Current TEAM
ROSALEEN MARCH, PhD Fellow
Major: Forestry
Education: M.S. Biology, Texas A&M University-Corpus Christi; Master of Marine Resources Management, Texas A&M University-Galveston;
B.A. Environmental Studies, Oberlin College
Professional Interests: I am interested in how the recent extreme droughts in Texas are affecting the landscape. The Texas Forest Service has estimated that approximately 500 million trees have died in 2011 alone due to the drought. My goal will be to quantify a more precise estimate by using remote sensing, and also quantify drought-related mortality during the past decade of drought conditions. I am also interested in how landscape features interact with species composition and mortality. I’d like to see how drought changes landscape pattern and what makes certain parts of the landscape more vulnerable to extreme drought than others. For example, are species on bottomland sites more vulnerable than those on the uplands? For these questions I will look specifically at the Edwards Plateau. Lastly, to broaden the perspective of ecosystem dynamics of drought, I’d like to look at drought mortality effects on wildlife. For now, the idea is to examine keystone species that range from specialist to generalist and develop a scenario for each.
Jean Devlin, Masters student
Major: Rangeland Ecology and Management
Education: B.S. Ecological Restoration (minor in Forest Science) Texas A&M University
Professional Interests: I am interested in observing how wetlands are evolving to adapt and filter out increased nutrient and pollutant loads from urban regions experiencing rapid expansion. Wetland regions, such as the ones that exist within Houston, Texas, must tolerate greater amounts of nutrients and pollutants contained within urban storm water runoff. Initiatives to maintain and restore degraded wetlands within this region are currently underway. I am also interested in how the infiltration rate of the soils within the "lost pines" ecoregion near Bastrop has changed as a result of fire as well as the fires’ effect on the watershed. The extreme fire that burned thousands of acres of loblolly pine trees, destroyed much of the vegetation and exposed the soil. Given the extreme drought conditions Texas has experienced for the past few years, fire stricken areas are more vulnerable to erosion. I anticipate that portions of the Colorado River, as well as many other rivers within Texas, are likely carrying an increased sediment load, leading to negative impacts on habitat downstream.
christina bishop, masters student
Major: Natural Resources Development
Deseri Nally, Undergraduate Research Fellow
Major: Ecological Restoration
Response of wetland soils to flow alterations in the Sabine River below Toledo Bend Dam for the Texas Instream Flows Program: Given the known alteration in flood pulses into wetlands below Toledo Bend Dam, my study addresses how this loss of flood pulses is affecting the floodplain soils that are vital to riparian vegetation. If altered hydrology has changed sediment delivery, and the length of time soils are saturated, I expect zones of the wetlands to transition from hydric to non-wetland soils, especially in locations that are topographically high. Soil samples should be able to show hydric to non-hydric transitions in specific zones (e.g. sloughs, levees, and floodplains). Hydric soils are indicated by mottles of anoxic and oxidized patches. Studies have shown that soils have a high pH and decrease in pH as they become more oxidized (Wharton 1982). This property of pH will help serve as an indicator for soil oxygenation that have increased following the construction of Toledo Bend Dam.
Fan Li, MS Student
Major: Rangeland Ecology and Management
Because Arundo donax has invaded the southern half of the United States, it is important to understand what mechanisms enable it to be such an effective competitor in riparian habitats. Fan Li's study seeks to determine the effect of Arundo on the interaction between the river and groundwater: If it’s a losing reach, the presence of Arundo may cause less river water to recharge the groundwater. If it’s a gaining reach, groundwater that should flow into the river may be intercepted by Arundo.
Fan Li's research questions are: (1) Does Arundo use groundwater as one water resource? (2) What’s the fraction of transpired water contributed by groundwater, precipitation, and river water? (3) Which method best estimates the consumption of water by Arundo?, and (4) How much groundwater is exchanged into or out of the river every day, and does the presence of Arundo impact the groundwater flux?
Past Team
Blake Alldredge, Masters Student
Major: Water Management and Hydrological Sciences
Sabine River Instream Flows Project: The basis for our study rested on two main questions: “Has Toledo Bend Dam reduced flooding downstream?” and “What is the condition of the vegetative communities in the floodplains along the Sabine River?” The question in reference to reduced flooding is essential to understand because of the role that hydrology plays as the “master variable” of ecological communities. There is no historical vegetation data for Sabine River floodplains, rather, research findings gathered from vegetation plots in this study convey a “snapshot” of the community composition at the present time. Information obtained from the literature can also lead us to understand what vegetative communities would be in a healthy floodplain of the Southeast U.S.
Li Kui, MS Student
Major: Rangeland Ecology and Management
Education: B.S. in Chemical Engineering and a M.S. in Environmental Science in Sichuan University, China.
Background: In 2006, she was involved in an international ecological restoration program in EarthCorps, Seattle, Washington. Later, she developed projects focused on invasive species control around Chengdu, China. She was previously executive director of the Green Student Organizations Society, which helps youth environmental activists to develop their environmental protection projects all over Southwest China. Li Kui also wrote a textbook on environmental education for middle school students of Chongqing, China.
