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Acclimation of plants to combinations of abiotic factors: connecting the lab to the field
Umeå University, Faculty of Science and Technology, Department of Plant Physiology. Umeå Plant Science Centre.
2017 (English)Doctoral thesis, comprehensive summary (Other academic)Alternative title
Acklimatisering av växter till en kombination av abiotiska faktorer : ett steg mot att länka laboratoriet till utemiljön (Swedish)
Abstract [en]

Increasing atmospheric CO2 and other greenhouse gasses coupled to the accelerated rate of global warming puts plants and ecosystems under the strain of a rapidly changing abiotic environment. Understanding the impacts of changing global climate is a strong focus of plant science and the establishment of more resilient crop variants is an important goal for breeding programs. Our understanding of plant responses and acclimation to abiotic conditions has improved substantially over the last decades but the combination of a complex abiotic environment and high biological diversity, both on molecular as well as on species level, leaves us still with a lot of uncertainties. The aim of this doctoral thesis was to establish a link between plant thermal responses and the carbon-nitrogen balance of plants. The work in this thesis focused on ecologically significant species of the boreal region: Picea abies, Pinus sylvestris and Betula pendula; and Betula utilis, which is one of the prominent tree species in the high altitudes of the Himalayas. The results presented demonstrate that sub-optimal temperatures combined with other abiotic factors can have additive effects that are not easily deducible from the effect of the two factors separately. Low nitrogen availability enhanced the negative effect of low temperature, while elevated CO2 enhanced plant growth under moderate increases in temperatures but under a more extreme temperature increase it exacerbated the negative effect of heat. I also show evidence that species, despite being grouped into the same functional group or inhabiting the same biome can have different thresholds to temperature and to shifts in the C/N balance of their environment and that these differences can, to some extent, be explained by their differential growth strategies. Furthermore, I demonstrate results supporting the hypothesis that the C-N fluxes between mycorrhizal fungi and tree are strongly dependent on the C and N in the environment, highlighting the significance of the tree-mycorrhiza associations in the C sequestration capacity of the boreal region. In this thesis I also present a generalised empirically based mathematical model that can describe the respiration-temperature response of plant functional types or biomes with high precision, giving a more accurate estimate of NPP when implemented in global climate models, and has the potential to incorporate the thermal acclimation of respiration, further increasing the precision of estimating carbon fluxes under future warming temperatures. My results provide novel insights into the interactive temperature-carbon-nitrogen responses of plants, taking a step towards better understanding the response of plants and forests to future climates.

Abstract [sv]

Ökande atmosfäriskt CO2 och andra växthusgaser kopplade till den accelererande globala uppvärmningen utsätter växter och ekosystem för stressen av en snabbt förändrande abiotisk miljö. Att förstå påverkan av ett globalt klimat i förändring står i fokus inom växtforskning och utvecklandet av mer motståndskraftiga grödor är ett viktigt mål inom programmen för växtförädling. Vår förståelse av växters responser och acklimatisering till abiotiska förhållanden har förbättrats avsevärt under de senaste decennierna, men på grund av kombinationen av en komplex abiotisk miljö och stor biologisk mångfald, både på molekylär nivå såväl som på art-nivå, kvarstår en del frågetecken. Syftet med denna avhandling var att upprätta ett samband mellan växters responser på temperaturförändringar och kol-kvävebalansen hos växter. Arbetet i denna avhandling inriktades på ekologiskt betydande arter i den boreala regionen, Picea abies, Pinus sylvestris and Betula pendula; samt Betula utilis som är en av de framträdande trädarterna på höga höjder i Himalaya. Resultaten som presenteras visar att suboptimala temperaturer i kombination med andra abiotiska faktorer kan ha additiva effekter som inte enkelt kan härledas från effekten av de två faktorerna var för sig. Låg kvävetillgänglighet ökade den negativa effekten av låg temperatur, medan förhöjd CO2-halt förbättrade planttillväxt under måttliga temperaturökningar, men under en mer extrem temperaturökning förvärrades dock den negativa effekten av värme. Jag framför även bevis på att arter, trots att de grupperas i samma funktionella grupp eller finns inom samma biom, kan ha olika tröskelvärden beträffande temperatur och förskjutningar i C/N-balansen i sin miljö och att dessa skillnader, i viss utsträckning, kan förklaras av deras olika tillväxtstrategier. Vidare visar jag resultat som stöder hypotesen att C-N - flöden mellan mykorrhiza och träd är starkt beroende av C och N i miljön. Detta belyser i sin tur betydelsen av samarbetet mellan träd och mykorrhiza gällande kolbindningskapaciteten i den boreala regionen. I denna avhandling presenterar jag även en generaliserad empiriskt baserad matematisk modell som med hög precision kan beskriva respiration-temperatur svar av växtfunktionella typer eller biom, vilken ger en mer exakt uppskattning av NPP i globala klimatmodeller. Mina resultat åstadkommer nya insikter i de interaktiva temperatur-kol-kväve-responserna hos växter, och tar ett steg mot bättre förståelse för växters och skogars reaktion på framtida klimat.

