Research Interests

In general, I am interested in ecosystem dynamics and management. As part of the interdisciplinary USDA National Needs program, I am working to link soil hydrology and carbon and nitrogen cycling. I am advised by Jason Kaye, a biogeochemist, and co-advised by Henry Lin, a hydropedologist. It is my goal to forge these two expertises.

My past work has focused on rangeland ecosystems, including both wildlife and vegetation. One portion of my M.S. thesis, which focused on the desertificaiton of arid and semiarid grasslands, sparked my interest in linking biogeochemistry and soil hydropedology (Castellano and Valone 2007). Two chief explanations (likely non-mutually exclusive) for the stability of desertified systems have been proposed; one focuses on soil hydology (e.g., Scheffer et al 2001 Nature 413, 591) and another focuses on biogeochemistry (e.g. Schlesinger et al 1990 Science 247, 1043). This work drew me to my current dissertation research with the USDA National Needs program.

Current Projects

Agricultural Systems

Abrupt changes in soil water status are “hot moments” for nutrient transport and transformation. Presently, I am working with John Schmidt at the USDA-ARS to examine soil hydrology and biogeochemical cycling in large (33 cm x 30 cm), relatively undisturbed soil cores. These cores were collected from a ditch-drained agricultural catena at the University of Maryland Eastern Shore’s research farm. We manipulate the cores’ water status to identify mechanisms controlling the tempo and mode of nutrient transport and transformation. To do this, we use a variety of instrumentation and analyses including soil moisture probes, tensiometers, gas flux analysis and lysimeters.

Natural Systems

Soil texture can control nutrient cycling through physical and biological mechanisms. In a small forested catchment located in suburban Baltimore, MD, we are examining these mechanisms’ relative importance during water transport down a hillslope. A gradient in sand content runs perpendicular to and parallel with the hillslope. In this setting, we are working to identify flow paths, their heterogeneity and importance for nutrient cycling and transport. For this work we make use of soil moisture monitoring sensors combined with chemical analyses and natural abundance stable isotope analyses of soil water. Additionally, we use stable isotope tracers to track nitrogen cycling within the soil.

Education

• M.S. Biology, Saint Louis University, 2004
• B.S. Wildlife Biology and Management, University of Rhode Island, 2001

Professional Experience

• 2004–2006, Research Associate, Department of Rangeland Ecology and Management, Texas A&M University
• 2002–2004, SLU 2000 Graduate Research Fellow, Department of Biology, Saint Louis University
• 2001–2002, Coastal Fellow, Department of Natural Resources Science, University of Rhode Island
• 2001, Research Technician, Department of Ecology and Organismal Biology, Indiana State University
• 2000, Research Technician, Southwestern Research Station, American Museum of Natural History, NY, NY.

Publications

1. Castellano, M.J., Schmidt, J.P., Kaye, J.P., Walker, C., Graham, C., Lin, H., Dell, C. In Press. Hydrological and biogeochemical controls on the timing and magnitude of nitrous oxide flux across an agricultural landscape. Global Change Biology
2. Castellano, M.J., Kaye, J.P. In Press. Global within-site variance in soil solution nitrogen and hydraulic conductivity are correlated with clay content. Ecosystems.1
3. 2007. Castellano, M.J., Valone, T.J. Livestock, soil compaction and water infiltration: evaluating a potential desertification recovery mechanism. Journal of Arid Environments, 71, 97-108.
4. 2007. Ansley, R.J., Castellano, M.J. Prickly pear cladode and whole plant responses to summer and winter Fires. Rangeland Ecology and Management (formerly J. Range Mgt.), 60, 244-252.
5. 2007. Castellano, M.J., Ansley, R.J. Fire season and simulated grazing differentially affect the stability and drought resilience of C4 bunchgrass, C3 bunchgrass and C4 lawngrass. Journal of Arid Environments. 69, 375-384.
6. 2007. Ansley, R.J., Castellano, M.J. Texas Wintergrass and buffalograss response to seasonal fires and clipping. Rangeland Ecology and Management. 60, 154-164.
7. 2006. Ansley, R.J., Castellano, M.J. Restoration strategies for shrub-encroached savanna: evaluating fire and herbicide. Restoration Ecology 14, 420–427.
8. 2006. Castellano, M.J., Valone, T.J. Effects of livestock removal and perennial grass recovery on the lizards of a desertified arid grassland. Journal of Arid Environments 66, 87–95.
9. 2006. Ansley, R.J., Wiedemann, H.T., Castellano, M.J., Slosser, J.E. Herbaceous response of juniper dominated grasslands with chaining and fire. Rangeland Ecology and Management 59, 171–178. (Best Technical Paper 2006, Texas SRM)
10. 2006. Ansley, R.J., Castellano, M.J., Pinchak, W.E. Sideoats grama responses to seasonal fires and clippings. Rangeland Ecology and Management 59, 258–266.
11. 2004. Hews, D.K., Castellano, M.J., Hara, E.H. Agression in females is also lateralized: left eye bias during aggression courtship rejection in Sceloporus virgatus lizards. Animal Behaviour 68, 1201–1207.