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1.
New Phytol ; 238(3): 1305-1317, 2023 05.
Artículo en Inglés | MEDLINE | ID: mdl-36444527

RESUMEN

The architecture of root systems is an important driver of plant fitness, competition and ecosystem processes. However, the methodological difficulty of mapping roots hampers the study of these processes. Existing approaches to match individual plants to belowground samples are low throughput and species specific. Here, we developed a scalable sequencing-based method to map the root systems of individual trees across multiple species. We successfully applied it to a tropical dry forest community in the Brazilian Caatinga containing 14 species. We sequenced all 42 individual shrubs and trees in a 14 × 14 m plot using double-digest restriction site-associated sequencing (ddRADseq). We identified species-specific markers and individual-specific haplotypes from the data. We matched these markers to the ddRADseq data from 100 mixed root samples from across the centre (10 × 10 m) of the plot at four different depths using a newly developed R package. We identified individual root samples for all species and all but one individual. There was a strong significant correlation between belowground and aboveground size measurements, and we also detected significant species-level root-depth preference for two species. The method is more scalable and less labour intensive than the current techniques and is broadly applicable to ecology, forestry and agricultural biology.


Asunto(s)
Ecosistema , Árboles , Árboles/genética , Genotipo , Bosques , Agricultura Forestal , Plantas , Raíces de Plantas
2.
Bioessays ; 41(7): e1800226, 2019 07.
Artículo en Inglés | MEDLINE | ID: mdl-31215669

RESUMEN

If we are to ensure the persistence of species in an increasingly warm world, of interest is the identification of drivers that affect the ability of an organism to resist thermal stress. Underpinning any organism's capacity for resistance is a complex interplay between biological and physical factors occurring over multiple scales. Tropical coral reefs are a unique system, in that their function is dependent upon the maintenance of a coral-algal symbiosis that is directly disrupted by increases in water temperature. A number of physical factors have been identified as affecting the biological responses of the coral organism under broadscale thermal anomalies. One such factor is water flow, which is capable of modulating both organismal metabolic functioning and thermal environments. Understanding the physiological and hydrodynamic drivers of organism response to thermal stress improves predictive capabilities and informs targeted management responses, thereby increasing the resilience of reefs into the future.


Asunto(s)
Antozoos/fisiología , Arrecifes de Coral , Calentamiento Global , Hidrodinámica , Estrés Fisiológico/fisiología , Animales , Clima , Calor , Océanos y Mares , Simbiosis/fisiología
3.
Glob Chang Biol ; 25(1): 39-56, 2019 01.
Artículo en Inglés | MEDLINE | ID: mdl-30406962

RESUMEN

Most of the planet's diversity is concentrated in the tropics, which includes many regions undergoing rapid climate change. Yet, while climate-induced biodiversity changes are widely documented elsewhere, few studies have addressed this issue for lowland tropical ecosystems. Here we investigate whether the floristic and functional composition of intact lowland Amazonian forests have been changing by evaluating records from 106 long-term inventory plots spanning 30 years. We analyse three traits that have been hypothesized to respond to different environmental drivers (increase in moisture stress and atmospheric CO2 concentrations): maximum tree size, biogeographic water-deficit affiliation and wood density. Tree communities have become increasingly dominated by large-statured taxa, but to date there has been no detectable change in mean wood density or water deficit affiliation at the community level, despite most forest plots having experienced an intensification of the dry season. However, among newly recruited trees, dry-affiliated genera have become more abundant, while the mortality of wet-affiliated genera has increased in those plots where the dry season has intensified most. Thus, a slow shift to a more dry-affiliated Amazonia is underway, with changes in compositional dynamics (recruits and mortality) consistent with climate-change drivers, but yet to significantly impact whole-community composition. The Amazon observational record suggests that the increase in atmospheric CO2 is driving a shift within tree communities to large-statured species and that climate changes to date will impact forest composition, but long generation times of tropical trees mean that biodiversity change is lagging behind climate change.


