Laura Dev GDPE Masters Thesis Defense
Thursday, June 28, 2012, 01:00 PM
NESB, Room B224

TIMING IS IMPORTANT: THE SEASONALITY OF PRECIPITATION CAN INFLUENCE HOW ECOSYSTEMS RESPOND TO GRAZING Water availability and grazing are both strong drivers of grassland community structure and function. We know that grassland communities, particularly those that are water limited, can be very sensitive to temporal changes in precipitation, but little is known about how the timing of water availability interacts with grazing. I first investigated the importance of precipitation seasonality in determining broad-scale patterns of plant community response to grazing by conducting a global meta-analysis. I focused on the relative importance of climatic factors compared with grazing variables in influencing changes in plant species composition and primary production due to grazing. Species composition was more responsive to grazing covariates, whereas production was more responsive to climatic variables, particularly the length of the growing season. I did find that locations with more summer precipitation experienced greater grazing-induced changes in species composition. I further explored potential mechanisms for this pattern by conducting a trait study at a climate change experiment on the Tibetan Plateau. I investigated how shifting the timing of water availability toward the winter, as is predicted by future climate scenarios, affects community-level plant traits associated with grazing avoidance and grazing tolerance, and how grazing acts as a feedback. I found that climate and grazing treatments both altered community-level plant traits, and that these drivers also affected some within-species traits. Furthermore, grazing did act as a feedback (both positive and negative) to the effect of climate on certain plant traits. Work from my thesis provides compelling evidence that the timing of precipitation can interact with grazing to drive changes in plant community structure and function. In light of predicted climate changes that may shift the timing of precipitation in many systems worldwide, these changes are increasingly important to understand.

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Event Contact: Jeri Morgan can be reached at (970) 491-4373

Sponsored by the Graduate Degree Program in Ecology.