Ongoing Research


Active research projects at the Soltis Center 2013-2014

Principal Investigators Gretchen R. Miller - Texas A&M University; Co-PIs: Anthony T. Cahill - Texas A&M University, Georgianne W. Moore - Texas A&M University, L. Ruby Leung - Pacific Northwest National Laboratory
Project Title Improving Land-Surface Modeling of Evapotranspiration Processes in Tropical Forests
Abstract  Land surface models are used to represent terrestrial processes that shape global climate; examples of these processes include evaporation, plant water use, and photosynthesis. While much progress has been made to improve and refine these models, some hydrological processes are not well captured, which hinders our ability to understand land-atmosphere interactions and ultimately to predict impacts of climate change on water resources. The inadequate representation of evapotranspiration may partly explain why global climate models do not match observed precipitation patterns. Multiple factors contribute to this problem. In moist tropical regions, high humidity, leaf wetness, and cloud cover combine to suppress forest water use and possibly reduce forest growth in ways that are poorly understood. Mountainous areas pose additional difficulties, as standard modeling and measurement techniques are not readily applied in rough terrain. The overall goal of this project is to improve the modeling of fluxes of water vapor and carbon dioxide to and from tropical forests. This goal will be achieved through a combined program of field-based measurements in a mountainous tropical forest in Costa Rica and regional scale modeling of land surface fluxes in the Neotropic ecozone of South America, Central America, and the Caribbean. Specifically, the project will: 1) collect targeted hydrological and meteorological measurements along in-canopy and above-canopy profiles at locations throughout a mountainous forest watershed at the Texas A&M Soltis Center; 2) develop a new conceptual framework for modeling wet canopy processes based on the new dataset; 3) appropriately revise the Community Land Model (CLM) to improve its estimates of evapotranspiration in tropical forests; and 4) model tropical forests and their interactions with rainfall using the improved CLM coupled with the Weather Research and Forecasting (WRF) model capable of resolving processes in mountainous forests.
Funding Sources U.S. Department of Energy, Office of Science, Earth Systems Modeling Program
Associated activities One Ph.D. student, two M.S. students, and one undergraduate student
Publications / presentations ·         Miller, G. R. (2014), Modeling Ecohydrological Processes at Both Extremes: Challenges for Very Wet and Very Dry Environments, invited seminar for the University of California, Berkeley Environmental Engineering Seminar Series.
·         Cahill, A.T., Miller, G.R., Moore, G.W., and Merket, C. (2014 – upcoming), The effect of variation of rainfall across different time scales on subcanopy CO2 storage and flux in a Costa Rican rainforest, for presentation at the AGU Fall Meeting, San Francisco, California.
·         Aparecido, L.M.T., Moore, G. W., Miller, G.R. and Cahill, A.T. (2014 – upcoming), Ecohydrological response of trees to leaf wetness gradients under wet and dry canopy conditions in a montane tropical forest, for poster presentation at the AGU Fall Meeting, San Francisco, California.
·         Miller, G.R., Cahill, A.C., Moore, G.W., and Leung, R. (2014), Improving Land-Surface Modeling of Evapotranspiration Processes in Tropical Forests, poster presentation at the 2014 Climate Modeling PI Meeting, May 12-15, 2014, Potomac, Maryland.
·         Cahill, A.C., Miller, G.R., and Moore, G.W. (2014), Improving Land-Surface Modeling of Evapotranspiration Processes in Tropical Forests, poster presentation at the 2014 Joint Terrestrial Ecosystem Science and Subsurface Biogeochemistry PI Meeting, May 6-7, 2014, Potomac, Maryland.
Principal Investigators Gretchen R. Miller;  Collaborators: Brendan Roark, Tony Cahill, and Kelly Brumbelow, - Texas A&M University.