Asunto(s)
Biodiversidad , Cambio Climático , Bosques , Brasil , Dióxido de Carbono , Ecosistema , Estaciones del Año , Árboles/clasificación , Árboles/fisiología , Clima Tropical , Agua
4.
J Urol ; 200(2): 302-308, 2018 08.
Artículo en Inglés | MEDLINE | ID: mdl-29477717

RESUMEN

PURPOSE: In this study we evaluated the diagnostic performance of transrectal ultrasound guided biopsy and multiparametric magnetic resonance imaging to detect prostate cancer against transperineal prostate mapping biopsy as the reference test. MATERIALS AND METHODS: Transrectal ultrasound guided biopsy, multiparametric magnetic resonance imaging and transperineal prostate mapping biopsy were performed in 426 patients between April 2012 and January 2016. Patients initially underwent systematic 12 core transrectal ultrasound guided biopsy followed 3 months later by 1.5 Tesla, high resolution T2, diffusion-weighted, dynamic contrast enhanced multiparametric magnetic resonance imaging. Two specialist uroradiologists blinded to the results of transperineal prostate mapping biopsy allocated a PI-RADS™ (Prostate Imaging-Reporting and Data System) score to each multiparametric magnetic resonance imaging study. Transperineal prostate mapping biopsy with 5 mm interval sampling, which was performed within 6 months of multiparametric magnetic resonance imaging, served as the reference test. RESULTS: Transrectal ultrasound guided biopsy identified 247 of 426 patients with prostate cancer and 179 of 426 with benign histology. Transperineal prostate mapping biopsy detected prostate cancer in 321 of 426 patients. On transperineal prostate mapping biopsy 94 of 179 patients with benign transrectal ultrasound guided biopsy had prostate cancer and 95 of 247 with prostate cancer on transrectal ultrasound guided biopsy were identified with cancer of higher grade. Using a multiparametric magnetic resonance imaging PI-RADS score of 3 or greater to detect significant prostate cancer, defined as any core containing Gleason 4 + 3 or greater prostate cancer on transperineal prostate mapping biopsy, the ROC AUC was 0.754 (95% CI 0.677-0.819) with 87.0% sensitivity (95% CI 77.3-97.0), 55.3% specificity (95% CI 50.2-60.4) and 97.1% negative predictive value (95% CI 94.8-99.4). CONCLUSIONS: Multiparametric magnetic resonance imaging is a more accurate diagnostic test than transrectal ultrasound guided biopsy. However, a significant proportion of ISUP (International Society of Urological Pathology) Grade Group 2 prostate cancer remained undetected following multiparametric magnetic resonance imaging. Although multiparametric magnetic resonance imaging could avoid unnecessary biopsy in many patients with ISUP Grade Group 3 or greater prostate cancer, at less stringent definitions of significant cancer a substantial proportion of prostate cancer would remain undetected after multiparametric magnetic resonance imaging.


Asunto(s)
Imagen por Resonancia Magnética/métodos , Próstata/patología , Hiperplasia Prostática/diagnóstico , Neoplasias de la Próstata/diagnóstico , Adulto , Anciano , Humanos , Biopsia Guiada por Imagen/métodos , Masculino , Persona de Mediana Edad , Estudios Prospectivos , Próstata/diagnóstico por imagen , Hiperplasia Prostática/patología , Neoplasias de la Próstata/patología , Estudios Retrospectivos , Ultrasonografía Intervencional/métodos
5.
New Phytol ; 218(1): 153-166, 2018 04.
Artículo en Inglés | MEDLINE | ID: mdl-29315603

RESUMEN

We assessed data from 11 experiments examining the effects of the timing and/or frequency of fire on tropical forest and/or savanna vegetation structure over one decade or more. The initial 'control treatment' in many such cases consisted of previously cleared land. This is as opposed to natural vegetation subject to some sort of endogenous fire regime before the imposition of fire treatments. Effects of fire on fractional foliar cover are up to 10-fold greater when clearing pre-treatments are imposed. Moreover, because many of the 'classic' fire trials were initialised with applied management questions in mind, most have also used burning regimes much more frequent and/or severe than those occurring in the absence of human activity. Once these factors are taken into account, our modelling analysis shows that nonanthropogenic fire regimes serve to reduce canopy vegetative cover to a much lower extent than has previously been argued to be the case. These results call into question the notion that fire effects on tropical vegetation can be of a sufficient magnitude to maintain open-type savanna ecosystems under climatic/soil regimes otherwise sufficient to give rise to a more luxurious forest-type vegetation cover.


