Carbon dynamics of organic layer in three forest stands dominated by different tree species

ABSTRACT

The organic (O) layer on top of forest soil is important in forest carbon (C) cycling, but not many studies have investigated integrated C dynamics, including dissolved organic C (DOC) fluxes. To clarify the DOC contribution and C dynamics in the O layer, this study quantified the C stock of the O layer, C input (litter fall (LF) and throughfall DOC (TF-DOC)), and C output (CO₂ emission and litter leachate DOC (LL-DOC)) over the course of a year for three forest stands in the same region (middle slopes of Mt. Asama, Nagano, Japan) dominated separately by Quercus serrata (Q), Larix kaempferi (L), and Pinus densiflora (P). The TF-DOC contribution to C input was high in the rainy season. Additionally, TF-DOC was greater in the L forest than in the Q and P forests because of relatively small LF production in the L forest. The contribution of LL-DOC to C output also tended to be high in the rainy season, but the contribution increased in winter owing to the small emission of CO₂ at low temperatures. Annual contribution of LL-DOC was much higher in the P forest than in the Q and L forests, reflecting differences in litter quality. The DOC contribution rate to C flux was generally < 20%, suggesting that DOC flux is a minor but non-negligible process in C cycling in the O layer depending on season and forest type. Our comprehensive C flux data provide better understanding of C cycling in the O layer of temperate forests.

KEYWORDS:

• Organic layer
• dissolved organic carbon (DOC)
• carbon cycling
• litter decomposition
• throughfall

Acknowledgments

We are grateful to the members of the Laboratory for Environmental Ecology, Waseda University, for their support with the fieldwork and experiments. We would also like to thank the staff of both the Karuizawa Seminar House of Waseda University and the Tohshin District Forest Office for their support. Additionally, we thank James Buxton MSc, from Edanz (https://jp.edanz.com/ac), for editing a draft of this manuscript.

Disclosure statement

The authors declare that they have no known competing financial interests or personal relationships that influenced the work reported in this paper.

Supplemental material

Supplemental data for this article can be accessed online at https://doi.org/10.1080/13416979.2024.2358255