Critical Zone Exploration Network

Top site proposals listed by peer review committee
Following the October CZEN meeting in Delaware, a peer committee reviewed and ranked 23 sites that were proposed to form the framework for the Critical Zone Exploration Network.

The 8 top-ranked site proposals from the CZEN meeting follow:

Rasmussen: Semi-Arid Environmental Gradient
Chadwick: Hawaii Soil-Weathering Sequence
Kurtz: Rio Icacos, Luquillo Mountains, Puerto Rico
Harden-Waldrop: Bonanza Creek, Alaska Carbon & Moisture Gradients
Lin: Shale Hills, Pennsylvania
Harden-Amundson: Merced Chronosequence, California
Peters: Panola Mountain, Georgia
Kumar: Illinois River Basin, USA
These sites have been given approximately $10K each as seed money to initiate their work. To view the presentation for these site proposals, please click on the link below. Information regarding the site proposal selection process can also be found on the following link.
CZEN Site Proposal Presentations from the Delaware Meeting
Site Characteristics

CZEN sites will be used to define and characterize the effects of individual variables on important Critical Zone phenomena measured across environmental gradients. These sites will be distinguished from most previous site-based studies by an interdisciplinary focus on soil, biota, water, and gas.

Each site will be characterized by a suite of instrumentation and analyses: some sites will be heavily instrumented and others will be less so. The most heavily instrumented sites will be true Soil Observatories wherein subterranean access to deep regolith will be enabled for visualization and measurement. Other network sites may be less heavily instrumented.

The most highly instrumented network sites will be hierarchically-nested field sites designed to investigate weathering simultaneously at the soil profile and catchment scales (Figure 1; see Table 1 for a list of proposed instrumentation). Such a CZO will be instrumented for a variety of hydrogeochemical measurements, as well as sampled for soil, canopy, and bedrock materials. Basic hydrological instrumentation will include nested tensiometers, piezometers, time domain reflectometry, stream gauges, meteorological stations, linked to data loggers and/or wireless transmitters. Hydrochemical instrumentation will include event-triggered stream samplers, tension and zero-tension lysimeters, saturated zone wells, and precipitation samplers. Sampling tubes will be placed for soil gas sampling.

An initial number of Critical Zone Observatories will be chosen by peer review from new or previously investigated sites. We envision dedicated funding to support each site for ~ 5 year increments, but the possibility of renewal must be assessed against the value of new sites. The minimum criteria for CZO selection are presented in Table 2.

Figure 1. Schematic diagramming how the instrumentation at the soil site will be nested within instrumentation to monitor the catchment. Soil instrumentation will include rhizotrons, lysimeters, tensiometers, gas samplers, and piezometers.

CZEN will not be comprised solely of heavily instrumented sites but will also include sites to analyze the environmental gradients with less high-resource investigations. These less-instrumented CZEN sites will be measured for a standard set of parameters over a range of depths (Table 3). By standardizing data and sample collection for these sites, CZEN will promote inter-comparison of Critical Zone processes across a variety of lithologies, ecosystems, climate zones, and topographies. A large number of network sites will be established in order to investigate the full matrix of variables (Table 2). Some CZEN sites will be groundwater aquifers where Critical Zone processes could be investigated in the saturated zone (beneath groundwater surface) as a comparison to weathering in the unsaturated zone.

Data and samples from these sites will be incorporated into a CZEN database and will be made available to any CZEN scientist (probably after an embargo period). CZEN will design a mechanism to coordinate efforts (perhaps through the annual meeting), and will encourage multi-PI proposals that would bring together CZO-like integrated science efforts.