Asunto(s)
Incendios , Árboles/fisiología , Clima Tropical , Biomasa , Clima , Modelos Teóricos , Hojas de la Planta/fisiología , Suelo , Factores de Tiempo
6.
New Phytol ; 214(3): 1002-1018, 2017 May.
Artículo en Inglés | MEDLINE | ID: mdl-27389684

RESUMEN

We examined whether variations in photosynthetic capacity are linked to variations in the environment and/or associated leaf traits for tropical moist forests (TMFs) in the Andes/western Amazon regions of Peru. We compared photosynthetic capacity (maximal rate of carboxylation of Rubisco (Vcmax ), and the maximum rate of electron transport (Jmax )), leaf mass, nitrogen (N) and phosphorus (P) per unit leaf area (Ma , Na and Pa , respectively), and chlorophyll from 210 species at 18 field sites along a 3300-m elevation gradient. Western blots were used to quantify the abundance of the CO2 -fixing enzyme Rubisco. Area- and N-based rates of photosynthetic capacity at 25°C were higher in upland than lowland TMFs, underpinned by greater investment of N in photosynthesis in high-elevation trees. Soil [P] and leaf Pa were key explanatory factors for models of area-based Vcmax and Jmax but did not account for variations in photosynthetic N-use efficiency. At any given Na and Pa , the fraction of N allocated to photosynthesis was higher in upland than lowland species. For a small subset of lowland TMF trees examined, a substantial fraction of Rubisco was inactive. These results highlight the importance of soil- and leaf-P in defining the photosynthetic capacity of TMFs, with variations in N allocation and Rubisco activation state further influencing photosynthetic rates and N-use efficiency of these critically important forests.


Asunto(s)
Altitud , Bosques , Humedad , Fotosíntesis/fisiología , Hojas de la Planta/fisiología , Clima Tropical , Dióxido de Carbono/metabolismo , Pruebas de Enzimas , Cinética , Modelos Biológicos , Nitrógeno/metabolismo , Perú , Hojas de la Planta/anatomía & histología , Hojas de la Planta/química , Ribulosa-Bifosfato Carboxilasa/metabolismo , Especificidad de la Especie , Temperatura
7.
Health Info Libr J ; 34(1): 32-44, 2017 Mar.
Artículo en Inglés | MEDLINE | ID: mdl-28244256

RESUMEN

OBJECTIVE: The aim of this research was to explore the library and information needs of health and social care students whilst on placement. METHODS: Both desk and primary research were conducted and included an online questionnaire to students and semi-structured interviews. RESULTS: The questionnaire was completed by 252 students from a variety of programmes, equivalent to a 10% response rate. The results indicate a wide range of factors impacting on the library and information experiences of students. Whilst differences in the availability of a physical library in hospital or community locations still exist, these are mitigated by technology and a preference for home study. A significant result is that 77% (n = 193) of students on placement study at home, using a variety of Internet-connected devices. This highlights a marked change in practice and underlines the need for mobile-compliant e-resources and accessible at-a-distance services. CONCLUSION: As a result of this research, practical recommendations on how library support can be improved were developed including enhanced collaboration and learning with NHS colleagues, and knowledge sharing with other departments within the University who support our students.


Asunto(s)
Difusión de la Información , Bibliotecas Médicas/organización & administración , Preceptoría , Estudiantes del Área de la Salud , Humanos , Almacenamiento y Recuperación de la Información/métodos , Internet , Materiales Bibliográficos/organización & administración , Servicios de Biblioteca/organización & administración , Encuestas y Cuestionarios
8.
Proc Biol Sci ; 283(1844)2016 12 14.
Artículo en Inglés | MEDLINE | ID: mdl-27974517

