Carbon storage and understory plant diversity in boreal Larix gmelinii–Carex schmidtii forested wetlands: A comparison of harvest, fire and draining disturbance

Abstract

Background: Forested wetlands are an important factor in carbon (C) sequestration. In this study, we compared the short-term effects (5 years) of three harvest intensities and two wildfire severities, and the mid-term effects (25 years) of four groundwater table depth (WTD) drainage for forestry on eco-system C storage and understory vegetation structures in Daxing’anling, northeast of China. Results: We found that: Low intensity harvest slightly enhanced ecosystem C storage, whereas moderate- and high-intensity harvest led to significant reductions (33.2-41.6%) in comparison with the control natural forested wetlands stand (274.54 t C·ha -1), and light and heavy burn caused the ecosystem C storage sig-nificant decreases by 27.8% and 45.2%. As for the drainage for forestry, the ecosystem C storage was higher at the low WTD (316.78 t C·ha -1), and diminished significantly by 24.1-28.1% with the increasing WTD on the forested wetland plantation transect. Compared with the control and high intensity harvest stands (8.28 t ha -1 yr -1, 5.08 t C·ha -1 yr -1 and 6.48 t ha -1 yr -1, 3.52 t C·ha -1 yr -1), significantly higher NPP (net primary productivity, defined by the biomass difference of two measurements) (69.1-83.2%) and annual C sequestration (52.0-78.7%) were observed in the low- and moderate-intensity harvest stands. Significant increases by 48.6% and decreases by 31.5% in NPP or by 52.9% in annual C sequestration were in light and heavy burn stands, respectively. In contrast, the NPP and annual C sequestration (3. 67-10. 34 t ha -1 yr -1 and 1. 59-4. 87 t C·ha -1 yr -1) showed a significant in-creasing trend with increasing WTD, respectively. The understory species diversity indices were generally lower in the harvest and burned stands than the control natural forested wetlands and more pioneer tree species regeneration occurred after the disturbances. Conclusion: Therefore, it seems that low intensity harvest and wildfire could sustain the ecosystem C sink and drainage for forestry is an effect way to restore C sequestration for this forested wetland type.