The Importance of Incorporating Landscape Change for Predictions of Climate-Induced Plant Phenological Shifts.

Chelsea Chisholm,Michael S Becker,Wayne H Pollard

doi:10.3389/fpls.2020.00759

Abstract

Warming in the high Arctic is occurring at the fastest rate on the planet, raising concerns over how this global change driver will influence plant community composition, the timing of vegetation phenological events, and the wildlife that rely on them. In this region, as much as 50% of near-surface permafrost is composed of thermally sensitive ground ice that when melted produces substantial changes in topography and microbiome conditions. We take advantage of natural variations in permafrost melt to conduct a space-for-time study on Ellesmere Island in northern Canada. We demonstrate that phenological timing can be delayed in thermokarst areas when compared to stable ground, and that this change is a function of shifting species composition in these vegetation communities as well as delayed timing within species. These findings suggest that a warming climate could result in an overall broadening of blooming and leafing windows at the landscape level when these delayed timings are taken into consideration with the projected advance of phenological timings in ice-poor areas. We emphasize that the impacts of geomorphic processes on key phenological drivers are essential for enhancing our understanding of community response to climate warming in the high Arctic, with implications for ecosystem functioning and trophic interactions.

Highlights

The high Arctic is warming at twice the global average and is anticipated to have significant effects on the landscape, flora, and fauna of the region (IPCC, 2014)
These cold conditions result in deep permafrost that is over 500 m thick (Taylor, 1991), exceptionally thin average seasonal ground thaw compared to other areas of the Arctic, and a small species pool estimated at ∼140 vascular plant species (Edlund et al, 1990)
The delays we found in three key phenological traits for plant communities in thermokarst troughs demonstrate the impact of a geomorphological process that has largely been overlooked in ecology literature

Summary

Introduction

The high Arctic is warming at twice the global average and is anticipated to have significant effects on the landscape, flora, and fauna of the region (IPCC, 2014). Warming air temperatures have already resulted in the increased thawing of permafrost and accelerated melting of ground ice (Callaghan et al, 2011; Lewkowicz and Way, 2019). It is predicted that with increased ground and air temperatures there will be large shifts in the region’s flora (Elmendorf et al, 2012a) with consequences for both ecosystem functioning (Schuur and Mack, 2018) and the carbon balance (Turetsky et al, 2020). The sensitivity of plant communities to phenological change is expected to be greater in cold, high latitude sites than warmer sites (Prevéy et al, 2017). Variation in phenology can have strong influences on competitive interactions and species

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