Assessing the Impacts of Environmental Change on Plant Form and Function
1) Do climate and biotic interactions influence the growth rates of juvenile trees?
January - May 2014, Alec Baird & Dr.Steve Kroiss
Abies amabilis (Pacific silver fir), a dominant conifer species of the pacific NW, exhibited drastic declines in sapling growth rate with increasing elevation, suggesting strong constraints imposed by temperature and thus growing season length (diurnal and seasonal).
Light availability (competition due to above canopy shading) had small negative effects on sapling growth rates, but these effects did not vary with elevation.
Finally, sapling survival did not vary considerably, possibly due to modifications in growth and differences in other adaptations. If anthropogenic warming increases, will saplings at these higher elevations experience increased growth rates? Warming might induce faster snow melt and thus a longer growing season (diurnal and whole season). Perhaps increased growth rates from increased warming will decrease the time that saplings require to reach reproductive maturity.
Populus tremuloides (trembling aspen), the most widespread tree species in North America, exhibited much younger overall age in saplings. Quantifying growth as shoot length growth per year (cm/year) on juvenile trees in the La Plata Mountains, SW Colorado (where water deficit limits this species' southern range edge) showed no quantified significant differences across elevation. Below ground growth rates are uncertain and may be different as this gradient occupies climate space of high moisture deficit. How might leaf traits facilitate adaptation in occupying an elevational gradient of elevated moisture deficit with decreasing elevation? See below!
2) How do climate and biotic interactions influence leaf growth? Does leaf growth mediate organismal function across environmental heterogeneity?
2014 - 2015
With collaborator and PhD Candidate Leander Love-Anderegg, we found 1) that the trait specific leaf area (SLA, inverse of leaf mass per area: LMA) was strongly influenced by light availability and marginally influenced by precipitation (elevation), and 2) that growth rate quantified as centimeters of shoot growth per year (age calculated via dendrochronological analyses) did not differ across climatic or sunlight gradients. We suspect that the changes in leaf growth may mediate function across these climatic gradients, possibly contributing to the maintenance of shoot growth (as cm per year ).
(right) Presented at the 2015 Undergraduate Research Symposium at the University of Washington. Presented at Plant Biology 2015 (American Society of Plant Biologists) and ESA 2015 (Ecological Society of America) If interested in a more legible/clear file feel free to email me.
3) What strategies (specifically: trait coordination, mechanistic physiology) do leaves of juvenile trees employ when acclimating to climatic and biotic stressors?
2015 - 2016
To investigate the leaf morphological, anatomical, and functional changes associated with environmental change stressors, I conducted a greenhouse experiment and subjected aspen saplings to low-water or low-light availability. This work will soon be published in the journal Tree Physiology (currently in press, February 2017).
(below) Plant physiological measurements require the necessary equipment. Osmometer on the left measures osmolality or osmolute potential, and a pH meter in the center for measuring pH.
(above) Measuring photosynthesis via LiCor
6400 at several different light quantities to
construct photosynthesis light curves.
(above, left) Low-watered plants produce leaves with less area and increased density (thereby elevated mass) compared to well-watered plants that produce leaves (above, right) with greater area and reduced relative density (thereby reduced mass per area). Interestingly, these leaves were indifferent in cross sectional thickness, suggesting adequate acclimation to high light (under low-water availability) These leaves are the same age (give or take ~2 days of differential emergence -> ~2 months old)