Molina-Montenegro M.A., Peñuelas J., Munné-Bosch S., Sardans J. (2012) Higher plasticity in ecophysiological traits enhances the performance and invasion success of Taraxacum officinale (dandelion) in alpine environments. Biological Invasions. 14: 21-33.EnlaceDoi: 10.1007/s10530-011-0055-2
Phenotypic plasticity has long been suggested to facilitate biological invasions in changing environments, allowing a species to maintain a good ecophysiological performance. High-mountain habitats have been particularly useful for evaluation of the relative importance of environmental conditions in the colonization and invasion process, because they have heterogeneous and stressful climatic conditions, inducing photoinhibition. Light intensity is one of the most changing conditions along altitudinal gradients, showing more variability in higher altitudes. In this study, we analyzed the plasticity in photoprotective strategies and performance of the invasive Taraxacum officinale. Additionally, we tested whether higher plasticity enhances competitive ability in an alpine environment We conducted an experiment to evaluate plasticity with a second generation (F2) of T. officinale individuals from 1,600 to 3,600 m, in a greenhouse with variation in light intensity. Treatments consisted of transferring 120 individuals from each altitude to two conditions of light intensity. We then recorded concentrations of photoprotection pigment, de-epoxidation state of the xanthophyll cycle, foliar angles, photochemical efficiency by fluorescence of photosystem II, total dry biomass and flower production. Additionally, we compared plasticity in both photoprotective and performance traits between T. officinale and the co-occurring native species Hypochaeris thrincioides. Finally, we performed a manipulative experiment under two light regimes in order to assess the competitive outcome between the invasive T. officinale and the native H. thrincioides. Individuals from higher altitude showed significantly greater plasticity than individuals from lower altitude. Similarly, individuals under high light intensity showed higher levels of photoprotective pigments, biomass and flower production. On the other hand, the invasive plant species showed significantly greater plasticity than the co-occurring native species, and a strong negative impact on the biomass of the native plant. Phenotypic plasticity seems to be a successful strategy in T. officinale to compete with native species and may be positively associated with the success of invasions, being greater in individuals from more heterogeneous and stressful environments. © 2011 Springer Science+Business Media B.V.
Nogués I., Peñuelas J., Llusià J., Estiarte M., Munné-Bosch S., Sardans J., Loreto F. (2012) Physiological and antioxidant responses of Erica multiflora to drought and warming through different seasons. Plant Ecology. 213: 649-661.EnlaceDoi: 10.1007/s11258-012-0029-1
Climate change projections forecast a warming and an associated change in the distribution and intensity of rainfalls. In the case of the Mediterranean area, this will be reflected in more frequent and severe drought periods in the future. Within a long-term (9 years) manipulation experiment, we aimed to study the effect of the soil drought (15-20% decreased soil moisture) and warming conditions (+1°C warming) projected for the next decades onto photosynthetic rates and water relations, and onto the antioxidant and anti-stress defense capacity of Erica multiflora, a common species of the dry Mediterranean coastal scrublands, in two different seasons, spring and summer. Results indicated that none of the applied treatments was severe enough to induce a pronounced negative response of photosynthesis in this species well adapted to harsh Mediterranean conditions, but also highlighted important seasonal differences. Photosynthesis was limited by photoinhibition in spring and by stomatal closure in summer. Isoprenoid emission and the level of enzymatic and non-enzymatic antioxidants were lower in summer than in spring, whereas pigment and total phenolic contents were generally higher in summer. Volatile isoprenoid emissions were largely inhibited by drought and were not stimulated by warming. Drought and warming increased the oxidation state of ascorbate and reduced total glutathione levels in spring, but not in summer. It is concluded that E. multiflora plants can adapt to prolonged drought and warming, at least at the level simulated by our manipulative experiment, through changes in the seasonal physiological and antioxidant response of leaves. © 2012 Springer Science+Business Media B.V.