RESUMEN

Lineages tend to retain ecological characteristics of their ancestors through time. However, for some traits, selection during evolutionary history may have also played a role in determining trait values. To address the relative importance of these processes requires large-scale quantification of traits and evolutionary relationships among species. The Amazonian tree flora comprises a high diversity of angiosperm lineages and species with widely differing life-history characteristics, providing an excellent system to investigate the combined influences of evolutionary heritage and selection in determining trait variation. We used trait data related to the major axes of life-history variation among tropical trees (e.g. growth and mortality rates) from 577 inventory plots in closed-canopy forest, mapped onto a phylogenetic hypothesis spanning more than 300 genera including all major angiosperm clades to test for evolutionary constraints on traits. We found significant phylogenetic signal (PS) for all traits, consistent with evolutionarily related genera having more similar characteristics than expected by chance. Although there is also evidence for repeated evolution of pioneer and shade tolerant life-history strategies within independent lineages, the existence of significant PS allows clearer predictions of the links between evolutionary diversity, ecosystem function and the response of tropical forests to global change.


Asunto(s)
Bosques , Filogenia , Árboles/clasificación , Clima Tropical , Evolución Biológica , Ecología , América del Sur
10.
New Phytol ; 206(2): 614-36, 2015 Apr.
Artículo en Inglés | MEDLINE | ID: mdl-25581061

RESUMEN

Leaf dark respiration (Rdark ) is an important yet poorly quantified component of the global carbon cycle. Given this, we analyzed a new global database of Rdark and associated leaf traits. Data for 899 species were compiled from 100 sites (from the Arctic to the tropics). Several woody and nonwoody plant functional types (PFTs) were represented. Mixed-effects models were used to disentangle sources of variation in Rdark . Area-based Rdark at the prevailing average daily growth temperature (T) of each site increased only twofold from the Arctic to the tropics, despite a 20°C increase in growing T (8-28°C). By contrast, Rdark at a standard T (25°C, Rdark (25) ) was threefold higher in the Arctic than in the tropics, and twofold higher at arid than at mesic sites. Species and PFTs at cold sites exhibited higher Rdark (25) at a given photosynthetic capacity (Vcmax (25) ) or leaf nitrogen concentration ([N]) than species at warmer sites. Rdark (25) values at any given Vcmax (25) or [N] were higher in herbs than in woody plants. The results highlight variation in Rdark among species and across global gradients in T and aridity. In addition to their ecological significance, the results provide a framework for improving representation of Rdark in terrestrial biosphere models (TBMs) and associated land-surface components of Earth system models (ESMs).


Asunto(s)
Ciclo del Carbono , Dióxido de Carbono/metabolismo , Nitrógeno/metabolismo , Hojas de la Planta/metabolismo , Plantas/metabolismo , Aclimatación , Respiración de la Célula , Clima , Modelos Teóricos , Fenotipo , Fotosíntesis , Hojas de la Planta/efectos de la radiación , Plantas/efectos de la radiación , Temperatura
11.
Oecologia ; 178(3): 659-72, 2015 Jul.
Artículo en Inglés | MEDLINE | ID: mdl-25752617

RESUMEN

Photosynthesis/nutrient relationships of proximally growing forest and savanna trees were determined in an ecotonal region of Cameroon (Africa). Although area-based foliar N concentrations were typically lower for savanna trees, there was no difference in photosynthetic rates between the two vegetation formation types. Opposite to N, area-based P concentrations were-on average-slightly lower for forest trees; a dependency of photosynthetic characteristics on foliar P was only evident for savanna trees. Thus savanna trees use N more efficiently than their forest counterparts, but only in the presence of relatively high foliar P. Along with some other recent studies, these results suggest that both N and P are important modulators of woody tropical plant photosynthetic capacities, influencing photosynthetic metabolism in different ways that are also biome specific. Attempts to find simple unifying equations to describe woody tropical vegetation photosynthesis-nutrient relationships are likely to meet with failure, with ecophysiological distinctions between forest and savanna requiring acknowledgement.


