Sand Hills Biocomplexity: Integrating Biogeophysical Processes across Space and Time

该项目研究了过去几千年来，58000平方公里内布拉斯加州沙丘（西半球最大的沙丘区）中沙子、草和水之间的相互作用。地质记录表明，沙丘在全新世经历了多次沙漠化和恢复的循环，大多数沙丘被认为不到9000年。如今，沙丘几乎完全被原生草原所稳定。早在1000年前，严重的干旱就破坏了沙丘的大部分地区的稳定，但沙丘在随后的几次区域性干旱中保持了它们的草覆盖并抵抗了移动。本文提出的研究将启动大规模的可操作实验，以验证关于植被退化对地下水补给影响的四个假设。结合地表能量通量的微气象测量，该结果将为（无）植被地表与区域气候之间反馈的中尺度模拟情景提供输入。研究人员还将使用光学刺激发光测年法来绘制过去2500年沙丘活动的空间格局，湖泊沉积物分析提供过去干旱的更高分辨率（十年）记录。该系统将作为生物地球物理过程如何相互作用以产生景观抗性和生态弹性的模型。沙丘结构相对简单，面积大，足以影响边界层动力学。这将是第一个使用这样一个综合的、跨学科的项目来了解沙山的项目。为了这项任务，来自古生态学、地貌学、生态学、地理空间分析和气象学等学科的一系列科学家聚集在一起。就更广泛的影响而言，该项目可以作为K-12和大学水平的复杂环境变化跨学科教学的典范系统。非线性和反馈对任何走过这片景观的人来说都是非常真实的，尤其是在最近的沙丘井喷之后。该项目将整合一个已经取得成功的K-12科学教师网络，包括科学教育者的暑期实习和研讨会，以及一个带有数据可视化工具的网站，将数据提供给学生。该项目还将培训30多名研究生和本科生实习生，使他们接触到当代环境科学的广度。

This project addresses the interactions among sand, grass, and water over 58,000 km2 Nebraska Sand Hills, the largest sand dune area in the Western Hemisphere, over the last few thousand years. The geologic record indicates that the Sand Hills have gone through cycles of desertification and restoration several times in the Holocene and most dunes are thought to be less than 9000 years old. Today the dunes are almost entirely stabilized by native grasslands. Major droughts destabilized significant portions of the Sand Hills as recently as 1000 years before the present, but the dunes have maintained their grass cover and resisted mobilization during several subsequent regional droughts.The research proposed here would initiate a large-scale manipulative experiment to test four hypotheses regarding the effect of devegetation on groundwater recharge. Coupled with micrometeorological measurements of surface energy fluxes, the results will provide inputs for mesoscale modeling scenarios of the feedbacks between the (de-)vegetated land surface and the regional climate. The investigators will also use optically stimulated luminescence dating to map the spatial pattern of dune field activity during the last 2500 years, with lake sediment analyses providing a more high resolution (decadal) record of past droughts.This system will serve as a model for how biogeophysical processes interact to yield landscape resistance and ecological resilience. The structure of the Sand Hills is relatively simple and the area large enough to influence boundary layer dynamics. This will be the first project to understand the Sand Hills using such an integrated, cross-disciplinary project. A range of scientists from such disciplines as paleoecology, geomorphology, ecology, geospatial analysis, and meteorological has been assembled for this task.. In terms of Broader Impacts, this project can serve as a model system for interdisciplinary teaching about complex environmental change both at the K-12 as well as university levels. Nonlinearities and feedbacks are very real to anyone walking through this landscape, especially after recent dune blowouts. The project will incorporates an already successful ongoing K-12 science teacher network, including summer internships and workshops for science educators, and a web site with data visualization tools that puts data in the hands of students. The project will also train over 30 graduate students and undergraduate interns, exposing them to the breadth of contemporary environmental science.