Project Title Isotopic Analysis to Determine Groundwater and Stream Water Interactions in a Tropical Forest Catchment
Abstract Hydrologic, geologic, and biologic processes are critical to understanding the ecosystem in the tropical premontane transitional forests of Costa Rica. Precipitation is significantly lower during the dry season, and incoming rainfall can be completely intercepted and re-evaporated by the forest canopy during light events. This leaves groundwater as a main source of stream flow throughout the watershed which is used downstream for drinking water and hydropower uses.  By using stable isotope signatures we were able to reliably and precisely characterize the nature of these ecohydrologic processes to determine the influences on the groundwater system in a challenging environment with limited accessibility and complex subsurface conditions.  This study focuses on research conducted at the Texas A&M Soltis Center for Education and Research, near San Ramón, Costa Rica. We have monitored a 2.2 ha watershed there, measuring precipitation and transpiration rates for over two years, and groundwater levels and stream flow rates for nearly one year. Precipitation rates for the watershed averaged 4.4 m/yr since 2010. Stream flow (runoff, spring flow, and baseflow) averaged 0.09 m3/sec during the 2012-2013 wet seasons. At 1.2 mm/day, transpiration was a relatively minor component of the water budget. Over a 40-day span during summer 2013, we collected a combination of daily and rain-event based samples from locations throughout the watershed. Sources included: the main stream and two small tributaries, groundwater from piezometers, pore water from suction lysimeters, throughfall and stemflow from under canopy collection systems, and xylem water from 8 tree species across the watershed. We then measured stable isotope fractions (δ18O and δD) in the water using a Picarro L2120i CRDS. Isotope ratios for surface water averaged -5.50‰ for δ18O and -28.00‰ for δD; baseflow was measured at -5.45‰ for δ18O and -29.18‰ for δD.  Results of baseflow partitioning confirm that groundwater is the dominant source for stream water even in the wet season.  We additionally conclude that in this watershed, groundwater transport to the stream is characterized by short residence times attributed to macropore flow in the subsurface, despite a low permeability of the andisol clay.
Funding Sources National Groundwater Research and Education Foundation
Associated activities One M.S. student, one undergraduate REU student
Publications / presentations DuMont, A. and G.R. Miller, (2014), Groundwater dynamics in a premontane transitional rainforest using stable isotope techniques, oral presentation at the National Ground Water Association Summit 2014, Boulder, Colorado.
Miller, G.R., DuMont, A., Roarke, B., K. Cahill, A. T., Brumbelow, (2013), Baseflow separation in a premontane transitional rainforest using stable isotope techniques, poster presentation at the AGU Fall Meeting, San Francisco, California.
Paper in preparation:
DuMont, A., Miller, G.R., Roarke, B., Brumbelow, K. and Cahill, A. T., “Using stable isotope tracers to quantify baseflow in a Costa Rican watershed,” for submission to Groundwater.
Principal Investigators Margot A. Wood​,, 201 Old State Chem 2258, Texas A&M University, College Station Texas 77843-2258
PI: Dr. Thomas E. Lacher Jr.,, 201 Old State Chem 2258, Texas A&M University, College Station Texas 77843-2258.
​Co-PI: Eugenio Gonzalez, The Soltis Center for Research and Education, Texas A&M University, P.O. Box 80-4417 La Fortuna, Costa Rica.
Project Title Payment for Ecosystem Services and Mammals: Do mixed use biological corridors benefit conservation?
Abstract Land conversion is closely linked with agriculture throughout much of the world. Costa Rica had its share of land conversion due to agriculture, reaching its peak in the 1970s. Costa Rica is known for its proactive environmental policies that have been focused on curbing the rate of deforestation. Current government payments for ecosystem service (PES) policies, in place since 1997, were established to aid in water management, biodiversity protection, scenic beauty and carbon sequestration. PES participants that live in the SINAC (Sistema Nacional de Areas de Conservacion) designated biological corridors are given funding priority because these corridors are essential for connecting segregated wildlife populations held in the National Parks and other protected areas. Biological corridors are defined as regions to best facilitate movement of the target species between two habitat zones. The goal of these biological corridors is to promote conservation of biodiversity and sustainable use of natural resources by providing connectivity via reforestation. Although the enhancement of forest cover has been described in these corridors, there have been few studies assessing effectiveness of the payments for ecosystem services policy on biodiversity, and specifically mammalian dispersal.