Asunto(s)
Bosques , Pradera , Nitrógeno/metabolismo , Fósforo/metabolismo , Fotosíntesis , Árboles/metabolismo , África , Biodiversidad , Camerún , Ecosistema , Transporte de Electrón , Hojas de la Planta/metabolismo , Hojas de la Planta/fisiología , Ribulosa-Bifosfato Carboxilasa/metabolismo , Especificidad de la Especie , Árboles/fisiología , Clima Tropical
12.
Nature ; 457(7232): 1003-6, 2009 Feb 19.
Artículo en Inglés | MEDLINE | ID: mdl-19225523

RESUMEN

The response of terrestrial vegetation to a globally changing environment is central to predictions of future levels of atmospheric carbon dioxide. The role of tropical forests is critical because they are carbon-dense and highly productive. Inventory plots across Amazonia show that old-growth forests have increased in carbon storage over recent decades, but the response of one-third of the world's tropical forests in Africa is largely unknown owing to an absence of spatially extensive observation networks. Here we report data from a ten-country network of long-term monitoring plots in African tropical forests. We find that across 79 plots (163 ha) above-ground carbon storage in live trees increased by 0.63 Mg C ha(-1) yr(-1) between 1968 and 2007 (95% confidence interval (CI), 0.22-0.94; mean interval, 1987-96). Extrapolation to unmeasured forest components (live roots, small trees, necromass) and scaling to the continent implies a total increase in carbon storage in African tropical forest trees of 0.34 Pg C yr(-1) (CI, 0.15-0.43). These reported changes in carbon storage are similar to those reported for Amazonian forests per unit area, providing evidence that increasing carbon storage in old-growth forests is a pan-tropical phenomenon. Indeed, combining all standardized inventory data from this study and from tropical America and Asia together yields a comparable figure of 0.49 Mg C ha(-1) yr(-1) (n = 156; 562 ha; CI, 0.29-0.66; mean interval, 1987-97). This indicates a carbon sink of 1.3 Pg C yr(-1) (CI, 0.8-1.6) across all tropical forests during recent decades. Taxon-specific analyses of African inventory and other data suggest that widespread changes in resource availability, such as increasing atmospheric carbon dioxide concentrations, may be the cause of the increase in carbon stocks, as some theory and models predict.


Asunto(s)
Carbono/metabolismo , Árboles/metabolismo , Clima Tropical , África , Atmósfera/química , Biomasa , Carbono/análisis , Dióxido de Carbono/análisis , Dióxido de Carbono/metabolismo , Modelos Biológicos , Árboles/anatomía & histología , Árboles/química , Árboles/crecimiento & desarrollo , Vida Silvestre , Madera/análisis , Madera/química
13.
Glob Ecol Biogeogr ; 23(8): 935-946, 2014 Aug.
Artículo en Inglés | MEDLINE | ID: mdl-26430387

RESUMEN

AIM: The accurate mapping of forest carbon stocks is essential for understanding the global carbon cycle, for assessing emissions from deforestation, and for rational land-use planning. Remote sensing (RS) is currently the key tool for this purpose, but RS does not estimate vegetation biomass directly, and thus may miss significant spatial variations in forest structure. We test the stated accuracy of pantropical carbon maps using a large independent field dataset. LOCATION: Tropical forests of the Amazon basin. The permanent archive of the field plot data can be accessed at: http://dx.doi.org/10.5521/FORESTPLOTS.NET/2014_1. METHODS: Two recent pantropical RS maps of vegetation carbon are compared to a unique ground-plot dataset, involving tree measurements in 413 large inventory plots located in nine countries. The RS maps were compared directly to field plots, and kriging of the field data was used to allow area-based comparisons. RESULTS: The two RS carbon maps fail to capture the main gradient in Amazon forest carbon detected using 413 ground plots, from the densely wooded tall forests of the north-east, to the light-wooded, shorter forests of the south-west. The differences between plots and RS maps far exceed the uncertainties given in these studies, with whole regions over- or under-estimated by > 25%, whereas regional uncertainties for the maps were reported to be < 5%. MAIN CONCLUSIONS: Pantropical biomass maps are widely used by governments and by projects aiming to reduce deforestation using carbon offsets, but may have significant regional biases. Carbon-mapping techniques must be revised to account for the known ecological variation in tree wood density and allometry to create maps suitable for carbon accounting. The use of single relationships between tree canopy height and above-ground biomass inevitably yields large, spatially correlated errors. This presents a significant challenge to both the forest conservation and remote sensing communities, because neither wood density nor species assemblages can be reliably mapped from space.

