Flooding-related increases in CO<sub>2</sub> and N<sub>2</sub>O emissions from a temperate coastal grassland ecosystem

Abstract

Abstract. Given their increasing trend in Europe, an understanding of the role that flooding events play in carbon (C) and nitrogen (N) cycling and greenhouse gas (GHG) emissions will be important for improved assessments of local and regional GHG budgets. This study presents the results of an analysis of the CO 2 and N 2 O fluxes from a coastal grassland ecosystem affected by episodic flooding that was of either a relatively short (SFS) or long (LFS) duration. Compared to the SFS, the annual CO 2 and N 2 O emissions were 1.4 and 1.3 times higher at the LFS, respectively. Mean CO 2 emissions during the period of standing water were 144 ± 18.18 and 111 ± 9.51 mg CO 2 -C m −2 h −1 , respectively, for the LFS and SFS sites. During the growing season, when there was no standing water, the CO 2 emissions were significantly larger from the LFS (244 ± 24.88 mg CO 2 -C m −2 h −1 ) than the SFS (183 ± 14.90 mg CO 2 -C m −2 h −1 ). Fluxes of N 2 O ranged from −0.37 to 0.65 mg N 2 O-N m −2 h −1 at the LFS and from −0.50 to 0.55 mg N 2 O-N m −2 h −1 at the SFS, with the larger emissions associated with the presence of standing water at the LFS but during the growing season at the SFS. Overall, soil temperature and moisture were identified as the main drivers of the seasonal changes in CO 2 fluxes, but neither adequately explained the variations in N 2 O fluxes. Analysis of total C, N, microbial biomass and Q 10 values indicated that the higher CO 2 emissions from the LFS were linked to the flooding-associated influx of nutrients and alterations in soil microbial populations. These results demonstrate that annual CO 2 and N 2 O emissions can be higher in longer-term flooded sites that receive significant amounts of nutrients, although this may depend on the restriction of diffusional limitations due to the presence of standing water to periods of the year when the potential for gaseous emissions are low.

Investigating the controls on greenhouse gas emission in the riparian zone of a small headwater catchment using an automated monitoring system

“…Marín-Muñiz et al (2015) concluded that the Eh plays a vital role in GHG emissions in coastal wetlands. However, we found that the daily mean soil Eh had only a weak positive correlation with daily CO 2 emissions (r = .21) and similar to the results found by Gebremichael et al (2017). Overall, regarding the relationship between the monthly average soil Eh at −30 cm and CO 2 fluxes, the soil Eh may help to interpret the dominant CO 2 flux from aerobic and anaerobic respiration, but this still needs to be investigated in further studies.…”

Irrigation and Greenhouse Gas Emissions: A Review of Field-Based Studies

“…Finally, water delivery was recently demonstrated to also contribute to differences in N 2 O emissions from irrigated fields [97]. By comparing flood irrigation to sprinkler and drip irrigation, researchers determined that the hydrologic forms (irrigation or flooding frequency, timing, and duration) will cause contrasting GHG emission patterns [98]. Specifically, large volumes of soil pores are water-filled completely and simultaneously during furrow or flood irrigation, which leads to a singular large pulse in N 2 O release from wetted soils; whereas low volume methods, such as sprinkler and drip irrigation, leave a large volume of unfilled pores or partially filled pores, causing more variable and generally less intense pulses of N 2 O emissions [96].…”

The Effect of Cutting and Waterlogging on Plant-Related CO2 and N2O Fluxes Associated with the Invasive N-Fixing Species Gunnera tinctoria

“…While plant invasions may directly or indirectly facilitate GHG emissions, this may also be impacted by growth under waterlogged conditions. High water levels can have complex effects on soil biogeochemical and microbial processes that lead to modifications in soil GHG fluxes [21]. Whilst flooding-related increases in plant-mediated N 2 O emissions may be dependent on nitrate levels [19,22], this could also be related to the increased availability of labile carbon due to the increased decomposition of plant roots [9,23] and/or the extent of rhizosphere oxidation [24].…”