220 results on '"Medlyn BE"'
Search Results
2. Structural organization of the retriever–CCC endosomal recycling complex
- Author
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Boesch, Daniel J., Singla, Amika, Han, Yan, Kramer, Daniel A., Liu, Qi, Suzuki, Kohei, Juneja, Puneet, Zhao, Xuefeng, Long, Xin, Medlyn, Michael J., Billadeau, Daniel D., Chen, Zhe, Chen, Baoyu, and Burstein, Ezra
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- 2024
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- View/download PDF
3. The AusTraits plant dictionary
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Elizabeth H. Wenk, Hervé Sauquet, Rachael V. Gallagher, Rowan Brownlee, Carl Boettiger, David Coleman, Sophie Yang, Tony Auld, Russell Barrett, Timothy Brodribb, Brendan Choat, Lily Dun, David Ellsworth, Carl Gosper, Lydia Guja, Gregory J. Jordan, Tom Le Breton, Andrea Leigh, Patricia Lu-Irving, Belinda Medlyn, Rachael Nolan, Mark Ooi, Karen D. Sommerville, Peter Vesk, Matthew White, Ian J. Wright, and Daniel S. Falster
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Science - Abstract
Abstract Traits with intuitive names, a clear scope and explicit description are essential for all trait databases. The lack of unified, comprehensive, and machine-readable plant trait definitions limits the utility of trait databases, including reanalysis of data from a single database, or analyses that integrate data across multiple databases. Both can only occur if researchers are confident the trait concepts are consistent within and across sources. Here we describe the AusTraits Plant Dictionary (APD), a new data source of terms that extends the trait definitions included in a recent trait database, AusTraits. The development process of the APD included three steps: review and formalisation of the scope of each trait and the accompanying trait description; addition of trait metadata; and publication in both human and machine-readable forms. Trait definitions include keywords, references, and links to related trait concepts in other databases, enabling integration of AusTraits with other sources. The APD will both improve the usability of AusTraits and foster the integration of trait data across global and regional plant trait databases.
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- 2024
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4. A constraint on historic growth in global photosynthesis due to rising CO2
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Keenan, T. F., Luo, X., Stocker, B. D., De Kauwe, M. G., Medlyn, B. E., Prentice, I. C., Smith, N. G., Terrer, C., Wang, H., Zhang, Y., and Zhou, S.
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- 2023
- Full Text
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5. Environmental correlates of the forest carbon distribution in the Central Himalayas
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Shiva Khanal, Rachael H. Nolan, Belinda E. Medlyn, and Matthias M. Boer
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aboveground carbon ,disturbance ,environmental drivers ,forest ,Himalaya ,soil organic carbon ,Ecology ,QH540-549.5 - Abstract
Abstract Understanding the biophysical limitations on forest carbon across diverse ecological regions is crucial for accurately assessing and managing forest carbon stocks. This study investigates the role of climate and disturbance on the spatial variation of two key forest carbon pools: aboveground carbon (AGC) and soil organic carbon (SOC). Using plot‐level carbon pool estimates from Nepal's national forest inventory and structural equation modelling, we explore the relationship of forest carbon stocks to broad‐scale climatic water and energy availability and fine‐scale terrain and disturbance. The forest AGC and SOC models explained 25% and 59% of the observed spatial variation in forest AGC and SOC, respectively. Among the evaluated variables, disturbance exhibited the strongest negative correlation with AGC, while the availability of climatic energy demonstrated the strongest negative correlation with SOC. Disturbances such as selective logging and firewood collection result in immediate forest carbon loss, while soil carbon changes take longer to respond. The lower decomposition rates in the high‐elevation region, due to lower temperatures, preserve organic matter and contribute to the high SOC stocks observed there. These results highlight the critical role of climate and disturbance regimes in shaping landscape patterns of forest carbon stocks. Understanding the underlying drivers of these patterns is crucial for forest carbon management and conservation across diverse ecological zones including the Central Himalayas.
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- 2024
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6. Experiences of homeless people who use psychoactive substances: an interpretative phenomenological study
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Wagstaff, Chris, Davis, Anna, Jackson-McConnell, Elizabeth, MacDonald, Matilda, Medlyn, Ashley, and Pillon, Sandra
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- 2023
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7. Mapping soil organic carbon stocks in Nepal’s forests
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Khanal, Shiva, Nolan, Rachael H., Medlyn, Belinda E., and Boer, Matthias M.
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- 2023
- Full Text
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8. Microfluidic Organoid Cultures Derived from Pancreatic Cancer Biopsies for Personalized Testing of Chemotherapy and Immunotherapy
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Daheui Choi, Alan M. Gonzalez‐Suarez, Mihai G. Dumbrava, Michael Medlyn, Jose M. deHoyos‐Vega, Frank Cichocki, Jeffrey S. Miller, Li Ding, Mojun Zhu, Gulnaz Stybayeva, Alexandre Gaspar‐Maia, Daniel D. Billadeau, Wen Wee Ma, and Alexander Revzin
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chemotherapy ,immunotherapy ,microfluidic device ,pancreatic cancer ,patient‐derived organoid ,Science - Abstract
Abstract Patient‐derived cancer organoids (PDOs) hold considerable promise for personalizing therapy selection and improving patient outcomes. However, it is challenging to generate PDOs in sufficient numbers to test therapies in standard culture platforms. This challenge is particularly acute for pancreatic ductal adenocarcinoma (PDAC) where most patients are diagnosed at an advanced stage with non‐resectable tumors and where patient tissue is in the form of needle biopsies. Here the development and characterization of microfluidic devices for testing therapies using a limited amount of tissue or PDOs available from PDAC biopsies is described. It is demonstrated that microfluidic PDOs are phenotypically and genotypically similar to the gold‐standard Matrigel organoids with the advantages of 1) spheroid uniformity, 2) minimal cell number requirement, and 3) not relying on Matrigel. The utility of microfluidic PDOs is proven by testing PDO responses to several chemotherapies, including an inhibitor of glycogen synthase kinase (GSKI). In addition, microfluidic organoid cultures are used to test effectiveness of immunotherapy comprised of NK cells in combination with a novel biologic. In summary, our microfluidic device offers considerable benefits for personalizing oncology based on cancer biopsies and may, in the future, be developed into a companion diagnostic for chemotherapy or immunotherapy treatments.
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- 2024
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9. Convergence in phosphorus constraints to photosynthesis in forests around the world
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Ellsworth, David S, Crous, Kristine Y, De Kauwe, Martin G, Verryckt, Lore T, Goll, Daniel, Zaehle, Sönke, Bloomfield, Keith J, Ciais, Philippe, Cernusak, Lucas A, Domingues, Tomas F, Dusenge, Mirindi Eric, Garcia, Sabrina, Guerrieri, Rossella, Ishida, F Yoko, Janssens, Ivan A, Kenzo, Tanaka, Ichie, Tomoaki, Medlyn, Belinda E, Meir, Patrick, Norby, Richard J, Reich, Peter B, Rowland, Lucy, Santiago, Louis S, Sun, Yan, Uddling, Johan, Walker, Anthony P, Weerasinghe, KW Lasantha K, van de Weg, Martine J, Zhang, Yun-Bing, Zhang, Jiao-Lin, and Wright, Ian J
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Carbon ,Forests ,Phosphorus ,Photosynthesis ,Plant Leaves ,Trees - Abstract
Tropical forests take up more carbon (C) from the atmosphere per annum by photosynthesis than any other type of vegetation. Phosphorus (P) limitations to C uptake are paramount for tropical and subtropical forests around the globe. Yet the generality of photosynthesis-P relationships underlying these limitations are in question, and hence are not represented well in terrestrial biosphere models. Here we demonstrate the dependence of photosynthesis and underlying processes on both leaf N and P concentrations. The regulation of photosynthetic capacity by P was similar across four continents. Implementing P constraints in the ORCHIDEE-CNP model, gross photosynthesis was reduced by 36% across the tropics and subtropics relative to traditional N constraints and unlimiting leaf P. Our results provide a quantitative relationship for the P dependence for photosynthesis for the front-end of global terrestrial C models that is consistent with canopy leaf measurements.