Peñuelas J., Sardans J., Rivas-ubach A., Janssens I.A. (2012) The human-induced imbalance between C, N and P in Earth's life system. Global Change Biology. 18: 3-6.EnlaceDoi: 10.1111/j.1365-2486.2011.02568.x
Human-induced carbon and nitrogen fertilization are generating a strong imbalance with P. This imbalance confers an increasingly important role to P availability and N: P ratio in the Earth's life system, affecting carbon sequestration potential and the structure, function and evolution of the Earth's ecosystems. © 2011 Blackwell Publishing Ltd.
Sardans J., Peñuelas J., Coll M., Vayreda J., Rivas-Ubach A. (2012) Stoichiometry of potassium is largely determined by water availability and growth in Catalonian forests. Functional Ecology. 26: 1077-1089.EnlaceDoi: 10.1111/j.1365-2435.2012.02023.x
The study of the relationships between organisms and environmental elemental stoichiometry and ecosystem structure and function has recently received increasing attention. Some elements, however, have been less studied or have even been neglected. One of these elements is K, despite its critical importance in the water economy of plants. We hypothesized that K concentrations and especially K contents (concentrations × biomass), their stoichiometries with respect to C, N, and P contents, and their relative allocations to foliar and woody compartments would be linked to climatic gradients in the availability of water, forest type and growth. We tested this hypothesis by analysing the data set of the Catalan Forest Inventory. Evergreens, the type of tree with the slowest growth, showed the highest K contents, especially in wood, and the lowest plasticity to change the stoichiometry of K within and between foliar and woody biomasses along climatic gradients. The allocation of K to leaves in relation to the allocation of C, N and P increased with mean annual precipitation (MAP) and was concomitant with decreases in the allocation of K to wood in relation to the allocation of C, N and P (higher K:C L/W, K:N L/W and K:P L/W). In summer, the driest period, higher K:C, K:N and K:P content ratios in leaves were accompanied by lower K:C, K:N and K:P content ratios in wood, mainly in the species at the driest sites. Higher K:C and K:N content ratios in leaves and above-ground biomass in all forest types, and higher K:C L/W and K:N L/W in conifers and deciduous trees were related to higher growth. K contents of leaves were better correlated with tree growth than were K concentrations of leaves in all forest types. These results show that the stoichiometry of K is strongly related to the availability of water and that the uptake of K is more related to the uptake of water than the uptake of N and P. Stoichiometric differences involving K are related to both the response of plants to drought and to plant growth. K thus plays a key role, together with N and P, in the response of plants to climatic gradients for improving the capacities for growth and adaptation to water stress along environmental gradients and through time (seasons). Moreover, these results show that the differences in stoichiometric composition and plasticity involving K contents can underlie the long-term adaptation of trees to different ecological styles of life. K should thus be considered in ecological stoichiometric studies of terrestrial plants. © 2012 The Authors. Functional Ecology © 2012 British Ecological Society.
Sardans J., Rivas-Ubach A., Peñuelas J. (2012) The C:N:P stoichiometry of organisms and ecosystems in a changing world: A review and perspectives. Perspectives in Plant Ecology, Evolution and Systematics. 14: 33-47.EnlaceDoi: 10.1016/j.ppees.2011.08.002
This study examined the literature in ISI Web of Science to identify the effects that the main drivers of global change have on the nutrient concentrations and C:N:P stoichiometry of organisms and ecosystems, and examined their relationship to changes in ecosystem structure and function. We have conducted a meta-analysis by comparing C:N:P ratios of plants and soils subjected to elevated [CO 2] with those subjected to ambient [CO 2]. A second meta-analysis compared the C:N:P ratios of plants and soils that received supplemental N to simulate N deposition and those that did not receive supplemental N. On average, an experimental increase in atmospheric [CO 2] increased the foliar C:N ratios of C3 grasses, forbs, and woody plants by 22%, but the foliar ratios of C4 grasses were unaffected. This trend may be enhanced in semi-arid areas by the increase in droughts that have been projected for the coming decades which can increase leaf C:N ratios. The available studies show an average 38% increase in foliar C:P ratios in C3 plants in response to elevated atmospheric [CO 2], but no significant effects were observed in C4 grasses. Furthermore, studies that examine the effects of elevated atmospheric [CO 2] on N:P ratio (on a mass basis) are warranted since its response remains elusive. N deposition increases the N:P ratio in the plants of terrestrial and freshwater ecosystems, and decreases plants and organic soil C:N ratio (25% on average for C3 plants), reducing soil and water N 2 fixation capacity and ecosystem species diversity. In contrast, in croplands subjected to intense fertilization, mostly, animal slurries, a reduction in soil N:P ratio can occur because of the greater solubility and loss of N. In the open ocean, there are experimental observations showing an ongoing increase in P-limited areas in response to several of the factors that promote global change, including the increase in atmospheric [CO 2] which increases the demand for P, the warming effect that leads to an increase in water column stratification, and increases in the N:P ratio of atmospheric inputs. Depending on the type of plant and the climate where it grows, warming can increase, reduce, or have no effect on foliar C:N ratios. The results suggest that warming and drought can increase C:N and C:P ratios in warm-dry and temperate-dry terrestrial ecosystems, especially, when high temperatures and drought coincide. Advances in this topic are a challenge because changes in stoichiometric ratios can favour different types of species and change ecosystem composition and structure. © 2011 Perspectives in Plant Ecology, Evolution and Systematics.
