Abstract

Changing water regimes (e.g. drought) have unknown long-term consequences on the stability and resilience of soil microorganisms who determine much of the carbon and nitrogen exchange between the biosphere and atmosphere. Shifts in their activity could feedback into ongoing climate change. In this study, we explored soil drought effects on soil greenhouse gas (GHG; CO₂, CH₄, N₂O) fluxes over time in two sites: a boreal, coniferous forest in Finland (Hyytiälä) and a temperate, broadleaf forest in Austria (Rosalia). Topsoil moisture and topsoil temperature data were used to identify soil drought events, defined as when soil moisture is below the soil moisture at the permanent wilting point. Data over multiple years from automated GHG flux chambers installed on the forest floor were then analyzed using generalized additive models (GAM) to study whether GHG fluxes differed before and after drought events and whether there was an overall, multiyear temporal trend. Results showed CO₂ and N₂O emissions to be more affected by drought and long-term trends at Hyytiälä with increased CO₂ emission and decreased N₂O emissions both following drought and over the entire measurement period. CH₄ uptake increased at both sites both during non-drought periods and as an overall, multiyear trend and was predominantly affected by soil moisture dynamics. Multiyear trends also suggest an increase in soil temperature in the boreal forest and a decrease in soil moisture in the temperate forest. These findings underline forests as an important sink for CH₄, possibly with an increasing rate in a future climate.

中文翻译：

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干旱对北方和温带森林土壤温室气体通量的影响

摘要

水情的变化（例如干旱）对土壤微生物的稳定性和恢复力产生未知的长期影响，土壤微生物决定了生物圈和大气之间的大部分碳和氮交换。他们活动的变化可能会反馈到持续的气候变化。在这项研究中，我们探讨了两个地点土壤干旱对土壤温室气体（GHG；CO ₂、CH ₄、N ₂ O）通量随时间变化的影响：芬兰（Hyytiälä）的北方针叶林和芬兰（Hyytiälä）的温带阔叶林。奥地利（罗萨莉亚）。表土湿度和表土温度数据用于识别土壤干旱事件，定义为土壤湿度低于永久萎蔫点的土壤湿度。然后使用广义加性模型（GAM）对安装在森林地面上的自动化温室气体通量室的多年数据进行分析，以研究干旱事件前后温室气体通量是否存在差异以及是否存在总体的多年时间趋势。结果显示，CO ₂和 N ₂ O 排放量更容易受到干旱和 Hyytiälä 长期趋势的影响，干旱后和整个测量期间 CO 2 排放量增加，N 2 O 排放_量减少_。两个地点的CH ₄吸收量在非干旱期间和总体多年趋势均有所增加，并且主要受到土壤湿度动态的影响。多年趋势还表明，北方森林土壤温度上升，温带森林土壤湿度下降。_{这些发现强调森林是 CH 4}的重要汇，并且在未来的气候中其比率可能会不断增加。