EAGER: Comparative Study of Critical Zones of Intensively Managed Loess Landscapes in China and United States

美国中西部和中国西部是世界上最大的粮食生产地区之一，它们已经通过人类活动进行了广泛的改造。虽然它们有不同的地质历史，但它们有一个共同的属性，因为它们都被风沉积的土壤覆盖，也称为黄土。美国的冰川遗产是在相对平坦的景观中形成的，历史上支持水，有机物和化学成分的长停留时间。这一点已经大大改变，以支持工业化农业。另一方面，中国的黄土高原具有陡峭的坡度，导致水和沉积物的停留时间短，运输迅速。虽然美国的主要挑战是通过瓦片排水和渠化来排水，使其适合农业，但黄土高原面临着限制水和沉积物流动的相反挑战。建议的工作的目标是发展一个预测性的了解中国黄土高原（CLP）的动态下的人为影响，并比较和对比，在美国中西部地区的集约化管理的景观（IML）。IML和CLP都在美国和中国的粮食生产的关键地区，分别经历了密集的人类活动。CLP和IML的联合研究，使用各自环境中的临界带观测站（CZO），与Xi的中国科学院地球环境研究所（IEE/CAS）合作，将促进合作和联合勘探具有非常不同的地质和人类影响历史的黄土系统。该项目将支持一名研究生，他将对美国和中国的对比景观形成独特的理解和欣赏。美国中西部的IML已经从一个主要以转化为主的系统转变为一个以运输为主的系统，其特征是水，碳和营养物质的长停留时间，其特征是水，沉积物，碳和营养物质的快速移动。和养分通过景观和瓷砖排水沟进入接收水体。这种通过土地用途转换实现的从变压器到运输器的框架适用于温带气候中的低梯度景观，如北美和北方欧洲通过冰川作用形成的景观。与此相反，本研究假设，中国黄土高原正在经历一个运输机到Transformer转换的高度解剖景观，半干旱半湿润的气候，由于大规模的政府领导的努力，以减少侵蚀，开垦农业用地的山坡上重新植被和填充山谷，创造土地的农业，不易受到侵蚀。这种土地用途的转换，历史上作为运输，Transformer通过增加停留时间，通过人为行为是突出的许多部分的中电。在IML和中电的CZO中，景观通过人类基础设施和能源投入保持不平衡，以实现社会目标。通过建立临界区观测站来探测近地表环境的做法正在地球仪上广泛开展。这为利用基于地点的研究得出普遍的结论和发展广泛适用的原则提供了巨大的机会，并建立了当地行为的独特特征。IMLCZO在理解人类改造对关键区的影响方面是独一无二的，特别是在美国过去10，000年至500，000年发展的黄土表面环境中。 与之相反，中国黄土高原经过2000多万年的形成，其地貌形态与黄土高原有很大的不同，如高度侵蚀造成的解剖地貌。 然而，这一景观也受到人类的重大影响，并正在积极地重新塑造，以维持农业，减少侵蚀，保护自然植被。两种环境之间的比较研究将有助于通过制定更好地支持可持续做法的一般原则来推进科学。

Midwestern United States and Western China are among the largest food producing regions of the world, and they have been extensively modified for this purpose through human activities. Although they have different geologic history, they share a common attribute as both are overlain by wind deposited soil, also called loess. The glacial legacy in the U.S. was created in relatively flat landscape that has historically supported long residence times of water, organic matter, and chemical constituents. This has been significantly altered to support industrial agriculture. On the other hand, the loess plateau in China exhibits sharp gradients resulting in small residence times and rapid transport of water and sediment. While the primary challenge in the U.S. has been to drain the landscape through tile drain and channelization to make it suitable for agriculture, the loess plateau faces the opposite challenge of constraining the flow of water and sediment. The objective of the proposed work is to develop a predictive understanding of the dynamics of Chinese Loess Plateau (CLP) under anthropogenic impacts, and compare and contrast them to that in intensively managed landscapes (IML) in the Midwestern U.S. Both IML and CLP are in critical food production regions of the U.S. and China, respectively, and have experienced intensive human alternations. The joint study of CLP and IML, using Critical Zone Observatories (CZOs) in the respective environments, proposed here in collaboration with the Institute of Earth Environment, Chinese Academy of Science (IEE/CAS) in Xi'an, will foster collaboration and joint exploration of loess systems with very different geologic and human impact histories. The project will support a graduate student who will develop a unique understanding and appreciation of the contrasting landscapes in the U.S. and China.The IML in the U.S. Midwest has been transformed from a primarily transformation-dominated system, characterized by long residence times of water, carbon, and nutrients, to a transport-dominated system characterized by fast movement of water, sediment, carbon, and nutrients through the landscapes and tile-drains into receiving water bodies. Such a transformer-to-transporter framework through land use conversion is applicable to low-gradient landscapes in temperate climate such as those in North America and northern Europe that have been sculpted through glaciation. In contrast, this study hypotheses that the Chinese loess plateau is experiencing a transporter-to-transformer conversion in the highly dissected landscapes, with semi-arid to semi-humid climate, due to the large scale government led effort to reduce erosion by reclaiming agricultural land on hillslopes for re-vegetation and filling valleys to create land for agriculture that are less prone to erosion. This land use conversion, which has historically functioned as transporter, to transformer by increasing residence time through human action is prominent in many parts of the CLP. In both the IML and the CLP CZOs, the landscapes are maintained out of equilibrium through human infrastructure and energy input to achieve societal goals. The exploration of the near-surface environment through the establishment of Critical Zone observatories is becoming wide spread across the globe. This provides tremendous opportunities for using place-based studies to draw generalized conclusion and develop principles that are broadly applicable, and also establish distinguishing characteristics of local behavior. IMLCZO is unique in understanding the impact of human modification in the Critical Zone, particularly in the loess surficial environment developed over the last 10,000 years to 500,000 years in the United States. In contrast, the Chinese loess plateau has formed over 20 million years and has dramatically different landscape, such as dissected landscape caused by high erosion. However, this landscape is also under significant human influence and is actively being re-sculpted to sustain agriculture, reduce erosion, and conserve natural vegetation. A comparative study between the two environments will allow to advance science by developing generalized principles that better support sustainable practices.