FAPESP - Amazon PyroCarbon: Quantifying soil carbon responses to fire and climate change

野火正在成为亚马逊地区的新常态。森林砍伐正在以每年约10，000平方公里的速度改变该地区（威尔士面积的一半），现在每年退化的面积-森林砍伐和燃烧但没有砍伐-大于森林砍伐面积。亚马逊河流域历来很少发生火灾，这意味着森林不适应火灾，树木经常死于火灾-将碳（C）释放回大气层并放大全球气候变化。在整个欧洲，燃烧热带森林已经释放出比燃烧化石燃料更多的气候变暖二氧化碳。亚马逊地区的树木所含的碳是人类每年释放的碳的7倍，土壤中的碳含量也是相同的，因此了解碳的变化并将排放量降至最低至关重要。随着植物的叶子、树枝和根脱落，或者死亡，一些释放的C保留在土壤中，一些随后分解并释放回大气中。碳以许多不同的形式存在于土壤中，从分解植物材料的新输入到数千年来形成的古老C。燃烧将热解碳（PyC）添加到土壤中，这是一种部分燃烧的C形式，它能抵抗分解，并能使土壤更加肥沃。由于土壤碳需要很长时间才能形成，因此其保护尤为重要。尽管亚马逊河流域的火灾普遍增加，但对烧毁地区土壤碳组分和动态的测量很少-大多数都集中在天然林上。被烧毁的森林将有不同的组成，森林结构和C动态。了解不同土壤碳组分的形成和损失对于了解火灾和气候变化如何影响碳储存至关重要。我们建议在理解火灾影响方面取得重大进展，包括影响土壤碳形成的类型和数量的过程，以及碳的获得/损失如何随时间变化，土壤类型和气候。我们将联合收割机与创新的模型相结合，为土地管理战略和C预算提供信息。至关重要的是，我们的项目将从人类改造的森林中收集一个新的、全面的数据集，包括砍伐、烧毁和废弃的土地。我们将使用一种称为时间序列的方法，在过去不同时间被烧毁的地点采集样本，这样我们就可以看到土壤C在火灾后1年、2年或20年内的变化。这将用于开发一个最先进的陆地表面模型，JULES，它是英国地球系统模型的一部分。在我们的采样点，我们将评估不同的烧伤严重程度如何影响土壤C，无论是在表层和深层土壤，以及这些如何随着时间的推移后燃烧和土壤，气候和土地利用，如伐木变化。在3个重点地点，我们将采取详细的测量分解率的C超过4年，比较测量不同的土地利用，烧伤的严重程度和干湿季节。知道C在火灾后的形式以及在不同条件下分解的速度将使我们能够将这些过程构建到JULES模型中。我们将首次在全球范围内对PyC进行建模，并在未来40-60年内，在不同的管理实践下，对亚马逊地区的土地碳变化进行预测。除了改变对火灾后土壤碳及其对气候和管理的适应能力的科学认识外，我们的项目还将为可持续资源利用的社会环境规划提供信息，以保护土壤碳。我们将与区域合作伙伴，消防管理人员，州和国家政策制定者合作，将我们的调查结果纳入决策，以尽量减少火灾的负面影响。由于我们的工作是在亚马逊流域进行的，这些策略是限制土壤碳大规模流失风险的关键一步。

Wildfires are becoming the new normal across Amazonia. Deforestation is transforming the region at a rate of around 10,000 square km/year (half the area of Wales), and now the area degraded annually -forest logged and burned but not cut down-is greater than the area deforested. Fire has historically been rare in Amazonia, meaning that the forests are not adapted to fire and the trees often die from fires - releasing carbon (C) back to the atmosphere and amplifying global climate change. Burning of tropical forests is already releasing more climate-warming carbon dioxide than fossil fuel burning in the whole of Europe. Trees in Amazonia contain around 7x more C than humans are releasing every year, and soils contain the same amount again, so it is vital to understand what is happening to this C and minimize emissions. As vegetation sheds its leaves, branches, and roots, or dies, some of the C released remains in the soil, and some is later decomposed and released back to the atmosphere. Carbon exists in the soil in many different forms, from new inputs from decomposing plant material to ancient C formed over millennia. Burning adds pyrogenic carbon (PyC) to the soil, a partially burnt form of C that is resistant to decomposition and could make the soil more fertile. Because soil C takes a long time to form, its conservation is particularly important. Despite the widespread increase in fire in Amazonia, there have been few measurements of soil C fractions and dynamics in burned areas - most have focussed on natural forests. Burned forests will have different composition, forest structure, and C dynamics. Understanding how different soil C fractions are formed and lost is crucial to understand how fire and climate change affect C storage. We propose to make major advances in understanding fire impacts, including the processes that affect the type and quantifies of soil C formed, and how C gains/losses vary over time, with soil type, and climate. We will combine new measurements with innovative modelling to inform land management strategies and C budgets.We have already collected data from across Amazonia in intact forests that have not recently burned. Crucially our project will collect a new, comprehensive dataset from human-modified forests, including logged, burned and abandoned land. We will use an approach known as a chronosequence, where we take samples at sites that were burnt at different times in the past, so we can see how the soil C has changed after e.g. 1 year, 2 years, or up to 20 years after a fire. This will then be used to develop a state-of-the-art land surface model, JULES, which forms part of the UK Earth System Model. At our sample sites, we will evaluate how different burn severities affect soil C, both in surface and deep soils, and how these change over time post-burning and with soil, climate, and land-use such as logging. At 3 focal sites, we will take detailed measurements of the decomposition rate of the C over 4 years, comparing measurements with different land-use, burn severity and wet vs dry seasons. Knowing what forms C takes after a fire and how fast it decomposes under different conditions will enable us to build these processes into the JULES model. We will model PyC globally for the first time and make projections of land C changes in Amazonia over the next ~40-60 years under different management practices. As well as transforming scientific understanding of post-fire soil C and its resilience to climate and management, our project will inform socio-environmental planning for sustainable resource use to conserve soil C. We will work with regional partners, fire managers, state and national policymakers to integrate our findings into decision-making to minimise negative fire impacts. Due to the Amazon Basin-scale of our work, these strategies are a crucial step to limit the risk of large-scale loss of soil C.