Funding Sources EarthWatch, Ecology and Evolutionary Biology at Texas A&M University, ​NSF-IGERT Applied Biodiversity Science Program
Associated activities Three undergraduate students participate in this project. Two undergraduates from Texas A&M University and 1 undergraduate from the National University of Costa Rica. ​We also had 31 Earth Watch citizen scientists participate during the summer of 2014.
Publications / presentations Wood, M.A. and  T. E. Lacher. 2014. Payment for Ecosystem Services: Landholder Perspectives and Decisions. Poster presentation: Student Research Week, March 2014, Texas A&M University.
Wood, M.A. and T. E. Lacher. 2014. Payment for Ecosystem Services: Landholder Perspectives and Decisions. Poster presentation: Ecological Integration Symposium, March 2014, Texas A&M University
Wood, M.A. and T. E. Lacher. 2014. Payment for Ecosystem Services and Mammals: Do Working Agricultural Landscapes Benefit Conservation?. Poster presentations: Organization of Tropical Studies Conference, June 2013, San Jose, Costa Rica.
Wood, M.A. 2013. Do Payments for Ecosystem Services in Working Landscapes Benefit Conservation? Oral presentation: Louis Stokes Alliance for Minority Participation Annual Symposium, February 2013, Texas A&M University.
Principal Investigators PI: Kelsey Neam,, Texas A&M University, Department of Wildlife and Fisheries Sciences, 210 Nagle Hall MS 2258 TAMU, College Station, TX 77843
PI: Dr. Thomas E. Lacher Jr.,, 201 Old State Chem 2258, Texas A&M University, College Station Texas 77843-2258.​
Project Title The Spatial Ecology of a Dispersal Limited Vertebrate on a Mosaic Landscape
Abstract Land use change, often driven by a complex array of socio-economic factors, is a key driver of the loss of biodiversity, particularly in the tropics. As human population, food consumption, and the demand for forest products continue to rise over the next century, the impacts of land use change on biodiversity and ecosystem services are projected to intensify.  Analyses of IUCN Red List criteria have revealed that conversion of complex natural ecosystems into high-intensity croplands is among the most significant causes of species endangerment for mammals. Mammals are widely used as indicators of habitat disturbance and fragmentation due to their close relationships with forest cover and structural complexity. The behavioral responses of mammals to spatial elements are often directly related to their body size, life history traits, and ability to move through the landscape. For example, costs of movement (i.e. predation risk and energetic expenditure) are likely to be greater for species with low vagility and high dependence on tree cover than they are for species with high vagility. Therefore, these species could serve as model organisms when studying the impacts of land use change and may be used as an umbrella to conserve a larger group of species.
The purpose of this study is to assess the effects of land use change on brown-throated sloth (Bradypus variegatus) populations along the Caribbean slope of the Monteverde Cloud Forest Reserve in Costa Rica. This region is a landscape mosaic of forest and human-modified habitats. In my research, B. variegatus will be used as a model organism to investigate the impacts of land use change on the abundance and distribution of a species of low vagility across multiple land use types The sedentary lifestyle of sloths compounded by their low metabolic rate, weak dispersal potential, and reliance on forest cover make them especially susceptible to habitat fragmentation and land use change.
I will generate a land use map of the region and overlay the distribution of B. variegatus to produce a density of use map, incorporating ecological niche modeling and spatial dynamics. This information will be used to generate inferences about the ability of B. variegatus to inhabit and traverse areas experiencing varying degrees of land use intensity. I anticipate that this research will provide a deeper understanding of the spatial ecology of species with low dispersal ability within human-modified landscapes and improve the capacity of policy makers to conserve biodiversity while sustaining agricultural productivity, ecosystem functioning, and rural livelihoods.