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- 2022
10. Disentangling contributions of allometry, species composition and structure to high aboveground biomass density of high-elevation forests
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Khanal, Shiva, Nolan, Rachael H., Medlyn, Belinda E., and Boer, Matthias M.
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- 2024
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11. Temporal Dynamics of Canopy Properties and Carbon and Water Fluxes in a Temperate Evergreen Angiosperm Forest
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Alexandre A. Renchon, Vanessa Haverd, Cathy M. Trudinger, Belinda E. Medlyn, Anne Griebel, Daniel Metzen, Jürgen Knauer, Matthias M. Boer, and Elise Pendall
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land–atmosphere exchange ,land surface model ,canopy properties ,phenology ,Plant ecology ,QK900-989 - Abstract
The forest–atmosphere exchange of carbon and water is regulated by meteorological conditions as well as canopy properties such as leaf area index (LAI, m2 m−2), photosynthetic capacity (PC μmol m−2 s−1), or surface conductance in optimal conditions (Gs,opt, mmol m−2 s−1), which can vary seasonally and inter-annually. This variability is well understood for deciduous species but is poorly characterized in evergreen forests. Here, we quantify the seasonal dynamics of a temperate evergreen eucalypt forest with estimates of LAI, litterfall, carbon and water fluxes, and meteorological conditions from measurements and model simulations. We merged MODIS Enhanced Vegetation Index (EVI) values with site-based LAI measurements to establish a 17-year sequence of monthly LAI. We ran the Community Atmosphere Biosphere Land Exchange model (CABLE-POP (version r5046)) with constant and varying LAI for our site to quantify the influence of seasonal canopy dynamics on carbon and water fluxes. We observed that the peak of LAI occurred in late summer–early autumn, with a higher and earlier peak occurring in years when summer rainfall was greater. Seasonality in litterfall and allocation of net primary productivity (FNPP) to leaf growth (af, 0–1) drove this pattern, suggesting a complete renewal of the canopy before the timing of peak LAI. Litterfall peaked in spring, followed by a high af in summer, at the end of which LAI peaked, and PC and Gs,opt reached their maximum values in autumn, resulting from a combination of high LAI and efficient mature leaves. These canopy dynamics helped explain observations of maximum gross ecosystem production (FGEP) in spring and autumn and net ecosystem carbon loss in summer at our site. Inter-annual variability in LAI was positively correlated with Net Ecosystem Production (FNEP). It would be valuable to apply a similar approach to other temperate evergreen forests to identify broad patterns of seasonality in leaf growth and turnover. Because incorporating dynamic LAI was insufficient to fully capture the dynamics of FGEP, observations of seasonal variation in photosynthetic capacity, such as from solar-induced fluorescence, should be incorporated in land surface models to improve ecosystem flux estimates in evergreen forests.
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- 2024
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12. Mapping soil organic carbon stocks in Nepal’s forests
- Author
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Shiva Khanal, Rachael H. Nolan, Belinda E. Medlyn, and Matthias M. Boer
- Subjects
Medicine ,Science - Abstract
Abstract Comprehensive forest carbon accounting requires reliable estimation of soil organic carbon (SOC) stocks. Despite being an important carbon pool, limited information is available on SOC stocks in global forests, particularly for forests in mountainous regions, such as the Central Himalayas. The availability of consistently measured new field data enabled us to accurately estimate forest soil organic carbon (SOC) stocks in Nepal, addressing a previously existing knowledge gap. Our method involved modelling plot-based estimates of forest SOC using covariates related to climate, soil, and topographic position. Our quantile random forest model resulted in the high spatial resolution prediction of Nepal’s national forest SOC stock together with prediction uncertainties. Our spatially explicit forest SOC map showed the high SOC levels in high-elevation forests and a significant underrepresentation of these stocks in global-scale assessments. Our results offer an improved baseline on the distribution of total carbon in the forests of the Central Himalayas. The benchmark maps of predicted forest SOC and associated errors, along with our estimate of 494 million tonnes (SE = 16) of total SOC in the topsoil (0–30 cm) of forested areas in Nepal, carry important implications for understanding the spatial variability of forest SOC in mountainous regions with complex terrains.
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- 2023
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13. Canopy dieback and recovery in Australian native forests following extreme drought
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Adriano Losso, Anthea Challis, Alice Gauthey, Rachael H. Nolan, Samuel Hislop, Adam Roff, Matthias M. Boer, Mingkai Jiang, Belinda E. Medlyn, and Brendan Choat
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Medicine ,Science - Abstract
Abstract In 2019, south-eastern Australia experienced its driest and hottest year on record, resulting in massive canopy dieback events in eucalypt dominated forests. A subsequent period of high precipitation in 2020 provided a rare opportunity to quantify the impacts of extreme drought and consequent recovery. We quantified canopy health and hydraulic impairment (native percent loss of hydraulic conductivity, PLC) of 18 native tree species growing at 15 sites that were heavily impacted by the drought both during and 8–10 months after the drought. Most species exhibited high PLC during drought (PLC:65.1 ± 3.3%), with no clear patterns across sites or species. Heavily impaired trees (PLC > 70%) showed extensive canopy browning. In the post-drought period, most surviving trees exhibited hydraulic recovery (PLC:26.1 ± 5.1%), although PLC remained high in some trees (50–70%). Regained hydraulic function (PLC
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- 2022
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14. Explaining changes in rainfall–runoff relationships during and after Australia's Millennium Drought: a community perspective
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K. Fowler, M. Peel, M. Saft, T. J. Peterson, A. Western, L. Band, C. Petheram, S. Dharmadi, K. S. Tan, L. Zhang, P. Lane, A. Kiem, L. Marshall, A. Griebel, B. E. Medlyn, D. Ryu, G. Bonotto, C. Wasko, A. Ukkola, C. Stephens, A. Frost, H. Gardiya Weligamage, P. Saco, H. Zheng, F. Chiew, E. Daly, G. Walker, R. W. Vervoort, J. Hughes, L. Trotter, B. Neal, I. Cartwright, and R. Nathan
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Technology ,Environmental technology. Sanitary engineering ,TD1-1066 ,Geography. Anthropology. Recreation ,Environmental sciences ,GE1-350 - Abstract
The Millennium Drought lasted more than a decade and is notable for causing persistent shifts in the relationship between rainfall and runoff in many southeastern Australian catchments. Research to date has successfully characterised where and when shifts occurred and explored relationships with potential drivers, but a convincing physical explanation for observed changes in catchment behaviour is still lacking. Originating from a large multi-disciplinary workshop, this paper presents and evaluates a range of hypothesised process explanations of flow response to the Millennium Drought. The hypotheses consider climatic forcing, vegetation, soil moisture dynamics, groundwater, and anthropogenic influence. The hypotheses are assessed against evidence both temporally (e.g. why was the Millennium Drought different to previous droughts?) and spatially (e.g. why did rainfall–runoff relationships shift in some catchments but not in others?). Thus, the strength of this work is a large-scale assessment of hydrologic changes and potential drivers. Of 24 hypotheses, 3 are considered plausible, 10 are considered inconsistent with evidence, and 11 are in a category in between, whereby they are plausible yet with reservations (e.g. applicable in some catchments but not others). The results point to the unprecedented length of the drought as the primary climatic driver, paired with interrelated groundwater processes, including declines in groundwater storage, altered recharge associated with vadose zone expansion, and reduced connection between subsurface and surface water processes. Other causes include increased evaporative demand and harvesting of runoff by small private dams. Finally, we discuss the need for long-term field monitoring, particularly targeting internal catchment processes and subsurface dynamics. We recommend continued investment in the understanding of hydrological shifts, particularly given their relevance to water planning under climate variability and change.
