Human-induced nitrogen-phosphorus imbalances alter natural and managed ecosystems across the globe

Penuelas J., Poulter B., Sardans J., Ciais P., Van Der Velde M., Bopp L., Boucher O., Godderis Y., Hinsinger P., Llusia J., Nardin E., Vicca S., Obersteiner M., Janssens I.A. (2013) Human-induced nitrogen-phosphorus imbalances alter natural and managed ecosystems across the globe. Nature Communications. 4: 0-0.
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Doi: 10.1038/ncomms3934

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The availability of carbon from rising atmospheric carbon dioxide levels and of nitrogen from various human-induced inputs to ecosystems is continuously increasing; however, these increases are not paralleled by a similar increase in phosphorus inputs. The inexorable change in the stoichiometry of carbon and nitrogen relative to phosphorus has no equivalent in Earth's history. Here we report the profound and yet uncertain consequences of the human imprint on the phosphorus cycle and nitrogen:phosphorus stoichiometry for the structure, functioning and diversity of terrestrial and aquatic organisms and ecosystems. A mass balance approach is used to show that limited phosphorus and nitrogen availability are likely to jointly reduce future carbon storage by natural ecosystems during this century. Further, if phosphorus fertilizers cannot be made increasingly accessible, the crop yields projections of the Millennium Ecosystem Assessment imply an increase of the nutrient deficit in developing regions. © 2013 Macmillan Publishers Limited.

Llegeix més

Evidence of current impact of climate change on life: A walk from genes to the biosphere

Penuelas J., Sardans J., Estiarte M., Ogaya R., Carnicer J., Coll M., Barbeta A., Rivas-Ubach A., Llusia J., Garbulsky M., Filella I., Jump A.S. (2013) Evidence of current impact of climate change on life: A walk from genes to the biosphere. Global Change Biology. 19: 2303-2338.
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Doi: 10.1111/gcb.12143

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We review the evidence of how organisms and populations are currently responding to climate change through phenotypic plasticity, genotypic evolution, changes in distribution and, in some cases, local extinction. Organisms alter their gene expression and metabolism to increase the concentrations of several antistress compounds and to change their physiology, phenology, growth and reproduction in response to climate change. Rapid adaptation and microevolution occur at the population level. Together with these phenotypic and genotypic adaptations, the movement of organisms and the turnover of populations can lead to migration toward habitats with better conditions unless hindered by barriers. Both migration and local extinction of populations have occurred. However, many unknowns for all these processes remain. The roles of phenotypic plasticity and genotypic evolution and their possible trade-offs and links with population structure warrant further research. The application of omic techniques to ecological studies will greatly favor this research. It remains poorly understood how climate change will result in asymmetrical responses of species and how it will interact with other increasing global impacts, such as N eutrophication, changes in environmental N : P ratios and species invasion, among many others. The biogeochemical and biophysical feedbacks on climate of all these changes in vegetation are also poorly understood. We here review the evidence of responses to climate change and discuss the perspectives for increasing our knowledge of the interactions between climate change and life. © 2013 John Wiley & Sons Ltd.

Llegeix més

Foliar chemistry and standing folivory of early and late-successional species in a Bornean rainforest

Penuelas J., Sardans J., Llusia J., Silva J., Owen S.M., Bala-Ola B., Linatoc A.C., Dalimin M.N., Niinemets U. (2013) Foliar chemistry and standing folivory of early and late-successional species in a Bornean rainforest. Plant Ecology and Diversity. 6: 245-256.
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Doi: 10.1080/17550874.2013.768713

