Geographical variation in reproductive capacity of sugar maple (Acer saccharum Marshall) northern peripheral populations

Abstract

Aim Several models have predicted that, with climate change, Northern Hemisphere species will migrate northwards from their present distribution ranges. Sugar maple (Acer saccharum Marshall) reaches its northern continuous distributional limit in north-eastern North America at the transition between boreal mixed-wood and temperate deciduous forest. Our objective was to determine whether lower sugar maple recruitment potential accounts for this gradual transition between the continuous and discontinuous zones of the distribution.Location The northern limit of sugar maple in eastern Canada.Methods We analysed the reproductive capacity of sugar maple populations along three latitudinal transects (located in the west, centre and east of Qu ebec) in 24 sites located between 45°51′-48°59′ N and 70°21′-79°27′ W. The study area was divided into two zones, continuous and discontinuous, based on sugar maple stand abundance. We examined stand structure, sugar maple seed abundance and germination, and sugar maple seedling density and age structure.Results Sugar maple regeneration was uneven-aged and similar between continuous (south) and discontinuous (north) zones. For the western transect, more filled seeds and more seedlings were recorded in the continuous zone than in the discontinuous zone. Sugar maple seedling density was positively influenced by (1) basal area of mature sugar maple and saplings of all species, and (2) July mean temperature and precipitation. Four mast seed years were identified that were well synchronized across all sites; mast seeding covaried significantly with July mean temperature and July mean precipitation of the previous year.Main conclusions Our study clearly demonstrated an effect of climatic variables and stand characteristics on sugar maple regeneration. However, these factors did not explain the transition from a continuous to a discontinuous distribution for this species. Most of our northern sites exhibited constant sugar maple recruitment over time. These results highlight the importance of including non-climatic factors in models predicting species change in abundance.

Non-climatic constraints on upper elevational plant range expansion under climate change

“…Based on the density of first-year seedlings in 2012 (electronic supplementary material, figure S1), there were at least six viable seeds m 22 (mean; range ¼ 1-42 viable seeds m 22 ) dispersed in 2011, known regionally as a sugar maple mast year [27], and exceedingly few in 2012 (C.D.B. & M.V.…”

“…It occurs at low-to mid-elevation stands throughout its range, notably in the Appalachian Mountains in which our study area occurs, where the upper-elevational species limit is thought to be controlled by climatic factors [25]. It is anticipated that sugar maple will shift its distribution as environmental conditions become more favourable at the northern limit of its range with climate change [27]. Sugar maple is a monoecious species that flowers in early spring prior to leaf flush, and winddisperses its seed in autumn.…”

Assessing tree germination resilience to global warming: a manipulative experiment using sugar maple (Acer saccharum)

“…While some studies have assessed germination percentage (directly or indirectly) within the sugar maple range, most have been limited to either a single seed origin or have only provided minimal insight into the influence of temperature on germination (Webb and Dumbroff, 1969;Simmonds and Dumbroff, 1974;McCarragher et al, 2011). To our knowledge, only limited research in Acer has been conducted at the northern range margin (Tremblay et al, 1996;Graignic et al, 2014), while largely ignoring the mid-and southern species range. While it has long been known that seed germination is likely to be linked to seed origin (Mayer and Poljakoff-Mayber, 1975), this has yet to be thoroughly assessed with the influence of temperature and temperature shifts.…”

“…Solarik et al 154 feed sorter, where filled seeds were separated from unfilled seeds, which ensured seed viability (filled seeds) above 95% for each seed origin. To further reinforce that seeds were filled, we used either X-rays on a subset of seeds from each origin or pressed the seeds between fingers during counting, prior to the commencement of the germination trials (Graignic et al, 2014). Seeds were stored at −3°C for 2 months before initiating the experiment (Yawney and Carl, 1974).…”

Nuclear microsatellite markers for population genetic studies in sugar maple (Acer saccharum Marsh.)

“…Recent research has predicted that climate change has the potential to affect species distributions, alter ecosystem functions and species interactions (Iverson et al 2008, Whitham et al 2008. Other important predicted consequences of global temperature increase are range shifts and northward migration of forest trees (Gunter et al 2000, Graignic et al 2014. Range edge populations are especially prone to geographical isolation and environmental changes.…”