Trends in soil solution dissolved organic carbon (DOC) concentrations across European forests

Camino-Serrano M., Graf Pannatier E., Vicca S., Luyssaert S., Jonard M., Ciais P., Guenet B., Gielen B., Peñuelas J., Sardans J., Waldner P., Etzold S., Cecchini G., Clarke N., Galić Z., Gandois L., Hansen K., Johnson J., Klinck U., Lachmanová Z., Lindroos A.J., Meesenburg H., Nieminen T.M., Sanders T.G.M., Sawicka K., Seidling W., Thimonier A., Vanguelova E., Verstraeten A., Vesterdal L., Janssens I.A. (2016) Trends in soil solution dissolved organic carbon (DOC) concentrations across European forests. Biogeosciences Discussions. 2016: 0-0.
Link
Doi: 10.5194/bg-2015-632

Abstract:

Dissolved organic carbon (DOC) in soil solution is connected to DOC in surface waters through hydrological flows. Therefore, it is expected that long-term dynamics of DOC in surface waters reflect DOC trends in soil solution. However, a multitude of site-studies has failed so far to establish consistent trends in soil solution DOC, whereas increasing concentrations in European surface waters over the past decades appear to be the norm, possibly as a result from acidification recovery. The objectives of this study were therefore to understand the long-term trends of soil solution DOC from a large number of European forests (ICP Forests Level II plots) and determine their main physico-chemical and biological controls. We applied trend analys is at two levels: 1) to the entire European dataset and 2) to the individual time series and related trends with plot characteristics, i.e., soil and vegetation properties, soil solution chemistry and atmospheric deposition loads. Analyses of the entire dataset showed an overall increasing trend in DOC concentrations in the organic layers, but, at individual plots and depths, there was no clear overall trend in soil solution DOC across Europe with temporal slopes of soil solution DOC ranging between -16.8% yr-1 and +23% yr-1 (median= +0.4% yr-1). The non-significant trends (40%) outnumbered the increasing (35%) and decreasing trends (25%) across the 97 ICP Forests Level II sites. By means of multivariate statistics, we found increasing DOC concentrations with increasing mean nitrate (NO3 -) deposition and decreasing DOC concentrations with decreasing mean sulphate (SO4 2-) deposition, with the magnitude of these relationships depending on plot deposition history. While the attribution of increasing trends in DOC to the reduction of SO4 2- deposition could be confirmed in N-poorer forests, in agreement with observations in surface waters, this was not the case in N-richer forests. In conclusion, long-term trends of soil solution DOC reflected the interactions between controls acting at local (soil and vegetation properties) and regional (atmospheric deposition of SO4 2- and inorganic N) scales. © Author(s) 2016.

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Trends in soil solution dissolved organic carbon (DOC) concentrations across European forests

Camino-Serrano, M., Graf Pannatier, E., Vicca, S., Luyssaert, S., Jonard, M., Ciais, P., Guenet, B., Gielen, B., Peñuelas, J., Sardans, J., Waldner, P., Etzold, S., Cecchini, G., Clarke, N., GaliÄ, Z., Gandois, L., Hansen, K., Johnson, J., Klinck, U., Lachmanová, Z., Lindroos, A.-J., Meesenburg, H., Nieminen, T.M., Sanders, T.G.M., Sawicka, K., Seidling, W., Thimonier, A., Vanguelova, E., Verstraeten, A., Vesterdal, L., Janssens, I.A. (2016) Trends in soil solution dissolved organic carbon (DOC) concentrations across European forests. Biogeosciences. 13: 5567-5585.
Link
Doi: 10.5194/bg-13-5567-2016

Abstract:

Shifts in plant foliar and floral metabolomes in response to the suppression of the associated microbiota

Gargallo-Garriga A., Sardans J., Pérez-Trujillo M., Guenther A., Llusià J., Rico L., Terradas J., Farré-Armengol G., Filella I., Parella T., Peñuelas J. (2016) Shifts in plant foliar and floral metabolomes in response to the suppression of the associated microbiota. BMC Plant Biology. 16: 0-0.
Link
Doi: 10.1186/s12870-016-0767-7

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Background: The phyllospheric microbiota is assumed to play a key role in the metabolism of host plants. Its role in determining the epiphytic and internal plant metabolome, however, remains to be investigated. We analyzed the Liquid Chromatography-Mass Spectrometry (LC-MS) profiles of the epiphytic and internal metabolomes of the leaves and flowers of Sambucus nigra with and without external antibiotic treatment application. Results: The epiphytic metabolism showed a degree of complexity similar to that of the plant organs. The suppression of microbial communities by topical applications of antibiotics had a greater impact on the epiphytic metabolome than on the internal metabolomes of the plant organs, although even the latter changed significantly both in leaves and flowers. The application of antibiotics decreased the concentration of lactate in both epiphytic and organ metabolomes, and the concentrations of citraconic acid, acetyl-CoA, isoleucine, and several secondary compounds such as terpenes and phenols in the epiphytic extracts. The metabolite pyrogallol appeared in the floral epiphytic community only after the treatment. The concentrations of the amino acid precursors of the ketoglutarate-synthesis pathway tended to decrease in the leaves and to increase in the foliar epiphytic extracts. Conclusions: These results suggest that anaerobic and/or facultative anaerobic bacteria were present in high numbers in the phyllosphere and in the apoplasts of S. nigra. The results also show that microbial communities play a significant role in the metabolomes of plant organs and could have more complex and frequent mutualistic, saprophytic, and/or parasitic relationships with internal plant metabolism than currently assumed. © 2016 Gargallo-Garriga et al.

