UC Berkeley

A process-based model (MAIDEN, modeling and analysis in dendroecology) is compared with statistical response functions to analyze the climate-growth relationship for two different species (sessile oak (Quercus petraea (Matt.) Liebl.) and Aleppo pine (Pinus halepensis Mill.)) growing in contrasting climates (temperate and Mediterranean). Growth data were obtained using dendroecological sampling procedures. Results obtained with both methods are consistent, but the MAIDEN model provides a more explanatory analysis than classical statistical tools. Analyses with MAIDEN indicate that oak stomatal conductance is sensitive to atmospheric vapor deficit, whereas precipitation and soil water deficit are not limiting factors in the study area. In contrast, the soil water regime is the major controlling factor of bole growth variability for Aleppo pine. The model shows that remobilization of the carbohydrate reserves in spring is of major importance for leaf and root expansion, and it affects the subsequent bole increment of oak. Because the amount of carbon that can be mobilized in spring is linked to carbon stored the previous year, these processes explain how the growth of oak trees is linked in this way from one year to the next. In contrast, the MAIDEN model shows that carbohydrate-reserve dynamics, phenology, and bole growth are less connected for Aleppo pine trees.