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- 2022
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15. Green-up and brown-down: Modelling grassland foliage phenology responses to soil moisture availability
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Yang, Jinyan, Medlyn, Belinda E., Barton, Craig V.M., Churchill, Amber C., De Kauwe, Martin G., Jiang, Mingkai, Krishnananthaselvan, Arjunan, Tissue, David T., Pendall, Elise, and Power, Sally A.
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- 2023
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16. Convergence in phosphorus constraints to photosynthesis in forests around the world
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David S. Ellsworth, Kristine Y. Crous, Martin G. De Kauwe, Lore T. Verryckt, Daniel Goll, Sönke Zaehle, Keith J. Bloomfield, Philippe Ciais, Lucas A. Cernusak, Tomas F. Domingues, Mirindi Eric Dusenge, Sabrina Garcia, Rossella Guerrieri, F. Yoko Ishida, Ivan A. Janssens, Tanaka Kenzo, Tomoaki Ichie, Belinda E. Medlyn, Patrick Meir, Richard J. Norby, Peter B. Reich, Lucy Rowland, Louis S. Santiago, Yan Sun, Johan Uddling, Anthony P. Walker, K. W. Lasantha K. Weerasinghe, Martine J. van de Weg, Yun-Bing Zhang, Jiao-Lin Zhang, and Ian J. Wright
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Science - Abstract
Phosphorus (P) limitation is pervasive in tropical forests. Here the authors analyse the dependence of photosynthesis on leaf N and P in tropical forests, and show that incorporating leaf P constraints in a terrestrial biosphere model enhances its predictive power.
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- 2022
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17. Improved representation of plant physiology in the JULES-vn5.6 land surface model: photosynthesis, stomatal conductance and thermal acclimation
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R. J. Oliver, L. M. Mercado, D. B. Clark, C. Huntingford, C. M. Taylor, P. L. Vidale, P. C. McGuire, M. Todt, S. Folwell, V. Shamsudheen Semeena, and B. E. Medlyn
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Geology ,QE1-996.5 - Abstract
Carbon and water cycle dynamics of vegetation are controlled primarily by photosynthesis and stomatal conductance (gs). Our goal is to improve the representation of these key physiological processes within the JULES land surface model, with a particular focus on refining the temperature sensitivity of photosynthesis, impacting modelled carbon, energy and water fluxes. We test (1) an implementation of the Farquhar et al. (1980) photosynthesis scheme and associated plant functional type-dependent photosynthetic temperature response functions, (2) the optimality-based gs scheme from Medlyn et al. (2011) and (3) the Kattge and Knorr (2007) photosynthetic capacity thermal acclimation scheme. New parameters for each model configuration are adopted from recent large observational datasets that synthesise global experimental data. These developments to JULES incorporate current physiological understanding of vegetation behaviour into the model and enable users to derive direct links between model parameters and ongoing measurement campaigns that refine such parameter values. Replacement of the original Collatz et al. (1991) C3 photosynthesis model with the Farquhar scheme results in large changes in GPP for the current day, with ∼ 10 % reduction in seasonal (June–August, JJA, and December–February, DJF) mean GPP in tropical forests and ∼ 20 % increase in the northern high-latitude forests in JJA. The optimality-based gs model decreases the latent heat flux for the present day (∼ 10 %, with an associated increase in sensible heat flux) across regions dominated by needleleaf evergreen forest in the Northern Hemisphere summer. Thermal acclimation of photosynthesis coupled with the Medlyn gs scheme reduced tropical forest GPP by up to 5 % and increased GPP in the high-northern-latitude forests by between 2 % and 5 %. Evaluation of simulated carbon and water fluxes by each model configuration against global data products shows this latter configuration generates improvements in these key areas. Thermal acclimation of photosynthesis coupled with the Medlyn gs scheme improved modelled carbon fluxes in tropical and high-northern-latitude forests in JJA and improved the simulation of evapotranspiration across much of the Northern Hemisphere in JJA. Having established good model performance for the contemporary period, we force this new version of JULES offline with a future climate scenario corresponding to rising atmospheric greenhouse gases (Shared Socioeconomic Pathway (SSP5), Representative Concentration Pathway 8.5 (RCP8.5)). In particular, these calculations allow for understanding of the effects of long-term warming. We find that the impact of thermal acclimation coupled with the optimality-based gs model on simulated fluxes increases latent heat flux (+50 %) by the year 2050 compared to the JULES model configuration without acclimation. This new JULES configuration also projects increased GPP across tropical (+10 %) and northern-latitude regions (+30 %) by 2050. We conclude that thermal acclimation of photosynthesis with the Farquhar photosynthesis scheme and the new optimality-based gs scheme together improve the simulation of carbon and water fluxes for the current day and have a large impact on modelled future carbon cycle dynamics in a warming world.
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- 2022
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18. The AusTraits plant dictionary
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Wenk, Elizabeth H., primary, Sauquet, Hervé, additional, Gallagher, Rachael V., additional, Brownlee, Rowan, additional, Boettiger, Carl, additional, Coleman, David, additional, Yang, Sophie, additional, Auld, Tony, additional, Barrett, Russell, additional, Brodribb, Timothy, additional, Choat, Brendan, additional, Dun, Lily, additional, Ellsworth, David, additional, Gosper, Carl, additional, Guja, Lydia, additional, Jordan, Gregory J., additional, Le Breton, Tom, additional, Leigh, Andrea, additional, Lu-Irving, Patricia, additional, Medlyn, Belinda, additional, Nolan, Rachael, additional, Ooi, Mark, additional, Sommerville, Karen D., additional, Vesk, Peter, additional, White, Matthew, additional, Wright, Ian J., additional, and Falster, Daniel S., additional
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- 2024
- Full Text
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19. Mechanisms of woody-plant mortality under rising drought, CO2 and vapour pressure deficit
- Author
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McDowell, Nate G., Sapes, Gerard, Pivovaroff, Alexandria, Adams, Henry D., Allen, Craig D., Anderegg, William R. L., Arend, Matthias, Breshears, David D., Brodribb, Tim, Choat, Brendan, Cochard, Hervé, De Cáceres, Miquel, De Kauwe, Martin G., Grossiord, Charlotte, Hammond, William M., Hartmann, Henrik, Hoch, Günter, Kahmen, Ansgar, Klein, Tamir, Mackay, D. Scott, Mantova, Marylou, Martínez-Vilalta, Jordi, Medlyn, Belinda E., Mencuccini, Maurizio, Nardini, Andrea, Oliveira, Rafael S., Sala, Anna, Tissue, David T., Torres-Ruiz, José M., Trowbridge, Amy M., Trugman, Anna T., Wiley, Erin, and Xu, Chonggang
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- 2022
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20. Drought-related leaf functional traits control spatial and temporal dynamics of live fuel moisture content
- Author
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Nolan, Rachael H., Foster, Benjamin, Griebel, Anne, Choat, Brendan, Medlyn, Belinda E., Yebra, Marta, Younes, Nicolás, and Boer, Matthias M.
