Patterns of Cross-Continental Variation in Tree Seed Mass in the Canadian Boreal Forest

Abstract

Seed mass is an adaptive trait affecting species distribution, population dynamics and community structure. In widely distributed species, variation in seed mass may reflect both genetic adaptation to local environments and adaptive phenotypic plasticity. Acknowledging the difficulty in separating these two aspects, we examined the causal relationships determining seed mass variation to better understand adaptability and/or plasticity of selected tree species to spatial/climatic variation. A total of 504, 481 and 454 seed collections of black spruce (Picea mariana (Mill.) B.S.P.), white spruce (Picea glauca (Moench) Voss) and jack pine (Pinus banksiana Lamb) across the Canadian Boreal Forest, respectively, were selected. Correlation analyses were used to determine how seed mass vary with latitude, longitude, and altitude. Structural Equation Modeling was used to examine how geographic and climatic variables influence seed mass. Climatic factors explained a large portion of the variation in seed mass (34, 14 and 29%, for black spruce, white spruce and jack pine, respectively), indicating species-specific adaptation to long term climate conditions. Higher annual mean temperature and winter precipitation caused greater seed mass in black spruce, but annual precipitation was the controlling factor for white spruce. The combination of factors such as growing season temperature and evapotranspiration, temperature seasonality and annual precipitation together determined seed mass of jack pine. Overall, sites with higher winter temperatures were correlated with larger seeds. Thus, long-term climatic conditions, at least in part, determined spatial variation in seed mass. Black spruce and Jack pine, species with relatively more specific habitat requirements and less plasticity, had more variation in seed mass explained by climate than did the more plastic species white spruce. As traits such as seed mass are related to seedling growth and survival, they potentially influence forest species composition in a changing climate and should be included in future modeling of vegetation shifts.

Potential Effects of Awn Length Variation on Seed Yield and Components, Seed Dispersal and Germination Performance in Siberian Wildrye (Elymus sibiricus L.)

“…Awn length and TSW exhibited a positive correlation with altitude. Interestingly, other study has found negative correlations between seed mass and geographical factors, such as latitude and longitude, in several species [40]. These findings indicated that geographical factors have multi-lateral impacts and complex interactions with seed yield and components.…”

Provenance and seed mass determine seed tolerance to high temperatures associated to forest fires in Pinus pinaster

“…Moreover, extremely high variability in seed mass exists within and among P. pinaster provenances (Escudero et al 2000;Zas and Sampedro 2015;Zas et al 2013), similarly to other pine species (e.g. Court-Picon et al 2004;Ganatsas et al 2008;Liu et al 2013;Parker et al 2006). Seed mass is often positively associated with post-fire seedling establishment, growth, and survival (Álvarez et al 2007;Bladé and Vallejo 2008;Escudero et al 2000), but no consensus exists on the relationship between seed mass and germination rates following fire (Escudero et al 2002;Hanley et al 2003;Casal 1995, 2004;Vasques et al 2012).…”

Will among‐population variation in seed traits improve the chance of species persistence under climate change?

“…We hypothesized that patterns of among‐population variation in traits that underpin seedling emergence, growth and establishment would reflect those observed across species. For instance, on a global scale, seed mass commonly increases as temperature rises and rainfall and latitude decrease (Moles & Westoby, ; Kattge et al ., ; Liu et al ., ), with smaller seeds germinating faster than larger seeds (Norden et al ., ), seed longevity increasing with rising temperature and aridity (Probert et al ., ) and seed dormancy status being greater at higher elevations where temperature and rainfall are lower (Fernández‐Pascual et al ., ). We expected to see similar among‐population patterns in species with distributions along environmental gradients (i.e.…”