Projects

Savanna C cycle processes

With initial funding from the Sid Kyle Endowment, we are conducting research on C cycle processes in temperate savanna ecosystems. Research emphasizes vegetation-mediated C cycle processes and how these respond to direct anthropogenic drivers (fire, herbivory). The work will encompass a range of spatiotemporal scales (from short-term leaf-level processes to long-term regional to global processes) and utilizes a range of experimental and observational tools. Nicole Havrilchak is a PhD student on the project studying the physiology of C4 grasses and is particularly interested in how the different clades may exhibit distinct resource use strategies. We are excited to be part of the The Prairie Project (https://www.theprairieproject.org/), a USDA-funded initiative (Award # 2019-68012-29819) led by Dr. Brad Wilcox to improve the sustainability of livestock production in the Southern Great Plains. Check out the project website for more information.

Recent graduate Harrison Raub completed a MS thesis on better constraining what can be inferred about photosynthetic pigments and stress from leaf and canopy reflectance measurements. We've also benefited from the productive efforts of Dr. Aline Jaimes who worked on the project as a postdoctoral scholar and established our eddy flux tower and micromet stations and Ane Fortes, a visiting Brazilian student, who worked on a project that will produce allometric equations for aboveground biomass and C for the dominant woody species based on non-destructive measurements. These observations are also being related to visible-spectrum camera images and lidar, work led by Sorin Popescu's lab. Our undergraduate intern Dillon See is also working on characterizing fungal decay of living trees and its impact on these estimates.

Thicketization of oak savannas and groundwater recharge

A USDA-funded project, also led by Dr. Brad Wilcox, seeks to develop a better understanding of the ecohydrological implications of thicketization in oak savannas. We are particularly interested in determining if groundwater recharge could be enhanced via the creation of a more open structure. We are focusing our field studies on the Post Oak Savanna ecoregion in eastern Texas. We believe that this ecoregion holds particular promise for increasing groundwater recharge at a regional scale because about one-third of its area is underlain by the deep sandy soils of the Carrizo–Wilcox recharge zone. We are employing a variety of field measurements at two locations in the Post Oak Savanna, all of which are designed to better quantify water fluxes across these landscapes (especially recharge). Using both remote sensing and hydrological modeling, we will be able to scale up our results to the entire region and apply them to other oak savannas. 

Deep rooting in seasonally dry ecosystems

A project led by recent PhD graduate Dr. Rachel Adams explored the role of deep rooting in woody plants and to close key gaps in our understanding of this potentially important phenomenon. The project was focused on the degree to which climate, species characteristics and regional geology interact to affect the occurrence of deep rooting, as well as the dependence on deep water sources during dry periods. We were drawn to Quintana Roo, Mexico, a region with widespread deep rooting, as observed by tree roots emerging from the ceilings and walls of shallow caves. Rachel employed DNA barcoding to identify the roots to species for the first time. The overall objective of the research is to assess the relationships between above and below ground biodiversity and biomass as well as investigate water use strategies among co-occurring species in a seasonally dry subtropical forest. 

Caatinga ecohydrology and biogeochemistry

A collaborative project in the fascinating Caatinga of northeastern Brazil featured the work of recent PhD graduate Dr. Cynthia Wright who focused on key ecohydrologic processes. The Caatinga is a contiguous semiarid shrubland in northeastern Brazil that covers some 90,000 km2 or 12% of the country. From a socioeconomic standpoint it is of enormous importance—being home to a population of some 20 million people, many of whom are impoverished. The environmental conditions of the Caatinga are quite harsh; rainfall is generally low, the soils are poor, and droughts are frequent. In addition, the population of the region is continuing to increase.The goal of our project is to elucidate the fundamental ecophysiological, ecohydrological and biogeochemical processes that characterize Caatinga landscapes. We are collaborating in this effort with Brad Wilcox and several faculty at the Universidade Federal de Pernambuco and the Universidade Federal Rural de Pernambuco.

Improving loblolly pine water use efficiency and productivity

In a collaboration with Carol Loopstra and Claudio Casola we are studying the water use characteristics of a wide range of loblolly pine genotypes (USDA-NIFA Award # 2019-67013-29165). The project supports public breeding efforts to improve pine productivity and local adaptation in the face of increasing temperatures and drought, problems affecting forest trees in many parts of the U.S. Loblolly pine is one of the most important tree species in the U.S. and is critical for providing the goods and services used by people throughout the country. We are developing molecular markers and biomarkers that can be used to breed for increased water use efficiency (WUE), photosynthetic efficiency, survival and growth. 

Isoscapes capacity building

Isoscapes are maps of spatio-temporal variation in isotope ratios and are typically gridded products of spatially explicit modeling. Isotopes modeled can be stable (e.g., 18O) or radioactive (e.g., 14C) and include radiogenic isotopes such as 87Sr. Our group is interested primarily in the stable isotope ratios of the "light" elements : carbon (δ13C), nitrogen (δ15N), hydrogen (δ2H), and oxygen (δ18O) and their utility in understanding a range of questions and systems. In a collaboration with Gabriel Bowen and colleagues at Purdue, we developed web-based cyberinfrastructure for isoscapes

products and modeling, including access to necessary data sets and interactive data and model sharing. The IsoMAP project web page containing more in-depth description of the project may be found here. This project was funded through a grant from the National Science Foundation Division of Biological Infrastructure (0743543-DBI).

Ongoing work focuses on the degree to which spatial variation in precipitation and hydrologic processes interact with plant biophysical processes to affect the H and O isotope ratios of organic matter. Much of this work is collaborative and is designed to permit better interpretations of lipid H isotope ratios derived from sediments (e.g., from river systems in the Alps and Himalayas), but it also includes interpretation of tree rings and other paleo-records.