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The hidden season: growing season is 50% longer below than above ground along an arctic elevation gradient
Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. (Climate Impacts Research Centre ; Arcum)
Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Department of Biology, University of Regina, Regina, Saskatchewan S4S 0A2 Canada. (Climate Impacts Research Centre)
Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. Research Institute for Nature and Forest INBO, Kliniekstraat 25, 1070 Brussels, Belgium. (Climate Impacts Research Centre ; Arcum)
2016 (English)In: New Phytologist, ISSN 0028-646X, E-ISSN 1469-8137, Vol. 209, no 3, 978-986 p.Article in journal (Refereed) PublishedText
Abstract [en]

There is compelling evidence from experiments and observations that climate warming prolongs the growing season in arctic regions. Until now, the start, peak, and end of the growing season, which are used to model influences of vegetation on biogeochemical cycles, were commonly quantified using above-ground phenological data. Yet, over 80% of the plant biomass in arctic regions can be below ground, and the timing of root growth affects biogeochemical processes by influencing plant water and nutrient uptake, soil carbon input and microbial activity. We measured timing of above- and below-ground production in three plant communities along an arctic elevation gradient over two growing seasons. Below-ground production peaked later in the season and was more temporally uniform than above-ground production. Most importantly, the growing season continued c. 50% longer below than above ground. Our results strongly suggest that traditional above-ground estimates of phenology in arctic regions, including remotely sensed information, are not as complete a representation of whole-plant production intensity or duration, as studies that include root phenology. We therefore argue for explicit consideration of root phenology in studies of carbon and nutrient cycling, in terrestrial biosphere models, and scenarios of how arctic ecosystems will respond to climate warming.

Place, publisher, year, edition, pages
2016. Vol. 209, no 3, 978-986 p.
Keyword [en]
below ground, belowground, below-ground, fine roots, phenology, root growth, root production, sub-Arctic
National Category
Ecology Climate Research Physical Geography
URN: urn:nbn:se:umu:diva-120667DOI: 10.1111/nph.13655ISI: 000373378000013PubMedID: 26390239OAI: diva2:950227
Available from: 2016-07-28 Created: 2016-05-18 Last updated: 2016-09-23Bibliographically approved
In thesis
1. The hidden life of plants: fine root dynamics in northern ecosystems
Open this publication in new window or tab >>The hidden life of plants: fine root dynamics in northern ecosystems
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

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.

Place, publisher, year, edition, pages
Umeå: Umeå Universitet, 2016. 24 p.
Arctic, belowground, boreal, climate change, fine roots, heath, meadow, minirhizotron, permafrost, phenology, plant community, root biomass, root growth, root litter, root production, subarctic, tundra
National Category
urn:nbn:se:umu:diva-124757 (URN)978-91-7601-533-9 (ISBN)
Public defence
2016-09-16, Björken, Sveriges Lantbruksuniversitet, Umeå, 09:00 (English)
Available from: 2016-08-26 Created: 2016-08-23 Last updated: 2016-09-23Bibliographically approved

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Blume-Werry, GescheMilbau, Ann
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