Monitoring New Zealand's soil carbon reservoir
As a signatory to the Framework Convention for Climate Change, New Zealand must report on and preserve major carbon (C) reservoirs. The Government identified plantation forests as the country's major C sink, and adopted a policy for offsetting increased carbon dioxide (CO2) emissions by increasing plantings of new (exotic) forests. The consequences of this and other changes in land use on soil C and sustainable land management are poorly understood. Soils are our largest reservoir of C.
Kevin Tate in collaboration with Forest Research colleagues, is developing a national system for monitoring changes in soil C caused by altered land-use. ‘Land use coefficients' were generated by linking updated 1990 baseline soil C estimates to discrete combinations of the three major factors (climate, land use, and soil type) influencing soil C. These coefficients can be applied regionally and nationally to assess the effects of changing land use on soil C and CO2 emissions.
The ‘land use coefficients' can also be used to determine how soil C has been affected by significant historical changes to land use e.g., indigenous forest converted to pastures, scrub or pine plantations. They do not, however, reveal any information about the temporal changes occurring during the transition from one land use to another. Process-based models (being developed in our PGSF research), present and future soil C monitoring, and up-dated land-use information will all be needed to address this issue.
In preliminary tests of the monitoring system, the land-use coefficients were better at predicting soil C for an area of the South Island than previous techiques based on soil type alone. Estimates based on the monitoring system compared favorably with soil C estimates for the same area based on extensive sampling and detailed land surface information. Future work will test the system at a wider range of sites and compare soil C changes with results from paired site studies (PGSF research) examining land-use change effects on soil C.
Contact:
Kevin Tate Email
Collaborators:
Forest ResearchFunding for this work was provided by the Ministry for the Environment (MfE)