Collaborative Research: BoCP-Design: US-South Africa: Turning CO2 to stone: the ecosystem service of the oxalate-carbonate pathway and its sensitivity to land use change

缓解全球变暖需要对大气和陆地之间的碳交换有一个全面的了解。近地表的碳储存通常集中在地上植物和土壤中的有机碳上，尽管这些形式的碳相对不稳定。碳酸钙(CaCO3)是一种经常被忽视的矿物，被认为是土壤中长期稳定的碳库。在植物富含草酸钙的干燥环境中，某些细菌和真菌可以分解枯死植物材料中的草酸钙，这可能导致CaCO3的形成。这种草酸盐-碳酸盐途径(OCP)提供了一种天然的、潜在的快速将大气中的CO2-碳以固体CaCO3的形式隔离的方法。该项目将调查通过土地利用变化和农业实践造成的生物多样性丧失如何减少转化为CaCO3的碳量。该项目将通过一系列实地考察、研究生交流和工作包，建立一个由生态学家、土壤科学家和地球化学家组成的国际团队，利用多学科方法了解南非大开普省弗洛里斯特地区OCP生态系统的重要性和弹性。该项目旨在开发一种工具集，最终可用于调查世界各地的其他候选生态系统。许多这样的生态系统正在被转变为农业，但只是略微具有生产力。该项目将与土地使用者分享产生的知识，为土地转换、碳的潜在估值以及如何将其应用于提高货币收益的决策提供信息。该项目将调查功能生物多样性的丧失如何在两个重要方面限制OCP对碳的固定：1)移除富含草酸钙的原生植被(通过耕作和/或过度放牧)和物理破坏(通过深耕)限制向土壤供应草酸钙；2)土壤微生物多样性的丧失限制了有效草酸钙的分解。该跨学科项目将使用基于EDNA的功能生物多样性方法来确定作为拟议的碳固定途径的基石的土壤微生物组合及其在干扰下的变化；监测土壤孔隙空间表观呼吸商(产生的二氧化碳与消耗的O2的比率)，以在空间和时间上非破坏性地解决土壤中的OCP；使用稳定的钙同位素追踪钙在植物和土壤中的移动，以帮助评估OCP的时间整合重要性；并开发一种近红外和中红外光谱方法来测量草酸钙和方解石的浓度，而不依赖于先前的溶解或沉淀。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Mitigation of global warming requires a complete understanding of carbon exchange between the atmosphere and the land. Near-surface terrestrial carbon storage typically focuses on above-ground plants and organic carbon in soils, even though these forms of carbon are relatively unstable. Calcium carbonate (CaCO3) is a mineral that is regularly overlooked as a long-term and stable carbon store in soils. In dry environments where plants are rich in calcium oxalate, certain bacteria and fungi can decompose the calcium oxalate in dead plant material, which can lead to the formation of CaCO3. This oxalate-carbonate pathway (OCP) provides a natural and potentially rapid way to sequester atmospheric CO2-carbon as solid CaCO3. This project will investigate how loss of biodiversity through land-use change and agricultural practices may reduce the amount of carbon that is transformed into CaCO3. The project will develop an international team of ecologists, soil scientists, and geochemists through a series of fieldtrips, graduate student exchanges, and work packages that uses a multidisciplinary approach to understanding the importance and resilience of OCP ecosystems within the Greater Cape Floristic Region of South Africa. The project aims to develop a toolset that can ultimately be applied to investigate other candidate ecosystems worldwide. Many such ecosystems are being converted to agriculture but are only marginally productive. Knowledge generated from this project will be shared with land users to inform decisions on land conversion, the potential valuation of carbon, and how this could be applied to improve monetary yields.This project will investigate how the loss of functional biodiversity limits sequestration of carbon by the OCP in two important ways: 1) removal of native, calcium-oxalate rich vegetation (through farming and/or overgrazing) and physical disruption of giant termite mounds (through deep tillage) limits the supply of calcium-oxalate to the soil, and 2) loss of soil microbial diversity limits the breakdown of available calcium-oxalate. The interdisciplinary project will use eDNA-based functional biodiversity methods to identify the soil microbial assemblage that is the cornerstone of the proposed carbon sequestration pathway and how it changes upon disturbance; monitor the soil pore space apparent respiratory quotient (ratio of CO2 produced to O2 consumed) to spatially and temporally resolve the OCP non-destructively in soils; use stable Ca isotopes to trace the movement of calcium through plants and soils to help evaluate the time-integrated importance of the OCP; and develop a method for near and mid-infrared spectroscopy to measure Ca oxalate and calcite concentration that does not rely on prior dissolutions or precipitation.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.