Quantifying carbon accumulation and loss in Russian Arctic peatlands

俄罗斯（和北美）的泥炭地是全新世期间主要的陆地碳库和大气二氧化碳的天然汇（Charman et al., 2013），其碳储量约为6120亿吨，比世界上的活植被储量还要大。这种碳储量的持久性取决于内涝，而内涝可能受到大气温度上升、降雨模式变化、人为干扰、灌木主导群落的覆盖和高度增加以及高纬度生态系统中更频繁的火灾的威胁（Young et al., 2017）。在泥炭层中记录的“自然实验”使得测量和确定以前湿润/干燥气候条件时期的碳积累率成为可能。通过计算泥炭剖面样品中保存的大化石木炭碎片的数量，可以很容易地确定燃烧。以前火灾的燃烧强度也可以使用拉曼光谱来估计（Muirhead et al., 2017）。降雨和蒸发平衡的变化驱动泥炭地地表湿度的变化，利用前植被的保存遗迹（植物大化石）可以在年代际、百年和千年时间尺度上重建泥炭地地表湿度的变化。保存的微生物组合的变化（无性变形虫）也可以用来提供以前地下水位深度的定量重建，在这些生态系统中，地下水位依赖于大气水分平衡（降雨减去蒸发）。为了了解俄罗斯北极泥炭地碳积累速率、燃烧时的火灾强度、泥炭地表湿度和植物类型之间的长期相互作用，必须采用多代理方法。这种水平的研究细节仍然相对罕见，所以这个学生将提供一个令人兴奋的机会，在以前的燃烧扰动和气候变化时期（十年，百年和千年时间尺度）对俄罗斯北极泥炭地的长期碳封存进行取样和调查。如果没有可靠的年表，这些环境重建的价值将受到限制，因此本研究的关键部分将指向贝叶斯年龄/建模技术。

Peatlands in Russia (and North America) are a major terrestrial carbon store and a natural sink for atmospheric CO2 during the Holocene (Charman et al., 2013, holding around 612 gigatonnes of carbon, which represents a larger stock than the worlds live vegetation. Persistence of this carbon store depends upon waterlogging, which may be threatened by rising atmospheric temperatures, shifting rainfall patterns, anthropogenic disturbance, increases in the cover and height of shrub dominated communities and more frequent fires in high-latitude ecosystems (Young et al., 2017). 'Natural Experiments' recorded in the peat layers make it possible to measure and date carbon accumulation rates during former periods of wetter/drier climatic conditions. Burning can be readily identified by counting the number of macrofossil charcoal fragments preserved in peat profile samples. The burning intensity of former fires can also be estimated using Raman spectroscopy (Muirhead et al., 2017). Changes in the balance between rainfall and evaporation drive changes in peatland surface wetness, which can be reconstructed on decadal, centennial and millennial timescales using the preserved remains of the former vegetation (plant macrofossils). Changes in the preserved microorganism assemblages (testate amoebae) can also be used to provide quantitative reconstructions of former water table depths, which in these ecosystems is dependent upon the atmospheric moisture balance (rainfall minus evaporation). In order to understand the long-term interaction between carbon accumulation rates, fire intensity during burning, mire surface wetness and the types of plants growing in Russian Arctic peatlands, a multiproxy approach is essential. This level of research detail is still relatively rare, so this studentship will offer an exciting opportunity to sample and investigate the long-term carbon sequestration of Russian Arctic peatlands during previous periods of burning disturbance and climate change (on decadal, centennial and millennial timescales). Without robust chronologies the value of these environmental reconstructions will be limited, so a key part of this research will be directed towards Bayesian age/modelling techniques.