14.
MAbs ; 16(1): 2310248, 2024.
Artículo en Inglés | MEDLINE | ID: mdl-38349008

RESUMEN

Cluster of differentiation 47 (CD47) is a transmembrane protein highly expressed in tumor cells that interacts with signal regulatory protein alpha (SIRPα) and triggers a "don't eat me" signal to the macrophage, inhibiting phagocytosis and enabling tumor escape from immunosurveillance. The CD47-SIRPα axis has become an important target for cancer immunotherapy. To date, the advancement of CD47-targeted modalities is hindered by the ubiquitous expression of the target, often leading to rapid drug elimination and hematologic toxicity including anemia. To overcome those challenges a bispecific approach was taken. CC-96673, a humanized IgG1 bispecific antibody co-targeting CD47 and CD20, is designed to bind CD20 with high affinity and CD47 with optimally lowered affinity. As a result of the detuned CD47 affinity, CC-96673 selectively binds to CD20-expressing cells, blocking the interaction of CD47 with SIRPα. This increased selectivity of CC-96673 over monospecific anti-CD47 approaches allows for the use of wild-type IgG1 Fc, which engages activating crystallizable fragment gamma receptors (FcγRs) to fully potentiate macrophages to engulf and destroy CD20+ cells, while sparing CD47+CD20- normal cells. The combined targeting of anti-CD20 and anti-CD47 results in enhanced anti- tumor activity compared to anti-CD20 targeting antibodies alone. Furthermore, preclinical studies have demonstrated that CC-96673 exhibits acceptable pharmacokinetic properties with a favorable toxicity profile in non-human primates. Collectively, these findings define CC-96673 as a promising CD47 × CD20 bispecific antibody that selectively destroys CD20+ cancer cells via enhanced phagocytosis and other effector functions.


Asunto(s)
Anticuerpos Biespecíficos , Linfoma no Hodgkin , Neoplasias , Animales , Antígeno CD47 , Neoplasias/tratamiento farmacológico , Fagocitosis , Inmunoterapia , Inmunoglobulina G/uso terapéutico
15.
New Phytol ; 197(4): 1077-1094, 2013 Mar.
Artículo en Inglés | MEDLINE | ID: mdl-23346950

RESUMEN

The rate of CO(2) assimilation by plants is directly influenced by the concentration of CO(2) in the atmosphere, c(a). As an environmental variable, c(a) also has a unique global and historic significance. Although relatively stable and uniform in the short term, global c(a) has varied substantially on the timescale of thousands to millions of years, and currently is increasing at seemingly an unprecedented rate. This may exert profound impacts on both climate and plant function. Here we utilise extensive datasets and models to develop an integrated, multi-scale assessment of the impact of changing c(a) on plant carbon dioxide uptake and water use. We find that, overall, the sensitivity of plants to rising or falling c(a) is qualitatively similar across all scales considered. It is characterised by an adaptive feedback response that tends to maintain 1 - c(i)/c(a), the relative gradient for CO(2) diffusion into the leaf, relatively constant. This is achieved through predictable adjustments to stomatal anatomy and chloroplast biochemistry. Importantly, the long-term response to changing c(a) can be described by simple equations rooted in the formulation of more commonly studied short-term responses.


Asunto(s)
Dióxido de Carbono/metabolismo , Cambio Climático/estadística & datos numéricos , Modelos Teóricos , Plantas/metabolismo , Aclimatación , Dióxido de Carbono/análisis , Ecosistema , Fósiles , Estomas de Plantas/fisiología , Estrés Fisiológico , Agua/metabolismo
16.
Rapid Commun Mass Spectrom ; 26(23): 2690-6, 2012 Dec 15.
Artículo en Inglés | MEDLINE | ID: mdl-23124659

