Soil organic matter quality influences mineralization and GHG emissions in cryosols: a field‐based study of sub‐ to high Arctic

Abstract

Arctic soils store large amounts of labile soil organic matter (SOM) and several studies have suggested that SOM characteristics may explain variations in SOM cycling rates across Arctic landscapes and Arctic ecosystems. The objective of this study was to investigate the influence of routinely measured soil properties and SOM characteristics on soil gross N mineralization and soil GHG emissions at the landscape scale. This study was carried out in three Canadian Arctic ecosystems: Sub-Arctic (Churchill, MB), Low-Arctic (Daring Lake, NWT), and High-Arctic (Truelove Lowlands, NU). The landscapes were divided into five landform units: (1) upper slope, (2) back slope, (3) lower slope, (4) hummock, and (5) interhummock, which represented a great diversity of Static and Turbic Cryosolic soils including Brunisolic, Gleysolic, and Organic subgroups. Soil gross N mineralization was measured using the (15) N dilution technique, whereas soil GHG emissions (N2 O, CH4 , and CO2 ) were measured using a multicomponent Fourier transform infrared gas analyzer. Soil organic matter characteristics were determined by (1) water-extractable organic matter, (2) density fractionation of SOM, and (3) solid-state CPMAS (13) C nuclear magnetic resonance (NMR) spectroscopy. Results showed that gross N mineralization, N2 O, and CO2 emissions were affected by SOM quantity and SOM characteristics. Soil moisture, soil organic carbon (SOC), light fraction (LF) of SOM, and O-Alkyl-C to Aromatic-C ratio positively influenced gross N mineralization, N2 O and CO2 emissions, whereas the relative proportion of Aromatic-C negatively influenced those N and C cycling processes. Relationships between SOM characteristics and CH4 emissions were not significant throughout all Arctic ecosystems. Furthermore, results showed that lower slope and interhummock areas store relatively more labile C than upper and back slope locations. These results are particularly important because they can be used to produce better models that evaluate SOM stocks and dynamics under several climate scenarios and across Arctic landscapes and ecosystems.

Greenhouse Gas Dynamics in a Tree-Based Intercropping System Compared to an Organic Conventional System

“…Soil WC, C total , and clay content explained another 7% of the variation in N 2 O -flux , which agrees with Clemens et al (1999). Clay content influenced N 2 O formation by affecting the soil moisture regime, whereas soil carbon (C total ) may interfere with N 2 O formation (Paré and Bedard-Haughn 2013). All of these parameters, except for clay content, were significantly influenced by the presence of trees.…”

Permafrost soils and carbon cycling

“…To date, most incubation studies have been relatively short term (weeks to a few months) and thus are assessments of the most bioavailable components of SOM. Some studies have combined chemical or physical characterizations with incubations in an effort to relate SOM composition to decomposition rates or to identify indices of decomposability (e.g., White et al, 2002White et al, , 2004Weintraub and Schimel, 2003;Waldrop et al, 2010;Diochon et al, 2013;Paré and Bedard-Haughn, 2013;Pengerud et al, 2013;Treat et al, 2014). In general, SOM of higher quality (less decomposed and rich in polysaccharides and proteins) is positively related to mineralization rates.…”

“…In another case, Wild et al (2014) showed that the mineralization rates of surface organic soil, mineral subsoil, and cyroturbated organic material in the subsoil (all from the active layer) were each differentially limited by the availability of labile organic carbon substrates or nitrogen. Importantly, however, many of the conditions impacting mineralization rates in incubation studies are indicative of factors responsible for variations in overall SOC storage, turnover times, and the intrinsic relative degradation state of SOM on subregion, landscape, and local scales (e.g., Kaiser et al, 2007;Hugelius et al, 2012;Paré and Bedard-Haughn, 2013;Pengerud et al, 2013).…”

Impacts of freezing and thawing dynamics on foliar litter carbon release in alpine/subalpine forests along an altitudinal gradient in the eastern Tibetan Plateau

“…After the temperatures peak in summer, C release would decrease, owing to labile C components lost and decreasing temperature in the "later stage of the growing season" (LG). Nevertheless, litter or organic matter of different quality may exhibit various responses to freezing and thawing dynamics under a scenario of climate change (Pare and Bedard-Haughn, 2013). Many more works must, however, be carried out to more clearly understand litter C release processes in cold biomes.…”