Refining Estimates of Tropical Forest Greenhouse Gas Exchange using Plant Traits

利用植物性状对热带森林温室气体交换进行细化估计

• 批准号: NE/W006111/1
• 负责人: Niall McNamara
• 金额: $ 36.6万
• 依托单位: UK CENTRE FOR ECOLOGY & HYDROLOGY
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2022
• 资助国家: 英国
• 起止时间: 2022 至 无数据
• 项目状态: 未结题
• 来源: https://gtr.ukri.org/projects?ref=NE%2FW006111%2F1
• 关键词: Refining; Estimates; Tropical; Forest; Greenhouse

Tropical forests play a crucial role in regulating global concentrations of greenhouse gases, exchanging vast amounts of carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) with the atmosphere. The importance of tropical forests as both a source and substantial sink of CO2 is well established, but we know much less about the contribution of tropical forests to global CH4 and N2O budgets. Quantifying CH4 and N2O exchange in tropical forests is important because, although wetland tropical forests are a large source of CH4, free-draining tropical soils are a source of N2O but a sink for CH4. Trees can also act as conduits for greenhouse gases, and our recent work demonstrated that tropical trees on free-draining soils can emit or take up both CH4 and N2O. However, the contribution of trees to tropical forest greenhouse gas budgets is entirely unknown and we do not know whether tropical forest trees on free-draining soils will act as an overall sink or source for CH4 and N2O. We urgently need to address this knowledge gap because tropical forests on free-draining soils cover vast areas of land and are being destroyed or disturbed by human activities at an alarming rate. To quantify the role of tropical trees in global greenhouse gas budgets, we need an approach that allows us to translate local or regional measurements into models that can represent tropical forests across much larger scales. Our project will develop such an approach by quantifying the emissions and uptake of CH4 and N2O by tropical forest soils and trees, and determining the extent to which these greenhouse gas fluxes are influenced by specific characteristics of tropical trees.Trees can influence the production or consumption of greenhouse gases in the soil because root activity and plant litter inputs alter soil chemistry and microbial activity. Similarly, uptake or emission of greenhouse gases through stems, branches and leaves varies widely among tree species with distinct traits such as wood density, growth rate, or foliar chemistry. Our project will establish how such tree traits influence greenhouse gas fluxes by taking detailed measurements of CH4 and N2O fluxes from trees and the surrounding soil. In the first year of the project, we will determine the relationships between greenhouse gas fluxes and differences in soil chemistry or tree traits for six tree species at an intensive study site in tropical forest in Panama, Central America. In the second year of the project, we will expand our studies to multiple sites along a rainfall gradient to assess greenhouse gas fluxes from soils and trees for a larger range of species, and to identify the influence of changes in rainfall. Hence, our field measurements will provide the first ever comprehensive assessment of CH4 and N2O fluxes from tropical trees on free-draining soils, representing an entirely new component of the tropical greenhouse gas budget. In the final year of the project, we will use our data on variation within and among sites, species and individual trees to construct models that estimate total forest greenhouse gas fluxes using a combination of relevant plant traits and rainfall data. We will apply our models to 15 plots along the rainfall gradient to obtain estimates of forest greenhouse gas exchange across the landscape. By using tree traits rather than species identities, our approach will offer a way to estimate greenhouse gas uptake and emissions across wide areas of the tropics, which will improve the representation of tropical forests in global greenhouse gas budgets and inform impact assessments of tropical land-use change.

热带森林在调节全球温室气体浓度，将大量二氧化碳（CO2），甲烷（CH4）和一氧化二氮（N2O）与大气中交换。热带森林作为二氧化碳的来源和实质性水槽的重要性已经确立，但是我们对热带森林对全球CH4和N2O预算的贡献的了解较少。量化热带森林中的CH4和N2O交换很重要，因为尽管湿地热带森林是CH4的大量来源，但自由饮用的热带土壤是N2O的来源，但CH4的水槽是水。树木还可以充当温室气体的管道，我们最近的工作表明，自由枯燥的土壤上的热带树可以散发或占用CH4和N2O。但是，树木对热带森林温室气体预算的贡献是完全未知的，我们不知道自由流血的土壤上的热带林木是否会充当CH4和N2O的整体水槽或来源。我们迫切需要解决这一知识差距，因为自由流血的土壤上的热带森林涵盖了广阔的土地，并以惊人的速度被人类活动摧毁或打扰。为了量化热带树在全球温室气体预算中的作用，我们需要一种方法，使我们能够将局部或区域测量值转化为可以代表大量尺度上热带森林的模型。我们的项目将通过量化热带森林土壤和树木对CH4和N2O的排放和吸收来开发这种方法，并确定这些温室气通量在多大程度上受热带树木的特定特征的影响。树可以影响土壤中温室气体的生产或消费，因为根活动和植物杂货不多，因为根源和植物垃圾散布了土壤化的土壤化学活动。同样，通过茎，树枝和叶子的温室气体吸收或排放在具有不同特征的树种中，木材密度，生长速率或叶面化学的不同。我们的项目将通过对树木和周围土壤中的CH4和N2O通量进行详细测量来确定此类树状如何影响温室气通量。在项目的第一年，我们将在中美洲巴拿马的热带森林中的一个密集的研究地点确定温室气通量与六种树种的土壤化学或树木特征之间的差异之间的关系。在该项目的第二年，我们将沿降雨梯度扩展到多个地点，以评估来自土壤和树木的温室气体通量，以确定降雨变化的影响。因此，我们的现场测量将对自由干燥的土壤中热带树木的CH4和N2O通量进行首次全面评估，这是热带温室气体预算的全新组成部分。在项目的最后一年中，我们将使用有关地点，物种和单个树木内以及各个树木之间的变化数据来构建模型，以使用相关植物特征和降雨数据的组合来估算森林温室气体通量。我们将把模型应用于沿降雨梯度的15个地块，以获取整个景观中森林温室气体交换的估计。通过使用树状特征而不是物种身份，我们的方法将提供一种估计热带地区广泛地区温室气体吸收和排放的方法，这将改善热带森林在全球温室气体预算中的代表，并为热带土地利用变化的影响评估提供影响。