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Thresholds in decoupled soil-plant elements under changing climatic conditions

Luo W., Sardans J., Dijkstra F.A., Peñuelas J., Lü X.-T., Wu H., Li M.-H., Bai E., Wang Z., Han X., Jiang Y. (2016) Thresholds in decoupled soil-plant elements under changing climatic conditions. Plant and Soil. : 1-15.
Link
Doi: 10.1007/s11104-016-2955-5

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Background and aims: Aridity has increased in the past decades and will probably continue to increase in arid and semiarid regions. Here we decipher the plant and soil capacity to retain metal cations when climate evolves to more arid conditions. Methods: We analyzed K, Na, Ca, Mg, Fe, Mn, Zn and Cu concentrations in 580 soil samples and 666 plant (shoot and root) samples along a 3600 km aridity gradient in northern China. Results: The concentrations of soil exchangeable K, Mg, Mn, Fe and Cu clearly decreased with increasing aridity due to the relationships of aridity with soil clay content and soil pH. Increases in exchangeable Na and Ca concentrations at mid- and high-aridity levels are probably due to the soil salinization, whereas increased exchangeable Fe concentrations at extreme levels of aridity may be more related to a reduced pH. Element concentrations in both plant shoots and roots were unrelated to soil exchangeable element concentrations; instead they increased monotonously with increasing aridity, corresponding with decreases in plant size and shoot/root ratios. The shoot/root mineralomass ratios in general increased with increasing aridity. The proportional higher element contents in shoots than in roots with increasing aridity are related to increased water uptake and/or use efficiency. Conclusions: The extractability of soil elements in response to changing climate varied with the nature of specific elements that are controlled by biological and geochemical processes, i.e., some decreased linearly with increasing aridity, whereas others first decreased and then increased with different thresholds. These contrasting effects of aridity on nutrient availability could further constrain plant growth and should be incorporated into biogeochemical models. The prevailing paradigm of a positive relationship between concentrations of plant and soil elements needs to be reconsidered under changing climatic conditions. © 2016 Springer International Publishing Switzerland

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Assessment of the impacts of climate change on Mediterranean terrestrial ecosystems based on data from field experiments and long-term monitored field gradients in Catalonia

Peñuelas, J., Sardans, J., Filella, I., Estiarte, M., Llusià, J., Ogaya, R., Carnicer, J., Bartrons, M., Rivas-Ubach, A., Grau, O., Peguero, G., Margalef, O., Pla-Rabés, S., Stefanescu, C., Asensio, D., Preece, C., Liu, L., Verger, A., Rico, L., Barbeta, A., Achotegui-Castells, A., Gargallo-Garriga, A., Sperlich, D., Farré-Armengol, G., Fernández-Martínez, M., Liu, D., Zhang, C., Urbina, I., Camino, M., Vives, M., Nadal-Sala, D., Sabaté, S., Gracia, C., Terradas, J. (2016) Assessment of the impacts of climate change on Mediterranean terrestrial ecosystems based on data from field experiments and long-term monitored field gradients in Catalonia. Environmental and Experimental Botany. : 0-0.
Link
Doi: 10.1016/j.envexpbot.2017.05.012

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Topsoil depth substantially influences the responses to drought of the foliar metabolomes of Mediterranean forests

Rivas-Ubach A., Barbeta A., Sardans J., Guenther A., Ogaya R., Oravec M., Urban O., Peñuelas J. (2016) Topsoil depth substantially influences the responses to drought of the foliar metabolomes of Mediterranean forests. Perspectives in Plant Ecology, Evolution and Systematics. 21: 41-54.
Link
Doi: 10.1016/j.ppees.2016.06.001

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The upper soil provides support, water, and nutrients to terrestrial plants and is therefore crucial for forest dynamics. We hypothesised that a tree's metabolic activity (and therefore its metabolome; the total set of metabolites) would be affected by both the depth of upper soil layers and water availability. We sampled leaves for stoichiometric and metabolomic analyses once per season from differently sized Quercus ilex trees under natural and experimental drought conditions representing the likely conditions in the coming decades). Although the metabolomes varied according to tree size, smaller trees did not show higher concentrations of biomarker metabolites related to drought stress. However, the effect of the drought treatment on the metabolomes was greatest for small trees growing in shallow soils. Our results suggest that tree size is more dependent on the depth of the upper soil, which indirectly affects a tree's metabolome, rather than on the moisture content in the upper soil. Metabolomic profiling of Q. ilex supports our finding that water availability in the upper soil is not necessarily correlated with tree size. The higher impact of drought on trees growing in shallower soils nevertheless indicates that any increase in the frequency, intensity, and duration of drought - as has been projected for the Mediterranean Basin and other areas - would affect small trees most. Metabolomics has proved to be a useful means for investigating the links between plant metabolism and environmental conditions. © 2016.