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- 2022
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21. Satellite-observed shifts in C3/C4 abundance in Australian grasslands are associated with rainfall patterns
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Xie, Qiaoyun, Huete, Alfredo, Hall, Christopher C., Medlyn, Belinda E., Power, Sally A., Davies, Janet M., Medek, Danielle E., and Beggs, Paul J.
- Published
- 2022
- Full Text
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22. Canopy dieback and recovery in Australian native forests following extreme drought
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Losso, Adriano, Challis, Anthea, Gauthey, Alice, Nolan, Rachael H., Hislop, Samuel, Roff, Adam, Boer, Matthias M., Jiang, Mingkai, Medlyn, Belinda E., and Choat, Brendan
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- 2022
- Full Text
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23. Thirty-eight years of CO2 fertilization has outpaced growing aridity to drive greening of Australian woody ecosystems
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S. W. Rifai, M. G. De Kauwe, A. M. Ukkola, L. A. Cernusak, P. Meir, B. E. Medlyn, and A. J. Pitman
- Subjects
Ecology ,QH540-549.5 ,Life ,QH501-531 ,Geology ,QE1-996.5 - Abstract
Climate change is projected to increase the imbalance between the supply (precipitation) and atmospheric demand for water (i.e., increased potential evapotranspiration), stressing plants in water-limited environments. Plants may be able to offset increasing aridity because rising CO2 increases water use efficiency. CO2 fertilization has also been cited as one of the drivers of the widespread “greening” phenomenon. However, attributing the size of this CO2 fertilization effect is complicated, due in part to a lack of long-term vegetation monitoring and interannual- to decadal-scale climate variability. In this study we asked the question of how much CO2 has contributed towards greening. We focused our analysis on a broad aridity gradient spanning eastern Australia's woody ecosystems. Next we analyzed 38 years of satellite remote sensing estimates of vegetation greenness (normalized difference vegetation index, NDVI) to examine the role of CO2 in ameliorating climate change impacts. Multiple statistical techniques were applied to separate the CO2-attributable effects on greening from the changes in water supply and atmospheric aridity. Widespread vegetation greening occurred despite a warming climate, increases in vapor pressure deficit, and repeated record-breaking droughts and heat waves. Between 1982–2019 we found that NDVI increased (median 11.3 %) across 90.5 % of the woody regions. After masking disturbance effects (e.g., fire), we statistically estimated an 11.7 % increase in NDVI attributable to CO2, broadly consistent with a hypothesized theoretical expectation of an 8.6 % increase in water use efficiency due to rising CO2. In contrast to reports of a weakening CO2 fertilization effect, we found no consistent temporal change in the CO2 effect. We conclude rising CO2 has mitigated the effects of increasing aridity, repeated record-breaking droughts, and record-breaking heat waves in eastern Australia. However, we were unable to determine whether trees or grasses were the primary beneficiary of the CO2-induced change in water use efficiency, which has implications for projecting future ecosystem resilience. A more complete understanding of how CO2-induced changes in water use efficiency affect trees and non-tree vegetation is needed.
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- 2022
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24. Carbon-phosphorus cycle models overestimate CO2 enrichment response in a mature Eucalyptus forest.
- Author
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Mingkai Jiang, Medlyn, Belinda E., Wårlind, David, Knauer, Jürgen, Fleischer, Katrin, Goll, Daniel S., Olin, Stefan, Xiaojuan Yang, Lin Yu, Zaehle, Sönke, Haicheng Zhang, He Lv, Crous, Kristine Y., Carrillo, Yolima, Macdonald, Catriona, Anderson, Ian, Boer, Matthias M., Farrell, Mark, Gherlenda, Andrew, and Castañeda-Gómez, Laura
- Subjects
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EUCALYPTUS , *CARBON cycle , *PLANT cells & tissues , *CLIMATE change - Abstract
The importance of phosphorus (P) in regulating ecosystem responses to climate change has fostered P-cycle implementation in land surface models, but their CO2 effects predictions have not been evaluated against measurements. Here, we perform a data-driven model evaluation where simulations of eight widely used P-enabled models were confronted with observations from a long-term free-air CO2 enrichment experiment in a mature, P-limited Eucalyptus forest. We show that most models predicted the correct sign and magnitude of the CO2 effect on ecosystem carbon (C) sequestration, but they generally overestimated the effects on plant C uptake and growth. We identify leaf-to-canopy scaling of photosynthesis, plant tissue stoichiometry, plant belowground C allocation, and the subsequent consequences for plant-microbial interaction as key areas in which models of ecosystem C-P interaction can be improved. Together, this data-model intercomparison reveals data-driven insights into the performance and functionality of P-enabled models and adds to the existing evidence that the global CO2-driven carbon sink is overestimated by models. [ABSTRACT FROM AUTHOR]
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- 2024
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25. Demographic change and loss of big trees in resprouting eucalypt forests exposed to megadisturbance.
- Author
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Bendall, Eli R., Collins, Luke C., Milner, Kirsty V., Bedward, Michael, Boer, Matthias M., Choat, Brendan, Gallagher, Rachael V., Medlyn, Belinda E., and Nolan, Rachael H.
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DEMOGRAPHIC change ,CARBON sequestration in forests ,DEMOGRAPHIC surveys ,TREE mortality ,TROPICAL dry forests ,DEAD trees ,EUCALYPTUS - Abstract
Aim: Increased tree mortality linked to droughts and fires is occurring across temperate regions globally. Vegetation recovery has been widely reported; however, less is known about how disturbance may alter forests structurally and functionally across environmental gradients. We examined whether dry forests growing on low‐fertility soils were more resilient to coupled extreme drought and severe fire owing to lower tree mortality rates, higher resprouting success and persistence of juveniles relative to wetter forests on more fertile soils. Location: Fire‐tolerant eucalypt forests of temperate southeastern Australia. Time period: 2020–2023. Major taxa studied: Eucalyptus, Corymbia, Angophora. Methods: Demographic surveys of tree mortality and regeneration in all combinations of dry/wet forest, fertile/less fertile substrates exposed to extreme drought and fire were conducted. We used Bayesian regression modelling to compare tree mortality, diameter, response traits, population structure and occurrence of fire scars between substrates/forest types. Results: Overall mortality (20%–33%) and topkill (34%–41%) were within historically reported ranges for various forests and soil types. However, we observed an atypical trend of increased mortality and topkill in the largest trees, particularly when they had structural damage from past fires. Trees in wet forests on more fertile soils had the highest levels of mortality. Numbers of persistent resprouting juveniles were highest in dry forests on low‐fertility soils. Dry forests growing on low‐fertility soils appear more resilient to compound disturbances due to lower rates of mortality and higher rates of juvenile persistence. Wet forests on more fertile soils may experience greater demographic change due to higher mortality of small and large trees. Main conclusions: Mesic forests on relatively fertile soils were found to be at relatively high risk of demographic change from compound disturbances. Combined, fire and drought are likely to reduce the number of large trees in affected areas, with consequences for forest carbon cycling and storage. [ABSTRACT FROM AUTHOR]
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- 2024
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26. RETRACTED ARTICLE: A constraint on historic growth in global photosynthesis due to increasing CO2
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Keenan, T. F., Luo, X., De Kauwe, M. G., Medlyn, B. E., Prentice, I. C., Stocker, B. D., Smith, N. G., Terrer, C., Wang, H., Zhang, Y., and Zhou, S.
