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- Niemi, MEK, et al.
(författare)
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- 2021
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swepub:Mat__t
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| 5. |
- Medina-Vega, José A., et al.
(författare)
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Tropical tree ectomycorrhiza are distributed independently of soil nutrients
- 2024
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Ingår i: Nature Ecology and Evolution. - 2397-334X. ; 8, s. 400-410
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Tidskriftsartikel (refereegranskat)abstract
- Mycorrhizae, a form of plant–fungal symbioses, mediate vegetation impacts on ecosystem functioning. Climatic effects on decomposition and soil quality are suggested to drive mycorrhizal distributions, with arbuscular mycorrhizal plants prevailing in low-latitude/high-soil-quality areas and ectomycorrhizal (EcM) plants in high-latitude/low-soil-quality areas. However, these generalizations, based on coarse-resolution data, obscure finer-scale variations and result in high uncertainties in the predicted distributions of mycorrhizal types and their drivers. Using data from 31 lowland tropical forests, both at a coarse scale (mean-plot-level data) and fine scale (20 × 20 metres from a subset of 16 sites), we demonstrate that the distribution and abundance of EcM-associated trees are independent of soil quality. Resource exchange differences among mycorrhizal partners, stemming from diverse evolutionary origins of mycorrhizal fungi, may decouple soil fertility from the advantage provided by mycorrhizal associations. Additionally, distinct historical biogeographies and diversification patterns have led to differences in forest composition and nutrient-acquisition strategies across three major tropical regions. Notably, Africa and Asia’s lowland tropical forests have abundant EcM trees, whereas they are relatively scarce in lowland neotropical forests. A greater understanding of the functional biology of mycorrhizal symbiosis is required, especially in the lowland tropics, to overcome biases from assuming similarity to temperate and boreal regions.
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- Couvreur, Valentin, et al.
(författare)
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Water transport through tall trees : A vertically explicit, analytical model of xylem hydraulic conductance in stems
- 2018
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Ingår i: Plant, Cell and Environment. - : Wiley. - 0140-7791 .- 1365-3040. ; 41:8, s. 1821-1839
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Tidskriftsartikel (refereegranskat)abstract
- Trees grow by vertically extending their stems, so accurate stem hydraulic models are fundamental to understanding the hydraulic challenges faced by tall trees. Using a literature survey, we showed that many tree species exhibit continuous vertical variation in hydraulic traits. To examine the effects of this variation on hydraulic function, we developed a spatially explicit, analytical water transport model for stems. Our model allows Huber ratio, stem-saturated conductivity, pressure at 50% loss of conductivity, leaf area, and transpiration rate to vary continuously along the hydraulic path. Predictions from our model differ from a matric flux potential model parameterized with uniform traits. Analyses show that cavitation is a whole-stem emergent property resulting from non-linear pressure-conductivity feedbacks that, with gravity, cause impaired water transport to accumulate along the path. Because of the compounding effects of vertical trait variation on hydraulic function, growing proportionally more sapwood and building tapered xylem with height, as well as reducing xylem vulnerability only at branch tips while maintaining transport capacity at the stem base, can compensate for these effects. We therefore conclude that the adaptive significance of vertical variation in stem hydraulic traits is to allow trees to grow tall and tolerate operating near their hydraulic limits.
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| 7. |
- Zuleta, Daniel, 1990, et al.
(författare)
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Importance of topography for tree species habitat distributions in a terra firme forest in the Colombian Amazon
- 2020
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Ingår i: Plant and Soil. - : Springer Science and Business Media LLC. - 0032-079X .- 1573-5036. ; 450, s. 133-149
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Tidskriftsartikel (refereegranskat)abstract
- Aims: To test the relative importance of topography versus soil chemistry in defining tree species-habitat associations in a terra firme Amazonian forest. Method: We evaluated habitat associations for 612 woody species using alternative habitat maps generated from topography and soil chemistry in the 25-ha Amacayacu Forest Dynamics Plot, Colombian Amazon. We assessed the ability of each habitat map to explain the community-level patterns of species-habitat associations using two methods of habitat randomization and different sample size thresholds (i.e., species’ abundance). Results: The greatest proportion of species-habitat associations arose from topographically-defined habitats (55% to 63%) compared to soil chemistry-defined (19% to 40%) or topography plus soil chemistry-defined habitats (18% to 42%). Results were robust to the method of habitat randomization and to sample size threshold. Conclusions: Our results demonstrate that certain environmental factors may be more influential than others in defining forest-level patterns of community assembly and that comparison of the ability of different environmental variables to explain habitat associations is a crucial step in testing hypotheses about the mechanisms underlying assembly. Our results point to topography-driven hydrological variation as a key factor structuring tree species distributions in what are commonly considered homogeneous Amazonian terra firme forests.
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