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Background: Few studies have investigated the chemical, morphological and physiological foliar traits and the intensity of standing folivory in a representative set of species of tropical rainforests including species of different successional stages. Aims: (i) To quantify leaf elemental composition, leaf phenolics and tannin concentrations, physical leaf traits and the intensity of standing folivory in a representative set of species of different successional stages in a Bornean tropical rainforest, and (ii) to investigate the relationships among leaf traits and between leaf traits and accumulated standing folivory. Methods: Analyses of leaf elemental concentrations, phenolics (Ph) and tannin (Tan) concentrations, leaf mass area (LMA), C assimilation rate and accumulated standing folivory in 88 common rainforest species of Borneo. Results and Conclusions: Accumulated standing folivory was correlated with the scores of the first axis of the elemental concentrations principal component analysis (mainly loaded by K and C:K and N:K ratios) with lower accumulated standing folivory at high leaf K concentrations (R = -0.33, P = 0.0016). The results show that consistent with growth rate hypothesis, fast-growing pioneer species have lower leaf N:P ratios than late-successional species, that species with higher leaf N concentration have lower LMA according with the 'leaf economics spectrum' hypothesis, and that species with lower leaf nutrient concentration allocate more C to leaf phenolics. This study also shows that species with different ecological roles have different biogeochemical 'niches' assessed as foliar elemental composition. © 2013 Copyright 2013 Botanical Society of Scotland and Taylor & Francis.

Llegeix més

Physical ecology: The search for life law

Penuelas J., Terradas J. (2013) Physical ecology: The search for life law. Open Ecology Journal. 6: 7-9.
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Doi: 10.2174/1874213020130516001

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Life on Earth is the result of a continuous accumulation of information by combination and innovation riding on endo and exosomatic energy gradients and discontinuous destructions. © Penuelas and Terradas; Licensee Bentham Open.

Llegeix més

Photochemical reflectance index as an indirect estimator of foliar isoprenoid emissions at the ecosystem level

Peñuelas J., Marino G., Llusia J., Morfopoulos C., Farré-Armengol G., Filella I. (2013) Photochemical reflectance index as an indirect estimator of foliar isoprenoid emissions at the ecosystem level. Nature Communications. 4: 0-0.
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Doi: 10.1038/ncomms3604

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Terrestrial plants re-emit around 1-2% of the carbon they fix as isoprene and monoterpenes. These emissions have major roles in the ecological relationships among living organisms and in atmospheric chemistry and climate, and yet their actual quantification at the ecosystem level in different regions is far from being resolved with available models and field measurements. Here we provide evidence that a simple remote sensing index, the photochemical reflectance index, which is indicative of light use efficiency, is a good indirect estimator of foliar isoprenoid emissions and can therefore be used to sense them remotely. These results open new perspectives for the potential use of remote sensing techniques to track isoprenoid emissions from vegetation at larger scales. On the other hand, our study shows the potential of this photochemical reflectance index technique to validate the availability of photosynthetic reducing power as a factor involved in isoprenoid production. © 2013 Macmillan Publishers Limited. All rights reserved.

Llegeix més

Ecometabolomics: Optimized NMR-based method

Rivas-Ubach A., Perez-Trujillo M., Sardans J., Gargallo-Garriga A., Parella T., Penuelas J. (2013) Ecometabolomics: Optimized NMR-based method. Methods in Ecology and Evolution. 4: 464-473.
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Doi: 10.1111/2041-210X.12028

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Metabolomics is allowing great advances in biological sciences. Recently, an increasing number of ecological studies are using a metabolomic approach to answer ecological questions (ecometabolomics). Ecometabolomics is becoming a powerful tool which allows following the responses of the metabolome of an organism environmental changes and the comparison of populations. Some Nuclear Magnetic Resonance (NMR) protocols have been published for metabolomics analyses oriented to other disciplines such as biomedicine, but there is a lack of a description of a detailed protocol applied to ecological studies. Here we propose a NMR-based protocol for ecometabolomic studies that provides an unbiased overview of the metabolome of an organism, including polar and nonpolar metabolites. This protocol is aimed to facilitate the analysis of many samples, as typically required in ecological studies. In addition to NMR fingerprinting, it identifies metabolites for generating metabolic profiles applying strategies of elucidation of small molecules typically used in natural-product research, and allowing the identification of secondary and unknown metabolites. We also provide a detailed description to obtain the numerical data from the 1H-NMR spectra needed to perform the statistical analyses. We tested and optimized this protocol by using two field plant species (Erica multiflora and Quercus ilex) sampled once per season. Both species showed high levels of polar compounds such as sugars and amino acids during the spring, the growing season. E. multiflora was also experimentally submitted to drought and the NMR analyses were sensitive enough to detect some compounds related to the avoidance of water loses. This protocol has been designed for ecometabolomic studies. It identifies changes in the compositions of metabolites between individuals and detects and identifies biological markers associated with environmental changes. © 2013 The Authors. Methods in Ecology and Evolution © 2013 British Ecological Society.

