Grasslands are threatened
by urbanization, agricultural conversion, over-grazing, tree-encroachment, and
invasive plants. Simultaneously, climate change acts on all levels of
biological organization, from entire communities to the physiology of
individuals. The environmental stresses induced by climate change have the
potential to interact with human-caused disturbance, but the response of plants
to these stresses and disturbances, and how they may interact, are not well
known. To conserve grasslands it is critical to know which types of grassland
and which plant species will be most affected. To understand the mechanisms of
change at the ecosystem level it is necessary to study the response at lower
levels of biological organization. Using a variety of approaches I studied the
potentially interacting effects of stress (primarily reduced water
availability) and disturbance (plant biomass removal) on different levels of
biological organization. I ran a 4-year field experiment in which I manipulated
water availability, temperature and clipping in three different grassland
types. I found complex plant community structure and biomass response; treatments
often interacted but the different grassland types had their own particular
responses. As part of this experiment I monitored the effects of treatments on
soil moisture and temperature and found that the effects are generally
consistent with expectations, but treatments do not act exclusively or
independently on target variables. In addition to stress and disturbance,
competition is a key process structuring grasslands. In the greenhouse, I
examined how plant competition is affected by stress and disturbance. I found
that the interpretation of how competition is affected is dependent on the way
competition is measured. Some measures of competition showed reduced
competition across stress and disturbance gradients, but other measures showed
no change. Finally, I examined the root traits of 18 species of grass in the
greenhouse in response to reduced water availability. I found significant
variation in traits among species, maintenance of trait hierarchies across
environments and little evidence of plasticity, except for root: shoot ratio.
Overall, stress, disturbance and their interactions are important in
influencing individual plant performance, competition, structuring plant
communities, and ecosystem function.
am co-supervised by Lauchlan
Fraser at Thompson
Rivers University in Kamloops, BC.
P, Fraser LH, Carlyle CN and Tucker R. Accepted. Forage production potential in
a Ponderosa pine stand: effects of tree spacing on understory plants after 45
years. BC Journal of Ecosystems and Management.
SR, Carlyle CN, Fraser LH and Cahill JF. 2011. Climate change experiments in
temperate grasslands: synthesis and future directions.
Letters. doi: 10.1098/rsbl.2011.0956
CN, Fraser LH and Turkington R. 2011. Tracking soil temperature and moisture in
a multi-factor climate and disturbance experiment in temperate grassland: do climate manipulation methods produced
their intended effects? Ecosystems 14: 489 - 502.
LH and Carlyle CN. 2011. Is spotted knapweed (Centaurea stoebe L.) patch size
related to the effect on soil and vegetation properties? Plant Ecology 212: 975
CN, Fraser LH and Turkington R. 2010. Using three pairs of competitive indices
to test for changes in plant competition along a resource and disturbance
gradient. Journal of Vegetation Science 25:1025 – 1034.
the 2010 Journal of Vegetation Science Editor’s Award, see Wilson et al. 2011.
JVS 22: 1 – 5.
the J. S. Rowe Award for best published paper in plant ecology by a student at
a Canadian University, Canadian Botanical Association
CN, Haddow C, Bings B, Harrower W and Fraser LH. 2010. Use of digital photos to
measure visual obstruction for wildlife in grasslands. Journal of Environmental
Management 91: 1366 – 1370.
LH, Greenall AL, Carlyle CN, Turkington R and Ross-Friedman C.
Adaptive phenotypic plasticity of Pseudoroegneria spicata: response of stomatal
density, leaf area and biomass to changes in water supply and increased
temperature. Annals of Botany
CN and Fraser LH. 2006. A test of three
juvenile plant competitive response strategies. Journal of Vegetation Science 17:11-18.
the 2006 JVS Editor’s Award, see Chiarucci et al. 2007. Journal of Vegetation
T, Carlyle CN, Picard C, Landaw A, and Fraser LH. 2005.
water chemistry and vegetation characteristics of a tamarack bog in Bath
Township, Ohio. Ohio Journal of Science 105:21-30.