2003-2007 Sand
Hills Biocomplexity: Integrating Biogeophysical
Processes across Space and Time (funded by NSF).
Today,
the Sand Hills are stable and covered by native grassland interspersed with wetlands
and lakes. The starting point for the Biocomplexity Project was the recent observation
by UNL geoscientists (David Loope et al.) that many
of these dunes lost their grass cover and were destabilized and active as
recently as 900 years ago. Our multi-disciplinary team of fourteen UNL scientists studied grassland
ecology, geology, meteorology, and groundwater to address reasons of stability
of the modern ecosystem. My students and I explored groundwater
recharge under various climate change scenarios. Using experimental data at the
Grassland Destabilization Experiment Site at Barta
Brothers and coupled land-surface-vegetation-root zone-vadose soil moisture
model in the framework of HYDRUS1D (Jirka Simunek), we
investigated the magnitude and factors affecting groundwater recharge in
different soil conditions, spatial patterns of soil saturated hydraulic
conductivity in dune environments, and trends in actual evapotranspiration. Tiejun Wang defended his dissertation in 2008
Publications
Szilagyi,
J., V.A. Zlotnik, J.B. Gates, J. Jozsa, 2011, Mapping
mean annual groundwater recharge in the Nebraska Sand Hills, Hydrogeology Journal, 2011, v. 19: 1503-1513, DOI 10.1007/s10040-011-0769-3
Wang, T., V.A. Zlotnik, J. Simunek, M. Schaap, 2009, Using process-based models and pedotransfer
functions for soil hydraulic characteristics to estimate groundwater recharge
in semi-arid regions. Water Resour. Res., Vol. vol. 45, W04412, doi:10.1029/2008WR006903
Wang, T., D. Wedin, V.A. Zlotnik, 2009, Field evidence of a negative correlation between
saturated hydraulic conductivity and soil carbon in a sandy Soil, Water
Resour. Res., Vol. 45, W07503, doi:10.1029/2008WR006865
Wang, T.,V.A. Zlotnik, D. Wedin, K.D.
Wally, 2007, Spatial trends in saturated hydraulic conductivity of vegetated
dunes in the Nebraska Sand Hills: Effects of depth and topography, J. Hydrol., v.
349, 88-97, doi: 10.1016/j.jhydrol.2007.10.027
Measurements of Energy
Budget and Surficial Vadose Zone Parameters
Preparing a borehole near water-budget for water budget assessment |
Tiejun Wang measuring hydraulic
conductivity |
Grass Destabilization Experiment
(GDEX) |
Constant Head Permeameter |
Annual Recharge Histogram, loamy sand
soils, GDEX Recharge ranges from 0 to 20 cm (Computed with HPRCC data) |
Annual Recharge Histogram, sand
soils, GDEX Recharge ranges from 3 to 32 cm (Computed with HPRCC data) |
Vertical Profiles of Surficial Hydraulic Conductivity at Barta Brothers ranch (average Kf
from all tested plots)
|
Contour maps of Kf
at three depths for Plot 2. |