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Authors: Tian, Xin; Advisor: -; Participants: - (2013) - We propose a long-term parameterization scheme for two critical parameters, zero-plane displacement height (d) and aerodynamic roughness length (z0m), that we further use in the Surface Energy Balance System (SEBS). A sensitivity analysis of SEBS indicated that these two parameters largely impact the estimated sensible heat and latent heat fluxes. First, we calibrated regression relationships between measured forest vertical parameters (Lorey’s height and the frontal area index (FAI)) and forest aboveground biomass (AGB). Next, we derived the interannual Lorey’s height and FAI values from our calibrated regression models and corresponding forest AGB dynamics that were converted from interannual carbon fluxes, as simulated from two incorporated ecological models and a 2009 forest bas...
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Authors: Atchley, A.L.; Advisor: -; Participants: Kinoshita, A.M.; Lopez, S.R.; Trader, L.; Middleton, R. (2018) - The reduction of evapotranspiration often dominated the new water balance compared with the increase in overland flow, resulting in higher soil moisture. However, this modeling experiment also identified a tipping point where increased overland flow from high burn severity sites eclipses the effect of reduced evapotranspiration on the water balance, causing comparatively drier post‐fire soils. In particular, high burn severity sites approach a threshold that results in larger changes to overland flow than changes in evapotranspiration, potentially moving the site to an overland flow dominated regime. The shifts in water balance components have implications for how site conditions will change under a range of burn severity scenarios.
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Authors: Brantley, S.L.; Advisor: -; Participants: White, T.; West, N.; Williams, J.Z.; Forsythe, B. (2018) - The Susquehanna Shale Hills Critical Zone Observatory (SSHCZO) was established to investigate the form, function, and dynamics of the critical zone developed on sedimentary rocks in the Appalachian Mountains in central Pennsylvania. When first established, the SSHCZO encompassed only the Shale Hills catchment, a 0.08‐km2 subcatchment within Shaver's Creek watershed. The SSHCZO has now grown to include 120 km2 of the Shaver's Creek watershed. With that growth, the science team designed a strategy to measure a parsimonious set of data to characterize the critical zone in such a large watershed. This parsimonious design includes three targeted subcatchments (including the original Shale Hills), observations along the main stem of Shaver's Creek, and broad topographic and geophysical ob...
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Authors: Kuchta, S.; Advisor: -; Participants: Neilsen, D.; Forge, T.; Zebarth, B.J.; Nichol, C. (2020) - The temporal pattern of drainage and NO3 leaching was driven by seasonal precipitation and growing season irrigation. Growing season drainage and NO3 leaching were much lower under ET‐scheduled irrigation compared with fixed irrigation. Nitrate leaching was high (up to 90 kg N ha−1), even with no managed N inputs due to high inherent soil fertility and large quantities of N applied in irrigation water. Nitrate leaching was insensitive to N fertilizer rate. Application of N as poultry manure more than doubled NO3 leaching compared with fertilizer, emphasizing the need to use organic N inputs judiciously. The perennial grass alley cover crop resulted in the greatest overall reduction in NO3 leaching. Our data indicate that no single management strategy is sufficient to protect groundw...
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Authors: Eberhard, J.; Advisor: -; Participants: Schibalski, A.; Gräff, T. (2020) - Salinization is a well‐known problem in agricultural areas worldwide. In the last 20–30 yr, rising salinity in the upper, unconfined aquifer has been observed in the Freepsumer Meer, a grassland near the German North Sea coast. For investigating long‐term development of salinity and water balance during 1961–2099, the one‐dimensional Soil–Water–Atmosphere–Plant (SWAP) model was set up and calibrated for a soil column in the area. The model setup involves a deep aquifer as the source of salt through upward seepage. In the vertical salt transport equation, dispersion and advection are included. Six different regional outputs of statistical downscaling methods were used as climate scenarios. These comprise different rates of increasing surface temperature and different trends in season...
