EAR-PF Cracking the Critical Zone: Tree roots in fractures and a proposed mechanistic soil production function

Jill Marshall博士获得了美国国家科学基金会EAR博士后奖学金，在加州大学伯克利分校与科罗拉多大学博尔德分校合作开展一项研究和教育计划。她将开发数值模型来描述树根对土壤生产的影响。从了解景观演变到量化土壤可持续性，这项研究在关键地带科学的广泛问题中具有重要意义。调查将使用三个关键区域观测站（鳗鱼河、博尔德溪和南塞拉CZOs）收集的数据，这些观测站的地形很薄，甚至没有土壤和基岩暴露。这使得能够定量观察不同岩性和裂缝模式下不同地点的裂缝中生长的树根。生物力学土壤生产模型的发展将使人们更好地了解植被在土壤可持续性和恢复力中的作用。该教育计划位于加州圆谷（一个围绕圆谷印第安部落土地的鳗鱼流域的农村地区），有两个组成部分：针对学区学生的多年龄实地科学活动，以及为部落自然资源部举办的激光雷达研讨会。教育计划是在广泛的社区投入下制定的，这些协同活动满足了社区扩大科学活动的需要，并为未来的努力提供了工具。这个项目的研究将检验一个假设，即深度依赖的土壤产量是根压力、根密度随深度的变化以及由岩石特性调节的树摇的函数。为了建立一个描述土壤生成速率如何以及为何随深度变化的地貌运输规律，该项目将结合离散元法模拟，结合结合颗粒、岩石特性和基岩界面根压力的现场导出值，这些数据来自三个关键区域观测站收集的数据。将用力传感器监测一组受基岩阻碍的树根，以测量生长产生的外部树根压力、树木水分通量的日波动以及风和雪事件造成的树基部扭矩。水文路线、净初级生产力、土壤中的碳储量和地球化学反应器的矿物供应都与土壤生产速率有关。通过将树木驱动的过程纳入土壤生产的地貌过程规律，该项目将使数值实验能够探索植被的存在和缺失如何控制地表和近地表过程和景观形成。

Dr. Jill Marshall has been granted an NSF EAR Postdoctoral Fellowship to carry out a research and education plan at the University of California, Berkeley, in collaboration with the University of Colorado, Boulder. She will develop numerical models to describe the effect tree roots have on soil production. The investigation is important across a broad range of problems in critical zone science, from understanding landscape evolution to quantifying soils sustainability. The investigation will use data collected at three Critical Zone Observatories (Eel River, Boulder Creek, and Southern Sierra CZOs) that have patches of terrain with thin to no soils and bedrock exposures. This enables quantitative observations of tree roots growing in fractures across sites underlain by different lithologies and fracture patterns. The development of a biomechanical soil production model will allow for improved insight into the role of vegetation in soil sustainability and resilience. The education plan, based in Round Valley, CA (a rural region in the Eel watershed encompassing the Round Valley Indian Tribal Lands) has two components: multi-age field-based science activities directed at the school district's students and a LiDAR workshop for the Tribes' Natural Resource Department. The educational plans were developed with extensive community input and these synergistic activities meet the community's needs of expanding access to science activities and providing tools for future endeavors.Research in this project will test the hypothesis that depth-dependent soil production is a function of root pressures, variations in root density with depth, and tree sway modulated by rock properties. To develop a geomorphic transport law that describes how and why soil production rates vary with depth, this project will combine Discrete Element Method simulations incorporating bonded grains, rock properties, and field-derived values for root pressures at the bedrock interface from data collected at the three Critical Zone Observatories. A suite of bedrock-impeded tree roots will be monitored with force sensors to measure external root pressures generated from growth, diurnal fluctuations due to tree water fluxes, and torque about the tree base from wind and snow events. Hydrologic routing, net primary productivity, carbon storage in soils, and mineral supplies for the geochemical reactor are all linked to rates of soil production. By including tree-driven processes in a geomorphic process law for soil production, this project will enable numerical experiments that explore how the presence and absence of vegetation control surface and near-surface processes and landscape form.