Long-term elevation of temperature affects organic N turnover and associated N<sub>2</sub>O emissions in a permanent grassland soil

Abstract

Abstract. Over the last century an increase in mean soil surface temperature has been observed, and it is predicted to increase further in the future. In order to evaluate the legacy effects of increased temperature on both nitrogen (N) transformation rates in the soil and nitrous oxide (N 2 O) emissions, an incubation experiment and modelling approaches were combined. Based on previous observations that gross N transformations in soils are affected by long-term elevated-temperature treatments we hypothesized that any associated effects on gaseous N emissions (e.g. N 2 O) can be confirmed by a change in the relative emission rates from various pathways. Soils were taken from a long-term in situ warming experiment on temperate permanent grassland. In this experiment the soil temperature was elevated by 0 (control), 1, 2 or 3 • C (four replicates per treatment) using IR (infrared) lamps over a period of 6 years. The soil was subsequently incubated under common conditions (20 • C and 50 % humidity) and labelled as NO ) and NO − 3 contents were higher in soil subjected to the +2 and +3 • C temperature elevations (preand post-incubation). Analyses of N transformations using a 15 N tracing model showed that, following incubation, gross organic (but not inorganic) N transformation rates decreased in response to the prior soil warming treatment. This was also reflected in reduced N 2 O emissions associated with organic N oxidation and denitrification. Furthermore, a newly developed source-partitioning model showed the importance of oxidation of organic N as a source of N 2 O. In conclusion, long-term soil warming can cause a legacy effect which diminishes organic N turnover and the release of N 2 O from organic N and denitrification.

Contributions of Ammonia-Oxidizing Archaea and Bacteria to Nitrous Oxide Production in Intensive Greenhouse Vegetable Fields

“…This finding is consistent with previous studies [13,28]. Soil N 2 O production processes primarily involve autotrophic nitrification, heterotrophic nitrification, nitrobacteria denitrification, and chemical denitrification [7][8][9]. Excessive N input and frequent tillage in greenhouse vegetable fields provide substrates and aerobic conditions for ammonia-oxidizing microorganisms [32,33].…”

“…N 2 O is mainly produced after N fertilizer application and by a series of N conversion processes involving autotrophic nitrification, heterotrophic nitrification, nitrobacteria denitrification, chemical denitrification, etc. [7,8]. However, ammonia oxidation, as a necessary step of nitrification, is the main process of N 2 O production in greenhouse vegetable fields [9].…”

Explaining the doubling of N2O emissions under elevated CO2 in the Giessen FACE via in‐field 15N tracing

“…Increased soil temperature may result in lower soil moisture and less N 2 O production as shown for a grassland warming experiment at the GiFACE field site (Jansen-Willems, Lanigan, Clough, Andresen, & M€ uller, 2016), which may counterbalance eCO 2 effects. In contrast, Griffis et al (2017) found a positive correlation between N 2 O emissions and temperature in a 6-year data series from the US corn belt.…”