Llegeix més

Dynamics of non-structural carbohydrates in three mediterranean woody species following long-term experimental drought

Rosas T., Galiano L., Ogaya R., Penuelas J., Martinez-Vilalta J. (2013) Dynamics of non-structural carbohydrates in three mediterranean woody species following long-term experimental drought. Frontiers in Plant Science. 4: 0-0.
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Doi: 10.3389/fpls.2013.00400

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Stored non-structural carbohydrates (NSC) have been proposed as a key determinant of drought resistance in plants. However, the evidence for this role is controversial, as it comes mostly from observational, short-term studies. Here, we take advantage of a long-term experimental throughfall reduction to elucidate the response of NSC to increased drought 14 years after the beginning of the treatment in three Mediterranean resprouter trees (Quercus ilex L., Arbutus unedo L. and Phillyrea latifclia L.). In addition, we selected 20. Q. ilex individuals outside the experimental plots to directly assess the relationship between defoliation and NSC at the individual level. We measured the seasonal course of NSC concentrations in leaves, branches and lignotuber in late winter, late spring, summer, and autumn 2012. Total concentrations of NSC were highest in the lignotuber for all species. In the long-term drought experiment we found significant depletion in concentrations of total NSC in treatment plots only in the lignotuber of A. unedo. At the same time, A. unedo was the only species showing a significant reduction in BAI under the drought treatment during the 14 years of the experiment. By contrast, Q. ilex just reduced stem growth only during the first 4 years of treatment and P latifclia remained unaffected over the whole study period. However, we found a clear association between the concentrations of NSC and defoliation in Q. ilex individuals sampled outside the experimental plots, with lower total concentrations of NSC and lower proportion of starch in defoliated individuals. Taken together, our results suggest that stabilizing processes, probably at the stand level, may have been operating in the long-term to mitigate any impact of drought on NSC levels, and highlight the necessity to incorporate long-term experimental studies of plant responses to drought. © 2013 Rosas, Galiano, Ogaya, Peñuelas and Martínez-Vilalta.

Llegeix més

Tree growth changes with climate and forest type are associated with relative allocation of nutrients, especially phosphorus, to leaves and wood

Sardans J., Penuelas J. (2013) Tree growth changes with climate and forest type are associated with relative allocation of nutrients, especially phosphorus, to leaves and wood. Global Ecology and Biogeography. 22: 494-507.
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Doi: 10.1111/geb.12015

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Aim: To test our hypothesis that trees change the allocation and the proportion of different nutrients between leaves and wood to maximize growth along climatic gradients. Location: Catalonia, Iberian Peninsula. Methods: We tested the relationships of total forest nutrient content, stoichiometry and allocation between leaves and wood in trees with growth along environmental gradients using data from the Catalan Forest Inventory and a suite of multivariate mixed models, ANOVAs and principal components analyses. Results: The aboveground growth of trees and the nutrient content of leaves and wood were positively correlated with mean annual precipitation (MAP). The changes in C:nutrient ratios were proportionally higher in leaves than in wood, mainly in deciduous forests. Higher MAP was also related to a lower N:P content ratio in leaves and wood but was not related to a greater allocation of P than N in leaves relative to wood (N:PL/W). Conifers, which presented the highest relative aboveground growth, had the lowest N:PL/W (0.99 ± 0.02), whereas the slow-growing evergreens had the highest N:PL/W (2.26 ± 0.23). Main conclusions: In all forest types, growth was related to a higher allocation of nutrients to leaves than to wood, especially of P, coinciding with better climatic conditions for growth (higher MAP in this Mediterranean context). The highest rates of growth were linked to the lowest N:P ratios. The allocation of P relative to N in leaves is higher in conifers than in evergreen and deciduous trees. © 2012 Blackwell Publishing Ltd.

