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

减缓全球变暖需要全面了解大气和土地之间的碳交换。近地表陆地碳储存通常集中在地上植物和土壤中的有机碳，尽管这些形式的碳相对不稳定。碳酸钙（CaCO 3）是一种经常被忽视的矿物，作为土壤中长期稳定的碳储存。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死亡植物材料中的草酸钙，从而形成CaCO 3。这种碳酸盐-碳酸盐途径（OCP）提供了一种天然的、潜在的快速方式，将大气中的CO2-碳以固体CaCO 3形式封存。该项目将调查如何通过土地利用变化和农业实践减少生物多样性的损失可能会减少转化为CaCO 3的碳量。该项目将通过一系列的实地考察，研究生交流和工作包，使用多学科的方法来了解OCP生态系统的重要性和恢复力，开发一个由生态学家，土壤科学家和地球化学家组成的国际团队。该项目旨在开发一套工具，最终可用于调查全球其他候选生态系统。许多这样的生态系统正在转变为农业，但生产力很低。该项目产生的知识将与土地使用者分享，为有关土地转换、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。该项目将调查功能性生物多样性的丧失如何以两种重要方式限制OCP的碳固存：1）清除原生的富含草酸钙的植被（通过耕作和/或过度放牧）和对巨型白蚁土丘的物理破坏（通过深耕）限制了草酸钙向土壤的供应; 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的功能性生物多样性方法来确定土壤微生物组合，这是拟议的碳封存途径的基石，以及它在干扰时如何变化;监测土壤孔隙空间表观呼吸商（产生的CO2与消耗的O2的比率）来空间和时间地非破坏性地解析土壤中的OCP;使用稳定的钙同位素来追踪钙在植物和土壤中的运动，以帮助评估OCP的时间综合重要性;并制定一种方法，红外光谱测量草酸钙和方解石的浓度，不依赖于先前的溶解或沉淀。这个奖项反映了NSF的基金会的使命是履行其法定使命，并通过使用基金会的知识价值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.