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

泥炭地是陆地碳储量最大的地区之一，约占全球土壤碳储量的21%。排干的泥炭地每年约占英国估计的人为温室气体排放总量的4%。气候变暖、干旱增加和这些脆弱生态系统的火灾加剧了对泥炭地碳命运的不确定性。因此，需要加大努力制定泥炭地的可持续管理方法，这有望为减缓苏格兰的气候变化做出重要贡献。排水和气候压力因素，如干旱和变暖，影响湿地的水文，从而消除积水的缺氧条件，导致以其他方式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；Timeyer等人，2016)。这种条件可能会减少甲烷排放，但就长期的全球变暖潜力而言，增加的二氧化碳排放超过了减少甲烷的气候好处(Huang等人，2021年)。另一方面，火主要通过地上有机质的变化影响地下碳循环，从而影响分解速度和二氧化碳通量。微生物(细菌、古细菌、病毒、真菌和其他微真核生物)充当土壤-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碳输入的命运(Malik等人，2018年)。然而，对于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的敏感性，如变暖、干旱和火灾，缺乏机械上的了解(Ritson等人，2021年)。因此，迫切需要了解土壤分解者群落的生态和生理，以应对土地利用和气候的变化。该项目旨在研究受极端气候影响的完整和退化系统中的微生物碳循环过程，极端气候正变得越来越频繁。普遍的共识是，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)。这个博士项目将严格测试微生物功能和碳固存速率对极端气候的响应。基因和表型测量的组合将使该项目能够将微生物特征与不同处理组合下的碳固留率联系起来。综上所述，这些知识将为更好地预测和管理泥炭地微生物过程提供基础，以加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.