Natasja C. van Gestel

Before I joined Texas Tech University in 2002, I had worked on several projects, one of which took me to the Center for Ecology and Hydrology (CEH), formerly known as the Institute of Terrestrial Ecology in Edinburgh, Scotland, in 1995 where I compiled data from literature on N content of trees that may prove useful for agroforestry.  

Afterwards, I worked mostly on forest soils and their soil chemistry. In oak forests which varied in age from 0 (agricultural field) to at least 100 years, a fellow student and I collected soil samples and looked at the soil chemistry (organic matter content, pH, cations) and soil biota. For soil biota we especially focused on soil nematodes and determined number per species and species composition. The objective was to determine how long it would take for the soil in an agricultural field, when planted with oak trees, to return to more “natural” forest conditions.  

In another forest, which took me to the Institute of Ecosystem Studies, Millbrook, NY, I looked at the calcium cycle in forest soils under three different tree species: sugar maple (Acer saccharum), eastern hemlock (Tsuga canadensis), and American beech (Fagus grandifolia). I took soil samples from beneath the different tree canopies and incubated the samples in the lab and measured concentrations of basic cations in the soil, the cation exchange capacity (CEC), pH, and organic matter content pre- and post-incubation. Major differences were found especially between hemlock and maple: soils beneath sugar maple had much higher exchangeable calcium, higher pH, and lower organic matter content than soils beneath hemlock.  

In 1999 I worked with Dr. Scott Franklin on a project in Tennessee that studied the effects of channel modification (unchannelized, channelized, and channelized & leveed) on hydrology and nutrient pools in floodplain forests.

In 2000, I went back to the Institute of Ecosystem Studies to work as a research assistant in the same forest where I did my previous research. Soils around different tree saplings were fertilized and the impact of fertilization on tree growth was studied.  

Following my research, I worked in the Grants Department at the Institute of Ecosystem Studies as a Grants Administrative Assistant for a couple of years. I dealt with proposal submissions, accounting, subcontracts, financial reports, and many other tasks.  

Currently, I’m working with David Tissue as a Research Associate. My first 2 major projects involved NASA-funded research to study the impact of increased source (i.e. photosynthesis) on plants that differ in carbohydrate storage capacity (bulbing vs. non-bulbing onions). We increased the source in two different ways: exposing plants to either continuous light or to elevated CO₂. When exposed to continuous light, Allium fistulosum had higher foliar carbohydrate levels, which resulted in photosynthetic down-regulation due to a carbohydrate feedback effect. In contrast, A. cepa responded to the longer irradiance period by forming large bulbs to which the carbohydrates were transported into. Elevated CO₂ (120 Pa vs. 40 Pa) did not have a significant effect on either growth or physiology. This suggests that plants may not show a response to elevated CO₂ when grown at relatively low (~350 umol m^-2 s^-1) light levels.  

In addition to the NASA project, I’ve worked on several other projects including the Big Bend National Park Project. This project involves simulating a 25% increase in precipitation at different times of the year (summer, winter and both summer/winter) and see how the plants respond in terms of physiology, growth, and species composition.

Publications

Franklin, Scott B., John A. Kupfer, S. Reza Pezeshki, Natasja van Gestel & Randy Gentry. 2001. Channelization effects on floodplain functions in western Tennessee. Pp. 189-201 In: R.A. Falconer & W.R. Blain (eds.) River Basin Management WITpress, Southampton, Boston. 

Van Gestel, N.C., A.D. Nesbit, E.P. Gordon, C. Green, P.W. Paré, L. Thompson, E.B. Peffley, and D.T. Tissue. 2005. Continuous light may induce photosynthetic downregulation in onion -- consequences for growth and biomass partitioning . Physiologia Plantarum 125: 235-246.

Publication in Preparation

Van Gestel, N.C., E.P. Gordon, T.R. Robertson, L.D. Patrick, , P. Payton, C. Green, P.W. Paré, L. Thompson, E.B. Peffley, D.T. Tissue. In prep. Effects of elevated CO₂ on Allium grown under controlled conditions

Meetings

Franklin, S.B., J.A. Kupfer, S.R. Pezeshki, and N. van Gestel. 2001. Channelization effects on floodplain nutrient pools in western Tennessee. Annual Meeting of the Association of Southeastern Biologists, New Orleans, LA

Gordon, E.P., N. van Gestel, T.R. Robertson, L.D. Patrick, P. Payton, D.T. Tissue. 2004. Effects of elevated CO₂ on Allium plants grown under controlled conditions. Ecological Society of America (ESA), Annual Meeting, Portland, OR. (poster presentation) p. 183.

Patrick, L.D., T.R. Robertson, N.C. van Gestel, and D.T. Tissue. 2005. Responses of daytime net ecosystem and water exchange to increased seasonal precipitation in a sotol-grassland at Big Bend National Park, Texas. Ecological Society of America (ESA), Annual Meeting, Montréal, Canada (poster presentation) 

Robertson, T.R., N. van Gestel, E. Walker, J.C. Zak, M. Loik, and D.T. Tissue. 2004. Plant growth responses to simulated rainfall events for three perennial Chihuahuan desert species of Big Bend National Park. Ecological Society of America (ESA), Annual Meeting, Portland, OR. (oral presentation) p. 432  

Robertson, T.R. N. van Gestel, E. Walker, L. Patrick, E. Gordon, J.C. Zak, M. Loik, and D.T. Tissue. 2005. Species composition response to variation in timing and magnitude of precipitation in a sotol grassland in Big Bend National Park, Texas. Southwestern Association of Naturalists (SWAN), Huntsville, Texas

Van Gestel, N.C., A.D. Nesbit, E.P. Gordon, J. Nagel, L.D. Haley, E.B. Peffley, and D.T. Tissue. 2004.  Effect of continuous light on the physiology and biochemistry of A. fistulosum and A. cepa. Ecological Society of America (ESA), Annual Meeting, Portland, OR. (oral presentation) p. 518. 

Van Gestel, N.C., A.D. Nesbit, E.B. Peffley, and D.T. Tissue. 2003. Effect of Photoperiod on Photosynthetic Performance and Carbon Flux of Allium fistulosum and A. cepa. Ecological Society of America (ESA), Annual Meeting, Savannah, GA. (poster presentation)