Variation in carbon and nitrogen concentrations among peatland categories at the global scale

Abstract

Peatlands account for 15 to 30% of the world’s soil carbon (C) stock and are important controls over global nitrogen (N) cycles. However, C and N concentrations are known to vary among peatlands contributing to the uncertainty of global C inventories, but there are few global studies that relate peatland classification to peat chemistry. We analyzed 436 peat cores sampled in 24 countries across six continents and measured C, N, and organic matter (OM) content at three depths down to 70 cm. Sites were distinguished between northern (387) and tropical (49) peatlands and assigned to one of six distinct broadly recognized peatland categories that vary primarily along a pH gradient. Peat C and N concentrations, OM content, and C:N ratios differed significantly among peatland categories, but few differences in chemistry with depth were found within each category. Across all peatlands C and N concentrations in the 10–20 cm layer, were 440 ± 85.1 g kg-1 and 13.9 ± 7.4 g kg-1, with an average C:N ratio of 30.1 ± 20.8. Among peatland categories, median C concentrations were highest in bogs, poor fens and tropical swamps (446–532 g kg-1) and lowest in intermediate and extremely rich fens (375–414 g kg-1). The C:OM ratio in peat was similar across most peatland categories, except in deeper samples from ombrotrophic tropical peat swamps that were higher than other peatlands categories. Peat N concentrations and C:N ratios varied approximately two-fold among peatland categories and N concentrations tended to be higher (and C:N lower) in intermediate fens compared with other peatland types. This study reports on a unique data set and demonstrates that differences in peat C and OM concentrations among broadly classified peatland categories are predictable, which can aid future studies that use land cover assessments to refine global peatland C and N stocks.

Driving Mechanism Controlling Cultivated Tropical Peat Physicochemical Characteristics and Stoichiometry: Case Study of a Microtopographical Sequence

“…All of the average values of peat properties and stoichiometry in this study were in accordance with the general values that previously reported from tropical peats that occupied by various land uses (Hikmatullah and Sukarman 2014;Könönen et al 2015;Lampela et al 2014;Sabiham 1988;Sabiham 2010;Yin et al 2022;Watmough et al 2022; Table 2). The average of SM, BD, and porosity of studied peat were 1,004.10%, 0.10 g/cm 3 , and 93.67%, respectively, with their median values were relatively close, particularly for BD and porosity (961.50%, 0.10 g/cm 3 , and 93.57%, respectively; Table 2).…”

Carbon Stocks and Recent Rates of Carbon Sequestration in Nutrient‐Rich Freshwater Wetlands From Lake Simcoe Watershed (Southern Canada)

“…The total N content by mass and C org /N ratios of swamp and marsh soils differed significantly. Nitrogen concentration in our swamps averaged 2.42 ± 0.6%, approximately twice that reported for global peatlands (Loisel et al., 2014; Watmough et al., 2022), while marshes average much lower (0.9 ± 0.8%), on a par with other freshwater wetlands in North America (Craft & Casey, 2000). Since there are no obvious differences in upland land use and thus potential sources of N inputs, the higher N concentration in Simcoe swamps compared to marshes, and particularly in the wetlands with a longer hydroperiod/higher water table compared to drier sites (Figure 5), may indicate fundamental differences in ecological and/or soil processes that govern these ecosystem types.…”

“…The underrepresentation (under‐appreciation?) of marshes (often equated with mineral‐soils) as important carbon stores and/or potential nature‐based climate solutions (NbCS) for mitigation of anthropogenic GHG emissions recognized by many authors (e.g., Creed et al., 2022; Drever et al., 2021; Loder & Finkelstein, 2020) has been perpetuated, in part, by their relative “invisibility” in C cycling research, still largely focused on peatlands, particularly from boreal and subarctic regions (Loisel et al., 2014; Watmough et al., 2022). An additional factor is that most temperate freshwater wetlands, in particular marshes, are embedded in agricultural landscapes with poor natural ecosystem connectivity (Cohen et al., 2016; Creed et al., 2022; Marton et al., 2015) making them vulnerable to the increasing human pressure (Nahlik & Fennessy, 2016).…”

Physical Properties and Crop Performance of Four Substrate Fibers in Greenhouse Petunia Production

“…These characteristics raise concerns for nitrogen immobilization due to microbially mediated decomposition and subsequent substrate shrinkage, which can reduce available N to the growing plants, hindering finished crop quality or requiring higher fertilizer inputs. For reference, the C:N of peat ranges from 20 to 80 [18,[32][33][34]. Coir has a C:N around 75 to 186 [18,35], bagasse ranges from 65 to 213 [36][37][38][39], and wood can be much higher, ranging from 222 to 749 [40] but typically greater than 300 [21].…”