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Are the metabolomic responses to folivory of closely related plant species linked to macroevolutionary and plant–folivore coevolutionary processes?

Rivas-Ubach A., Hódar J.A., Sardans J., Kyle J.E., Kim Y.-M., Oravec M., Urban O., Guenther A., Peñuelas J. (2016) Are the metabolomic responses to folivory of closely related plant species linked to macroevolutionary and plant–folivore coevolutionary processes?. Ecology and Evolution. 6: 4372-4386.
Link
Doi: 10.1002/ece3.2206

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The debate whether the coevolution of plants and insects or macroevolutionary processes (phylogeny) is the main driver determining the arsenal of molecular defensive compounds of plants remains unresolved. Attacks by herbivorous insects affect not only the composition of defensive compounds in plants but also the entire metabolome. Metabolomes are the final products of genotypes and are constrained by macroevolutionary processes, so closely related species should have similar metabolomic compositions and may respond in similar ways to attacks by folivores. We analyzed the elemental compositions and metabolomes of needles from three closely related Pinus species with distant coevolutionary histories with the caterpillar of the processionary moth respond similarly to its attack. All pines had different metabolomes and metabolic responses to herbivorous attack. The metabolomic variation among the species and the responses to folivory reflected their macroevolutionary relationships, with P. pinaster having the most divergent metabolome. The concentrations of terpenes were in the attacked trees supporting the hypothesis that herbivores avoid plant individuals with higher concentrations. Our results suggest that macroevolutionary history plays important roles in the metabolomic responses of these pine species to folivory, but plant–insect coevolution probably constrains those responses. Combinations of different evolutionary factors and trade-offs are likely responsible for the different responses of each species to folivory, which is not necessarily exclusively linked to plant–insect coevolution. © 2016 The Authors. Ecology and Evolution published by John Wiley & Sons Ltd.

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Factors influencing the foliar elemental composition and stoichiometry in forest trees in Spain

Sardans J., Alonso R., Carnicer J., Fernández-Martínez M., Vivanco M.G., Peñuelas J. (2016) Factors influencing the foliar elemental composition and stoichiometry in forest trees in Spain. Perspectives in Plant Ecology, Evolution and Systematics. 18: 52-69.
Link
Doi: 10.1016/j.ppees.2016.01.001

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Concentrations of nutrient elements in organisms and in the abiotic environment are key factors influencing ecosystem structure and function. We studied how concentrations and stoichiometries of nitrogen (N), phosphorus (P) and potassium (K) in leaves of forest trees are related to phylogeny and to environmental factors (mean annual precipitation, mean annual temperature, forest type, and nitrogen deposition). Using data for 4691 forest plots from across Spain, we tested the following hypotheses: (i) that foliar stoichiometries of forest trees are strongly influenced by phylogeny, (ii) that climate, as an important driver of plant uptake and nutrient use efficiency, affects foliar stoichiometry, (iii) that long-term loads of N influence N, P and K concentrations and ratios in natural vegetation, and (iv) that sympatric species are differentiated according to their foliar stoichiometry, thereby reducing the intensity of resource competition. Our analyses revealed that several factors contributed to interspecific variation in elemental composition and stoichiometry. These included phylogeny, forest type, climate, N deposition, and competitive neighborhood relationships (probably related to niche segregation effect).These findings support the notion that foliar elemental composition reflects adaptation both to regional factors such as climate and to local factors such as competition with co-occurring species. © 2016 Elsevier GmbH.

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Plant invasion is associated with higher plant-soil nutrient concentrations in nutrient-poor environments

Sardans, J., Bartrons, M., Margalef, O., Gargallo-Garriga, A., Janssens, I.A., Ciais, P., Obersteiner, M., Sigurdsson, B.D., Chen, H.Y.H., Peñuelas, J. (2016) Plant invasion is associated with higher plant-soil nutrient concentrations in nutrient-poor environments. Global Change Biology. : 0-0.
Link
Doi: 10.1111/gcb.13384

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Oak protein profile alterations upon root colonization by an ectomycorrhizal fungus

Sebastiana, M., Martins, J., Figueiredo, A., Monteiro, F., Sardans, J., Peñuelas, J., Silva, A., Roepstorff, P., Pais, M.S., Coelho, A.V. (2016) Oak protein profile alterations upon root colonization by an ectomycorrhizal fungus. Mycorrhiza. : 1-20.
Link
Doi: 10.1007/s00572-016-0734-z

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