森林演替和气候变暖对暖温带天然次生林植物根系呼吸的交互效应

为了揭示森林演替和气候变暖及交互过程对森林土壤自养呼吸和森林不同层次植物根系呼吸的影响,以关帝山不同演替阶段4种天然次生林(杨桦阔叶落叶林、油松针阔混交林、华北落叶松林和云杉林)为研究对象,于2016—2019年利用Li—6400便携式分析仪观测每种林型不同层次植物根系呼吸和土壤自养呼吸生长季的变化规律;同时采用温室加热法,模拟增温对土壤自养呼吸及各组分的影响。结果表明:(1)根系呼吸速率和土壤自养呼吸速率随演替的进行而降低。乔木层根系呼吸对土壤自养呼吸的贡献率随演替进行则显著上升,而灌木层和草本层的贡献率则显著下降。(2)增温显著提高了不同演替阶段自养呼吸速率,提高幅度为8.48%~8.76%,并随演替进行而升高。森林不同层次植物根系呼吸速率对增温的响应程度不同,其中增温显著提高了草本层和灌木层植物根系呼吸速率,提高幅度分别为10.88%~14.00%和8.37%~15.26%,而[JP]对乔木层植物根系呼吸速率作用则不显著。增温降低了土壤自养呼吸和乔木层根系呼吸的贡献率,则提高了草本层根系呼吸对土壤自养呼吸的贡献率。(3)增温和演替没有改变土壤自养呼吸及各组分在生长季变化规律,但演替和增温对土壤自养呼吸、草本层和灌木层植物根系呼吸有显著的耦合效应。综上所述,森林土壤自养呼吸和根系呼吸速率随演替进行具有降低的趋势,土壤自养呼吸速率、灌木层和草本层植物根系呼吸速率对增温响应程度显著,并且对演替和增温的交互过程有显著的耦合效应,为气候变暖背景下森林更新过程对森林土壤碳排放影响的研究提供数据支持和理论依据。

Interactive Effects of Climate Warming and Forest Succession on Root Respiration of Natural Secondary Forest in Warm Temperate Zone

In order to reveal the effects of forest succession and climate warming and their interactions on soil autotrophic respiration and plant root respiration at different forest levels, 4 natural secondary forests (Poplar-birch broad-leaved deciduous forest, Pinus tabulaeformis conifer broad-leaved mixed forest, Larix principis rupprechtii forest and Picea asperata forest) at different succession stages in Guandi Mountain were studied. From 2016 to 2019, Li-6400 portable analyzer was used to observe the changes of plant root respiration and soil autotrophic respiration rates at different levels of each forest type during the growing season. Greenhouse heating method was used to simulate the effects of temperature increase on autotrophic respiration and its components. The results showed that:(1) The root respiration rate and soil autotrophic respiration rate decreased with succession, and the contribution rate of soil autotrophic respiration to total soil respiration increased significantly with succession. The contribution rate of root respiration to soil autotrophic respiration increased significantly in arbor layer, but decreased significantly in shrub layer and herb layer. (2) Warming significantly increased soil autotrophic respiration ranging from 8.48% to 8.76% in different successional stages, and soil autotrophic respiration gradually increased with the successional process. The response of root respiration rate to warming was different in different forest layers. Warming significantly increased root respiration rate in herb layer (10.88%~14.00%) and shrub layer (8.37%~15.26%), but it had no significant effect on root respiration rate of arbor layer. Increasing temperature decreased the contribution rate of soil autotrophic respiration and root respiration in arbor layer, while it increased the contribution rate of root respiration in herb layer. (3) Warming and succession did not change the variation law of soil autotrophic respiration and its components in the growing season, but it had significant coupling effects on soil autotrophic respiration, herb layer and shrub layer plant root respiration. In conclusion, soil autotrophic respiration rate and root respiration rate of shrub layer and herbaceous layer had significant response to temperature increase, and had significant coupling effect on the interactive process of succession and temperature increase, which provide data support and theoretical basis for the study on the effect of forest regeneration process on forest soil carbon emission under the background of climate warming.