| 1. |
- Law, Simon R, et al.
(författare)
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Metatranscriptomics captures dynamic shifts in mycorrhizal coordination in boreal forests
- 2022
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : Proceedings of the National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 119:26
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Tidskriftsartikel (refereegranskat)abstract
- Carbon storage and cycling in boreal forests—the largest terrestrial carbon store—is moderated by complex interactions between trees and soil microorganisms. However, existing methods limit our ability to predict how changes in environmental conditions will alter these associations and the essential ecosystem services they provide. To address this, we developed a metatranscriptomic approach to analyze the impact of nutrient enrichment on Norway spruce fine roots and the community structure, function, and tree–microbe coordination of over 350 root-associated fungal species. In response to altered nutrient status, host trees redefined their relationship with the fungal community by reducing sugar efflux carriers and enhancing defense processes. This resulted in a profound restructuring of the fungal community and a collapse in functional coordination between the tree and the dominant Basidiomycete species, and an increase in functional coordination with versatile Ascomycete species. As such, there was a functional shift in community dominance from Basidiomycetes species, with important roles in enzymatically cycling recalcitrant carbon, to Ascomycete species that have melanized cell walls that are highly resistant to degradation. These changes were accompanied by prominent shifts in transcriptional coordination between over 60 predicted fungal effectors, with more than 5,000 Norway spruce transcripts, providing mechanistic insight into the complex molecular dialogue coordinating host trees and their fungal partners. The host–microbe dynamics captured by this study functionally inform how these complex and sensitive biological relationships may mediate the carbon storage potential of boreal soils under changing nutrient conditions.
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| 2. |
- Gundale, Michael, et al.
(författare)
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The biological controls of soil carbon accumulation following wildfire and harvest in boreal forests : a review
- 2024
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Ingår i: Global Change Biology. - : John Wiley & Sons. - 1354-1013 .- 1365-2486. ; 30:5
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Forskningsöversikt (refereegranskat)abstract
- Boreal forests are frequently subjected to disturbances, including wildfire and clear-cutting. While these disturbances can cause soil carbon (C) losses, the long-term accumulation dynamics of soil C stocks during subsequent stand development is controlled by biological processes related to the balance of net primary production (NPP) and outputs via heterotrophic respiration and leaching, many of which remain poorly understood. We review the biological processes suggested to influence soil C accumulation in boreal forests. Our review indicates that median C accumulation rates following wildfire and clear-cutting are similar (0.15 and 0.20 Mg ha−1 year−1, respectively), however, variation between studies is extremely high. Further, while many individual studies show linear increases in soil C stocks through time after disturbance, there are indications that C stock recovery is fastest early to mid-succession (e.g. 15–80 years) and then slows as forests mature (e.g. >100 years). We indicate that the rapid build-up of soil C in younger stands appears not only driven by higher plant production, but also by a high rate of mycorrhizal hyphal production, and mycorrhizal suppression of saprotrophs. As stands mature, the balance between reductions in plant and mycorrhizal production, increasing plant litter recalcitrance, and ectomycorrhizal decomposers and saprotrophs have been highlighted as key controls on soil C accumulation rates. While some of these controls appear well understood (e.g. temporal patterns in NPP, changes in aboveground litter quality), many others remain research frontiers. Notably, very little data exists describing and comparing successional patterns of root production, mycorrhizal functional traits, mycorrhizal-saprotroph interactions, or C outputs via heterotrophic respiration and dissolved organic C following different disturbances. We argue that these less frequently described controls require attention, as they will be key not only for understanding ecosystem C balances, but also for representing these dynamics more accurately in soil organic C and Earth system models.
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| 3. |
- Heskel, Mary A., et al.
(författare)
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Convergence in the temperature response of leaf respiration across biomes and plant functional types
- 2016
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Ingår i: Proceedings of the National Academy of Sciences of the United States of America. - : National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 113:14, s. 3832-3837
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 4. |
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| 5. |
- Kurepin, Leonid V., et al.
