Non-random recruitment in boreal forests

Yingying Zhu, Lakehead University, Thunder bay, ON, Canada, Eric B. Searle, Natural Resource Management, Lakehead University, Thunder Bay, ON, Canada and Han Y. H. Chen, Faculty of Natural Resources Management, Lakehead University, Thunder Bay, ON, Canada

Background/Question/Methods:
Tree recruitment, along with mortality and the growth of surviving trees, drives forest dynamics; however, it has long been regarded as a random process. An in-depth understanding of recruitment is essential for the modelling of forest dynamics. Using a dataset of spatially mapped individual stems, which were repeatedly measured at five-year intervals between 1986 to 2010 from 173 permanent sample plots in Canada, we tested recruitment may be predictable via local neighborhood competition, interspecific vs. conspecific interactions, and stand developmental stages.
Results/Conclusions:
We show that the probability of recruitment decreases with neighborhood competition but increases with neighborhood shade tolerance and phylogenetic dissimilarities, and stand age. The positive effects of shade tolerance and phylogenetic dissimilarities on recruitment are stronger with increasing neighborhood competition. While the positive effect of shade tolerance dissimilarity is stronger in young stands, that of phylogenetic dissimilarity increases with stand age. Our results demonstrate that neighborhood interactions determine tree recruitment in boreal forests and offer mechanistic insights into the modelling of the recruitment component of forest dynamics.