Science

NZAGRC Science Leadership Team

The role of NZAGRC Science Leadership Team (SLT) is to play a key part in the development, implementation and monitoring of all of the Centre’s science programmes and strategies.  It consists of respected New Zealand-based researchers with excellent science credentials accompanied by strong leadership, communication, strategic and inter-personal skills with expertise in those areas of science covered in the NZAGRC Strategy and Science Plan.

Membership is agreed by the Steering Group and includes the NZAGRC Principal Investigators in addition to the NZAGRC Director and NZAGRC Operations Manager.  

Dr Graeme Attwood  AgResearch  
Dr Cecile DeKlein   AgResearch 
Professor Hong Di  Lincoln University 
Dr Robyn Dynes  AgResearch  
Dr Peter Janssen  AgResearch  
Dr David Whitehead   Manaaki Whenua

 

Science leadership & capability building 

The NZAGRC is committed to providing opportunities for researchers to be trained and work with leading experts in New Zealand.  Some students go on to continue their studies or enter a postdoctoral position under guidance from NZAGRC science leaders, other enter into industry based positions.

The NZAGRC supports more than 50 researchers and students by providing funding via its core research programme or via its student scholarships programme.

Below are profiles of our scientists and past students. 

Low spatial and inter-annual variability of evaporation from a year-round intensively grazed temperate pasture system

J. Pronger, D.I. Campbell, M.J. Clearwater, S. Rutledge, A.M. Wall, L.A. Schipper, Low spatial and inter-annual variability of evaporation from a year-round intensively grazed temperate pasture system, Agriculture, Ecosystems & Environment, Volume 232, 2016, Pages 46-58, ISSN 0167-8809,

http://dx.doi.org/10.1016/j.agee.2016.07.011

Ecosystem scale measurements of evaporation (E) from intensively managed pasture systems are important for informing water resource decision making and validation of hydrologic models and remote sensing methods. We measured E from a year round intensively grazed temperate pasture system in New Zealand using the eddy covariance method for three years (2012-2014). Evaporation varied by less than 3% both spatially (770⿿783mm) and temporally (759-776mm) at an annual scale. The low spatial and temporal variation largely occurred because E was strongly controlled by net radiation (r2=0.81, p<0.01, daytime, half-hourly), which did not vary much between sites and years. However, E was strongly limited when volumetric moisture content (VMC) declined below permanent wilting point causing a strong reduction in the decoupling coefficient and an increase in the Bowen ratio. Grazing events appeared to have no effect on E during autumn and winter but reduced E by up to 5% during summer and spring while complete removal of vegetation during autumn herbicide application reduced E by ⿼30%. This implied that over the pasture regrowth period soil water evaporation (ES) could provide up to 70% of E relative to a vegetated site (during autumn) and, given that grazing events removed about 60% of leaf area, these findings suggest ES was likely able to compensate for decreased transpiration post-grazing. Agreement between measured E (EEC) and FAO-56 reference crop E (Eo) was good when soil moisture limitation was not occurring. However, during periods of soil moisture limitation Eo exceeded EEC and a correction factor was needed. We trialled the water stress coefficient (Ks) and a simple three bin VMC correction factor (KVMC) and found the KVMC approach worked better at a daily and monthly scale while both approaches worked well at an annual scale.


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