The impact of climate change on the flowering and fruiting phenology of Arctic plants in Nunavut, Canada

Abstract

Phenology is the timing of nature's seasonal events. Ambient temperature plays a key role in phenology and hence, as the climate warms, phenology will likely change. This thesis studied the impact of Arctic climate change on Arctic plant flowering and fruiting phenology in Nunavut, Canada. To establish a baseline for current plant phenology, the first question asked was 'How does flowering phenology vary across Nunavut?'.Contrary to what might be expected, plants at a more northerly location flower earlier or at the same time and for a shorter duration than conspecifics at a more southerly location.Observations of vast differences in flower abundance in three consecutive and climatically-contrasting years highlighted the challenges of reproductive success with weather extremes associated with contemporary climate change given that Arctic plants require three plus years to complete the sexual reproductive cycle. Finally, three methods, employing long-term phenology monitoring, historical phenological records and an elevation gradient, combined with temperature records, were used to ask the questions: 'How have temperatures in Nunavut changed?', 'How have Nunavut Arctic flowering and fruiting times responded to climate change?' and 'What is the predicted temperaturesensitivity of Arctic plants to rising temperatures of climate change?'. Annual temperatures in Nunavut are rising faster than the global average. However, in contrast to temperate regions where spring temperatures are rising the most, monthly temperatures in late summer, autumn and winter are rising significantly in Nunavut. Later-flowering species have advanced flowering times more than early-flowering species and seed dispersal times have advanced more than flowering times. Flowering time temperaturesensitivity is species specific and Nunavut region specific with mid-summer-floweringiii species more sensitive than early-and late-flowering species and Nunavut Arctic archipelago plants more sensitive than Nunavut mainland conspecifics. That Arctic plants' reproductive phenological events are temperature-sensitive is a good news story suggesting that they will respond to climate change and possibly experience greater reproductive success. Interspecific and inter-regional variation in phenological temperature-sensitivity suggests Arctic plant ecological community structure will alter with climate change but differentially across Nunavut.iv

Increases in graminoids after three decades of change in the High Arctic

“…On south-eastern Victoria Island, a region undergoing rapid climate change (Panchen 2016;Bush & Lemmen 2019;Buchkowski et al 2020), I discovered pronounced shifts in vegetation after three decades: a marked increase in graminoids, along with substantial declines in Dryas integrifolia, Polygonum viviparum and Saxifraga oppositifolia (Table 1, Figs. 2, 5).…”

“…Since the late 1940s, temperatures have risen substantially in the nearby community of Cambridge Bay, 60 km to the south-east-by 0.30 C°/decade in mean July temperature (Panchen 2016;Buchkowski et al 2020) and by 0.40 C°/decade in mean annual temperature (Buchkowski et al 2020). Since 1960, winter snow depth has increased by 1.1 cm/decade (Lam et al 2022).…”