Assessing local adaptation vs. plasticity under different resource conditions in seedlings of a dominant boreal tree species.

Anastasia E Sniderhan,Jennifer L Baltzer,Gordon G Mcnickle

doi:10.1093/aobpla/ply004

Anastasia E Sniderhan, Jennifer L Baltzer + Show 1 more

Open Access

https://doi.org/10.1093/aobpla/ply004

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Abstract

Under changing climate conditions, understanding local adaptation of plants is crucial to predicting the resilience of ecosystems. We selected black spruce (Picea mariana), the most dominant tree species in the North American boreal forest, in order to evaluate local adaptation vs. plasticity across regions experiencing some of the most extreme climate warming globally. Seeds from three provenances across the latitudinal extent of this species in northwestern Canada were planted in a common garden study in growth chambers. Two levels of two resource conditions were applied (low/high nutrient and ambient/elevated CO2) in a fully factorial design and we measured physiological traits, allocational traits, growth and survival. We found significant differences in height, root length and biomass among populations, with southern populations producing the largest seedlings. However, we did not detect meaningful significant differences among nutrient or CO2 treatments in any traits measured, and there were no consistent population-level differences in physiological traits or allocation patterns. We found that there was greater mortality after simulated winter in the high nutrient treatment, which may reflect an important shift in seedling growth strategies under increased resource availability. Our study provides important insight into how this dominant boreal tree species might respond to the changing climate conditions predicted in this region.

Highlights

Changes in global climate patterns over the past century have led to shifts in climate envelopes, that is, the set of climatological characteristics that delineate the extent of a species’ range (Walther et al 2002)
We investigated allocation patterns in the seedlings by calculating specific leaf area (SLA; fresh leaf area divided by dry leaf mass), specific root length (SRL; fresh root length divided by dry root mass), root/shoot ratio (R:S), root/mass ratio (RMR), leaf/mass ratio (LMR) and stem/mass ratio (SMR)
Over the course of the experiment, we found a significant interaction between population and time in our model of seedling height, driven by the fact that southern populations grew at a faster rate than northern populations (Fig. 2; Table 1)

Summary

Introduction

Changes in global climate patterns over the past century have led to shifts in climate envelopes, that is, the set of climatological characteristics that delineate the extent of a species’ range (Walther et al 2002). A study on Pinus sylvestris demonstrated latitudinal differentiation in plasticity of the timing of growth cessation under variable climate conditions (Savolainen et al 2004)—likely as a result of the high cost of maintaining plasticity in the face of resource limitations at some sites (DeWitt et al 1998). There is evidence that this fast–slow continuum corresponds with the degree of plasticity that species can maintain; individuals from populations adapted to higher resource conditions show greater plasticity in their traits than those from resource-limited populations, which take a slow and steady approach that does not support plasticity This pattern is seen in studies along elevational gradients that have found that plasticity of some tree seedlings is lower at higher altitudes This pattern is seen in studies along elevational gradients that have found that plasticity of some tree seedlings is lower at higher altitudes (e.g. Green 2005; Vitasse et al 2013), but the fast–slow spectrum has not been investigated across latitudinal ranges

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