排序方式: 共有46条查询结果,搜索用时 437 毫秒
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Paulo R. L. Bittencourt Rafael S. Oliveira Antonio C. L. da Costa Andre L. Giles Ingrid Coughlin Patricia B. Costa David C. Bartholomew Leandro V. Ferreira Steel S. Vasconcelos Fernanda V. Barros Joao A. S. Junior Alex A. R. Oliveira Maurizio Mencuccini Patrick Meir Lucy Rowland 《Global Change Biology》2020,26(6):3569-3584
The fate of tropical forests under future climate change is dependent on the capacity of their trees to adjust to drier conditions. The capacity of trees to withstand drought is likely to be determined by traits associated with their hydraulic systems. However, data on whether tropical trees can adjust hydraulic traits when experiencing drought remain rare. We measured plant hydraulic traits (e.g. hydraulic conductivity and embolism resistance) and plant hydraulic system status (e.g. leaf water potential, native embolism and safety margin) on >150 trees from 12 genera (36 species) and spanning a stem size range from 14 to 68 cm diameter at breast height at the world's only long‐running tropical forest drought experiment. Hydraulic traits showed no adjustment following 15 years of experimentally imposed moisture deficit. This failure to adjust resulted in these drought‐stressed trees experiencing significantly lower leaf water potentials, and higher, but variable, levels of native embolism in the branches. This result suggests that hydraulic damage caused by elevated levels of embolism is likely to be one of the key drivers of drought‐induced mortality following long‐term soil moisture deficit. We demonstrate that some hydraulic traits changed with tree size, however, the direction and magnitude of the change was controlled by taxonomic identity. Our results suggest that Amazonian trees, both small and large, have limited capacity to acclimate their hydraulic systems to future droughts, potentially making them more at risk of drought‐induced mortality. 相似文献
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David C. Bartholomew Paulo R. L. Bittencourt Antonio C. L. da Costa Lindsay F. Banin Patrícia de Britto Costa Sarah I. Coughlin Tomas F. Domingues Leandro V. Ferreira André Giles Maurizio Mencuccini Lina Mercado Raquel C. Miatto Alex Oliveira Rafael Oliveira Patrick Meir Lucy Rowland 《Plant, cell & environment》2020,43(10):2380-2393
The response of small understory trees to long-term drought is vital in determining the future composition, carbon stocks and dynamics of tropical forests. Long-term drought is, however, also likely to expose understory trees to increased light availability driven by drought-induced mortality. Relatively little is known about the potential for understory trees to adjust their physiology to both decreasing water and increasing light availability. We analysed data on maximum photosynthetic capacity (Jmax, Vcmax), leaf respiration (Rleaf), leaf mass per area (LMA), leaf thickness and leaf nitrogen and phosphorus concentrations from 66 small trees across 12 common genera at the world's longest running tropical rainfall exclusion experiment and compared responses to those from 61 surviving canopy trees. Small trees increased Jmax, Vcmax, Rleaf and LMA (71, 29, 32, 15% respectively) in response to the drought treatment, but leaf thickness and leaf nutrient concentrations did not change. Small trees were significantly more responsive than large canopy trees to the drought treatment, suggesting greater phenotypic plasticity and resilience to prolonged drought, although differences among taxa were observed. Our results highlight that small tropical trees have greater capacity to respond to ecosystem level changes and have the potential to regenerate resilient forests following future droughts. 相似文献
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Separating water‐potential induced swelling and shrinking from measured radial stem variations reveals a cambial growth and osmotic concentration signal 下载免费PDF全文
Tommy Chan Teemu Hölttä Frank Berninger Harri Mäkinen Pekka Nöjd Maurizio Mencuccini Eero Nikinmaa 《Plant, cell & environment》2016,39(2):233-244