RESUMEN

RATIONALE: Pyrogenic carbon (C(P)) is an important component of the global carbon budget. Accurate determination of the abundance and stable isotope composition of C(P) in soils and sediments is crucial for understanding the dynamics of the C(P) cycle and interpreting records of biomass burning, climate and vegetation change in the past. Here we test hydrogen pyrolysis (hypy) as a new technique potentially capable of eliminating labile organic carbon (C(L)) from total organic carbon (C(T)) in a range of matrices in order to enable reliable quantification of both the C(P) component of C(T) and the stable carbon isotope composition of C(P) (δ(13)C(P)). METHODS: We mixed C(P) at a range of concentrations with common C(P)-free matrices (C(L) = cellulose, chitin, keratin, decomposed wood, leaf litter, grass and algae) and determined the amount of residual carbon not removed by hydrogen pyrolysis (C(R)) as a ratio of C(T) (C(R)/C(T)). Mixing C(P) with a unique δ(13)C value provided a natural abundance isotope label from which to precisely determine the ratio of C(P) to residual C(L) remaining after hypy. RESULTS: All C(P)-free matrices contained trace carbon after hypy, indicating that hypy does not remove all the C(L). However, there was a strong correlation between C(R)/C(T) and C(P)/C(T), viz. C(R)/C(T)= 1.02(C(P)/C(T)) + 4.0 × 10(-3), r(2) = 0.99, p <0.001, suggesting that only a small and reasonably constant fraction of C(L) remains after hypy. Uncertainties associated with the correction for contamination of C(R) by residual C(L) are minimal allowing for reliable determinations of both C(P) and δ(13)C(P) in many cases. CONCLUSIONS: Hydrogen pyrolysis appears to be a robust technique for estimating C(P) abundance and δ(13)C(P) across a range of materials. Nevertheless, caution is required in interpreting δ(13)C(P) values when C(P)/C(T) is low, with C(P)/C(T)>4% being required for the determination of the δ(13)C(P) values within an interpretable error under our experimental conditions.

17.
Front Plant Sci ; 13: 778403, 2022.
Artículo en Inglés | MEDLINE | ID: mdl-35444675

RESUMEN

Tropical trees store a large amount of nutrients in their woody tissues, thus triggering the question of what the functional association of these elements with other wood traits is. Given the osmotic activity of mineral elements such as potassium, sodium, and calcium, these elements should be strong candidates in mediating the water storing capacity in tropical trees. We investigated the role of wood nutrients in facilitating wood water storage in trees by using branch samples from 48 tropical tree species in South America and examined their associations with wood density (ρ). Wood density varied from 316 kg/m3 in Peru plots, where the soil nutrient status is relatively higher, to 908 kg/m3 in Brazil plots, where the nutrient availability is lower. Phosphorus content in wood varied significantly between plots with lowest values found in French Guiana (1.2 mol/m3) and plots with highest values found in Peru (43.6 mol/m3). Conversely, potassium in woody tissues showed a significant cross-species variation with Minquartia guianensis in Brazil showing the lowest values (8.8 mol/m3) and with Neea divaricata in Peru having the highest values (114 mol/m3). We found that lower wood density trees store more water in their woody tissues with cations, especially potassium, having a positive association with water storage. Specific relationships between wood cation concentrations and stem water storage potential nevertheless depend on both species' identity and growing location. Tropical trees with increased water storage capacity show lower wood density and have an increased reliance on cations to regulate this reservoir. Our study highlights that cations play a more important role in tropical tree water relations than has previously been thought, with potassium being particularly important.

18.
New Phytol ; 187(3): 631-46, 2010 Aug.
Artículo en Inglés | MEDLINE | ID: mdl-20659252

RESUMEN

*The rich ecology of tropical forests is intimately tied to their moisture status. Multi-site syntheses can provide a macro-scale view of these linkages and their susceptibility to changing climates. Here, we report pan-tropical and regional-scale analyses of tree vulnerability to drought. *We assembled available data on tropical forest tree stem mortality before, during, and after recent drought events, from 119 monitoring plots in 10 countries concentrated in Amazonia and Borneo. *In most sites, larger trees are disproportionately at risk. At least within Amazonia, low wood density trees are also at greater risk of drought-associated mortality, independent of size. For comparable drought intensities, trees in Borneo are more vulnerable than trees in the Amazon. There is some evidence for lagged impacts of drought, with mortality rates remaining elevated 2 yr after the meteorological event is over. *These findings indicate that repeated droughts would shift the functional composition of tropical forests toward smaller, denser-wooded trees. At very high drought intensities, the linear relationship between tree mortality and moisture stress apparently breaks down, suggesting the existence of moisture stress thresholds beyond which some tropical forests would suffer catastrophic tree mortality.