- Published
- 2021
- Full Text
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27. MADD regulates natural killer cell degranulation through Rab27a activation
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Medlyn, Michael J., primary, Maeder, Easton, additional, Bradley, Claire, additional, Phatarpekar, Prasad, additional, Ham, Hyoungjun, additional, and Billadeau, Daniel D., additional
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- 2024
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28. Optimal carbon storage during drought
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Stefaniak, Elisa Z, primary, Tissue, David T, additional, Dewar, Roderick C, additional, and Medlyn, Belinda E, additional
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- 2024
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29. Locked and Loaded: Mechanisms Regulating Natural Killer Cell Lytic Granule Biogenesis and Release
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Hyoungjun Ham, Michael Medlyn, and Daniel D. Billadeau
- Subjects
natural killer cells ,lytic granule ,degranulation ,primary immunodeficiency ,cytotoxicity ,Immunologic diseases. Allergy ,RC581-607 - Abstract
NK cell-mediated cytotoxicity is a critical element of our immune system required for protection from microbial infections and cancer. NK cells bind to and eliminate infected or cancerous cells via direct secretion of cytotoxic molecules toward the bound target cells. In this review, we summarize the current understanding of the molecular regulations of NK cell cytotoxicity, focusing on lytic granule development and degranulation processes. NK cells synthesize apoptosis-inducing proteins and package them into specialized organelles known as lytic granules (LGs). Upon activation of NK cells, LGs converge with the microtubule organizing center through dynein-dependent movement along microtubules, ultimately polarizing to the cytotoxic synapse where they subsequently fuse with the NK plasma membrane. From LGs biogenesis to degranulation, NK cells utilize several strategies to protect themselves from their own cytotoxic molecules. Additionally, molecular pathways that enable NK cells to perform serial killing are beginning to be elucidated. These advances in the understanding of the molecular pathways behind NK cell cytotoxicity will be important to not only improve current NK cell-based anti-cancer therapies but also to support the discovery of additional therapeutic opportunities.
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- 2022
- Full Text
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30. The Role of Hydraulic Failure in a Massive Mangrove Die-Off Event
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Alice Gauthey, Diana Backes, Jeff Balland, Iftakharul Alam, Damien T. Maher, Lucas A. Cernusak, Norman C. Duke, Belinda E. Medlyn, David T. Tissue, and Brendan Choat
- Subjects
physiological drought ,hydraulic failure ,El Niño ,Avicennia marina ,dieback ,Plant culture ,SB1-1110 - Abstract
Between late 2015 and early 2016, more than 7,000 ha of mangrove forest died along the coastline of the Gulf of Carpentaria, in northern Australia. This massive die-off was preceded by a strong 2015/2016 El Niño event, resulting in lower precipitation, a drop in sea level and higher than average temperatures in northern Australia. In this study, we investigated the role of hydraulic failure in the mortality and recovery of the dominant species, Avicennia marina, 2 years after the mortality event. We measured predawn water potential (Ψpd) and percent loss of stem hydraulic conductivity (PLC) in surviving individuals across a gradient of impact. We also assessed the vulnerability to drought-induced embolism (Ψ50) for the species. Areas with severe canopy dieback had higher native PLC (39%) than minimally impacted areas (6%), suggesting that hydraulic recovery was ongoing. The high resistance of A. marina to water-stress-induced embolism (Ψ50 = −9.6 MPa), indicates that severe water stress (Ψpd < −10 MPa) would have been required to cause mortality in this species. Our data indicate that the natural gradient of water-stress enhanced the impact of El Niño, leading to hydraulic failure and mortality in A. marina growing on severely impacted (SI) zones. It is likely that lowered sea levels and less frequent inundation by seawater, combined with lower inputs of fresh water, high evaporative demand and high temperatures, led to the development of hyper-salinity and extreme water stress during the 2015/16 summer.
- Published
- 2022
- Full Text
- View/download PDF
31. One Stomatal Model to Rule Them All? Toward Improved Representation of Carbon and Water Exchange in Global Models
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Manon E. B. Sabot, Martin G. De Kauwe, Andy J. Pitman, Belinda E. Medlyn, David S. Ellsworth, Nicolas K. Martin‐StPaul, Jin Wu, Brendan Choat, Jean‐Marc Limousin, Patrick J. Mitchell, Alistair Rogers, and Shawn P. Serbin
- Subjects
gas exchange ,plant hydraulics ,stomatal optimization ,land‐surface models ,drought ,vapor pressure deficit ,Physical geography ,GB3-5030 ,Oceanography ,GC1-1581 - Abstract
Abstract Stomatal conductance schemes that optimize with respect to photosynthetic and hydraulic functions have been proposed to address biases in land‐surface model (LSM) simulations during drought. However, systematic evaluations of both optimality‐based and alternative empirical formulations for coupling carbon and water fluxes are lacking. Here, we embed 12 empirical and optimization approaches within a LSM framework. We use theoretical model experiments to explore parameter identifiability and understand how model behaviors differ in response to abiotic changes. We also evaluate the models against leaf‐level observations of gas‐exchange and hydraulic variables, from xeric to wet forest/woody species spanning a mean annual precipitation range of 361–3,286 mm yr−1. We find that models differ in how easily parameterized they are, due to: (a) poorly constrained optimality criteria (i.e., resulting in multiple solutions), (b) low influence parameters, (c) sensitivities to environmental drivers. In both the idealized experiments and compared to observations, sensitivities to variability in environmental drivers do not agree among models. Marked differences arise in sensitivities to soil moisture (soil water potential) and vapor pressure deficit. For example, stomatal closure rates at high vapor pressure deficit range between −45% and +70% of those observed. Although over half the new generation of stomatal schemes perform to a similar standard compared to observations of leaf‐gas exchange, two models do so through large biases in simulated leaf water potential (up to 11 MPa). Our results provide guidance for LSM development, by highlighting key areas in need for additional experimentation and theory, and by constraining currently viable stomatal hypotheses.
- Published
- 2022
- Full Text
- View/download PDF
32. Environmental correlates of the forest carbon distribution in the Central Himalayas.
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Khanal, Shiva, Nolan, Rachael H., Medlyn, Belinda E., and Boer, Matthias M.
