Network Cluster: Patterns and controls of ecohydrology, CO2 fluxes, and nutrient availability in pedogenic carbonate-dominated dryland critical zones

关键地带是地球表面从树木顶部到地下水底部的一层。岩石、土壤、水、空气和生物在临界区相互作用，提供维持生命的资源，如食物和水。干旱至半干旱气候的旱地覆盖了地球的45%，为20多亿人提供了家园。美国西部的旱地正面临着全球变化带来的重大挑战，比如干旱和植物群落的变化。人口和粮食需求的增加也使该地区的许多天然旱地变成了灌溉农田。这些土地利用和气候的变化极大地影响了旱地不同地区的水、碳、营养物质和盐的流动。所有这些变化都影响着自然和农业生态系统的可持续性。该项目将研究这些重要的关键区域过程，并提高我们预测未来变化的能力。具体来说，这个专题集群将调查干旱土壤中的碳酸盐矿物如何控制和影响水、营养物质、盐和碳进出临界区。该项目将有助于教育和培训初高中学生，以及大学本科生和研究生。这些学生将获得动力、技能和工具，成为未来科学、技术、工程、艺术和数学（STEAM）领域的专业人士。我们的研究和教育工作也将有助于提高公众对旱地关键地带功能和服务重要性的认识。旱地生态系统中的临界带是地球系统中一个尚未得到充分研究但又至关重要的部分。它与中土区相比，植被稀疏，土壤湿度有限但动态，地下水位深，土壤有机质低，pH值碱性，盐沉淀积聚，特别是成土碳酸盐，可以发育成厚的钙层，主导土壤结构。然而，这些系统在关键带研究中代表性不足，目前的概念模型不能完全解决旱地特有的现象，如成土碳酸盐的发育、沙尘暴、偶发性降水以及水文和生物地球化学过程的高时空变异性。为了填补这些知识空白，该项目的总体目标是通过研究水和养分有效性在调节旱地关键地带有机碳和无机碳运动中的作用，提高我们在土地利用和气候梯度上量化和预测旱地碳预算的能力。具体来说，该项目围绕着成土碳酸盐在决定典型旱地景观、山前、盐湖和灌溉农田的渗透带水动力学、深部地下水潜在补给和养分循环方面的多方面作用展开。这些反过来又推动了关键带结构和陆地-大气C交换的演变趋势。我们将通过使用一套全面的工具来解决这些问题，包括涡旋相关塔、深临界带钻探、水文地球物理调查、土壤和水文传感器、同位素分析、同步加速器、地球化学代理和基因测序。该项目建立在丰富的历史数据、知识和模型的基础上，这些数据来自Jornada LTER、Reynolds Creek CZO、爱达荷州的USDA-ARS金伯利遗址和德克萨斯州里约热内卢格兰德河谷沿岸的灌溉农业遗址。该专题集群将开发一个跨学科框架，以了解通过旱地关键地带的物质和能量流动，并为管理关键地带的功能、演变和服务以及预测未来旱地气候和土地利用变化的碳预算变化奠定基础。该项目由关键区域协作网络和地球科学司水文科学项目以及教育和人力资源部人力资源开发司的西班牙裔服务机构项目共同资助。该奖项反映了美国国家科学基金会的法定使命，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。

The Critical Zone is the layer of Earth’s surface from the top of the trees to the bottom of the groundwater. Rocks, soil, water, air, and living organisms interact in the Critical Zone to provide life-sustaining resources such as food and water. Drylands, with arid to semi-arid climates, cover 45% of the Earth and provide homes to more than 2 billion people. The drylands of the American West are facing significant challenges caused by global change, such as drought and changing plant communities. Increases in human population and food demand have also converted many natural drylands in this region to irrigated farms. These changes in land use and climate have greatly affected the movement of water, carbon, nutrients and salt through different parts of the drylands. All of these changes impact the sustainability of natural and agricultural ecosystems. This project will investigate these important Critical Zone processes and improve our ability to predict future change. Specifically, this thematic cluster will investigate how carbonate minerals in dryland soils control and impact water, nutrients, salts, and carbon moving in and out of the Critical Zone. This project will help to educate and train middle to high school students, and college undergraduate and graduate students. These students will be provided with the motivation, skills and tools to become future professionals in science, technology, engineering, arts, and mathematics (STEAM). Our research and education efforts will also help to grow public awareness of the importance of the Critical Zone function and service in drylands.The Critical Zone in dryland ecosystems is an understudied but crucial part of the Earth system. It contrasts with mesic areas by having sparse vegetation, limited but dynamic soil moisture, deep water table, low soil organic matter, alkaline pH, and buildup of salt precipitates, especially as pedogenic carbonates that can develop into a thick caliche layer and dominate the soil structure. However, these systems are underrepresented in Critical Zone research and current conceptual models do not fully address phenomena unique to drylands such as development of pedogenic carbonate, dust storms, episodic precipitation, and high spatiotemporal variability in hydrological and biogeochemical processes. To fill these knowledge gaps, the overarching goal of the project is to increase our capacity to quantify and predict dryland carbon budgets across land-use and climatic gradients by examining the role of water and nutrient availability in regulating the movement of organic and inorganic carbon in the dryland Critical Zone. Specifically, this project centers around the multifaceted roles of pedogenic carbonates in dictating vadose zone water dynamics, the potential recharge to deep water table, and nutrient cycling in typical dryland landscapes, piedmont, playa and irrigated agricultural fields. These in turn drive trends in evolution of Critical Zone architectures and land-atmosphere C exchange. We will tackle these problems by using a comprehensive set of tools including eddy covariance towers, deep Critical Zone drilling, hydrogeophysical surveys, soil and hydrologic sensors, isotopic analysis, synchrotron, geochemical proxies, and genetic sequencing. This project builds on the rich historical data, knowledge, and models at the Jornada LTER, the Reynolds Creek CZO, USDA-ARS Kimberly site in Idaho and irrigated agricultural sites along the Rio Grande Valley in Texas. This thematic cluster will develop an interdisciplinary framework to understand material and energy flow through dryland Critical Zones and lay the foundation for managing Critical Zone function, evolution, and services, as well as forecasting carbon budget changes with future shifts in climate and land use in drylands.This project is jointly funded by the Critical Zone Collaborative Network and the Hydrologic Sciences programs in the Division of Earth Sciences and the Hispanic Serving Institutions program in the Education and Human Resources Directorate's Division of Human Resource Development.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.