Impact of multiple climate stressors on microbial processes and carbon sequestration in peatlands

泥炭地是最大的陆地碳储存地之一，占全球土壤总碳储量的约21%。排干的泥炭地每年排放的温室气体约占英国人为温室气体排放总量的4%。在这些脆弱的生态系统中，气候变暖、干旱和火灾的增加加剧了泥炭地碳命运的不确定性。因此，需要加大努力，为泥炭地制定可持续的管理办法，预计这将对苏格兰缓解气候变化作出重要贡献。排水和气候压力因素，如干旱和变暖，会影响湿地的水文，从而去除水淹的缺氧条件，导致原本保存的泥炭有机质分解增加，并将二氧化碳释放回大气（Kitson & Bell, 2020； Tiemeyer等人，2016）。这些条件可能会减少甲烷排放，但就长期全球变暖潜势而言，二氧化碳释放的增加超过了甲烷减少的气候效益（Huang et al., 2021）。另一方面，火灾主要通过改变地上有机物影响地下碳循环，从而影响分解速率和二氧化碳通量。微生物（细菌、古细菌、病毒、真菌和其他微真核生物）是土壤-大气碳交换的守门人，因为它们的生长、活动和与环境的相互作用控制着碳输入的命运（Malik et al., 2018）。然而，对泥炭地中负责碳循环的微生物生理过程及其对多种气候压力源（如变暖、干旱和火灾）的敏感性缺乏机制理解（Ritson et al., 2021）。因此，迫切需要了解土壤分解体群落对土地利用和气候变化的生态生理响应。该项目旨在研究在日益频繁的极端气候影响下的完整和退化系统中的微生物碳循环过程。人们普遍认为，与完整的泥炭地相比，退化的泥炭地对极端气候（如严重干旱、热浪和火灾）的适应能力较差（Page & Baird, 2016）。本博士项目将严格测试微生物功能和碳固存率对极端气候的响应。基因型和表型测量的结合将使该项目能够将微生物性状与不同处理组合下的碳固存率联系起来。综上所述，这些知识将为更好地预测和管理泥炭地的微生物过程提供基础，以增强未来气候下的碳储存。

Peatlands represent one of the largest stores of terrestrial carbon, accounting for ~21% of the global total soil carbon stock. Drained peatlands contribute to around 4% of UK's estimated total anthropogenic greenhouse gas emissions each year. Climate warming, increased drought occurrences and fires in these fragile ecosystems exacerbate uncertainty over the fate of peatland carbon. Increased effort is therefore required to develop sustainable management approaches for peatlands, which is expected to make an important contribution to climate change mitigation in Scotland.Drainage and climate stressors such as drought and warming impact the hydrology of wetlands such that the removal of water-logged anoxic conditions leads to increased decomposition of the otherwise preserved peat organic matter and release of CO2 back to the atmosphere (Kitson & Bell, 2020; Tiemeyer et al., 2016). Such conditions may reduce methane emissions but increased CO2 release outweighs the climate benefits of methane reduction in terms of long-term global warming potential (Huang et al., 2021). Fires, on the other hand, primarily affect belowground carbon cycling through change in aboveground organic matter and therefore decomposition rates and CO2 flux.Microbes (bacteria, archaea, viruses, fungi and other microeukaryotes) act as gatekeepers of soil-atmosphere carbon exchange because their growth, activity and interactions with the environment control the fate of carbon inputs (Malik et al., 2018). However, there is a lack of mechanistic understanding of the microbial physiological processes in peatlands that are responsible for carbon cycling, and their sensitivity to multiple climate stressors such as warming, drought and fire (Ritson et al., 2021). Therefore, there is an urgent need to understand the ecology and physiology of soil decomposer communities in response to changes in land use and climate together.The project aims to investigate microbial carbon cycling processes in intact and degraded systems that are under the influence of climate extremes, which are becoming increasingly frequent. There is a general consensus that degraded peatlands are less resilient to climate extremes such as severe droughts, heatwaves and fires in comparison to intact peatlands (Page & Baird, 2016). This PhD project will rigorously test the response of microbial functions and carbon sequestration rates to climate extremes. A combination of genotypic and phenotypic measurements will enable the project to link microbial traits to carbon sequestration rates under different treatment combinations. Taken together, this knowledge will provide the basis for better prediction and management of microbial processes in peatlands to enhance carbon storage under future climate.