Factors controlling <i>Carex brevicuspis</i> leaf litter decomposition and its contribution to surface soil organic carbon pool at different water levels

Abstract

Abstract. Litter decomposition plays a vital role in wetland carbon cycling. However, the contribution of aboveground litter decomposition to the wetland soil organic carbon (SOC) pool has not yet been quantified. Here, we conducted a Carex brevicuspis leaf litter input experiment to clarify the intrinsic factors controlling litter decomposition and quantify its contribution to the SOC pool at different water levels. The Carex genus is ubiquitous in global freshwater wetlands. We sampled this plant leaf litter at −25, 0, and +25 cm relative to the soil surface over 280 d and analysed leaf litter decomposition and its contribution to the SOC pool. The percentage litter dry weight loss and the instantaneous litter dry weight decomposition rate were the highest at +25 cm water level (61.8 %, 0.01307 d−1), followed by the 0 cm water level (49.8 %, 0.00908 d−1), and the lowest at −25 cm water level (32.4 %, 0.00527 d−1). Significant amounts of litter carbon, nitrogen, and phosphorus were released at all three water levels. Litter input significantly increased the soil microbial biomass and fungal density but had nonsignificant impacts on soil bacteria, actinomycetes, and the fungal∕bacterial concentrations at all three water levels. Compared with litter removal, litter addition increased the SOC by 16.93 %, 9.44 %, and 2.51 % at the +25, 0, and −25 cm water levels, respectively. Hence, higher water levels facilitate the release of organic carbon from leaf litter into the soil via water leaching. In this way, they increase the soil carbon pool. At lower water levels, soil carbon is lost due to the slower litter decomposition rate and active microbial (actinomycete) respiration. Our results revealed that the water level in natural wetlands influenced litter decomposition mainly by leaching and microbial activity, by extension, and affected the wetland surface carbon pool.

Impact of dust addition on the metabolism of Mediterranean plankton communities and carbon export under present and future conditions of pH and temperature

“…This was reflected in the progressive increase in BP, their variable initial growth rates (µ BP ranged from 0.02 to 0.06 h −1 in control tanks according to the experiment) as well as increasing TAA/DOC ratios at the three stations. Finally, an initial increase in BP during incubations is generally described and classically attributed to a bottle effect, which favors large, fast-growing bacteria and often induces mortality of some phytoplankton cells (Calvo-Díaz et al, 2011;Ferguson et al, 1984;Zobell and Anderson, 1936).…”

Microbial race to colonise leaf litter in a littoral‐lake environment and its relation to nutrient dynamics

“…While ergosterol concentration was higher in the T‐A than in the AQ condition in N. antarctica , the opposite was found in P. anserina , where fungal biomass in submerged detritus surpassed the accrual under terrestrial conditions. Some authors found higher fungal biomass in water‐logging conditions compared to leaf litter incubated in wetlands (Zhu et al, 2021) and streams (Abelho & Descals, 2019) others found higher fungal biomass in the river channel than in floodplain ponds (Baldy et al, 2002; Langhans et al, 2008), and other reported no effect (Northington & Webster, 2017). Abelho and Descals (2019) found a decreased reproductive activity of aquatic fungi (hyphomycetes) in litter exposed to an initial terrestrial phase and suggested that this was because terrestrial fungi could not cope with the aquatic condition and therefore did not sporulate.…”

Effects of Interspecific Interactions on Aquatic Macrophyte Litter Decomposition and Its Influencing Factors

“…Consequently, the structural C content fundamentally determines the duration of the complete decomposition process. 78 For example, the decomposition rate of the submerged macrophyte C. demersum is faster than that of the emergent macrophyte P. australis owing to C. demersum's low C proportion. 79 Conversely, biological components containing N and P are chemically active and easily decomposed, and are released in large quantities during the initial leaching stage.…”

“…The predominantly C-based compounds in plant litter mainly comprise chemically inactive structural C. Structural C is composed mainly of cellulose, hemicellulose, and lignin, which are notably resistant to breakdown and decay compared with other plant components. Consequently, the structural C content fundamentally determines the duration of the complete decomposition process . For example, the decomposition rate of the submerged macrophyte C. demersum is faster than that of the emergent macrophyte P. australis owing to C. demersum ’s low C proportion .…”