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An improved empirical model of soil carbon dynamics in temperate ecosystems

温带生态系统土壤碳动态的改进经验模型

基本信息

批准号：
NE/D012848/1
负责人：
Guy Kirk
金额：
$ 22.54万
依托单位：
CRANFIELD UNIVERSITY
依托单位国家：
英国
项目类别：
Research Grant
财政年份：
2007
资助国家：
英国
起止时间：
2007 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=NE%2FD012848%2F1
关键词：
improved empirical model soil carbon

项目摘要

More than twice as much carbon is stored in soils as in vegetation or the atmosphere, and the global carbon budget and the concentration of carbon dioxide (CO2) in the atmosphere are sensitive to any changes in soil carbon. Previously it was thought that most soil carbon was safely locked away. But a recently-completed survey of the soils of England and Wales by members of the proposed project has shown losses of carbon over the past 25 years on an enormous scale: enough to cancel the UK's reductions in carbon emissions from fossil fuels. The survey measured carbon in soil samples from almost 6,000 sites across all types of land use / cropland, grassland, woodland, upland heath, bogs. It was first carried out in 1978-83 and then repeated at 40% of the sites between 1994 and 2003. Most sites showed losses, and the losses occurred across all types of land use. Whilst various changes in land management will have contributed to the losses / for example, the ploughing of grassland for crops in the 1950s / the fact that the losses occurred across all forms of land use suggests a link to climate change. The mechanisms for this are well known. At the moment, soils and vegetation are thought to absorb about a quarter of the CO2 emitted into the air from burning fossil fuels. The rate is increasing because plants are growing faster, fertilized by higher CO2 levels. But as temperatures rise, and the moisture content of the soil changes, the rate of turnover of dead vegetation and other organic matter in the soil and the corresponding release of CO2 are also increasing. At some point, the rate of release will overtake the rate of absorption, and the global land surface will switch from being a sink for CO2 to a source. Stabilising CO2 levels will then require much greater cuts in emissions. It was thought, based on computer modelling studies, this would take several decades. But the new results suggest it is happening already in England and Wales, implying an even greater urgency to cut emissions. Separating out the various possible causes of the losses across England and Wales is complicated. A huge variety of land management factors may be involved, and their effects interact with climate change. It is therefore impractical to make measurements of all the possible combinations of factors. In any case statistical relations derived from such measurements do not reveal cause-and-effect, and they are poor at revealing the sorts of non-linear relations and feedback processes that are operating. Some form of mathematical modelling is required, based on understanding of the underlying processes. But current models are inadequate for this. Here we propose to improve the best-existing soil carbon model for our purposes / the Century model / by improving its components dealing with soil carbon transformations, their dependences on soil moisture, temperature and other variables, and the calculations of soil moisture, temperature and other driving variables. We will bring together (1) the new, internationally-unique dataset discussed above on soil carbon changes over time across the large range of soils, climates and land uses in England and Wales; (2) the best existing models of soil carbon transformations and of the dynamics of associated soil conditions, and new approaches to modelling these; (3) new spatial statistical techniques for analyzing the datasets to be modelled and the soundness of the model's predictions; (4) four specialists in soil modelling with different perspectives on these topics, and two specialists in soil spatial statistics, all internationally-regarded for their expertise in these areas.

土壤中储存的碳是植被或大气中储存的碳的两倍多，全球碳预算和大气中二氧化碳（CO2）浓度对土壤碳的任何变化都很敏感。以前人们认为大多数土壤碳被安全地锁起来了。但该项目的成员最近完成的一项对英格兰和威尔士土壤的调查显示，过去25年来，碳损失规模巨大：足以抵消英国减少化石燃料碳排放的努力。该调查测量了来自所有类型土地使用/农田，草地，林地，高地荒地，沼泽的近6，000个地点的土壤样本中的碳。它于1978-83年首次进行，然后在1994年至2003年期间在40%的地点重复进行。大多数地点都出现了损失，损失发生在所有类型的土地使用中。虽然土地管理方面的各种变化可能是造成损失的原因之一，例如，1950年代开垦草地种植作物，但所有形式的土地使用都发生了损失，这一事实表明与气候变化有关。其机制是众所周知的。目前，土壤和植被被认为吸收了燃烧化石燃料排放到空气中的二氧化碳的四分之一。这一比率正在增加，因为植物生长得更快，二氧化碳含量更高。但是，随着温度的升高，土壤水分含量的变化，死亡植被和土壤中其他有机物的周转率以及相应的二氧化碳释放量也在增加。在某个时候，释放的速度将超过吸收的速度，全球陆地表面将从二氧化碳的汇转变为源。稳定二氧化碳水平将需要更大幅度的减排。根据计算机建模研究，人们认为这将需要几十年的时间。但新的结果表明，英格兰和威尔士已经发生了这种情况，这意味着减排的紧迫性更大。区分英格兰和威尔士损失的各种可能原因是复杂的。可能涉及各种各样的土地管理因素，其影响与气候变化相互作用。因此，对所有可能的因素组合进行测量是不切实际的。在任何情况下，从这种测量中得出的统计关系都不能揭示因果关系，而且它们也不善于揭示各种非线性关系和正在运作的反馈过程。需要在了解基本过程的基础上建立某种形式的数学模型。但目前的模型不足以做到这一点。在这里，我们建议改进现有的最好的土壤碳模型为我们的目的/世纪模型/通过改进其组件处理土壤碳转化，其依赖于土壤水分，温度和其他变量，土壤水分，温度和其他驱动变量的计算。我们将汇集（1）以上讨论的关于英格兰和威尔士大范围土壤、气候和土地利用随时间推移的土壤碳变化的新的、国际上独特的数据集;（2）现有的最佳土壤碳转化模型和相关土壤条件的动态模型，以及建模这些模型的新方法;（3）新的空间统计技术，用于分析拟建模的数据集和模型预测的可靠性;（4）四名对这些主题有不同看法的土壤建模专家和两名土壤空间统计专家，他们在这些领域的专业知识都受到国际认可。