The effect of climate on the occurrence and abundance of tree recruitment in the province of Quebec, Canada

Abstract Tree recruitment is affected by numerous biotic and abiotic factors, including climate. However, the relative importance of climate variables in empirical models of tree recruitment remains to be evaluated. We fitted models of tree recruitment to 26 species in the province of Quebec, Canada. For a better understanding of the recruitment process, we used a two-part model to distinguish recruitment occurrence from abundance. The relative importance of the different variables was assessed using Akaike weights. Our main hypothesis was that climate is one of the major drivers of tree recruitment. Our results showed that growing degree-days counted among the major drivers of recruitment occurrence but not of recruitment abundance. Stand variables, such as the presence and abundance of adult trees of the species, and broadleaved and coniferous basal areas were found to be relatively more important than all the climate variables for both recruitment occurrence and abundance. Species occupancy within a 10-km radius also had a significant effect on recruitment occurrence for two-thirds of the species, but it was less important than growing degree-days and other stand variables. Climate change is expected to improve the suitability of habitats located at the northern edge of species distributions. However, our model predictions point to a low probability of colonization in newly suitable habitats in the short term.