Early growth responses of black spruce seed sources selected for reforestation under climate change scenarios in Ontario

Abstract

Study area : Northern boreal forest: (Northeastern - Sault Ste. Marie region) ; (Northwestern : Dryden and Kakabeka regions)

Reforestation programmes under changing climates requires an understanding of species adaptive patterns of variation. Such information is vital in identifying and matching uniquely adapted seed sources to areas of optimum growth, conserving the genetic variation of the species as well as reducing the risk of using maladapted sources. This study examined early growth responses of selected black spruce (Picea mariana (Mill.) B.S.P) seed sources identified for reforestation through the application of a portfolio theory model and planted at three climatically diverse sites in Ontario. Two sequential modeling approaches were applied; 1) the species range impact model which uses biological growth responses and climatic data to determine how well a seed source will grow at a given site under different climate change scenarios, and 2) the portfolio model which selects a set of seed sources that collectively reduce risk of maladaptation. Significant variations were found in the growth responses of black spruce seed sources growing at the three sites. Seed sources originating from the southerly portions of the test locations demonstrated superior growth. Principal components analysis of fall height, spring height, increment and survival showed that a high proportion of the variation among the seed sources can be explained by fall height growth. Among climate variables, minimum and maximum temperatures and precipitation in the spring, summer and fall growing seasons were identified as good predictors of black spruce growth. The results suggest that black spruce seed sources are adapted to their local climates and that future climate can result in maladaptation of the species within their current ranges. The capability of the applied models to identify well adapted seed sources and match the sources into required future climates is novel and invaluable. The results and model predictions have wide implications for biodiversity conservation efforts and may be useful in seed transfer programmes under the changing climates. The early results suggest that the combination of species range impact model and portfolio decision support model identify an adaptive pattern of variation from multiple seed sources, and select a set of sources to succeed under a multiple climate change scenarios. Also, the result gives an indication that southern seed sources may well be suitable for future reforestation programmes in the Ontario Boreal Forest Region.