Developing stand transpiration model relating canopy conductance to stand sapwood area in a Korean pine plantation

With increasing concern for forest water use and anthropogenic alteration of forest structures, understanding the effects of structural changes in forests on transpiration is important. Our aim is to develop a stand transpiration model relating canopy conductance with stand sapwood area (SA) and environmental conditions for assessing the interannual variation in stand transpiration. The stand transpiration model is developed based on multiplicative empirical Gc estimations at eight Korean pine stands with different SAs. The model integrated the response of stomatal conductance to various environmental variables as vapor pressure deficit (D), photosynthetic active radiation (Q), air temperature (Ta), and soil water content (θ). The reference Gc (Gc at D=1kPa) and stomatal sensitivity to D was found to have a significant relationship with the SA, whereas other parameters like stomatal sensitivity to Q or Ta did not show significant relationships with it. The Gc model successfully reproduced changes in stand transpiration with changes in SA and climatic conditions. As this model uses SA, a simple and easily measurable structural variable, it can be easily applied to other Korean pine forests and can help estimate the spatial and temporal variations in stand transpiration.