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.

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Summer season and long-term drought increase the richness of bacteria and fungi in the foliar phyllosphere of Quercus ilex in a mixed Mediterranean forest

Peñuelas J., Rico L., Ogaya R., Jump A.S., Terradas J. (2012) Summer season and long-term drought increase the richness of bacteria and fungi in the foliar phyllosphere of Quercus ilex in a mixed Mediterranean forest. Plant Biology. 14: 565-575.
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Doi: 10.1111/j.1438-8677.2011.00532.x

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We explored the changes in richness, diversity and evenness of epiphytic (on the leaf surface) and endophytic (within leaf tissues) bacteria and fungi in the foliar phyllosphere of Quercus ilex, the dominant tree species of Mediterranean forests. Bacteria and fungi were assessed during ontogenic development of the leaves, from the wet spring to the dry summer season in control plots and in plots subjected to drought conditions mimicking those projected for future decades. Our aim was to monitor succession in microbiota during the colonisation of plant leaves and its response to climate change. Ontogeny and seasonality exerted a strong influence on richness and diversity of the microbial phyllosphere community, which decreased in summer in the whole leaf and increased in summer in the epiphytic phyllosphere. Drought precluded the decrease in whole leaf phyllosphere diversity and increased the rise in the epiphytic phyllosphere. Both whole leaf bacterial and fungal richness decreased with the decrease in physiological activity and productivity of the summer season in control trees. As expected, the richness of epiphytic bacteria and fungi increased in summer after increasing time of colonisation. Under summer dry conditions, there was a positive relationship between TRF (terminal restriction fragments) richness and drought, both for whole leaf and epiphytic phyllosphere, and especially for fungal communities. These results demonstrate that changes in climate are likely to significantly alter microbial abundance and composition of the phyllosphere. Given the diverse functions and large number of phyllospheric microbes, the potential functional implications of such community shifts warrant exploration. © 2012 German Botanical Society and The Royal Botanical Society of the Netherlands.

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Reduced tree health and seedling production in fragmented Fagus sylvatica forest patches in the Montseny Mountains (NE Spain)

Barbeta A., Peñuelas J., Ogaya R., Jump A.S. (2011) Reduced tree health and seedling production in fragmented Fagus sylvatica forest patches in the Montseny Mountains (NE Spain). Forest Ecology and Management. 261: 2029-2037.
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Doi: 10.1016/j.foreco.2011.02.029

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Habitat fragmentation results in smaller and more isolated populations that may be at higher risk of extirpation or further decline in comparison with their more continuously distributed progenitors. Risks to fragmented populations have frequently been considered from the perspective of population genetics, however, disruption of normal plant demography may be an equal or greater threat to population persistence. We compared demographic performance and tree health in continuous and fragmented forest plots with similar tree size structure and local climatic and physiographic conditions in order to determine if fragments are characterized by poor health and reproduction. We found that beech forest fragments showed lower seedling density, more tree crown damage and also higher percentage of dead trees. However, mortality of juveniles in the youngest age class was substantially lower in fragments such that long-term population structure remained similar between the two forest types. If reduced mortality compensates for reduced seedling establishment, as our data suggest, then fragmented populations should show greater long-term persistence than would be predicted based on comparison of young age cohorts alone. However, despite such demographic compensation, the decreased health of adult trees may pose an increasing future threat to the fragmented populations. Our results demonstrate the importance of integrating demographic patterns over long time periods and not relying on single year or cohort comparisons and may partly explain population genetic differences previously reported for the same populations. © 2011 Elsevier B.V.

