A model of frost impacts on seasonal photosynthesis of Eucalyptus pauciflora

Abstract

A model of the time course of frost impacts on seasonal photosynthesis of Eucalyptus pauciflora Sieb. ex Spreng. was constructed, incorporating seasonal shifts in frost hardiness and both short- and long-term impacts on the initial slope and saturated level of the photosynthetic light response curve. The approach is an extension of Sands' model (Australian Journal of Plant Physiology, 1995, 22, 603-614) which calculates daily canopy photosynthesis as a function of daily irradiance and temperatures without the impacts of cold nights. Modelled effects of frost on cumulative photosynthesis over 8 months were highly nonlinear and rather sensitive to the temporal sequence of minimum temperatures and extent of frost hardening. Most of the effects were associated with long-term damage caused by a few severe or unseasonal frosts. Shifting either plant sensitivity or minimum temperatures by several degrees had large impacts on predicted outcomes. These results are consistent with other observations that the increase in frost severity associated with land clearing is impeding eucalypt regeneration in interior Australia and may be applicable to other frost-prone areas.