Increased Arctic climate extremes constrain expected higher plant reproductive success in a warmer climate

Zoe A Panchen,Esther R Frei,Greg H.R Henry

doi:10.1139/as-2020-0045

Abstract

The low reproductive success of Arctic plants is predicted to increase as the climate warms. However, climate extremes add complexity to these predictions. In the extremely cold year of 2018, multiple Arctic trophic levels experienced reproductive failure. We analysed a unique long-term record of seed viability from experimentally warmed and ambient plots at Alexandra Fiord, Ellesmere Island, which has been running since 1992 and included 2018 and the extremely warm year of 2019. Positive and negative July temperature anomalies and summer temperatures have increased significantly by 0.5, −0.3, and 0.4 °C/decade since 1977, respectively, resulting in greater extremes and increased inter-annual variation. Seed viability of some species has increased with climate warming. Across years, seed viability of woody species was consistently higher in warmed than ambient plots while the opposite was true for forbs. In 2018, seed viability of woody species in ambient plots was significantly lower than normal but comparable with past years for forb species. Not all species returned to normal seed viability levels in 2019. Our study highlights the potential for greater sexual reproductive failure in tundra plants with increasing climate extremes. We suggest that poor seed viability of woody species in cold years could constrain shrub recruitment and may aid forb species establishment on bare tundra.

Highlights

The increase in frequency and severity of climate extremes are recognised as part of contemporary climate change (Boo et al 2006; Fischer and Knutti 2015; Stott et al 2016; Teng et al 2016)
There is some evidence that seed viability has increased in recent years due to climate warming (Müller et al 2011; Alsos et al 2013); these authors concede that the observed higher germination rates of Svalbard seeds in recent years may be due to improved methods compared to germination experiments in earlier years
Even though P. radicatum returned to typical germination rates following a cold year and has a germination strategy to overcome extreme weather events, given the species response to a cold year and possible lack of increase in seed viability in a warming climate, it is not clear how well this species will do in a climate with more extremes

Summary

Introduction

The increase in frequency and severity of climate extremes are recognised as part of contemporary climate change (Boo et al 2006; Fischer and Knutti 2015; Stott et al 2016; Teng et al 2016). As the climate warms, we might expect greater reproductive success of Arctic plant species as both seed viability and seed germination rates increase.

Results

Conclusion