Using portfolio theory to evaluate the regional deployment of transferring tree seeds under uncertain future climates

Abstract

In this study, the problem of deploying seed from multiple tree improvement orchards to multiple sites in an environment of uncertain climate change is addressed. A modeling approach is designed and applied with the objective providing a robust solution, i.e., transferred seed sources perform well across multiple climatic scenarios. The approach involves two steps. First, the focal point seed zone method is employed to predict seed deployment zones under multiple future climate scenarios. Next, a portfolio model is applied to minimize the risk of maladaptation of the transferred seed under multiple climatic scenarios. The method was applied using black spruce (Picea mariana ) field data from 7 sites using 24 seed sources from the Great Lakes area. The focal point seed zone method generated deployment zones for 24 seed sources over three 30-years periods under 12 predicted future climate scenarios. Next, the optimization procedure searched for eligible sites that can receive improved seed sources from 7 provenances considering 12 different climatic scenarios. The portfolio model also produced the optimal composition of candidate seed sources at each eligible site. Sensitivity of the solutions to different emission scenarios is compared. Finally, geographic representations of results were illustrated in Geographic Information System. It was concluded that this modeling framework provides a useful approach for decision-makers to address the problem of deploying seed at regional scale, such that the risk of climatic maladaptation is minimized.