CZO: Critical Zone Observatory--Snowline Processes in the Southern Sierra Nevada

美国西部山区的雨雪过渡区特别容易受到气候和土地覆盖的大规模和潜在快速变化的影响。 虽然这一地区具有快速的季节变化特征，在1-2个月的时间内从积雪到湿土再到干土，但气候变暖将提前或完全消除这一过渡期。 其结果将是重大变化的季节性到年际关键区过程，涉及水，养分和生态系统的反应，主要是混合针叶林在雨雪过渡带。 降水模式的陡峭梯度，沿着海拔和纵横向，加上快速的季节变化，使这一地区成为研究临界区过程如何对扰动作出反应的极好的天然实验室，特别是水循环如何驱动临界区过程。拟议的临界区观测站（CZO）将利用这些特征，建立一个雪线CZO作为社区资源，为来自多个学科的研究人员提供了一个研究平台，并提供了一个有力的研究计划，旨在获得一般知识和工具，以了解水，大气，生态系统和地貌之间的相互作用。 CZO的数据和知识还将增强数千名初中和高中学生以及多名大学生的科学体验。 CZO将位于国王河实验流域（KREW），这是一个流域级的综合生态系统项目，用于对Sierra国家森林的源头集水区进行长期研究;它利用了KREW（37.053oN，119.194oW，1，400 - 2，000 m海拔）的多个仪器齐全和特征化的集水区和长期数据集。 一个主要的，总体目标是了解关键区过程如何控制整个景观的水通量和储存，以及水循环如何调节（生物）地球化学，生物，地貌和土壤过程中的关键区。 五个直接的研究问题将定义和关注核心测量和研究计划：i）耦合的水文和生态地球化学通量如何在雨雪过渡期间变化，ii）极端水文事件在水文和生态地球化学平衡中的作用是什么，iii）植被在多大程度上调节或主动控制水和营养物的主要地下通量，而不是充当被动代理人，㈣在什么时间和空间尺度上，在什么季节，大孔隙和其他短路路径在临界区占主导地位，㈤季节性积雪的存在如何影响地下、临界区、土壤、地貌、生物地球化学和塞拉利昂流域和山坡的水文学，以及随着气候变暖和积雪消退，相关过程和水库将如何应对。

The rain-snow transition zone in mountains of the Western United States is particularly vulnerable to large and potentially rapid changes in climate and landcover. While this zone has characteristically rapid seasonal changes, going from snowcover to wet soil to dry soil over a 1-2 month period, climate warming will shift this transition period earlier or eliminate it entirely. The result will be major changes in seasonal-to-interannual critical zone processes involving water, nutrients and ecosystem response of the largely mixed conifer forest found in the rain-snow transition zone. Steep gradients in precipitation patterns, along both elevation and aspect, plus rapid seasonal changes, make this zone an excellent natural laboratory for studying how critical zone processes respond to perturbations, and particularly how the water cycle drives critical zone processes.The proposed Critical Zone Observatory (CZO) will take advantage of these features by establishing a snowline CZO as a community resource, providing both a platform for research by investigators from multiple disciplines and a vigorous research program aimed at yielding general knowledge and tools for understanding the interactions between water, atmosphere, ecosystems and landforms in the critical zone. CZO data and knowledge will also enhance the science experience of thousands of middle and high school students, and multiple university students. The CZO will be located in the Kings River Experimental Watershed (KREW), a watershed-level, integrated ecosystem project for long-term research in headwater catchments in the Sierra National Forest; it takes advantage of multiple well-instrumented and characterized catchments and long-term data sets at KREW (37.053oN, 119.194oW, 1,400-2,000 m elevation). A primary, overarching goal is to understand how critical zone processes control fluxes and stores of water across the landscape, and how the water cycle modulates (bio)geochemical, biological, geomorphological and pedological processes in the critical zone. Five immediate research questions will define and focus the core measurement and research program: i) how do coupled hydrologic and biogeochemical fluxes vary across the rain-snow transition, ii) what is the role of extreme hydrologic events in hydrologic and biogeochemical balances, iii) to what extent does vegetation modulate or actively control the primary subsurface fluxes of water and nutrients, versus act as passive agents, iv) over what time and space scales, and during what seasons, are macropores and other short-circuit pathways dominant in the critical zone, and v) how does the presence of a seasonal snowpack affect the subsurface, critical zone, soils, geomorphology, biogeochemistry and hydrology in Sierra watersheds and hillslopes, and how will the relevant processes and reservoirs respond as the climate warms and snowpacks recede.