(författare)
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Contrasting acclimation abilities of two dominant boreal conifers to elevated CO2 and temperature
- 2018
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Ingår i: Plant, Cell and Environment. - : Wiley. - 0140-7791 .- 1365-3040. ; 41:6, s. 1331-1345
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Tidskriftsartikel (refereegranskat)abstract
- High latitude forests will experience large changes in temperature and CO2 concentrations this century. We evaluated the effects of future climate conditions on 2 dominant boreal tree species, Pinus sylvestris L. and Picea abies (L.) H. Karst, exposing seedlings to 3 seasons of ambient (430 ppm) or elevated CO2 (750 ppm) and ambient temperatures, a + 4 degrees C warming or a + 8 degrees C warming. Pinus sylvestris responded positively to warming: seedlings developed a larger canopy, maintained high net CO2 assimilation rates (Anet), and acclimated dark respiration (Rdark). In contrast, carbon fluxes in Picea abies were negatively impacted by warming: maximum rates of Anet decreased, electron transport was redirected to alternative electron acceptors, and thermal acclimation of Rdark was weak. Elevated CO2 tended to exacerbate these effects in warm-grown Picea abies, and by the end of the experiment Picea abies from the +8 degrees C, high CO2 treatment produced fewer buds than they had 3 years earlier. Treatments had little effect on leaf and wood anatomy. Our results highlight that species within the same plant functional type may show opposite responses to warming and imply that Picea abies may be particularly vulnerable to warming due to low plasticity in photosynthetic and respiratory metabolism.
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| 8. |
- Schiestl-Aalto, Pauliina, et al.
(författare)
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Linking canopy-scale mesophyll conductance and phloem sugar δ13C using empirical and modelling approaches
- 2021
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Ingår i: New Phytologist. - : Wiley. - 0028-646X .- 1469-8137. ; 229:6, s. 3141-3155
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Tidskriftsartikel (refereegranskat)abstract
- © 2020 The Authors. New Phytologist © 2020 New Phytologist Trust Interpreting phloem carbohydrate or xylem tissue carbon isotopic composition as measures of water-use efficiency or past tree productivity requires in-depth knowledge of the factors altering the isotopic composition within the pathway from ambient air to phloem contents and tree ring. One of least understood of these factors is mesophyll conductance (gm). We formulated a dynamic model describing the leaf photosynthetic pathway including seven alternative gm descriptions and a simple transport of sugars from foliage down the trunk. We parameterised the model for a boreal Scots pine stand and compared simulated gm responses with weather variations. We further compared the simulated δ13C of new photosynthates among the different gm descriptions and against measured phloem sugar δ13C. Simulated gm estimates of the seven descriptions varied according to weather conditions, resulting in varying estimates of phloem δ13C during cold/moist and warm/dry periods. The model succeeded in predicting a drought response and a postdrought release in phloem sugar δ13C indicating suitability of the model for inverse prediction of leaf processes from phloem isotopic composition. We suggest short-interval phloem sampling during and after extreme weather conditions to distinguish between mesophyll conductance drivers for future model development.
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| 9. |
- Stangl, Zsofia R., et al.
(författare)
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Limits to photosynthesis: seasonal shifts in supply and demand for CO2 in Scots pine
- 2022
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Ingår i: New Phytologist. - : Wiley. - 0028-646X .- 1469-8137. ; 233:3, s. 1108-1120
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Tidskriftsartikel (refereegranskat)abstract
- Boreal forests undergo a strong seasonal photosynthetic cycle; however, the underlying processes remain incompletely characterized. Here, we present a novel analysis of the seasonal diffusional and biochemical limits to photosynthesis (Anet) relative to temperature and light limitations in high-latitude mature Pinus sylvestris, including a high-resolution analysis of the seasonality of mesophyll conductance (gm) and its effect on the estimation of carboxylation capacity ((Formula presented.)). We used a custom-built gas-exchange system coupled to a carbon isotope analyser to obtain continuous measurements for the estimation of the relevant shoot gas-exchange parameters and quantified the biochemical and diffusional controls alongside the environmental controls over Anet. The seasonality of Anet was strongly dependent on (Formula presented.) and the diffusional limitations. Stomatal limitation was low in spring and autumn but increased to 31% in June. By contrast, mesophyll limitation was nearly constant (19%). We found that (Formula presented.) limited Anet in the spring, whereas daily temperatures and the gradual reduction of light availability limited Anet in the autumn, despite relatively high (Formula presented.). We describe for the first time the role of mesophyll conductance in connection with seasonal trends in net photosynthesis of P. sylvestris, revealing a strong coordination between gm and Anet, but not between gm and stomatal conductance.
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