- Subjects
LOGGING ,STRUCTURAL equation modeling ,ECOLOGICAL zones ,ECOLOGICAL regions ,FOREST surveys ,FOREST management - Abstract
Understanding the biophysical limitations on forest carbon across diverse ecological regions is crucial for accurately assessing and managing forest carbon stocks. This study investigates the role of climate and disturbance on the spatial variation of two key forest carbon pools: aboveground carbon (AGC) and soil organic carbon (SOC). Using plot‐level carbon pool estimates from Nepal's national forest inventory and structural equation modelling, we explore the relationship of forest carbon stocks to broad‐scale climatic water and energy availability and fine‐scale terrain and disturbance. The forest AGC and SOC models explained 25% and 59% of the observed spatial variation in forest AGC and SOC, respectively. Among the evaluated variables, disturbance exhibited the strongest negative correlation with AGC, while the availability of climatic energy demonstrated the strongest negative correlation with SOC. Disturbances such as selective logging and firewood collection result in immediate forest carbon loss, while soil carbon changes take longer to respond. The lower decomposition rates in the high‐elevation region, due to lower temperatures, preserve organic matter and contribute to the high SOC stocks observed there. These results highlight the critical role of climate and disturbance regimes in shaping landscape patterns of forest carbon stocks. Understanding the underlying drivers of these patterns is crucial for forest carbon management and conservation across diverse ecological zones including the Central Himalayas. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
33. Temporal Dynamics of Canopy Properties and Carbon and Water Fluxes in a Temperate Evergreen Angiosperm Forest.
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Renchon, Alexandre A., Haverd, Vanessa, Trudinger, Cathy M., Medlyn, Belinda E., Griebel, Anne, Metzen, Daniel, Knauer, Jürgen, Boer, Matthias M., and Pendall, Elise
- Subjects
EUCALYPTUS ,FOREST dynamics ,LEAF area index ,SPRING ,AUTUMN ,EVERGREENS ,LEAF growth - Abstract
The forest–atmosphere exchange of carbon and water is regulated by meteorological conditions as well as canopy properties such as leaf area index (LAI, m
2 m−2 ), photosynthetic capacity (PC μmol m−2 s−1 ), or surface conductance in optimal conditions (Gs,opt , mmol m−2 s−1 ), which can vary seasonally and inter-annually. This variability is well understood for deciduous species but is poorly characterized in evergreen forests. Here, we quantify the seasonal dynamics of a temperate evergreen eucalypt forest with estimates of LAI, litterfall, carbon and water fluxes, and meteorological conditions from measurements and model simulations. We merged MODIS Enhanced Vegetation Index (EVI) values with site-based LAI measurements to establish a 17-year sequence of monthly LAI. We ran the Community Atmosphere Biosphere Land Exchange model (CABLE-POP (version r5046)) with constant and varying LAI for our site to quantify the influence of seasonal canopy dynamics on carbon and water fluxes. We observed that the peak of LAI occurred in late summer–early autumn, with a higher and earlier peak occurring in years when summer rainfall was greater. Seasonality in litterfall and allocation of net primary productivity (FNPP ) to leaf growth (af , 0–1) drove this pattern, suggesting a complete renewal of the canopy before the timing of peak LAI. Litterfall peaked in spring, followed by a high af in summer, at the end of which LAI peaked, and PC and Gs,opt reached their maximum values in autumn, resulting from a combination of high LAI and efficient mature leaves. These canopy dynamics helped explain observations of maximum gross ecosystem production (FGEP ) in spring and autumn and net ecosystem carbon loss in summer at our site. Inter-annual variability in LAI was positively correlated with Net Ecosystem Production (FNEP ). It would be valuable to apply a similar approach to other temperate evergreen forests to identify broad patterns of seasonality in leaf growth and turnover. Because incorporating dynamic LAI was insufficient to fully capture the dynamics of FGEP , observations of seasonal variation in photosynthetic capacity, such as from solar-induced fluorescence, should be incorporated in land surface models to improve ecosystem flux estimates in evergreen forests. [ABSTRACT FROM AUTHOR]- Published
- 2024
- Full Text
- View/download PDF
34. Pastures and Climate Extremes: Impacts of Cool Season Warming and Drought on the Productivity of Key Pasture Species in a Field Experiment
- Author
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Amber C. Churchill, Haiyang Zhang, Kathryn J. Fuller, Burhan Amiji, Ian C. Anderson, Craig V. M. Barton, Yolima Carrillo, Karen L. M. Catunda, Manjunatha H. Chandregowda, Chioma Igwenagu, Vinod Jacob, Gil Won Kim, Catriona A. Macdonald, Belinda E. Medlyn, Ben D. Moore, Elise Pendall, Jonathan M. Plett, Alison K. Post, Jeff R. Powell, David T. Tissue, Mark G. Tjoelker, and Sally A. Power
- Subjects
climate warming ,seasonal drought ,plant functional groups ,grassland ,rangeland ,aboveground production ,Plant culture ,SB1-1110 - Abstract
Shifts in the timing, intensity and/or frequency of climate extremes, such as severe drought and heatwaves, can generate sustained shifts in ecosystem function with important ecological and economic impacts for rangelands and managed pastures. The Pastures and Climate Extremes experiment (PACE) in Southeast Australia was designed to investigate the impacts of a severe winter/spring drought (60% rainfall reduction) and, for a subset of species, a factorial combination of drought and elevated temperature (ambient +3°C) on pasture productivity. The experiment included nine common pasture and Australian rangeland species from three plant functional groups (C3 grasses, C4 grasses and legumes) planted in monoculture. Winter/spring drought resulted in productivity declines of 45% on average and up to 74% for the most affected species (Digitaria eriantha) during the 6-month treatment period, with eight of the nine species exhibiting significant yield reductions. Despite considerable variation in species’ sensitivity to drought, C4 grasses were more strongly affected by this treatment than C3 grasses or legumes. Warming also had negative effects on cool-season productivity, associated at least partially with exceedance of optimum growth temperatures in spring and indirect effects on soil water content. The combination of winter/spring drought and year-round warming resulted in the greatest yield reductions. We identified responses that were either additive (Festuca), or less-than-additive (Medicago), where warming reduced the magnitude of drought effects. Results from this study highlight the sensitivity of diverse pasture species to increases in winter and spring drought severity similar to those predicted for this region, and that anticipated benefits of cool-season warming are unlikely to be realized. Overall, the substantial negative impacts on productivity suggest that future, warmer, drier climates will result in shortfalls in cool-season forage availability, with profound implications for the livestock industry and natural grazer communities.
- Published
- 2022
- Full Text
- View/download PDF
35. Structural organization of the retriever–CCC endosomal recycling complex
- Author
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Boesch, Daniel J., primary, Singla, Amika, additional, Han, Yan, additional, Kramer, Daniel A., additional, Liu, Qi, additional, Suzuki, Kohei, additional, Juneja, Puneet, additional, Zhao, Xuefeng, additional, Long, Xin, additional, Medlyn, Michael J., additional, Billadeau, Daniel D., additional, Chen, Zhe, additional, Chen, Baoyu, additional, and Burstein, Ezra, additional
- Published
- 2023
- Full Text
- View/download PDF
36. Microfluidic Organoid Cultures Derived from Pancreatic Cancer Biopsies for Personalized Testing of Chemotherapy and Immunotherapy
- Author
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Choi, Daheui, primary, Gonzalez‐Suarez, Alan M., additional, Dumbrava, Mihai G., additional, Medlyn, Michael, additional, de Hoyos‐Vega, Jose M., additional, Cichocki, Frank, additional, Miller, Jeffrey S., additional, Ding, Li, additional, Zhu, Mojun, additional, Stybayeva, Gulnaz, additional, Gaspar‐Maia, Alexandre, additional, Billadeau, Daniel D., additional, Ma, Wen Wee, additional, and Revzin, Alexander, additional
- Published
- 2023
- Full Text
- View/download PDF
37. Higher global gross primary productivity under future climate with more advanced representations of photosynthesis
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Knauer, Jürgen, primary, Cuntz, Matthias, additional, Smith, Benjamin, additional, Canadell, Josep G., additional, Medlyn, Belinda E., additional, Bennett, Alison C., additional, Caldararu, Silvia, additional, and Haverd, Vanessa, additional
- Published
- 2023
- Full Text
- View/download PDF
38. Changes in Blue/Green Water Partitioning Under Severe Drought
- Author
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Stephens, C. M., primary, Band, L. E., additional, Johnson, F. M., additional, Marshall, L. A., additional, Medlyn, B. E., additional, De Kauwe, M. G., additional, and Ukkola, A. M., additional
- Published
- 2023
- Full Text
- View/download PDF
39. Microbial competition for phosphorus limits the CO2response of a mature forest
- Author
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Jiang, Mingkai, Crous, Kristine Y., Carrillo, Yolima, Macdonald, Catriona A., Anderson, Ian C., Boer, Matthias M., Farrell, Mark, Gherlenda, Andrew N., Castañeda-Gómez, Laura, Hasegawa, Shun, Jarosch, Klaus, Milham, Paul J., Ochoa-Hueso, Rául, Pathare, Varsha, Pihlblad, Johanna, Piñeiro, Juan, Powell, Jeff R., Power, Sally A., Reich, Peter B., Riegler, Markus, Zaehle, Sönke, Smith, Benjamin, Medlyn, Belinda E., and Ellsworth, David S.