Place, publisher, year, edition, pages
Umeå: Umeå University , 2017. , 67 p.
Keyword [en]
nitrogen, carbon dioxide, temperature, thermal acclimation, mycorrhiza, boreal forest, climate change, C:N balance, allocation, respiration, photosynthesis, terrestrial biosphere model
National Category
Botany
Identifiers
URN: urn:nbn:se:umu:diva-133982ISBN: 978-91-7601-700-5 (print)OAI: oai:DiVA.org:umu-133982DiVA: diva2:1090494
Public defence
2017-05-24, KB.E3.03 (KB3B1, Stora hörsalen), KBC Huset, Umeå University, Umeå, 13:00 (English)
Opponent
Supervisors
Available from: 2017-05-03 Created: 2017-04-24 Last updated: 2017-05-09Bibliographically approved
List of papers
1. Convergence in the temperature response of leaf respiration across biomes and plant functional types
Open this publication in new window or tab >>Convergence in the temperature response of leaf respiration across biomes and plant functional types
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2016 (English)In: Proceedings of the National Academy of Sciences of the United States of America, ISSN 0027-8424, E-ISSN 1091-6490, Vol. 113, no 14, 3832-3837 p.Article in journal (Refereed) Published
Abstract [en]

Plant respiration constitutes a massive carbon flux to the atmosphere, and a major control on the evolution of the global carbon cycle. It therefore has the potential to modulate levels of climate change due to the human burning of fossil fuels. Neither current physiological nor terrestrial biosphere models adequately describe its short-term temperature response, and even minor differences in the shape of the response curve can significantly impact estimates of ecosystem carbon release and/or storage. Given this, it is critical to establish whether there are predictable patterns in the shape of the respiration-temperature response curve, and thus in the intrinsic temperature sensitivity of respiration across the globe. Analyzing measurements in a comprehensive database for 231 species spanning 7 biomes, we demonstrate that temperature-dependent increases in leaf respiration do not follow a commonly used exponential function. Instead, we find a decelerating function as leaves warm, reflecting a declining sensitivity to higher temperatures that is remarkably uniform across all biomes and plant functional types. Such convergence in the temperature sensitivity of leaf respiration suggests that there are universally applicable controls on the temperature response of plant energy metabolism, such that a single new function can predict the temperature dependence of leaf respiration for global vegetation. This simple function enables straightforward description of plant respiration in the land-surface components of coupled earth system models. Our cross-biome analyses shows significant implications for such fluxes in cold climates, generally projecting lower values compared with previous estimates.

