For the last two decades, we have explored how adding carbon sources, such as wood chips, into the landscape might increase nitrate removal through enhanced denitrification. We have examined denitrification walls and beds for treating nitrate in different hydraulic flow pathways (groundwater, tile drainage, wastewaters). Recently, we have expanded our interests to the performance of these systems for removing pathogens and ammonium. A focus now is whether there are simple ways to enhance the performance of these systems focusing on laboratory and field testing of approaches to reversibly trap nitrate (via surface modification of wood), control redox potential to reduce undesired product formation (through addition of specific metals) and enhance denitrification through carbon dosing.
A great opportunity to work in a team addressing agricultural nutrient losses. See hyperlinks to find out more and how to apply. Some good background on doing a PhD in New Zealand can be found here.
Rambags, F.; Tanner, C.C.; Stott, R.; Schipper, L.A. (2016) Fecal bacteria, bacteriophage, and nutrient reductions in a full-scale denitrifying woodchip bioreactor. Journal of Environmental Quality. 45:847-854.
Addy, K.; Gold, A.J.; Christianson, L.E.; David, M.B.; Schipper, L.A.; Sacha, N.A. (2016). Denitrifying bioreactors for nitrate removal: an meta-analysis. Journal of Environmental Quality. 45:873-881.
Schipper, L.A.; Robertson, W.D.; Gold A.J.; Jaynes, D.B.; Cameron, S.G. (2010) Denitrifying bioreactors – an approach for reducing nitrate loads to receiving waters. Ecological Engineering. 36 (11): 1532-1543.
We have a wide variety of other research interests and below we list a few of our most recent specific interests. These projects can be tailored to fit an MSc or PhD thesis.
Currently, these projects do not have funding but the University does offer PhD scholarships for both New Zealanders and international students through the general MSc and PhD University of Waikato scholarships. These are very competitive and require careful consultation between the potential applicant and an academic at the University.
We are happy to discuss potential projects and receive frequent requests to work with us on projects. We can only support a few applicants and our support does not guarantee success in obtaining a scholarship. Consequently, if you are interested in one of these projects it is important that you demonstrate to us that you understand and are genuinely engaged in the topic.
The criteria for success also depends on prior academic achievement, e.g., high GPA or equivalent and also a desire to fit into our team.
When you do contact us, it is really helpful if you are specific about your interests rather than asking us to generically look at your CV. We are also wary of opening attachments as these have been used in the past as Malware.
Grazing timing and intensity effects on carbon budget and grass production (PhD). One of the major influences on CO2 fluxes and the overall carbon balance of pastures is the frequency and intensity of grazing. We are hoping to put some more effort into designing experiments around this, but for now we have multiple datasets for grazed paddocks (and a fallow paddock) as well as a modelling approach that might help us quantify the scale of variation in net CO2 fluxes caused by variations in grazing timing and intensity. We recently developed a methodology for quantifying the impact of grazing events on CO2 exchange.
Campbell, D.I.; Wall, A.A.; Nieveen, J.P.; Schipper L.A. (2015) Variations in CO2 exchange for dairy farms with year-round rotational grazing on peat soils. Agriculture, Ecosystems and Environment. 202: 68-78.
Temperature dependence of soil biology. With Vic Arcus, we have developed a new theory of temperature dependence of biological rates. We are interested in determining testing how well this theory predicts a range of soil biological processes. We have specific interest in how carbon cycling in soil (e.g., carbon quality and supply, respiration) is responsive to temperature. See:
Schipper, L.A.; Hobbs, J.K.; Rutledge S.; Arcus, V.L. (2014) Thermodynamic theory explains the temperature optima of soil microbial processes and high Q10 values at low temperatures. Global Change Biology. 20, 3578–3586. DOI: 10.1111/gcb.12596.
Arcus, V.L.; Prentice, E.; Hobbs, J.K.; Mulholland, A.J.; Vander Kamp, M.W.; Pudney, C.R.; Parker, E.J.; Schipper, L.A. (2016) On the temperature dependence of enzyme-catalysed rates. Biochemistry. 55: 1681-1688. ACS Editors’ Choice
Ecohydrology of the Kopuatai peat bog (MSc). An unusual feature of the large raised bogs of northern New Zealand is that they exist in a climate zone that suffers from frequent large seasonal water deficits, with projected increased severity of summer droughts. Our previous research has shown that the vascular plant canopy in these bogs is highly conservative in its water use via transpiration and evaporation, and it is hypothesised that this is a key factor enabling them to accumulate peat over many thousands of years. However, our early work in the 1990’s was for summertime conditions. We are looking for a student to test this hypothesis in terms of the annual water balance of Kopuatai bog. The research methods will combine field experiments on the water balance of the vascular plant canopy, and analysis of eddy covariance (EC) and supporting data accumulated over the last three years. In a parallel study we have been using the EC method to measure ecosystem carbon balance components at the Kopuatai peat bog since late 2011, and are currently writing up our research on CO2 and CH4 exchanges as well as on the overall peatland carbon balance. For background references, see:
Campbell, D.I. and Williamson, J.L., 1997. Evaporation from a raised peat bog. Journal of Hydrology, 193: 142–160.
Thompson, M.A., Campbell, D.I., and Spronken-Smith, R.A., 1999. Evaporation from natural and modified raised peat bogs in New Zealand. Agricultural and Forest Meteorology, 95: 85–98.
Carbon balance and the status of peat accumulation in a remnant raised peat bog (PhD). We previously measured CO2 exchanges in the remnant Moanatuatua raised peat bog in NZ about 15 years ago. We had hypothesised that the lowered water table would have led to net CO2 losses resulting in a loss of peat mass. In fact we found that the year-round growing conditions in our mild climate, combined with relatively small respired CO2 losses, actually led to the bog being a very strong sink for CO2. There is renewed interest in restoring this bog, and we need to understand what its current carbon balance (and peat accumulation rate) is compared to the relatively pristine Kopuatai bog, where we have been measuring C balance components for the last 3 years. This study will include the establishment and operation of a new eddy covariance system at Moanatuatua bog, and the design of experiments to determine whether carbon is being partitioned into accumulating peat. There is the opportunity to compare carbon balance exchange processes between “wet” (Kopuatai) and “dry” (Moanatuatua) bogs. See:
Campbell, D.I., Smith, J., Goodrich, J.P., Wall, A.M. and Schipper, L.A., 2014. Year-round growing conditions explains large CO2 sink strength in a New Zealand raised peat bog. Agricultural and Forest Meteorology, 192-193: 59-68.
Optimising drainage design for peat soils (MSc). Around 80% of the Waikato Region’s 94,000 ha of peatland area has been drained for agriculture and continues to suffer from ongoing surface shrinkage and emission of large amounts of CO2 to the atmosphere. Farm drains also threaten water-dependent ecosystems such as the remnant Moanatuatua bog. This research project will investigate the optimal design of farm drainage systems that will allow maximal pasture production without threatening ecosystem sustainability. See:
Pronger, J.; Schipper, L.A.; Hill, R.; Campbell D.I.; McLeod, M. (2014) Subsidence rates of drained agricultural peatlands in New Zealand and the relationship with time since drainage. Journal of Environmental Quality. 43: 1442-1449
Note that the ideas/descriptions/opinions on these pages are ours and may not reflect those of the University of Waikato.