Landscape gradient of autumn photosynthetic decline in Abies sachalinensis seedlings

Understanding what environmental factors are genetically linked to a phenological event is critical for predicting responses to climate change. Photosynthetic phenology often varies among a species of evergreen conifers due to local adaptation. However, few empirical studies have revealed relevant relationships between climatic factors in provenance environments and photosynthetic phenology. This study evaluated the effects of environmental conditions of the growing site and seed source provenance on the seasonal changes in maximal photochemical quantum yield of photosystem II ( F v / F m ) in a common garden experiment with 2-year-old seedlings of Sakhalin fir ( Abies sachalinensis ), a representative species with local adaptation, from four seed source provenances. A logistic model was constructed to explain the seasonal variation of F v / F m from July to October and the relationships between the estimated model parameters and representative factors featuring provenance environments were evaluated. The landscape gradient of the detected model parameters responsible for the provenance environments was visualized in a map of the distribution area. The lowest temperature was the most plausible factor in the growing environment to explain the seasonal changes of F v / F m . Among the representative meteorological factors of provenance environments, the lowest temperatures in July showed significant relationships with two model parameters, explaining the lower limit of F v / F m and the higher sensitivity of autumn F v / F m decline. The estimated spatial maps of model parameters consistently showed that the higher the lowest temperature in July in the provenance environment, the lower the F v / F m in October and the greater the decrease in the autumn F v / F m decline. Therefore, the lowest summer temperature could be associated with the local adaptation of autumn photosynthetic phenology in A. sachalinensis.