Sardans J., Rivas-Ubach A., Peñuelas J. (2012) The elemental stoichiometry of aquatic and terrestrial ecosystems and its relationships with organismic lifestyle and ecosystem structure and function: A review and perspectives. Biogeochemistry. 111: 1-39.EnlaceDoi: 10.1007/s10533-011-9640-9
C, N and P are three of the most important elements used to build living beings, and their uptake from the environment is consequently essential for all organisms. We have reviewed the available studies on water, soils and organism elemental content ratios (stoichiometry) with the aim of identifying the general links between stoichiometry and the structure and function of organisms and ecosystems, in both aquatic and terrestrial contexts. Oceans have variable C:N:P ratios in coastal areas and a narrow range approximating the Redfield ratio in deep water and inner oceanic areas. Terrestrial ecosystems have a general trend towards an increase in soil and plant N:P ratios from cool and temperate to tropical ecosystems, but with great variation within each climatic area. The C:N:P content ratio (from now on C:N:P ratio) is more constrained in organisms than in the water and soil environments they inhabit. The capacity to adjust this ratio involves several mechanisms, from leaf re-absorption in plants to the control of excretion in animals. Several differences in C:N:P ratios are observed when comparing different taxa and ecosystems. For freshwater ecosystems, the growth rate hypothesis (GRH), which has consistent experimental support, states that low N:P supply determines trophic web structures by favoring organisms with a high growth rate. For terrestrial organisms, however, evidence not yet conclusive on the relevance of the GRH. Recent studies suggest that the N:P ratio could play a role, even in the evolution of the genomes of organisms. Further research is warranted to study the stoichiometry of different trophic levels under different C:N:P environment ratios in long-term ecosystem-scale studies. Other nutrients such as K or Fe should also be taken into account. Further assessment of the GRH requires more studies on the effects of C:N:P ratios on anabolic (growth), catabolic (respiration), storage and/or defensive allocation. Combining elemental stoichiometry with metabolomics and/or genomics should improve our understanding of the coupling of different levels of biological organization, from elemental composition to the structure and evolution of ecosystems, via cellular metabolism and nutrient cycling. © 2011 Springer Science+Business Media B.V.
Vicca S., Gilgen A.K., Camino Serrano M., Dreesen F.E., Dukes J.S., Estiarte M., Gray S.B., Guidolotti G., Hoeppner S.S., Leakey A.D.B., Ogaya R., Ort D.R., Ostrogovic M.Z., Rambal S., Sardans J., Schmitt M., Siebers M., van der Linden L., van Straaten O., Granier A. (2012) Urgent need for a common metric to make precipitation manipulation experiments comparable. New Phytologist. 195: 518-522.EnlaceDoi: 10.1111/j.1469-8137.2012.04224.x
[No abstract available]
Sardans J, Montes F, Peñuelas J (2011) Seguint la traça als elements traça. UABdivulga 10/2011
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