Morphological and physiological responses of balsam fir provenances in eastern Canada to climatic variation

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University of New Brunswick
Trees are vulnerable to climate change due to their long lifespan and low adaptation capability. However, the long-term impacts of climate change on tree growth and survival remain unclear. The objectives of this dissertation were to characterise (i) the long-term morphological, (ii) survival, and (iii) short-to-intermediate term physiological response in balsam fir [Abies balsamea (L.) Mill.] to climatic variation. Morphological, survival, and physiological characteristics of balsam fir provenances from seed sources with different climatic conditions, planted in a common garden in New Brunswick, Canada, were studied to facilitate the understanding of the dynamics of these characteristics under changing climatic conditions. Also studied was the effect of detachment on gas-exchange in balsam fir foliage, as gas-exchange measurements were made on detached branches from trees ≥ 10 m in height. The findings of these studies indicate that the response of balsam fir to climatic variation will likely differ based on genetic characteristics of northern and southern populations of the species, and be more evident in growth traits, than survival. Flexibility of the species’ foliage under variable climate may enable adjustment of its photosynthetic activities in response. Reliable gas-exchange measurements can be done up to 30 minutes after detachment, using foliage on detached branches 50–80 cm long in cooler growing-season months. There was no intraspecific variation in balsam fir photosynthetic parameters, whereas it was evident in stomatal conductance. Balsam fir intrinsic water-use efficiency variation was strongly linked to intraspecific variation in stomatal conductance. Balsam fir shade tolerance may likely be important in the survival of its populations under changes in forest dynamics, projected to accompany climate change. Temperature and morphological traits are strongly linked, with temperature and precipitation influencing survival. The relationship between climatic factors and physiological traits is minimal. Vigorous diameter growth in balsam fir, and the effect of tree size on survival in the species is maintained under climatic variation. There is a clear, positive association between intrinsic water use efficiency and radial growth in balsam fir. These can be important factors for modelling of balsam fir traits under changing climatic conditions and selection in the species for forest management strategies.