forest ecosystems (Butterbach-Bahl and Gundersen 2011), causing changes in C sequestration (Thomas et al 2010; Yue et al 2016), increased nitrate leaching (Gundersen et al 2006), increased gaseous N emissions and the loss of plant species susceptible to high nutrient availability (Dirnböck et al 2014)
By following Lovett and Goodale (2011), we focused on the temporal dynamics of N in plant biomass, N in the forest floor, N in the mineral soil, soil N loss via gaseous emissions (N2O, N2 and NO) and via leaching in seepage water (NO3− and NH4+)
Summary
Nitrogen deposition has led to changes in carbon and nitrogen dynamics in forest ecosystems (Butterbach-Bahl and Gundersen 2011), causing changes in C sequestration (Thomas et al 2010; Yue et al 2016), increased nitrate leaching (Gundersen et al 2006), increased gaseous N emissions (van Groenigen et al 2015) and the loss of plant species susceptible to high nutrient availability (Dirnböck et al 2014). In addition to climatic conditions, N processes depend to a large extent upon soil characteristics, management and vegetation type. Soil properties such as soil texture and porosity can affect N turnover in soils, via their impacts on soil hydrology, N adsorption and soil organic carbon concentrations (Butterbach-Bahl and Gundersen 2011). Vegetation type has major effects on ecosystem N cycling controlling litter quality, root distribution and canopy structure that affect soil moisture, temperature and substrate availability, microbial N turnover as well as nitrate leaching and gaseous N loss (Brumme et al 1999; Butterbach-Bahl et al 2002; Rothe et al 2002)
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