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site. Over the course of the experiment, ERT will also be used to monitor relative changes in water
<br />content and distribution.
<br />In -cave measurements
<br />Using collection tarps, drip water will be collected from speleothems or cracks and fissures in the
<br />ceiling. Drip rates and amounts will be measured by funneling water from the collection tarp to a tipping
<br />bucket rain gauge connected to a data logger. After passing through the rain gauge, some or all of this
<br />water (depending on flow rates) will be filtered through plankton netting to collect copepods, which will
<br />be retained in water to keep them alive until collection. Initially, samples will be analyzed by Dr. Janet
<br />Reid (see letter of support), an internationally recognized copepod expert. Eventually, we hope to build
<br />local expertise in copepod analysis.
<br />In a separate sealed collection system, which prevents drip water interactions with the cave
<br />atmosphere, water will be collected and passed through a special flow cell which was designed and built
<br />for the Virginia study. The flow cell will house a multi - parameter data - logging water quality probe which
<br />continuously records key geochemical parameters (temperature, specific conductance, oxidationreduction
<br />potential, dissolved oxygen, and pH). These parameters provide information on flow - paths,
<br />residence times, and flow mechanisms (e.g., piston flow) for water draining from the epikarst. This probe
<br />is excluded from the budget as Schwartz will purchase it from TSU start-up funds. In addition, water
<br />samples for analysis of major cations, anions, dissolved organic carbon, total organic carbon, N, P, and
<br />stable isotope ratios in water will be collected weekly from the sealed collection system. In addition to the
<br />weekly sampling schedule, we will also sample at higher frequency during periods of special interest, for
<br />example, when large precipitation events follow a significant drought period, to learn more about epikarst
<br />storage volume and recharge rates.
<br />Surface measurements
<br />Above every cave site, we will at a minimum record precipitation, air temperature and humidity.
<br />Three sites will be equipped with full weather stations to calculate potential evapotranspiration. We
<br />expect that each weather station can serve two sites, based on physical proximity. In addition, we will
<br />install soil moisture probes (EcH2O, Decagon) to directly assess water availability in the one element of
<br />the soil /epikarst system that is relatively accessible. Depending on soil thickness, we will install one to
<br />three probes at different depths. We will also collect precipitation water in mineral oil topped buckets (to
<br />prevent evaporation), and samples from events >10 mm, i.e. those that have a chance to infiltrate past the
<br />immediate soil or epikarst surface, will be sent out for stable isotope analysis.
<br />At each site, we will fit an automated heat dissipation sap flow sensor system to six mature trees of
<br />the two most dominant tree species (live oak, Ashe juniper, honey mesquite). These devices, which record
<br />stem flow velocity continuously, have been successfully tried and tested on these or closely related
<br />species before. Sensor output will be calibrated to the cross sectional sapwood area to allow estimates of
<br />whole -tree transpiration rates, which can be further scaled to area -based tree transpiration, based on stem
<br />thickness and density. Periodically, we will assess the physiological status of trees more completely,
<br />measuring predawn and midday water potentials and leaf gas exchange rates.
<br />Previous experiments have shown that extreme events, such as long droughts, or hail storms which
<br />input a natural isotope marker into the system, can convey the most information on water transport
<br />phenomena and the spatial extent of the root system. During such periods, and concurrent with high
<br />frequency sampling below - ground, we will also take samples of stem water and soil isotope ratios.
<br />A contaminant transport experiment
<br />After running the above experiment for one full year, we will conduct contaminant transport
<br />experiments at all six sites to address our third research question. Granulated ammonium nitrate fertilizer
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