林下植被和凋落物对我国寒温带天然林土壤CO_(2)通量的短期影响

Short-term effects of understory vegetation and litter on soil CO_(2)flux of natural forests in cold temperate zone of China

【目的】为研究林下植被和凋落物对我国寒温带天然林土壤CO_(2)通量的影响,对不同处理下CO_(2)通量排放特征进行分析探究,为大兴安岭地区森林生态系统的经营管理和土壤温室气体研究提供参考。【方法】在2019年5-9月采用静态箱-气相色谱法对大兴安岭北部4种主要林型(白桦林、山杨林、樟子松林和兴安落叶松林)土壤CO_(2)通量排放特征进行原位监测研究。【结果】4种林型不同处理后的土壤CO_(2)通量都呈现相似的单峰曲线变化趋势,峰值出现在7月或8月。去除凋落物会提高阔叶林土壤呼吸,降低针叶林土壤呼吸,但变化幅度较小,没有达到显著水平(P>0.05)。与自然状态相比,去除林下植被后,白桦林、山杨林和兴安落叶松林的CO_(2)通量均值分别升高了27.57%、15.84%和24.13%,达到显著水平(P<0.05),但樟子松林则下降了0.68%(P>0.05)。去除林下植被和凋落物状态下,白桦林、山杨林和兴安落叶松林土壤CO_(2)通量均值升高了20.05%~25.34%,但樟子松林则下降了12.36%,且去除林下植被和凋落物的阔叶林的平均通量显著大于针叶林(P<0.05)。【结论】凋落物和林下植被的存在与否会对土壤CO_(2)通量产生不同影响,且影响程度因林型而异,科学合理的林下管理对调控森林生态系统CO_(2)排放和生态环境保护都有着重大的作用。

[Objective]In order to study the effects of understory vegetation and litter on soil CO_(2)flux in cold temperate natural forests in China,we analyzed and explored the characteristics of CO_(2)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 CO_(2)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 CO_(2)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 CO_(2)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 CO_(2)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 nonexistence of litter and understory vegetation would have different effects on soil CO_(2)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.