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Twentieth century changes of tree-ring δ13C at the southern range-edge of Fagus sylvatica: Increasing water-use efficiency does not avoid the growth decline induced by warming at low altitudes

Peñuelas J., Hunt J.M., Ogaya R., Jump A.S. (2008) Twentieth century changes of tree-ring δ13C at the southern range-edge of Fagus sylvatica: Increasing water-use efficiency does not avoid the growth decline induced by warming at low altitudes. Global Change Biology. 14: 1076-1088.
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Doi: 10.1111/j.1365-2486.2008.01563.x

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We aimed to gain knowledge on the changes in intrinsic water use efficiency (iWUE) in response to increasing atmospheric CO2 concentrations and climate change over the last century. We investigated the variation in the iWUE of mature Fagus sylvatica trees located in the higher, central and lower altitudinal forest limits (HFL, CFA and LFL) of one of the southernmost sites of beech distribution in Europe, the Montseny Mountains in Catalonia (northeast Spain), during the last century by analysing the δ13C of their tree rings. Pre- and post-maturation phases of the trees presented different trends in δ13C, Δ13C, Ci (internal CO2 concentration), iWUE and basal area increment (BAI). Moreover, these variables showed different trends and absolute values in the LFL than in the other altitudinal sites, CFA and HFL. Our results show the existence of an age effect on δ13C in the CFA and HFL (values increased by ca. 1.25‰ coinciding with the BAI suppression and release phases, previous to maturation). These age-related changes were not found in the LFL, whose beech trees arrived to maturation earlier and experienced drier conditions during the suppression phase. In the last 26 years of comparable mature trees, the increase of iWUE deduced from the Δ13C analyses was ca. 10% in LFL, ca. 6% in CFA and not significant in HFL. These results show that climate change towards more arid conditions accounted for these higher Δ13C-values and increases in the LFL more than the continuous increase in atmospheric CO2 concentrations. This increased iWUE in the LFL did not avoid a decline in growth in these lowest altitudes of this beech southern range-edge as a result of warming. Furthermore, since there was no apparent change in iWUE and growth in the beech forests growing in the more standard-adequate environments of higher altitudes in the last 26 years, the rate of sequestration of C into temperate ecosystems may not increase with increasing atmospheric CO2 concentrations as predicted by most models based on short-term small scale experiments. © 2008 The Authors Journal compilation © 2008 Blackwell Publishing Ltd.

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Migration, invasion and decline: Changes in recruitment and forest structure in a warming-linked shift of European beech forest in Catalonia (NE Spain)

Peñuelas J., Ogaya R., Boada M., Jump A.S. (2007) Migration, invasion and decline: Changes in recruitment and forest structure in a warming-linked shift of European beech forest in Catalonia (NE Spain). Ecography. 30: 829-837.
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Doi: 10.1111/j.2007.0906-7590.05247.x

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Altitudinal upward shifts of species' ranges have occurred across a wide range of taxonomic groups and geographical locations during the twentieth century in response to current climate warming. However, actual data of plant species' altitudinal shifts are still scarce and not always clear. Here we provide a more detailed investigation of a previously reported European beech Fagus sylvatica forest altitudinal shift in the Montseny Mountains (Catalonia, NE Spain) now based on field photographic survey and on the population age structure and the recruitment patterns in the high Fagus limit (HFL), the central forest area (CFA) and the low Fagus limit (LFL). Monitoring of the lowest altitudinal range shows that beech forest is being progressively replaced by Mediterranean holm oak forest. Holm oaks are characterized by recruitment rates more than three times higher than those of beech in the LFL in the last decades. The percentage of young individuals in the LFL is only half that in the HFL and CFA. In the highest altitudinal range, present day and early 20th century photographs show that the HFL has gained density and has shifted altitudinally upwards, advancing with establishment of new, vigorous outpost trees (13 individuals per each 100 m of tree-line). They are mostly (89%) younger than 35 yr old and mostly (97%) located up to 70 m (with a few up to 105 m) ground surface distance above the current tree line (36-51 m altitude) at the highest altitudes (1600-1700 m). The beech forest upward shift is a likely consequence of warming, but land-use practice changes (cessation of burning by shepherds) have made it possible. These changes in vegetation distribution and population structure constitute a new indication of the complex global change effects on life in mountain ecosystems. © 2007 The Authors.

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