Llegeix més

Plant-soil interactions in Mediterranean forest and shrublands: Impacts of climatic change

Sardans J., Penuelas J. (2013) Plant-soil interactions in Mediterranean forest and shrublands: Impacts of climatic change. Plant and Soil. 365: 1-33.
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Doi: 10.1007/s11104-013-1591-6

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Background: In the Mediterranean climate, plants have evolved under conditions of low soil-water and nutrient availabilities and have acquired a series of adaptive traits that, in turn exert strong feedback on soil fertility, structure, and protection. As a result, plant-soil systems constitute complex interactive webs where these adaptive traits allow plants to maximize the use of scarce resources. Scope: It is necessary to review the current bibliography to highlight the most know characteristic mechanisms underlying Mediterranean plant-soil feed-backs and identify the processes that merit further research in order to reach an understanding of the plant-soil feed-backs and its capacity to cope with future global change scenarios. In this review, we characterize the functional and structural plant-soil relationships and feedbacks in Mediterranean regions. We thereafter discuss the effects of global change drivers on these complex interactions between plants and soil. Conclusions: The large plant diversity that characterizes Mediterranean ecosystems is associated to the success of coexisting species in avoiding competition for soil resources by differential exploitation in space (soil layers) and time (year and daily). Among plant and soil traits, high foliar nutrient re-translocation and large contents of recalcitrant compounds reduce nutrient cycling. Meanwhile increased allocation of resources to roots and soil enzymes help to protect against soil erosion and to improve soil fertility and capacity to retain water. The long-term evolutionary adaptation to drought of Mediterranean plants allows them to cope with moderate increases of drought without significant losses of production and survival in some species. However, other species have proved to be more sensitive decreasing their growth and increasing their mortality under moderate rising of drought. All these increases contribute to species composition shifts. Moreover, in more xeric sites, the desertification resulting from synergic interactions among some related process such as drought increases, torrential rainfall increases and human driven disturbances is an increasing concern. A research priority now is to discern the effects of long-term increases in atmospheric CO2 concentrations, warming, and drought on soil fertility and water availability and on the structure of soil communities (e. g., shifts from bacteria to fungi) and on patching vegetation and root-water uplift (from soil to plant and from soil deep layers to soil superficial layers) roles in desertification. © 2013 Springer Science+Business Media Dordrecht.

Llegeix més

Field-simulated droughts affect elemental leaf stoichiometry in Mediterranean forests and shrublands

Sardans J., Rivas-Ubach A., Estiarte M., Ogaya R., Penuelas J. (2013) Field-simulated droughts affect elemental leaf stoichiometry in Mediterranean forests and shrublands. Acta Oecologica. 50: 20-31.
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Doi: 10.1016/j.actao.2013.04.002

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This study evaluated the change induced by the year season and by experimentally induced drought on foliar element stoichiometry of the predominant woody species (. Quercus ilex and Erica multiflora) in two Mediterranean ecosystems, a forest and a shrubland. This study is based in two long-term (11yr) field experiments that simulated drought throughout the annual cycle.The effects of experimental droughts were significant but weaker than the changes produced by ontogeny and seasonality. Leaf N and P concentrations were higher in spring (the main growing season) in E. multiflora and, in Q.ilex in autumn (a period of additional growth). Leaf N:P ratios were lower in spring. In Q.ilex, the highest leaf K concentrations and leaf K:P ratios, and the lowest leaf C:K and N:K ratios, occurred in summer, the season when water stress was greatest. In E.multiflora, leaf K concentrations and K:P ratios were highest, and leaf C:K and N:K ratios were lowest in the plants from the drought-treated plots.The plant capacity to change K concentrations in response to seasonality and to drought is at least as great as the capacity to change N and P concentrations. The results underscore the importance of K and its stoichiometry relative to C, N and P in dry environments. These results indicate first, that N:P ratio shifts are not uniquely related to growth rate in Mediterranean plants but also to drought, and second, that there is a need to take into account K in ecological stoichiometry studies of terrestrial plants. © 2013 Elsevier Masson SAS.

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