- Abstract
The capacity for terrestrial ecosystems to sequester additional carbon (C) with rising CO2concentrations depends on soil nutrient availability1,2. Previous evidence suggested that mature forests growing on phosphorus (P)-deprived soils had limited capacity to sequester extra biomass under elevated CO2(refs. 3–6), but uncertainty about ecosystem P cycling and its CO2response represents a crucial bottleneck for mechanistic prediction of the land C sink under climate change7. Here, by compiling the first comprehensive P budget for a P-limited mature forest exposed to elevated CO2, we show a high likelihood that P captured by soil microorganisms constrains ecosystem P recycling and availability for plant uptake. Trees used P efficiently, but microbial pre-emption of mineralized soil P seemed to limit the capacity of trees for increased P uptake and assimilation under elevated CO2and, therefore, their capacity to sequester extra C. Plant strategies to stimulate microbial P cycling and plant P uptake, such as increasing rhizosphere C release to soil, will probably be necessary for P-limited forests to increase C capture into new biomass. Our results identify the key mechanisms by which P availability limits CO2fertilization of tree growth and will guide the development of Earth system models to predict future long-term C storage.
- Published
- 2024
- Full Text
- View/download PDF
40. Retraction Note: A constraint on historic growth in global photosynthesis due to increasing CO2
- Author
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Keenan, T. F., Luo, X., De Kauwe, M. G., Medlyn, B. E., Prentice, I. C., Stocker, B. D., Smith, N. G., Terrer, C., Wang, H., Zhang, Y., and Zhou, S.
- Published
- 2022
- Full Text
- View/download PDF
41. Microfluidic Organoid Cultures Derived from Pancreatic Cancer Biopsies for Personalized Testing of Chemotherapy and Immunotherapy.
- Author
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Choi, Daheui, Gonzalez‐Suarez, Alan M., Dumbrava, Mihai G., Medlyn, Michael, de Hoyos‐Vega, Jose M., Cichocki, Frank, Miller, Jeffrey S., Ding, Li, Zhu, Mojun, Stybayeva, Gulnaz, Gaspar‐Maia, Alexandre, Billadeau, Daniel D., Ma, Wen Wee, and Revzin, Alexander
- Subjects
MICROFLUIDIC devices ,PANCREATIC cancer ,GLYCOGEN synthase kinase ,IMMUNOTHERAPY ,CANCER chemotherapy ,NEEDLE biopsy - Abstract
Patient‐derived cancer organoids (PDOs) hold considerable promise for personalizing therapy selection and improving patient outcomes. However, it is challenging to generate PDOs in sufficient numbers to test therapies in standard culture platforms. This challenge is particularly acute for pancreatic ductal adenocarcinoma (PDAC) where most patients are diagnosed at an advanced stage with non‐resectable tumors and where patient tissue is in the form of needle biopsies. Here the development and characterization of microfluidic devices for testing therapies using a limited amount of tissue or PDOs available from PDAC biopsies is described. It is demonstrated that microfluidic PDOs are phenotypically and genotypically similar to the gold‐standard Matrigel organoids with the advantages of 1) spheroid uniformity, 2) minimal cell number requirement, and 3) not relying on Matrigel. The utility of microfluidic PDOs is proven by testing PDO responses to several chemotherapies, including an inhibitor of glycogen synthase kinase (GSKI). In addition, microfluidic organoid cultures are used to test effectiveness of immunotherapy comprised of NK cells in combination with a novel biologic. In summary, our microfluidic device offers considerable benefits for personalizing oncology based on cancer biopsies and may, in the future, be developed into a companion diagnostic for chemotherapy or immunotherapy treatments. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
42. Decoupling between stomatal conductance and photosynthesis occurs under extreme heat in broadleaf tree species regardless of water access
- Author
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Marchin, Renée M., primary, Medlyn, Belinda E., additional, Tjoelker, Mark G., additional, and Ellsworth, David S., additional
- Published
- 2023
- Full Text
- View/download PDF
43. Predicting sub‐continental fuel hazard under future climate and rising atmospheric CO2 concentration
- Author
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Yang, Jinyan, primary, Teckentrup, Lina, additional, Inbar, Assaf, additional, Knauer, Jürgen, additional, Jiang, Mingkai, additional, Medlyn, Belinda, additional, Price, Owen, additional, Bradstock, Ross, additional, and Boer, Matthias M., additional
- Published
- 2023
- Full Text
- View/download PDF
44. Optimal stomatal theory predicts <scp> CO 2 </scp> responses of stomatal conductance in both gymnosperm and angiosperm trees
- Author
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Anna Gardner, Mingkai Jiang, David S. Ellsworth, A. Robert MacKenzie, Jeremy Pritchard, Martin Karl‐Friedrich Bader, Craig V. M. Barton, Carl Bernacchi, Carlo Calfapietra, Kristine Y. Crous, Mirindi Eric Dusenge, Teresa E. Gimeno, Marianne Hall, Shubhangi Lamba, Sebastian Leuzinger, Johan Uddling, Jeffrey Warren, Göran Wallin, and Belinda E. Medlyn
- Subjects
evergreen ,climate change ,photosynthesis ,Physiology ,free-air CO enrichment 2 ,water-use efficiency ,Plant Science ,deciduous - Abstract
Optimal stomatal theory predicts that stomata operate to maximise photosynthesis (Anet) and minimise transpirational water loss to achieve optimal intrinsic water-use efficiency (iWUE). We tested whether this theory can predict stomatal responses to elevated atmospheric CO2 (eCO2), and whether it can capture differences in responsiveness among woody plant functional types (PFTs). We conducted a meta-analysis of tree studies of the effect of eCO2 on iWUE and its components Anet and stomatal conductance (gs). We compared three PFTs, using the unified stomatal optimisation (USO) model to account for confounding effects of leaf–air vapour pressure difference (D). We expected smaller gs, but greater Anet, responses to eCO2 in gymnosperms compared with angiosperm PFTs. We found that iWUE increased in proportion to increasing eCO2 in all PFTs, and that increases in Anet had stronger effects than reductions in gs. The USO model correctly captured stomatal behaviour with eCO2 across most datasets. The chief difference among PFTs was a lower stomatal slope parameter (g1) for the gymnosperm, compared with angiosperm, species. Land surface models can use the USO model to describe stomatal behaviour under changing atmospheric CO2 conditions. AG gratefully acknowledges a studentship provided by the John Horseman Trust and the University of Birmingham. The BIFoR FACE facility is supported by the JABBS Foundation, the University of Birmingham and the John Horseman Trust. ARMK acknowledges support from the UK Natural Environment Research Council through grant NE/S015833/1. MJ and BEM acknowledge funding from the Australian Research Council (DE210101654, FL190100003).