The quantification of cambial growth over short time periods has been hampered by problems to discern between growth and the swelling and shrinking of a tree stem. This paper presents a model, which separates cambial growth and reversible water‐potential induced diurnal changes from simultaneously measured whole stem and xylem radial variations, from field‐measured Scots pine trees in Finland. The modelled growth, which includes osmotic concentration changes, was compared with (direct) dendrometer measurements and microcore samples. In addition, the relationship of modelled growth and dendrometer measurements to environmental factors was analysed. The results showed that the water‐potential induced changes of tree radius were successfully separated from stem growth. Daily growth predicted by the model exhibited a high correlation with the modelled daily changes of osmotic concentration in phloem, and a temperature dependency in early summer. Late‐summer growth saw higher dependency on water availability and temperature. Evaluation of the model against dendrometer measurements showed that the latter masked a true environmental signal in stem growth due to water‐potential induced changes. The model provides better understanding of radial growth physiology and offers potential to examine growth dynamics and changes due to osmotic concentration, and how the environment affects growth. 相似文献
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Direct observation and modelling of embolism spread between xylem conduits: a case study in Scots pine 下载免费PDF全文
José M. Torres‐Ruiz Hervé Cochard Maurizio Mencuccini Sylvain Delzon Eric Badel 《Plant, cell & environment》2016,39(12):2774-2785
Xylem embolism is one of the main processes involved in drought‐related plant mortality. Although its consequences for plant physiology are already well described, embolism formation and spread are poorly evaluated and modelled, especially for tracheid‐based species. The aim of this study was to assess the embolism formation and spread in Pinus sylvestris as a case study using X‐ray microtomography and hydraulics methods. We also evaluated the potential effects of cavitation fatigue on vulnerability to embolism and the micro‐morphology of the bordered pits using scanning electron microscopy (SEM) to test for possible links between xylem anatomy and embolism spread. Finally, a novel model was developed to simulate the spread of embolism in a 2D anisotropic cellular structure. Results showed a large variability in the formation and spread of embolism within a ring despite no differences being observed in intertracheid pit membrane anatomical traits. Simulations from the model showed a highly anisotropic tracheid‐to‐tracheid embolism spreading pattern, which confirms the major role of tracheid‐to‐tracheid air seeding to explain how embolism spreads in Scots pine. The results also showed that prior embolism removal from the samples reduced the resistance to embolism of the xylem and could result in overestimates of vulnerability to embolism. 相似文献
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Antonio C. L. da Costa Lucy Rowland Rafael S. Oliveira Alex A. R. Oliveira Oliver J. Binks Yann Salmon Steel S. Vasconcelos João A. S. Junior Leandro V. Ferreira Rafael Poyatos Maurizio Mencuccini Patrick Meir 《Global Change Biology》2018,24(1):249-258
Transpiration from the Amazon rainforest generates an essential water source at a global and local scale. However, changes in rainforest function with climate change can disrupt this process, causing significant reductions in precipitation across Amazonia, and potentially at a global scale. We report the only study of forest transpiration following a long‐term (>10 year) experimental drought treatment in Amazonian forest. After 15 years of receiving half the normal rainfall, drought‐related tree mortality caused total forest transpiration to decrease by 30%. However, the surviving droughted trees maintained or increased transpiration because of reduced competition for water and increased light availability, which is consistent with increased growth rates. Consequently, the amount of water supplied as rainfall reaching the soil and directly recycled as transpiration increased to 100%. This value was 25% greater than for adjacent nondroughted forest. If these drought conditions were accompanied by a modest increase in temperature (e.g., 1.5°C), water demand would exceed supply, making the forest more prone to increased tree mortality. 相似文献
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Increase of rooting ability in the woody species kiwi (Actinidia deliciosa A. Chev.) by transformation with Agrobacterium rhizogenes rol genes 总被引:1,自引:0,他引:1
Eddo Rugini Alessandro Pellegrineschi Massimo Mencuccini Domenico Mariotti 《Plant cell reports》1991,10(6-7):291-295