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Authors: Lazik, D.; Advisor: -; Participants: Vetterlein, D; Salas, S.M.; Sood, P.; Apelt, B.; Vogel, H.J. (2019) - This variability is attributed to the spatiotemporal heterogeneity of both plant–soil–microbiome interactions and the local conditions governing gas transport. For the characterization of a given soil, the local heterogeneities should be replaced by some meaningful average. To this end, we introduce a line sensor based on tubular gas‐selective membranes that is applicable at the field scale for a wide range in water content. It provides the average CO2 concentration of the ambient soil along its length. The new technique corrects for fluctuating external conditions (i.e., temperature and air pressure) and the impact of water vapor without any further calibration. The new line sensor was tested in a laboratory mesocosm experiment where CO2 concentrations were monitored at two depths ...
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Authors: O'Geen, A.; Advisor: -; Participants: Safeeq, M.; Wagenbrenner, J.; Stacy, E.; Hartsough, P.; Devine, S. (2018) - Sensor networks within the Southern Sierra Critical Zone Observatory (SSCZO) and Kings River Experimental Watersheds (KREW) document changes in the water cycle spanning the west slope of the southern Sierra Nevada in California. The networks were established to document water dynamics throughout the critical zone spanning profile, hillslope, catchment, and watershed scales at key locations that reflect systematic differences in bioclimatic conditions imposed by a strong elevation gradient. The critical zone observatory attempts to constrain the hydrologic budget via representative measurements of streamflow, eddy flux covariance, snow depth, meteorological conditions, and water content and water potential in soil and deep regolith. These measurements reveal the complexity of interac...
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Authors: Zhu, W.; Advisor: -; Participants: Li, H.; Qu, H.; Wang, Y.; Misselbrook, T.; Li, X.; Jiang, R. (2018) - The soil water storage (SWS) decreased significantly during the early stage of the maize growing season, especially in 2014. The root depth and crop height were 20 cm deeper and 100 cm higher, respectively, in 2014 than in 2013 at the early stage. These results suggest that in the early stage of the maize growing season, pre‐seeding SWS can alleviate crop water stress effectively via deep roots. Model simulation showed that the plow pan layer (at a depth of 20–40 cm), with high soil bulk density and a lower soil water retention curve, significantly reduced infiltration. High evapotranspiration and low precipitation result in a temporary dry layer during the early stage, highlighting the plow pan as the sensitive layer for water stress during the drought period. Effective management ...
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Authors: Wang, Z.; Advisor: -; Participants: Luo, C.; Sauer, T.J.; Helmers, M.J.; Horton, R. (2018) - Crop canopy CO2 exchange rate (CER) includes crop photosynthesis and soil/plant respiration. A portable canopy chamber is effective in determining crop CER values at a relatively small spatial (m2) scale. The objectives of this study were to use a canopy chamber to measure CO2 fluxes in corn (Zea mays L.) and soybean [Glycine max (L.) Merr.]. Chamber measurements were performed for 18 and 15 d in 2013 and 2014, respectively. The canopy chamber measures instantaneous CER fluxes, and daily and daytime cumulative CO2 values were calculated from the instantaneous CER. The chamber CER results were compared with nearby eddy covariance (EC) flux tower measurements at a variety of time scales, i.e., instantaneous, daily, and daytime cumulative (multiple months). The daily and daytime cumula...
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Authors: Friedman, S.P.; Advisor: -; Participants: Gamliel, A. (2019) - A previously derived analytical solution to the quasi‐linear form of the water flow equation is used to analyze (i) steady, coupled plant water uptake from a surface water emitter in a confined cylindrical soil domain with a non‐evaporating surface in the presence of a shallow water table, and (ii) water uptake from only the water table in the absence of a surface emitter. Illustrative examples serve to analyze and discuss water‐uptake rates of a subsurface, spherical, conceived root zone and the complex water‐flow patterns occurring in either natural fields with shallow groundwater or artificial lysimeters. The coupled source–sink–water table model is also used to illustrate the dependence of the contributions of surface emitter and water table to the overall water‐uptake rate on c...
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