Upscaling greenhouse gas emissions and carbon sequestration

Our research priority area combines observed data and process-based insights and databases with advanced models to improve estimates of greenhouse gas emissions scaled from small plots to catchments and then to New Zealand.

We are working on two main process-based models to upscale greenhouse gas emissions and carbon.

First, we have used a process-based soil greenhouse gas flux model (NZ-DNDC) to generate look-up tables for potential nitrous oxide emission factors using 20 years of climate data over a range of soil types, climatic conditions, and farm management practices (Figure 1). The emission factors are the average emission rates of nitrous oxide relative to the amount of nitrogen inputs. By multiplying the emission factors by the inputs in nitrogen (from animals and fertilisers), we can estimate the spatial pattern of nitrous oxide emissions and chart the impact of land-use change on emissions from catchment to national scales. This approach incorporates variability associated with soil and climate and will improve the estimation of emissions nationally.

Second, we are also developing and applying a carbon and nutrient-cycling model, CenW, to model the exchange of carbon of different vegetation types under different soil and environmental factors (Figure 2). We used CenW in a recent contract for the Ministry for Primary Industries to generate productivity surfaces of Pinus radiata and kanuka/manuka under both current climatic conditions and various climate-change scenarios. Growth of both stand types is likely to benefit from moderate climate warming, especially in the South Island. Factoring in increases in carbon dioxide concentration is likely to result in enhanced growth across New Zealand.

Our aim is to combine and further develop these internationally recognised models to provide a comprehensive tool to predict current and future carbon storage and greenhouse gas emission trends.

Anne-Gaelle Ausseil, Donna Giltrap, Miko Kirschbaum And Kalish Thakur