Summary The woody species kiwi (Actinidia deliciosa A. Chev.), a male and late flowering clone of the cv Hayward, has been transformed by a T-DNA fragment encompassing rol A, B, C genes of A. rhizogenes. Transgenic plants, regenerated from leaf disc callus, showed the typical hairy root phenotype as described in herbaceous species. Explants from these plants (both leaf discs or 3 to 4 node leafy microcuttings) showed an increased ability to produce roots. Since root formation is one of the limiting factors in the vegetative propagation of woody species, the results have been discussed in relation to the use of A. rhizogenes rol genes in improving root morphogenesis in trees. 相似文献
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Early observations led Sanio [ Wissen. Bot. , 8 , (1872) 401] to state that xylem conduit diameters and lengths in a coniferous tree increase from the apex down to a height below which they begin to decrease towards the tree base. Sanio's law of vertical tapering has been repeatedly tested with contradictory results and the debate over the scaling of conduit diameters with distance from the apex has not been settled. The debate has recently acquired new vigour, as an accurate knowledge of the vertical changes in wood anatomy has been shown to be crucial to scaling metabolic properties to plant and ecosystem levels. Contrary to Sanio's hypothesis, a well known model (MST, metabolic scaling theory) assumes that xylem conduits monotonically increase in diameter with distance from the apex following a power law. This has been proposed to explain the three-fourth power scaling between size and metabolism seen across plants. Here, we (i) summarized available data on conduit tapering in trees and (ii) propose a new numerical model that could explain the observed patterns. Data from 101 datasets grouped into 48 independent profiles supported the notions that phylogenetic group (angiosperms versus gymnosperms) and tree size strongly affected the vertical tapering of conduit diameter. For both angiosperms and gymnosperms, within-tree tapering also varied with distance from the apex. The model (based on the concept that optimal conduit tapering occurs when the difference between photosynthetic gains and wall construction costs is maximal) successfully predicted all three major empirical patterns. Our results are consistent with Sanio's law only for large trees and reject the MST assumptions that vertical tapering in conduit diameter is universal and independent of rank number. 相似文献
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Isotopic evidence for the occurrence of biological nitrification and nitrogen deposition processing in forest canopies 下载免费PDF全文
Rossella Guerrieri Elena I. Vanguelova Greg Michalski Timothy H. E. Heaton Maurizio Mencuccini 《Global Change Biology》2015,21(12):4613-4626
This study examines the role of tree canopies in processing atmospheric nitrogen (Ndep) for four forests in the United Kingdom subjected to different Ndep: Scots pine and beech stands under high Ndep (HN, 13–19 kg N ha?1 yr?1), compared to Scots pine and beech stands under low Ndep (LN, 9 kg N ha?1 yr?1). Changes of NO3‐N and NH4‐N concentrations in rainfall (RF) and throughfall (TF) together with a quadruple isotope approach, which combines δ18O, Δ17O and δ15N in NO3? and δ15N in NH4+, were used to assess N transformations by the canopies. Generally, HN sites showed higher NH4‐N and NO3‐N concentrations in RF compared to the LN sites. Similar values of δ15N‐NO3? and δ18O in RF suggested similar source of atmospheric NO3? (i.e. local traffic), while more positive values for δ15N‐NH4+ at HN compared to LN likely reflected the contribution of dry NHx deposition from intensive local farming. The isotopic signatures of the N‐forms changed after interacting with tree canopies. Indeed, 15N‐enriched NH4+ in TF compared to RF at all sites suggested that canopies played an important role in buffering dry Ndep also at the low Ndep site. Using two independent methods, based on δ18O and Δ17O, we quantified for the first time the proportion of NO3? in TF, which derived from nitrification occurring in tree canopies at the HN site. Specifically, for Scots pine, all the considered isotope approaches detected biological nitrification. By contrast for the beech, only using the mixing model with Δ17O, we were able to depict the occurrence of nitrification within canopies. Our study suggests that tree canopies play an active role in the N cycling within forest ecosystems. Processing of Ndep within canopies should not be neglected and needs further exploration, with the combination of multiple isotope tracers, with particular reference to Δ17O. 相似文献