Place, publisher, year, edition, pages
National Academy of Sciences, 2016
Keyword
temperature sensitivity, climate models, carbon exchange, Q(10), thermal response
National Category
Climate Research Ecology
Identifiers
urn:nbn:se:umu:diva-119630 (URN)10.1073/pnas.1520282113 (DOI)000373354000049 ()
Available from: 2016-05-20 Created: 2016-04-25 Last updated: 2017-04-28Bibliographically approved
2. Greater carbon allocation to mycorrhizal fungi reduces tree nitrogen uptake in a boreal forest
Open this publication in new window or tab >>Greater carbon allocation to mycorrhizal fungi reduces tree nitrogen uptake in a boreal forest
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2016 (English)In: Ecology, ISSN 0012-9658, E-ISSN 1939-9170, Vol. 97, no 4, 1012-1022 p.Article in journal (Refereed) Published
Abstract [en]

The central role that ectomycorrhizal (EM) symbioses play in the structure and function of boreal forests pivots around the common assumption that carbon (C) and nitrogen (N) are exchanged at rates favorable for plant growth. However, this may not always be the case. It has been hypothesized that the benefits mycorrhizal fungi convey to their host plants strongly depends upon the availability of C and N, both of which are rapidly changing as a result of intensified human land use and climate change. Using large-scale shading and N addition treatments, we assessed the independent and interactive effects of changes in C and N supply on the transfer of N in intact EM associations with similar to 15 yr. old Scots pine trees. To assess the dynamics of N transfer in EM symbioses, we added trace amounts of highly enriched (NO3-)-N-15 label to the EM-dominated mor-layer and followed the fate of the N-15 label in tree foliage, fungal chitin on EM root tips, and EM sporocarps. Despite no change in leaf biomass, shading resulted in reduced tree C uptake, ca. 40% lower fungal biomass on EM root tips, and greater N-15 label in tree foliage compared to unshaded control plots, where more N-15 label was found in fungal biomass on EM colonized root tips. Short-term addition of N shifted the incorporation of N-15 label from EM fungi to tree foliage, despite no significant changes in below-ground tree C allocation to EM fungi. Contrary to the common assumption that C and N are exchanged at rates favorable for plant growth, our results show for the first time that under N-limited conditions greater C allocation to EM fungi in the field results in reduced, not increased, N transfer to host trees. Moreover, given the ubiquitous nature of mycorrhizal symbioses, our results stress the need to incorporate mycorrhizal dynamics into process-based ecosystem models to better predict forest C and N cycles in light of global climate change.

Keyword
N-15 pulse labeling, carbon supply, ectomycorrhizas, field experiment, mutualism, nitrogen availability, nitrogen limitation, Scots pine
National Category
Forest Science
Identifiers
urn:nbn:se:umu:diva-120100 (URN)10.1890/15-1222.1 (DOI)000373923100020 ()
Available from: 2016-06-09 Created: 2016-05-09 Last updated: 2017-04-28Bibliographically approved
3. Contrasting acclimation abilities of two dominant northern conifers to elevated CO2 and temperature
Open this publication in new window or tab >>Contrasting acclimation abilities of two dominant northern conifers to elevated CO2 and temperature
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(English)Manuscript (preprint) (Other academic)
National Category
Botany
Identifiers
urn:nbn:se:umu:diva-134160 (URN)
Available from: 2017-04-27 Created: 2017-04-27 Last updated: 2017-04-28
4. Elevated CO2 does not mitigate the effect of increased temperature at the whole plant or transcriptome scale
Open this publication in new window or tab >>Elevated CO2 does not mitigate the effect of increased temperature at the whole plant or transcriptome scale
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(English)Manuscript (preprint) (Other academic)
National Category
Botany
Identifiers
urn:nbn:se:umu:diva-134163 (URN)
Available from: 2017-04-27 Created: 2017-04-27 Last updated: 2017-04-28
5. Nitrogen limitation differentially affects acclimation by two contrasting Betula species to low and high growth temperatures and decreases the advantage of fast growth strategy under warming climates
Open this publication in new window or tab >>Nitrogen limitation differentially affects acclimation by two contrasting Betula species to low and high growth temperatures and decreases the advantage of fast growth strategy under warming climates
(English)Manuscript (preprint) (Other academic)
National Category
Botany
Identifiers
urn:nbn:se:umu:diva-134164 (URN)
Available from: 2017-04-27 Created: 2017-04-27 Last updated: 2017-04-28

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