Impact of the drought in England on carbon dioxide fluxes from lowland peatland in the East Anglian fens across a land use gradient

英格兰东南部和东部的大部分地区最近被宣布处于干旱状态。2012年2月20日，环境部长卡罗琳·斯佩尔曼宣布进入干旱状态，理由是担心饮用水供应、地下水资源减少以及可能的用水限制。干旱对东英吉利低地泥炭土壤造成了明显的影响，由于泥炭收缩，那里的路面已经开始破裂。干旱创造了一个意想不到的科学机会来衡量其对沼泽地生态系统温室气体排放的影响。这笔赠款将在剑桥郡威肯芬附近的一块农田上建立一个测量站，以测量温室气体排放。我们将测试干旱条件是否导致低地泥炭地二氧化碳排放增加，以及湿地恢复是否比农田更具抗旱能力。除了干旱对基础设施和供水的直接影响外，迫切需要研究对碳循环和辐射强迫的影响。气候模型的预测通常表明，以前罕见的极端事件发生的频率越来越高。因此，由于全球平均气温的上升，有理由预计，像英国今年春天经历的那样，长期干旱的情况可能会更频繁地发生。必须开始记录干旱条件下碳通量的直接测量，以获得干旱条件对碳影响的定量证据。英格兰低地泥炭土壤占地958平方公里，储存大量碳，由于其高农业生产力，受到非常高的土地利用压力。到目前为止，大多数来自英国泥炭地的二氧化碳和其他温室气体(GHG)通量的测量是在旱地毯状沼泽中收集的。有人怀疑，是否可以简单地假设地毯式沼泽温室气体通量适用于低地沼泽地。在英格兰，为了集约化农业，几乎所有的沼泽地都已被排干和耕种。在东安格利亚的沼泽，这导致泥炭的损失率约为1厘米年-1。自然英格兰(2010)是第一个提供英国泥炭土壤初始温室气体排放系数的国家。根据这份报告，仅退化的英国泥炭就被认为排放了大约300万吨二氧化碳。DEFRA和JNCC最近的泥炭地研究突出了对低地泥炭，特别是沼泽的温室气体通量估计的高度不确定性。在剑桥附近的威肯芬国家级自然保护区，生态和水文中心(CEH)和莱斯特大学(UOL)安装了两个涡旋协方差塔。在Sedge Fen的天然沼泽地(由CEH运营)和Baker Fen的湿地再生站点(由UOL运营)的二氧化碳通量测量提供了重要的时间序列数据，从而可以推断碳平衡。这两个通量塔是英国低地泥炭地唯一的测量站。目前测量的差距是在农业用沼泽地地区。这项NERC紧急拨款的目的是资助技术和研究人员在2012年及以后的生长季收集农业用沼泽地的涡动协方差二氧化碳测量数据，以记录当前干旱的影响和二氧化碳通量恢复到更正常的状态。

Large parts of South-Eastern and Eastern England have recently been declared to be in a state of drought. On 20 February 2012, Environment Secretary Caroline Spelman declared a state of drought, citing concerns about the drinking water supply, diminishing ground water resources and possible water use restrictions. The drought has led to visible impacts on East Anglian lowland peat soils in the fens, where road surfaces have started to crack due to peat contraction. The drought creates an unexpected scientific opportunity to measure its impacts on greenhouse gas emissions from fenland ecosystems. This grant will establish a measurement station on an agricultural field near Wicken Fen, Cambridgeshire, to measure greenhouse gas fluxes.We will test is whether the drought conditions lead to enhanced carbon dioxide emissions from lowland peatland, and whether wetland restoration increases resilience against drought in comparison to agricultural land.Besides the direct impacts of the drought on infrastructure and water supply, there is an urgent need to study the impacts on the carbon cycle and radiative forcing. Predictions by climate models generally suggest an increasing frequency of previously rare extreme events. As a result of the increase of global average temperature it is thus reasonable to expect that prolonged dry conditions like those currently experienced this spring in England could happen more often. It is imperative to start recording direct measurements of carbon fluxes during drought conditions to have quantitative evidence of the carbon impact of drought conditions.Lowland peat soils in England occupy 958 km2, store large amounts of carbon and are subject to very high levels of land use pressure because of their high agricultural productivity. To date, most measurements of CO2 and other greenhouse gas (GHG) fluxes from UK peatlands were collected in upland blanket bogs. There are doubts whether the blanket bog GHG fluxes can simply be assumed to apply to lowland fenland. In England, nearly all fenland has been drained and cultivated for intensive agriculture. In the fens of East Anglia, this has resulted in rates of peat loss of about 1 cm yr-1.Natural England (2010) were the first to provide initial GHG flux emission factors for English peat soils. According to this report, degraded English peats alone are thought to emit around 3 Mt CO2-eq yr-1. Recent peatland studies for DEFRA and JNCC have highlighted the high degree of uncertainty in GHG flux estimates for lowland peats and in particular for fens.At the Wicken Fen National Nature Reserve near Cambridge, the Centre for Ecology and Hydrology (CEH) and the University of Leicester (UoL) have installed two eddy covariance towers. The measurements of CO2 fluxes at the natural fenland site in Sedge Fen (operated by CEH) and the wetland regeneration site at Bakers Fen (operated by UoL) are providing important time-series data that allow inferences on the carbon balance. These two flux towers are the only measurement stations in lowland peatland in the UK.The gap in current measurements is in the agriculturally used fenland area.The purpose of this NERC urgency grant is to fund technical and research staff time to collect eddy covariance CO2 measurements over agriculturally used fenland in the growing season of 2012 and beyond to record the impacts of the current drought and the recovery of CO2 fluxes to a more usual state.