Asunto(s)
Sequías , Árboles/crecimiento & desarrollo , Clima Tropical , Adaptación Fisiológica , Biomasa , Brasil , Ecosistema , Modelos Biológicos , Tallos de la Planta/crecimiento & desarrollo , Lluvia , Estrés Fisiológico , Factores de Tiempo , Agua , Madera/crecimiento & desarrollo
19.
Plant Cell Environ ; 33(6): 959-80, 2010 Jun.
Artículo en Inglés | MEDLINE | ID: mdl-20102540

RESUMEN

Photosynthetic leaf traits were determined for savanna and forest ecosystems in West Africa, spanning a large range in precipitation. Standardized major axis fits revealed important differences between our data and reported global relationships. Especially for sites in the drier areas, plants showed higher photosynthetic rates for a given N or P when compared with relationships from the global data set. The best multiple regression for the pooled data set estimated V(cmax) and J(max) from N(DW) and S. However, the best regression for different vegetation types varied, suggesting that the scaling of photosynthesis with leaf traits changed with vegetation types. A new model is presented representing independent constraints by N and P on photosynthesis, which can be evaluated with or without interactions with S. It assumes that limitation of photosynthesis will result from the least abundant nutrient, thereby being less sensitive to the allocation of the non-limiting nutrient to non-photosynthetic pools. The model predicts an optimum proportionality for N and P, which is distinct for V(cmax) and J(max) and inversely proportional to S. Initial tests showed the model to predict V(cmax) and J(max) successfully for other tropical forests characterized by a range of different foliar N and P concentrations.


Asunto(s)
Nitrógeno/metabolismo , Fósforo/metabolismo , Fotosíntesis/fisiología , Árboles/fisiología , África Occidental , Biomasa , Hojas de la Planta/metabolismo , Carácter Cuantitativo Heredable , Análisis de Regresión , Estaciones del Año
20.
Front Plant Sci ; 11: 212, 2020.
Artículo en Inglés | MEDLINE | ID: mdl-32194599

RESUMEN

Plant structural and biochemical traits are frequently used to characterise the life history of plants. Although some common patterns of trait covariation have been identified, recent studies suggest these patterns of covariation may differ with growing location and/or plant functional type (PFT). Mediterranean forest tree/shrub species are often divided into three PFTs based on their leaf habit and form, being classified as either needleleaf evergreen (Ne), broadleaf evergreen (Be), or broadleaf deciduous (Bd). Working across 61 mountainous Mediterranean forest sites of contrasting climate and soil type, we sampled and analysed 626 individuals in order to evaluate differences in key foliage trait covariation as modulated by growing conditions both within and between the Ne, Be, and Bd functional types. We found significant differences between PFTs for most traits. When considered across PFTs and by ignoring intraspecific variation, three independent functional dimensions supporting the Leaf-Height-Seed framework were identified. Some traits illustrated a common scaling relationship across and within PFTs, but others scaled differently when considered across PFTs or even within PFTs. For most traits much of the observed variation was attributable to PFT identity and not to growing location, although for some traits there was a strong environmental component and considerable intraspecific and residual variation. Nevertheless, environmental conditions as related to water availability during the dry season and to a smaller extend to soil nutrient status and soil texture, clearly influenced trait values. When compared across species, about half of the trait-environment relationships were species-specific. Our study highlights the importance of the ecological scale within which trait covariation is considered and suggests that at regional to local scales, common trait-by-trait scaling relationships should be treated with caution. PFT definitions by themselves can potentially be an important predictor variable when inferring one trait from another. These findings have important implications for local scale dynamic vegetation models.

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