Aarhus University Seal / Aarhus Universitets segl

Jakob Assmann: Bridging the gap: Tundra leaf-out, flowering and greenness across space, time and observational scales

Seminar: Økoinformatik og biodiversitet

21.11.2018 | Anne Kirstine Mehlsen

Dato tor 22 nov
Tid 10:15 11:15
Sted Institut for Bioscience, Ny Munkegade 114-116, bygning 1540-324

Foredragsholder: Jakob Assmann, University of Edinburgh, Scotland, UK

Abstract:

 

The Arctic is warming at twice the rest of the globe with strong impacts on the vegetation of the tundra. Satellites indicate that spring phenology is advancing and that tundra plant productivity is increasing (the tundra is ”greening”). This vegetation change has knock-on effects on ecosystem functions, potentially affecting plant consumers and feedbacks to the global climate system. Yet, in situ (ground based) monitoring suggests no coherent directional trend in phenological change across the biome and a considerable amount of variation in the satellite observations of tundra greening remains unexplained, partially due to the discrepancy between the observational scales of medium- to coarse-grained satellite and in situ measurements. Here, I present the results of my recent research combining in situ, drone and satellite time-series of tundra greenness and phenology to study their change across space, time and observational scales. My findings show that snowmelt and temperature, but not, as frequently suggested, sea-ice conditions are the best predictors of spring plant phenology at coastal sites around the tundra. Furthermore, using tundra plots at my focal research site Qikiqtaruk in Canada, I demonstrate that satellite and drone observations of tundra greenness agree at landscape-scales, but that a considerable amount of variation is lost when changing from fine drone to medium satellite grain sizes. This suggests that satellite observations potentially miss important ecological variation in the landscape, likely created by microtopography and disturbance processes at Qikiqtaruk. Finally, I will show that landscape variation in greenness declines across the growing season in the tundra at Qikiqtaruk. If such trends are affected by warming, e.g. accelerated, they could alter plant consumer interactions that rely on resource variation in the landscape. Overall, these findings highlight the importance of localised drivers (such as snowmelt) on key ecological processes in tundra ecosystems and illustrates that novel drone technologies can help us to better understand them.

Institut for Bioscience, Offentligheden / Pressen, Medarbejdere