Li Kui's MS research is focused on the ecohydrology and distribution of giant reed (Arundo donax) in the Rio Grande valley. Project includes measurements of plant transpiration, soil moisture, stable isotopes, plot density, biomass and plant height in order to estimate the water use and distribution of the plant, by using such instruments as the LI-COR 6400, Diviner 2000 and a Thermo Delta V Isotope Ratio Mass Spectrometer.
Jose Franco, PhD Student
Education: M.S. Range Science, New Mexico State University, 2007. B.S. Biology/Geology, The University of Texas at El Paso, Cum Laude 2004
Hometown: El Paso, Texas
Thesis Topic: The influence of vegetation, soils, and topography on runoff dynamics and E. coli loading in a karstic system of central Texas.
David Watts, MS
Thesis: Dynamics of Water Use and Responses to Herbivory in the Invasive Reed, Arundo donax (L.). (May 2009)
Abstract: The first objective of this study was to investigate the role of an invasive grass
species, Arundo donax (L.), on the hydrologic cycle. At a site on the Rio Grande in
South Texas, we measured the gas exchange of carbon dioxide and water vapor at the
leaf scale and structural characteristics, such as leaf area and shoot density, at the stand
scale. In order to assess the effect of water availability, this study was conducted along
transects perpendicular to the edge of the river along a potential moisture gradient. The
second objective was to quantify the effect of two herbivores, an armored scale,
Rhizaspidiotus donacis (Leonardi), and a stem-galling wasp, Tetramesa romana
(Walker),on the photosynthetic and transpiration rates of A. donax. Leaf gas exchange
measurements were made to determine the direction and magnitude of the effect on
physiological processes and by what mechanisms any effects arose.
Stands of A. donax used approximately 9.1 ± 1.1 mm of water per day. This rate
of water use was at the high end of the spectrum for plants. The major controls on stand
scale transpiration were evaporative demand, leaf area index, and water availability.
During two summer seasons, stand scale transpiration varied greatly, following the
pattern of variability in precipitation, suggesting that recent rainfall constituted a
significant proportion of the water taken up by this species.
Herbivory by a stem-galling wasp and a sap-feeding scale, both separately and
together, reduced the rates of leaf scale physiological processes in A. donax. The
efficacy of the wasp was density dependent, and this herbivore reduced the
carboxylation rate of Rubisco. The effect of the scale took approximately five months to
manifest, which coincided with generation time. Scale reduced photosynthesis by
decreasing the maximum rate of electron transport. When the two insects were both
present, the effect of their herbivory seemed to be additive. These results will assist the
responsible management agencies in evaluating the propriety of using one or both of the
insect herbivores as biological control agents.
Dave Barre, MS
Thesis: Long-term hydrologic responses to shrub removal in a SW Texas rangeland: Using soil chloride to estimate deep drainage. (August 2009)
Abstract: The Carrizo-Wilcox aquifer is a valuable groundwater resource, situated in a semi-arid
landscape of Southwest Texas, where over-use by dependent farming practices has
lowered aquifer levels. In semi-arid regions, rates of groundwater recharge are
predominantly low due to high potential evapotranspiration rates; however, least
understood is the role that vegetation plays in soil-plant-water dynamics. Vegetation
management potentially plays a major role in countering the loss to recharge because
evapotranspiration (ET) varies with vegetation type and cover. The conversion from
shrubland to grassland likely reduces rooting depths and total plant cover. Subsequently,
deep drainage (percolation below the root zone) will likely increase and lead to
groundwater recharge, at least temporarily. The primary aims of the study were to
identify those biotic and abiotic factors facilitating deep drainage and to examine
differences in recharge for the years following clearing of natural shrub vegetation. Soil
chloride was examined to estimate long-term recharge rates, since its concentration in the soil is influenced by the movement of water. Short-term soil moisture trends were
also monitored for any water movement deep in the soil profile in response to individual
rain events. Rooting depths decreased following removal of vegetation; yet root biomass
unexpectedly increased due to successful grass establishment during the first five years
after treatment. Soil properties did not vary between treatments, indicating that the
majority of chloride differences seen were a consequence of vegetation change. Peak
and total soil chloride concentrations were expected to decrease and occur deeper in the
soil profile 15-30 years following the clearing of woody vegetation. Total chloride
decreased by up to 65% after 30 years and resulted in an estimated 14.9 mm/yr more
recharge compared to adjacent untreated controls. Evidence in this study suggest that
much of this chloride is leached during the first five years following treatment and that
more leaching occurs in especially wet periods. During the wet 2007 growing season,
soil moisture below the root zone increased by up to 17% after vegetation clearing. The
results of this study indicate that hydrologic changes following brush removal were
evident in this system and are likely to positively influence groundwater recharge in the
long-term.
