The hidden life of plants Fine root dynamics in northern ecosystems

Department of Ecology and Environmental Science Umeå University

Umeå 2016

The hidden life of plants

Fine root dynamics in northern ecosystems

Gesche Blume-Werry

Akademisk avhandling

som med vederbörligt tillstånd av Rektor vid Umeå universitet för avläggande av filosofie doktorsexamen framläggs till offentligt försvar i Sveriges lantbruksuniversitet (SLU), Björken,

fredagen den 16 september, kl. 09:00.

Avhandlingen kommer att försvaras på engelska.

Fakultetsopponent: Isla Myers-Smith, PhD

School of GeoSciences, University of Edinburgh, Edinburgh, United

Kingdom.

Organization Document type

Umeå University Doctoral thesis

Department of Ecology and Environmental Science

Date of publication August 2016

Author

Gesche Blume-Werry

Title

The hidden life of plants – Fine root dynamics in northern ecosystems

Abstract

Fine roots constitute a large part of the primary production in northern (arctic and boreal) ecosystems, and are key players in ecosystem fluxes of water, nutrients and carbon. Data on root dynamics are generally rare, especially so in northern ecosystems. However, those ecosystems undergo the most rapid climatic changes on the planet and a profound understanding of form, function and dynamics of roots in such ecosystems is essential.

This thesis aimed to advance our knowledge about fine root dynamics in northern ecosystems, with a focus on fine root phenology in natural plant communities and how climate change might alter it.

Factors considered included thickness and duration of snow cover, thawing of permafrost, as well as natural gradients in temperature. Experiments and observational studies were located around Abisko (68°21' N, 18°45' E), and in a boreal forest close to Vindeln (64°14'N, 19°46'E), northern Sweden. Root responses included root growth, total root length, and root litter input, always involving seasonal changes therein, measured with minirhizotrons. Root biomass was also determined with destructive soil sampling. Additionally, aboveground response parameters, such as phenology and growth, and environmental parameters, such as air and soil temperatures, were assessed.

This thesis reveals that aboveground patterns or responses cannot be directly translated belowground and urges a decoupling of above- and belowground phenology in terrestrial biosphere models. Specifically, root growth occurred outside of the photosynthetically active period of tundra plants. Moreover, patterns observed in arctic and boreal ecosystems diverged from those of temperate systems, and models including root parameters may thus need specific parameterization for northern ecosystems. In addition, this thesis showed that plant communities differ in root properties, and that changes in plant community compositions can thus induce changes in root dynamics and functioning. This underlines the importance of a thorough understanding of root dynamics in different plant community types in order to understand and predict how changes in plant communities in response to climate change will translate into root dynamics. Overall, this thesis describes root dynamics in response to a variety of factors, because a deeper knowledge about root dynamics will enable a better understanding of ecosystem processes, as well as improve model prediction of how northern ecosystems will respond to climate change.

Keywords

Arctic, belowground, boreal, climate change, fine roots, heath, meadow, minirhizotron, permafrost, phenology, plant community, root biomass, root growth, root litter, root production, subarctic, tundra

Language ISBN Number of pages

English 978-91-7601-533-9 24 + 4 papers