Funding Sources TAMU-Department of Wildlife and Fisheries Sciences (2014)
Texas A&M University Teaching Assistantship: Mammalogy (2012-2014)
Applied Biodiversity Science Program Scholarship (2013)
Associated activities Throughout this project, I have collaborated with over thirty citizen scientists from the Earthwatch Institute, an international non-profit organization that aims to bring together scientists and the public in an effort to promote the understand and action necessary for a sustainable environment. I am also working with several undergraduate students, Lilianna Wolf and Rebecca Langley from Texas A&M University and Pablo Castro from the Universidad Nacional de Costa Rica. These students are assisting with collecting data for this project, as well as developing their own practical skills and knowledge necessary for a path in scientific research. Lilianna Wolf is a recent recipient of an Undergraduate Research Scholar award as a result of her work in Costa Rica.
Publications / presentations Landon, A.C., Van Riper, C.J., Angeli, N.F., Fitzgerald, D.B., Neam, K.D. 2013. In review. Growing  Transdisciplinary Roots in the Peruvian Amazon. Target Journal: The Journal of Transdisciplinary Environmental Studies.
Neam, K.D., Wood, M.A. 2014. Collaboratory blogging: Many minds are better than one. Applied  Biodiversity Sciences Perspectives Series.
Neam, K. D., Petriello, M., Wood, M. (2014). [Blog] Central America: Applied Biodiversity Science. Available at:
Sloth Ecology and Conservation. 2014. Conservet Workshop. San Isidro de Peñas Blancas, Costa Rica.


Past Research Projects

Researchers Institution Project Title Period / Status
Dr. Miguel Mora and Ms. A. Maldonado Texas A&M University, Department of Wildlife and Fisheries Sciences Impact of agricultural pesticides and organic pollutes on migrant bird species. January – February 2012, ongoing
Dr. R. Hill and Dr. J. Hsu,
Harvard University, Faculty of Arts and Sciences, Center for Systems
Monarch migratory behavior, biogeography, and sexual dimorphism in mimetic  butterflies.
June-July 2012, ongoing
Mr. Ryan Chabaria and Dr. F. Pezold,
Texas A&M University-Corpus Christi, Department of Life
Taxonomic revision of the genus Sicydium (Gobiiformes: Sicydiinae):
phylogenic analysis of the taxagobiiformes.
June-July 2012, ongoing
Dr. B. Brown (1),
Dr. Dalton de Souza A. (2)
  1. Natural History Museum of Los Angeles County-National Biodiversity Institute of Costa Rica – InBio
  2. University of Sao Paulo (Brazil), Dept of Biology
Revision of Apocephalustaxa, morphological and phylogenetic relationships.
August 2010, August 2011, ongoing
Dr. B. Haber Associate Researcher at Monteverde, University of Massachusetts, Boston
Monteverde Flora Project, Missouri Botanical Garden.
Electronic Field Guide Project, on-line key for dragonflies and damselflies of the Tropics.
September 2010, ongoing
Dr. David E. Baumgardner
Texas A&M University, Department of Biology Biogeography of Central American mayflies: structure and function of tropical lotic systems. June 2011, ongoing
Dr.Gunther Kohler Senckenberg Gesellschaft fur Naturforschung–Germany. Taxonomic, zoogeographic and phylogenetic of Neotropica lHerpetofauna.
July 2010, ongoing
Dr. I. Hutter and Dr. C. Sneider. Institutfür Pflanzenkultur-Germany. Propagation and conservation of endangered tree species of the Neotropics.
April 2010, ongoing
Mr. Chris Wilson Texas A&M University, Dept of Entomology, The Ant Fauna of Casa
Verde (Soltis Center), Costa Rica, A biodiversity study.
March-May 2009, ongoing