根系对寒温带冻土区兴安落叶松林土壤碳通量的影响

土壤碳通量是森林生态系统碳循环的重要组成部分,根系对土壤碳通量起着关键作用,研究根系对土壤碳通量的影响对寒温带冻土区温室气体研究有重要意义。以杜香-兴安落叶松林(DXL)、杜鹃-兴安落叶松林(DJL)和苔藓-兴安落叶松林(TXL)为研究对象,通过壕沟法进行断根处理,采用便携式土壤呼吸仪G4301对土壤碳通量进行日动态和月动态变化测定与分析。结果表明:6-11月,断根对DXL和DJL土壤CH₄的吸收起抑制作用,降幅分别为15.16%-54.31%和11.26%-33.84%,对TXL土壤CH₄的排放起促进作用,增幅为19.22%-75.52%;对3种类型兴安落叶松林土壤CO₂的排放均起抑制作用,其中对TXL影响最大,对土壤CO₂降幅为32.29%-87.62%。断根对DXL和TXL土壤CH₄的影响在8月最为显著,增幅分别为-54.31%和75.52%,DJL在11月影响最为显著,降幅为33.84%。断根对3种类型兴安落叶松林土壤CO₂排放的影响在6-11月均达到显著程度,其中在11月最为显著,降幅为54.94%-87.62%。断根对3种类型兴安落叶松林土壤CH₄通量日动态影响差异不显著;而对土壤CO₂通量的影响显著,其中在 14:00-18:00影响最为显著,降幅为31.87%-62.26%。土壤温度和空气温度是根系影响土壤碳通量变化的主要因子,断根处理增强了土壤温度对其日变化和月变化的影响,减弱了空气温度对其日动态的影响。这表明,根系自养产生的土壤碳通量可能在日动态变化中更活跃,而在月动态变化中更稳定。

Effects of roots on soil carbon fluxes in Larix gmelinii forests of the cool-temperate tundra zone

Soil carbon fluxes are an important component of the carbon cycle in forest ecosystems. Roots play a key role in soil carbon fluxes. The study of root effects on soil carbon fluxes is important for studying greenhouse gases in the cold-temperate tundra. We selected Ledum palustre- Larix gmelinii (DXL), Rhododendron dauricum- Larix gmelinii (DJL), and Sphagnum-Bryum-Ledum palustre- Larix gmelinii (TXL) forests as research object. Further, the roots were broken off by the trench method. Finally, the soils carbon fluxes were measured and analyzed using the portable soil respirometer G4301 for daily and monthly dynamics. Results show that soil CH₄ uptake of DXL and DJL was inhibited by root-break treatments from June to November, with decrease by 15.16%-54.31% and 11.26%-33.84%, respectively. It contributed to the soil CH₄ emission of the TXL, with increase by 19.22%-75.52%. It suppressed soil CO₂ emissions from 3 types of Larix gmelinii forests by 32.29%-87.62%. The effect of root breakage on soil CH₄ in DXL and TXL was the most significant in August with increases of -54.31% and 75.52%, respectively. In DJL, the impact was the most significant in November, with a drop of 33.84%. The effect of root breakage on soil CO₂ emission of the 3 types of Larix gmelinii forests reached the significant degree from June to November. Among them, it was the most significant in November, with the reduction ranging from 54.94%-to 87.62%. Differences in the effects of root breakage on the daily dynamics of soil CH₄ fluxes in the 3 types of Larix gmelinii forests were not significant. However, the effect on soil CO₂ flux was significant. The most significant effects were observed from 14:00--18:00, with decreases ranging from 31.87%-to 62.26%. Soil and air temperatures were main factors that roots influenced changes in soil carbon fluxes. Treatment of root breaks enhanced the effect of soil temperature on daily and monthly changes in soil carbon fluxes. It also attenuated the effect of air temperature on the daily dynamics. It suggests that soil carbon fluxes from root autotrophy may be more active in daily dynamics and more stable in monthly dynamics.