Growth and yield modelling in a climate of change: How can we make good use of data from past epochs?

Authors: Euan Mason
Publication: New Zealand Journal of Forestry, Volume N.Z.J.For. 2009, Issue N.Z.J.For. 54(3) 2009, pp 19-25, Nov 2009
Publisher: New Zealand Institute of Forestry

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Abstract: Changes in climate projected by the National Institute of Water and Atmospheric Research imply that either past records from permanent sample plots (PSPs) will be redundant, or that we need to adopt some new approaches to growth and yield modelling. The heart of the issue is that traditional mensurational models employ time as a surrogate for inputs of radiation and changing capacities of plants to intercept and use radiation. If climatic conditions change, then time no longer has the same meaning within the context of such a model. This might not matter if climate change occurred at one point in time, outside the time period covered by a rotation. If the influence of time changes within a rotation, then traditional mensurational models will provide biased estimates. A new approach to mensurational modelling has been developed that employs radiation sums in mensurational equations instead of time. These sums are modified by impacts of monthly climate on a tree’s ability to make use of intercepted radiation. The new approach was tried using data from PSPs in radiata pine plantations in the Central North Island for models of mean top height and basal area/ha. Fits using the new approach were more precise than those using equivalent models based on time.

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