William K. Smith

Learn More
Invasive plants frequently have competitive advantages over native species. These advantages have been characterized in systems in which the invading species has already become well established. Surprisingly, invader impacts on native communities currently undergoing invasion are lacking from most ecological studies. In this work we document and quantify(More)
Cloud immersion can provide a potentially important moisture subsidy to plants in areas of frequent fog including the threatened spruce-fir communities of the southern Appalachian Mountains (USA). These mountaintop communities grow only above ~1,500 m elevation, harbor the endemic Abies fraseri, and have been proposed to exist because of frequent cloud(More)
Climate warming predicts changes to the frequency and height of cloud-immersion events in mountain communities. Threatened southern Appalachian spruce–fir forests have been suggested to persist because of frequent periods of cloud immersion. These relic forests exist on only seven mountaintop areas, grow only above ca. 1,500 m elevation (maximum 2,037 m),(More)
Leaves of many evergreen angiosperm species turn red under high light during winter due to the production of anthocyanin pigments, while leaves of other species remain green. There is currently no explanation for why some evergreen species exhibit winter reddening while others do not. Conditions associated with low leaf water potentials (Psi) have been(More)
Frequent cloud immersion events result in direct uptake of cloud water and improve plant water potentials during daylight hours in saplings of two dominant cloud forest species. In ecosystems with frequent cloud immersion, the influence on plant water balance can be important. While cloud immersion can reduce plant water loss via transpiration, recent(More)
A red/purple coloration of lower (abaxial) leaf surfaces is commonly observed in deeply-shaded understorey plants, especially in the tropics. However, the functional significance of red abaxial coloration, including its role in photosynthetic adaptation, remains unclear. The objective of this study was to test the back-scatter hypothesis for abaxial leaf(More)
Recent studies have shown that photosynthesis may increase under diffuse light regimes (e.g., cloud-generated) compared to direct (collimated) irradiance at the canopy and ecosystem levels. Yet, there are few comparative studies for individual species at the branch or leaf level. One of the strongest contrasts in the plant kingdom is the architectural(More)
Anthocyanins in upper (adaxial) leaf tissues provide greater photoprotection than in lower (abaxial) tissues, but also predispose tissues to increased shade acclimation and, consequently, reduced photosynthetic capacity. Abaxial anthocyanins may be a compromise between these costs/benefits. Plants adapted to shaded understory environments often exhibit(More)
comparisons of transpiration and photosynthesis in three subalpine Differences in water and photosynthetic relations were compared for three codominant conifers (Engelmann spruce (Picea engelmanii), subalpine fir (Abies lasiocurpa), and lodgepole pine (Pinus conforta)) at microhabitats within a subalpine forest (central Rochy Mountains, U.S .A.) that were(More)
Stomatal conductances to water vapor diffusion in Engelmann spruce (Picea engefmannii Parry ex Engelm.), subalpine fir (Abies fasiocarpa (Hook.) Nutt.), and lodgepole pine (Pinus contorta Engelm.) were compared to determine environmental influences on conductance at higher (3220 m) and lower (2860 m) elevations in the central Rocky Mountains. Measurements(More)