Short-term effects of understory vegetation and litter on soil CO₂ flux of natural forests in cold temperate zone of China

  Objective  In order to study the effects of understory vegetation and litter on soil CO₂ flux in cold temperate natural forests in China, we analyzed and explored the characteristics of CO₂ flux emission under different treatments, to provide reference for the management of forest ecosystem and the study of soil greenhouse gases in Daxing’an Mountains region and theoretical reference.

  Method  In the period from May to September in 2019, the method of static box-gas chromatography was used to study soil CO₂ flux emission characteristics in four main forest types (Betula platyphylla forest, Populus davidiana forest, Pinus sylvestris var. mongolica forest and Larix gmelinii forest) in the north of Daxing’an Mountains.

  Result  The soil CO₂ flux of the four forest types under different treatments all showed a single-peak curve changing trend, and the peak appeared in July or August. The removal of litter increased the soil respiration of broadleaved forests and decreased the soil respiration of coniferous forests. However, the changes did not reach a significant level (P > 0.05). Compared with the natural state, the removal of understory vegetation significantly (P < 0.05) increased the average CO₂ flux of Betula platyphylla forest, Populus davidiana forest and Larix gmelinii forest by 27.57%, 15.84% and 24.13%, respectively, but decreased it in Pinus sylvestris var. mongolica forest by 0.68% (P > 0.05). With the simultaneous removal of understory vegetation and litter, the average CO₂ fluxes of Betula platyphylla forest, Populus davidiana forest and Larix gmelinii forest increased by 20.05%−25.34%, but the Pinus sylvestris var. mongolica forest decreased by 12.36%. The average flux of broadleaved forest was significantly larger than that of coniferous forest (P < 0.05) when the understory vegetation and litter were both removed.

  Conclusion  The existence or non-existence of litter and understory vegetation would have different effects on soil CO₂ flux. Also, the impact on different forest types also varies. Scientific and reasonable understory management strategy plays a key role in regulating carbon dioxide emissions and the protection of ecological environment.