Stabilisation of pyrogenic carbon in tropical grasslands (SPECTRAL)

热带草原热解碳的稳定（光谱）

• 批准号: NE/T008040/1
• 负责人: Jens-Arne Subke
• 金额: $ 75.75万
• 依托单位: University of Stirling
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2020
• 资助国家: 英国
• 起止时间: 2020 至 无数据
• 项目状态: 未结题
• 来源: https://gtr.ukri.org/projects?ref=NE%2FT008040%2F1
• 关键词: Stabilisation; pyrogenic; carbon; tropical; grasslands

Every year, fires burn more than 500 million ha of the land surface on Earth. These fires leave residues of partially burned biomass which are deposited on the soil surface as "pyrogenic carbon" (PyC). It is estimated that as much as 114 to 379 Tg of PyC are added to soils each year, and global models predict that fire frequency and intensity will increase in many areas. Much of this PyC is deposited on to the soil surface and subsequently incorporated into deeper layers, so that it can account for as much as 50% of total carbon stored in soils in some fire prone ecosystems such as tropical savannahs.Storage of pyrogenic carbon in soils matters a lot to the way in which natural and managed ecosystems interact with the global climate system. PyC has an inherently slow turnover once it is in the soil, meaning that it will persist much longer than organic matter deposited on or in soils that have not been exposed to fire. Remarkably, however, we largely ignore the fate and overall contribution of PyC to global carbon cycling. This is due to the fact that the scientific community so far only has a rudimentary understanding of what determines PyC distribution and turnover in soils. There have been significant advances in understanding the role of charred biomass added to soil as an agricultural practice, and we have a reasonable understanding of these systems and how it interacts with soil organisms and physical factors. However, we require a much better understanding of processes underlying the changes of PyC particles, and stabilisation of carbon introduced to the soil after fire, in order to model current PyC dynamics, and be able to forecast these under future climates. Particularly biological processes, such as the role of invertebrate soil animals and different groups of soil microbial organisms have so far not received sufficient attention. We propose a programme of research directed at creating a novel soil-PyC model that can be linked to regional and global carbon-climate models, which so far ignore PyC. We will achieve this through a number of experiments based in a tropical savannah system in Gabon. This provides an ideal experimental set-up, as these fire prone systems have a significant abundance of PyC in the soil profile, and we will be able to link to a long-term fire manipulation field experiments in the Lopé National Park. Using targeted soil coring for contrasting fire return intervals, combined with the determination of the age of PyC (usingnatural 14C abundance) across the profile, we will be able to derive residence times of this stable soil carbon reservoir. By using isotopically labelled PyC (based on plants grown under enrichment with 13C, a non-harmful, stable isotope of carbon), we aim to gain a better mechanistic and quantitative understanding of soil PyC dynamics. This approach is linked to manipulations of soil animal presence, as these are hypothesised to have a significant influence over the distribution and turnover of PyC in the soil. Insights from the isotopic tracer study will be used to develop a novel soilorganic matter model to incorporate PyC dynamics for the first time, We will be able to parameterise this new model with our experimental data and validate simulated turnover against our independently assessed turnover time of PyC pools.

每年，大火烧毁了地球表面超过5亿公顷的土地。这些火灾留下了部分燃烧的生物质残留物，这些残留物以“热源碳”(PYC)的形式沉积在土壤表面。据估计，每年向土壤中添加的热解碳高达114至379Tg，全球模型预测，许多地区的火灾频率和强度将会增加。这些热解碳大部分沉积在土壤表面，然后结合到更深的层，因此在一些易起火的生态系统，如热带稀树草原，它可以占土壤中储存的总碳的50%。土壤中热源碳的储存对自然和管理的生态系统与全球气候系统相互作用的方式非常重要。PYC在土壤中的周转速度本来就很慢，这意味着它比沉积在没有暴露在火中的土壤上或土壤中的有机物持续的时间要长得多。然而，值得注意的是，我们在很大程度上忽视了PYC对全球碳循环的命运和总体贡献。这是因为到目前为止，科学界对决定土壤中热解碳分布和周转的因素只有一个初步的了解。在理解添加到土壤中的烧焦生物质作为一种农业实践的作用方面取得了重大进展，我们对这些系统以及它如何与土壤有机体和物理因素相互作用有了合理的理解。然而，我们需要更好地了解PYC颗粒变化的潜在过程，以及火灾后引入到土壤中的碳的稳定性，以便对当前的PYC动态进行建模，并能够在未来气候下预测这些变化。特别是生物过程，如无脊椎动物和不同类型的土壤微生物的作用，迄今没有得到足够的重视。我们提出了一个研究计划，旨在创建一种新的土壤-热带雨林模型，该模型可以与区域和全球碳-气候模型联系起来，而这些模型到目前为止还忽略了热带雨林。我们将通过以加蓬热带大草原系统为基础的一些实验来实现这一点。这提供了一个理想的实验装置，因为这些易着火系统的土壤剖面中有大量的PYC，我们将能够链接到洛佩国家公园的长期火灾操纵现场实验。使用目标土壤取心来对比火返时间间隔，结合整个剖面上PYC年龄的确定(使用自然14C丰度)，我们将能够推导出这个稳定的土壤碳库的停留时间。通过使用同位素标记的热解碳(基于富含13C的植物)，我们的目标是更好地从机理和定量上了解土壤热解碳的动态。这种方法与土壤动物存在的操纵有关，因为这些假设对土壤中PYC的分布和周转有重大影响。来自同位素示踪研究的见解将被用于开发一个新的土壤-有机质模型，首次纳入热解动力学，我们将能够用我们的实验数据对这一新模型进行参数化，并根据我们独立评估的热解碳池的周转时间来验证模拟的周转。