- Published
- 2022
45. Structural Organization of the Retriever-CCC Endosomal Recycling Complex
- Author
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Boesch, Daniel, primary, Singla, Amika, additional, Han, Yan, additional, Kramer, Daniel, additional, Liu, Qi, additional, Suzuki, Kohei, additional, Juneja, Puneet, additional, Zhao, Xuefeng, additional, Long, Xin, additional, Medlyn, Michael, additional, Billadeau, Daniel, additional, Chen, Zhe, additional, Chen, Baoyu, additional, and Burstein, Ezra, additional
- Published
- 2023
- Full Text
- View/download PDF
46. Limited Evidence of Cumulative Effects From Recurrent Droughts in Vegetation Responses to Australia's Millennium Drought
- Author
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Jiao, Tong, primary, Williams, Christopher A., additional, De Kauwe, Martin G., additional, and Medlyn, Belinda E., additional
- Published
- 2023
- Full Text
- View/download PDF
47. Environmental correlates of the forest carbon distribution in the Central Himalayas
- Author
-
Khanal, Shiva, primary, Nolan, Rachael, additional, Medlyn, Belinda, additional, and Boer, Matthias, additional
- Published
- 2023
- Full Text
- View/download PDF
48. Improved representation of plant physiology in the JULES-vn5.6 land surface model: photosynthesis, stomatal conductance and thermal acclimation
- Author
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Rebecca J. Oliver, Lina M. Mercado, Doug B. Clark, Chris Huntingford, Christopher M. Taylor, Pier Luigi Vidale, Patrick C. McGuire, Markus Todt, Sonja Folwell, Valiyaveetil Shamsudheen Semeena, and Belinda E. Medlyn
- Subjects
General Medicine ,JULES ,Atmospheric Sciences - Abstract
Carbon and water cycle dynamics of vegetation are controlled primarily by photosynthesis and stomatal conductance (gs). Our goal is to improve the representation of these key physiological processes within the JULES land surface model, with a particular focus on refining the temperature sensitivity of photosynthesis, impacting modelled carbon, energy and water fluxes. We test (1) an implementation of the Farquhar et al. (1980) photosynthesis scheme and associated plant functional type-dependent photosynthetic temperature response functions, (2) the optimality-based gs scheme from Medlyn et al. (2011) and (3) the Kattge and Knorr (2007) photosynthetic capacity thermal acclimation scheme. New parameters for each model configuration are adopted from recent large observational datasets that synthesise global experimental data. These developments to JULES incorporate current physiological understanding of vegetation behaviour into the model and enable users to derive direct links between model parameters and ongoing measurement campaigns that refine such parameter values. Replacement of the original Collatz et al. (1991) C3 photosynthesis model with the Farquhar scheme results in large changes in GPP for the current day, with ∼ 10 % reduction in seasonal (June–August, JJA, and December–February, DJF) mean GPP in tropical forests and ∼ 20 % increase in the northern high-latitude forests in JJA. The optimality-based gs model decreases the latent heat flux for the present day (∼ 10 %, with an associated increase in sensible heat flux) across regions dominated by needleleaf evergreen forest in the Northern Hemisphere summer. Thermal acclimation of photosynthesis coupled with the Medlyn gs scheme reduced tropical forest GPP by up to 5 % and increased GPP in the high-northern-latitude forests by between 2 % and 5 %. Evaluation of simulated carbon and water fluxes by each model configuration against global data products shows this latter configuration generates improvements in these key areas. Thermal acclimation of photosynthesis coupled with the Medlyn gs scheme improved modelled carbon fluxes in tropical and high-northern-latitude forests in JJA and improved the simulation of evapotranspiration across much of the Northern Hemisphere in JJA. Having established good model performance for the contemporary period, we force this new version of JULES offline with a future climate scenario corresponding to rising atmospheric greenhouse gases (Shared Socioeconomic Pathway (SSP5), Representative Concentration Pathway 8.5 (RCP8.5)). In particular, these calculations allow for understanding of the effects of long-term warming. We find that the impact of thermal acclimation coupled with the optimality-based gs model on simulated fluxes increases latent heat flux (+50 %) by the year 2050 compared to the JULES model configuration without acclimation. This new JULES configuration also projects increased GPP across tropical (+10 %) and northern-latitude regions (+30 %) by 2050. We conclude that thermal acclimation of photosynthesis with the Farquhar photosynthesis scheme and the new optimality-based gs scheme together improve the simulation of carbon and water fluxes for the current day and have a large impact on modelled future carbon cycle dynamics in a warming world.
- Published
- 2022
49. Confronting models with data: carbon-phosphorus interaction under elevated CO2 in a mature forest ecosystem (EucFACE)
- Author
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Mingkai Jiang, Belinda Medlyn, David Wårlind, Jürgen Knauer, Daniel Goll, Lin Yu, Katrin Fleischer, Haicheng Zhang, Xiaojuan Yang, Sönke Zaehle, David Ellsworth, and Benjamin Smith
- Abstract
The importance of phosphorus (P) in plant function and ecosystem biogeochemistry has led to the addition of a P cycle to a range of vegetation models, but the predictions of these P-enabled models have rarely been evaluated with ecosystem-scale data. Here, we confronted eight state-of-the-art, P-enabled models with data from EucFACE, a P-limited Eucalyptus forest subject to long-term Free-Air CO2 Enrichment. We evaluated the capability of the models to capture the observed elevated CO2 responses in this ecosystem. We show that the inclusion of phosphorus-cycle is necessary to more realistically simulate ecosystem function and biogeochemistry, but this enhanced capacity did not directly translate into improved prediction accuracy. Specifically, models diverged in capturing the observed CO2 responses, with simulation accuracy depending upon model assumptions about plant physiology, allocation, plant-soil interactions and soil nutrient processes. Confronting models with experimental responses observed at EucFACE represents a valuable opportunity to improve our understanding of the carbon-phosphorus interaction under rising CO2, and is an important step towards more accurate predictions of the future land carbon sink under climate change.
- Published
- 2023
50. Climate succession: a framework for predicting vegetation dynamics driven by climate change
- Author
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Belinda Medlyn, Laura Williams, Juergen Knauer, Assaf Inbar, Clare Stephens, Rachael Gallagher, Rachael Nolan, Brendan Choat, Matthias Boer, and Ben Smith
- Abstract
Climate change, driven by rising atmospheric CO2 concentrations, is well under way, and we are already starting to see significant shifts in the function and distribution of vegetation as a result. Dynamic vegetation models, the main platform used to predict the likely magnitude, rate and nature of these shifts, were originally rooted in theories of successional dynamics following disturbance. A key question for these models is how well they can capture vegetation responses to climatic change, which includes both press and pulse disturbances. Here we develop a general framework for representing climate-driven successional dynamics in vegetation models. The framework is illustrated with a series of case studies from Australia of vegetation responses to the major global change drivers of rising CO2, warming, drought and fire. The Australian environment, intrinsically characterized by high climate variability, has experienced increasingly challenging climate extremes in recent years and thus provides an excellent testbed for predictive models.
- Published
- 2023
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