Ecophysiological differences among Leymus mollis populations across a subarctic dune system caused by environmental, not genetic, factors

Abstract

Plant species that persist during succession, from the colonization to the stabilization stages, face major environmental changes. Such changes are believed to have significant effects on species performance. In subarctic coastal dune systems, Leymus mollis colonizes the embryo dunes, on the upper limit of the beach. It reaches its maximum density on the foredune, but also grows on older, stabilized ridges. This paper reports on the phenotypic variations of some ecophysiological traits associated with the persistence of L. mollis on a dune system on the east coast of Hudson Bay (northern Quebec). Leymus mollis ramets tend to have a lower net carbon assimilation rate and water use efficiency, and a higher substomatal CO2 concentration on the stabilized dune than on the foredune. However, these physiological differences cannot be explained by differences in leaf morphology or nitrogen content. Under controlled conditions, ecophysiological differences observed in the field disappear, suggesting that these are not genetic but determined by environmental changes along the foredune‐stabilized dune gradient. We propose that higher net carbon assimilation rate on the foredune might be related to higher sink strength in relation to the growth‐stimulating effect of sand burial.

Stress tolerance in plants via habitat-adapted symbiosis

“…In this habitat, plants are exposed to sea water during high tides and summer seasons are typically very dry. These plants are rhizome-forming perennial grass species that can achieve high population densities and remain green until they senesce in the fall (Imbert and Houle, 2000). Two hundred dunegrass individuals, all growing in similar beach habitats (course rocky soils, Figure 2), were collected from four geographically distant locations (X16 km) in Puget Sound and found to be colonized by one dominant class 2 fungal endophyte, which was isolated from surface sterilized roots, rhizomes, crowns and lower stems in 95% of the plants analyzed.…”

Primary succession of subarctic vegetation and soil on the fast‐rising coast of eastern Hudson Bay, Canada

“…The overall vegetation and soil patterns found along the emerging coast of Hudson Bay outline the dominant primary succession trajectory through initial colonization, soil stabilization and development, and forest development. The progressive colonization of vascular plants, bryophytes and lichens results in substrate stabilization and in soil development with an increasing content of nutrients and organic matter with time (see, for example, Matthews, 1992;Bates, 2000;Imbert & Houle, 2000;Brodo et al, 2001;Svensson & Jeglum, 2003a). Soil humidity is a limiting factor for white spruce establishment, with soil organic matter content and moss cover being factors contributing to water retention and reduced evaporation (Bates, 2000).…”

“…The extreme properties of the emerging sandy substrate forming the initial beach surface are generally unfavourable to most plant species during the first stages of primary succession (Imbert & Houle, 2000; Svensson & Jeglum, 2003a). Sandy flats and beaches are formed by storm waves that transport sediments from the tidal flats up onto the shore as the relative sea level lowers.…”

“…Generally, the influence of sand transportation and salt spray diminishes substantially as the distance from the coast increases. Once the pioneer vegetation is established on the littoral sand, the thickness of the organic horizon, along with nutrient availability and soil humidity increase and facilitate vegetation and tree establishment during the more advanced stages of primary succession (Connell & Slatyer, 1977;Bégin et al, 1993;Imbert & Houle, 2000;Svensson & Jeglum, 2003a). Vegetation and soil development on the emergent coastline varies with elevation above sea level and distance from the seashore.…”

Sensitivity of leaf size and shape to climate within Acer rubrum and Quercus kelloggii

“…First, such work bears directly on the broader issue of how plasticity and genotype influence the sensitivity of leaf form to climate. Many studies have sought to tease apart how plasticity and genotype affect the relationships between plant traits and climate, and considerable progress has been made in the areas of physiology, growth, stomatal patterning and leaf size (Gurevitch, 1988; Williams & Black, 1993; Morecraft & Woodward, 1996; Beerling & Kelly, 1997; Cordell et al ., 1998; Oleksyn et al ., 1998; Imbert & Houle, 2000; Hovenden, 2001; Flann et al ., 2002; Hovenden & Vander Schoor, 2004). By contrast, very little is known about the impact of plasticity vs genetic determination on the relationships between leaf shape and climate.…”