Climate change experiment suggests divergent responses of tree seedlings in eastern North America’s Acadian Forest Region over the 21st century

William R Vaughn,Anthony R Taylor,Loïc D’Orangeville,David A Maclean,Michael B Lavigne

doi:10.1139/cjfr-2021-0047

Abstract

In this study, we conducted a controlled experiment to assess the growth and survival of balsam fir (Abies balsamea (L.) Mill.), red spruce (Picea rubens Sarg.), and red maple (Acer rubrum L.) seedlings in response to warming, drought, and elevated CO2, as projected under RCP 8.5 for North America’s Acadian Forest Region. In response to warming, only red spruce increased in height; however, this effect varied by CO2 and soil moisture treatments. Under the drought treatment, red spruce biomass was not affected, but mortality increased by 2%. With warming, increases in balsam fir height growth were only detected under certain soil moisture and CO2 conditions. Balsam fir biomass decreased by 24% under drought, while mortality increased by 5%. Warming did not improve red maple height growth, but it remained 7–50 times greater than that of the conifers and no mortality was observed. Overall, CO2 enrichment increased height growth of droughted seedlings relative to the ambient treatment, demonstrating an amelioration of the negative drought effect. Balsam fir was the least adapted to warming and drought, while red spruce displayed some positive responses. Although growth of red maple seedlings did not increase with warming, they exhibited greater absolute growth and survival, which suggests red maple may outperform both conifers under a warming climate.

Highlights

The early life stages of plant species are the most sensitive to environmental stress and may greatly influence plant community assembly and succession under climate change (Johnstone et al., 2010; Kroel-Dulay et al, 2015)
Red spruce (Picea rubens Sarg.) seedlings grown under 713 CO2 ppm were 40% larger in both size and weight when compared to seedlings under ambient conditions (Samuelson & Seiler, 1994)
The drought soil moisture treatment, which produced soil water potential estimates similar to those of drought stress field studies (Major & Johnsen, 1996; Olesinski et al, 2011), generally reduced aboveground growth of all species; the negative effect of drought was alleviated under elevated CO2, in accordance with previous studies (Swann et al, 2016; Sperry et al, 2019). This was evident in the height growth of balsam fir, red spruce and red maple seedlings in the drought treatments, which exhibited significant increases under elevated CO2 relative to the ambient treatments

Summary

Introduction

The early life stages of plant species are the most sensitive to environmental stress and may greatly influence plant community assembly and succession under climate change (Johnstone et al., 2010; Kroel-Dulay et al, 2015). The AFR lies within North America’s boreal-temperate ecotone, an ecological transition zone where many constituent tree species are at either their northern or southern climatic range limits. Cold-adapted species, such as balsam fir (Abies balsamea (L.) Mill.), are projected to decline in abundance with warming, while warm-adapted, temperate species with more southerly range limits, such as red maple (Acer rubrum L.), are expected to thrive under climate change (Boulanger et al, 2018; Bourque & Hassan, 2008; Ashraf et al, 2015; Taylor et al, 2017). In the absence of moisture stress and nutrient limitations, rising atmospheric CO2 may increase forest growth; it is unclear whether this increase in productivity will be sustained over the long-term (Beedlow et al, 2004). Without additional mitigation efforts beyond those currently in place, atmospheric concentrations of carbon dioxide (CO2) are projected to exceed 1000 ppm by the year 2100 under the RCP 8.5 scenario (IPCC, 2014)

Methods

Results

Discussion

Conclusion