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Root phenology unresponsive to earlier snowmelt despite advanced aboveground phenology in two subarctic plant communities
Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. (Climate Impacts Research Centre)
Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences. (Climate Impacts Research Centre)
(English)Manuscript (preprint) (Other academic)
Abstract [en]

Earlier snowmelt at high latitudes advances aboveground plant phenology, thereby affecting water, nutrient and carbon cycles. Despite the key role of fine roots in these ecosystem processes, phenological responses to earlier snowmelt have never been assessed belowground. We experimentally advanced snowmelt in two contrasting plant community types (heath and meadow) in northern Sweden and measured above- and belowground phenology (leaf-out, flowering and fine root growth). We expected earlier snowmelt to advance both above- and belowground phenology, and shrub-dominated heath to be more responsive than meadow. Snow melted on average nine days earlier in the manipulated plots than in controls, and soil temperatures were on average 0.9 °C higher during the snowmelt period of three weeks. This resulted in small advances in aboveground phenology, but contrary to our expectations, root phenology was unresponsive, with root growth generally starting before leaf-out. Both plant community types responded similarly to the snowmelt treatment, despite strong differences in dominating plant functional types, and root properties, such as root length and turnover. The lack of a response in root phenology, despite warmer soil temperatures and aboveground phenological advances, adds evidence that aboveground plant responses might not be directly translated to belowground plant responses, and that our understanding of factors driving belowground phenology is still limited, although of major importance for water, nutrient and carbon cycling.

Keyword [en]
climate change, phenology, fine roots, snowmelt, arctic, alpine, root growth, root production
National Category
Ecology
Identifiers
URN: urn:nbn:se:umu:diva-124754OAI: oai:DiVA.org:umu-124754DiVA: diva2:954748
Available from: 2016-08-23 Created: 2016-08-23 Last updated: 2016-08-25
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.
Keyword
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
Ecology
Identifiers
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)
Opponent
Supervisors
Available from: 2016-08-26 Created: 2016-08-23 Last updated: 2016-09-23Bibliographically approved

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Blume-Werry, GescheJansson, RolandMilbau, Ann
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