Plant ranges, broadly constrained by climate, may be further shaped by interspecific interactions and intraspecific variation in growth and traits. Changing climate and species composition in plant communities lends urgency to the need to better define the factors determining species’ distributions. This research seeks to determine the effects of temperature and neighbors on sugar maple (Acer saccharum) seedling survival, growth, biomass allocation, and functional traits, and whether this response varies with populations’ climate of origin. I first examine survival and growth of forest-planted seedlings across a natural climate gradient and beyond range limits to determine whether populations’ climate of origin and contrasting neighbor density and light environments affect performance. I find no evidence of climate or competition limitation beyond range margins for populations grown near their region of origin, but populations differ in survival and net growth in a manner consistent with local adaptation and contrasting growth strategies: the northern population has high survival across sites but lower mass than the southern population, which has low survival and growth facilitated by neighbors at northern sites. I then examine whether patterns of root biomass allocation of these same seedlings is affected by climate of the planting site or each populations’ region of origin. I find higher root mass in southern population seedlings than in similarly sized northern population seedlings, and higher root mass fraction at colder sites in the southern (but not northern) population. Finally, I use growth chambers to examine the effects of temperature and light on growth rate and traits for three climatically distinct populations. Growth rate declines with increasing latitude of origin and is lower in the temperature treatment corresponding to the climate of origin for the southern population. High-latitude populations have low SLA and LMF, but populations do not differ in photosynthetic rates. In conclusion, I find potentially adaptive differences in populations’ growth, survival, and plant traits but no direct evidence of climate or competition limitation across the range. This study highlights intraspecific variation in growth and traits, its relevance at range limits, and the need to identify whether reproductive or phenological traits also vary within species.
University of Minnesota Ph.D. dissertation. December 2015. Major: Ecology, Evolution and Behavior. Advisors: Peter Reich, G. David Tilman. 1 computer file (PDF); viii, 151 pages.
Sugar maple (Acer saccharum Marsh.) provenances differ with climate of origin in survival, growth, and traits along a climate gradient: implications for the species' distribution under climate change.
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