High-Arctic phenology shifts: climate change consequences for reproductive success and plant community composition Zoe Panchen W. Garfield Weston Postdoctoral Fellow in Northern Research Phenology shifts due to climate change Phenology Willow (Day of Year green-up (DOY)) Arnica flower Year Temperature (°C) Tundra green-up, flowering and fruiting Cotton-grass fruit generally getting earlier as climate warms Phenology responses differ Flowering Time Fruiting Time Mountain avens flowering Mountain avens fruiting 3.6 days/decade earlier 5.8 days/decade earlier (-2.3 days/°C) (-3.4 days/°C) Purple saxifrage flowering no significant change (-1.8 days/°C) 5yr rolling average rolling 5yr Peak fruiting DOY fruiting Peak 5yr rolling average rolling 5yr Peak flowering DOY flowering Peak Purple saxifrage fruiting no significant change (0 days/°C) • Differences among species • Differences among phenological events of same species Panchen & Gorelick (2015) Arctic plant reproductive success With warmer Arctic temperatures … • greater germination • more viable seed Silene acaulis Moss campion Müller et al. (2011) Plant community composition changes With warmer Arctic temperatures … • change in Arctic plant community composition • Arctic shrub-ification 1966: Siberian tundra 2009: Siberian tundra Phenology – reproductive success - plant community structure What is the relationship between • Flowering times and reproductive success? • Phenology-reproductive success and species composition and abundance changes? Expect shift towards greater proportion of species that benefit most from climate change. Salix Dryas Poa Papaver Oxyria Pedicularis arctica integrifolia glauca radicatum digyna hirsuta Arctic Mountain Glaucous Arctic Mountain Hairy Willow Avens Bluegrass Poppy Sorrel Lousewort Alexandra Fiord Alexandra Fiord, Ellesmere Island (79°N) Open top chambers (OTC), Alexandra Fiord Phenology, reproductive success & plant community composition Warmed vs control plots Seed germination Point frame counts Phenology Reproductive Community success structure • flowering times • seed quantity • composition • green-up times • seed weight • abundance • fruiting times • seed viability Seed quantity Mountain Avens Mountain Sorrel Hairy Lousewort Arctic Willow Arctic Poppy (Dryas) (Oxyria) (Pedicularis) (Salix) (Papaver) Seed count per plant • Dryas: More seeds in warmed versus control plots • Oxyria and Pedicularis: No difference in warmed versus control plots • Salix and Papaver: Fewer seeds in warmed versus control plots Seed weight Mtn Avens Mtn Sorrel Lousewort Willow Poppy (Dryas) (Oxyria) (Pedicularis) (Salix) (Papaver) Mean seed weight (mg) Plants in warmed plots produce heavier seeds Except Poppy Seed viability Arctic Willow (Salix) Mountain Avens (Dryas) % germination R2=0.51, N=108, P<.0001 R2=0.73, N=166, P<.0001 Mountain Sorrel (Oxyria) Arctic Poppy (Papaver) % germination R2=0.04, N=70, P=.0774 R2=0.24, N=19, P=.0317 Mean seed weight (mg) Mean seed weight (mg) Heavier seeds = greater germination Phenology - reproductive success Hairy lousewort Mountain sorrel Mean seed weight Mean seed weight (mg) (Pedicularis hirsuta) (Oxyria digyna) Mean seed weight (mg) Peak flower day of year Mature fruit day of year Earlier flowering/fruiting Heavier seeds Reproductive successSalix – species composition 80 warmed 70 Salix arctica % 60 Arctic willow germi- 50 nation 40 is 30 control “taking over” 20 10 Arctic Willow 0 Papaver 80 70 Papaver % radicatum germi- 60 Arctic poppy 50 nation control is 40 30 “now seen less 20 often in 10 warmed Arctic Poppy 0 warmed plots” Germination day Reproductive success – species composition % germi- nation MountainDryas Avens (Dryas) MountainOxyria Sorrel (Dryas) 80 80 control 70 70 60 60 warmed 50 50 40 40 30 warmed 30 20 20 10 control 10 0 0 Germination day Germination day Poa Pedicularis glauca Only seeds from hirsuta Only 1/3650 seeds warmed plots germinated! germinated • tetrazolium test +ve • germination conditions Glaucous Hairy not met Bluegrass Lousewort Seedling vigor Seedling weight (mg) WillowSalix (Salix) PoppyPapaver (Papaver) 0.9 0.18 0.8 0.16 0.7 0.14 0.6 0.12 0.5 0.10 0.4 0.08 0.3 0.06 0.2 0.04 0.1 0.02 0 0.00 GD03 GD05 GD08 GD10 GD12 GD15 GD17 GD19 GD12 GD15 GD17 GD19 GD22 GD24 GD26 Mountain OxyriaSorrel (Oxyria) MountainDryas Avens (Dryas) 2.5 1.6 1.4 2.0 1.2 1.5 1.0 0.8 1.0 0.6 0.4 0.5 0.2 0.0 0.0 GD03 GD05 GD08 GD10 GD12 GD15 GD17 GD19 GD22 GD24 GD26 GD03 GD05 GD08 GD10 GD12 GD15 GD17 GD19 GD22 GD24 GD26 Germination day Germination day Salix warmed plots seedlings more vigorous Earlier germinating Salix seeds are more vigorous In warmed plots… Salix Papaver ↓ # seeds ↓ # seeds ↑ seed weight ↓ seed weight ↑ germination ↓ germination Arctic Arctic ↓ seedling vigor Willow ↑ seedling vigor Poppy Oxyria ~= # seeds Dryas ↑ # seeds ↑ seed weight ↑ seed weight ↓ germination ↑ germination Mountain ↑ seedling vigor Mountain ?↑seedling vigor Sorrel Avens % germination over the years Arctic Willow (Salix) Mountain Avens (Dryas) Mean % germination R2=0.39, N=280, P<0.0001 R2=0.30, N=323, P<0.0001 Mountain Sorrel (Oxyria) Arctic Poppy (Papaver) Mean % germination R2=0.51, N=113, P=0.0126 R2=0.45, N=105, P=0.8481 Preliminary analysis suggests … • Warmer temperatures appear to increase some reproductive success measures • Link between phenology, reproductive success and plant community composition/species abundance but ... further analysis required Salix Dryas Poa Papaver Oxyria Pedicularis arctica integrifolia glauca radicatum digyna hirsuta Arctic Mountain Glaucous Arctic Mountain Hairy Willow Avens Bluegrass Poppy Sorrel Lousewort Acknowledgements Greg Henry Esther Frei Elise Gallois Cassandra Elphinstone Sofie Agger Andrew Butt Hailey May Natalie Maslowski Isabel Hagen Alexandra Fiord, Ellesmere Is, Nunavut.