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

Zhu, Lianlian; Deng, Zhengmiao; Xie, Yonghong; Li, Xu; Li, Feng; Chen, Xinsheng; Zou, Yeai; Zhang, Chengyi; Wang, Wei

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 inline-formula−25, 0, and inline-formula+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 inline-formula+25 cm water level (61.8 %, 0.01307 dinline-formula−1), followed by the 0 cm water level (49.8 %, 0.00908 dinline-formula−1), and the lowest at inline-formula−25 cm water level (32.4 %, 0.00527 dinline-formula−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 inline-formulafungal∕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 inline-formula+25, 0, and inline-formula−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.

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Zhu, Lianlian / Deng, Zhengmiao / Xie, Yonghong / et al: Factors controlling Carex brevicuspis leaf litter decomposition and its contribution to surface soil organic carbon pool at different water levels. 2021. Copernicus Publications.

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