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Long-term experimental warming effects on tundra plant sexual reproduction in the high Arctic Klady, Rebecca A.

Abstract

Predictions that climate warming will enhance plant sexual reproduction in the High Arctic were examined using a field experiment at a polar oasis and a polar semi-desert site in the eastern Canadian High Arctic. Small open top chambers (OTCs), which simulated climate warming, were established in plant communities along a soil moisture gradient in 1992. Over two growing seasons, fresh and over-wintered seeds across a range of species were collected from aerial seed banks exposed to experimental warming and ambient conditions. Seeds were weighed and germinated to measure changes in reproductive effort and success in response to experimental warming. OTCs increased within-plot growing season air temperatures by 1 - 2°C, which is within range of general circulation model (GCM) predictions for climate warming in the Arctic. Reproductive effort and success of fresh seeds were enhanced by warming in most species, depending on initial site conditions. Enhanced reproductive effort and success may be attributed to warming conditions, which advanced dates of snowmelt and extended the growing season. Similar effects on over-wintered seeds were likely, but seed dispersal prior to over-wintered seed harvests confounded these results. Inter-annual variability in reproductive success appeared to be diminished by experimental warming. Further testing will verify if this result is an indicator of long-term (> 10 y) warming effects. Results of this study confirm predictions that long-term warming will enhance sexual reproduction in high arctic plants. These changes will have implications for plant demographics at the community-level and the rate and extent of bare-ground colonization, particularly if rates of seedling establishment also increase.

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