Isotopic evidence for the occurrence of biological nitrification and nitrogen deposition processing in forest canopies

Guerrieri R., Vanguelova E.I., Michalski G., Heaton T.H.E., Mencuccini M. (2015) Isotopic evidence for the occurrence of biological nitrification and nitrogen deposition processing in forest canopies. Global Change Biology. 21: 4613-4626.
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Doi: 10.1111/gcb.13018

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This study examines the role of tree canopies in processing atmospheric nitrogen (Ndep) for four forests in the United Kingdom subjected to different Ndep: Scots pine and beech stands under high Ndep (HN, 13-19 kg N ha-1 yr-1), compared to Scots pine and beech stands under low Ndep (LN, 9 kg N ha-1 yr-1). Changes of NO3-N and NH4-N concentrations in rainfall (RF) and throughfall (TF) together with a quadruple isotope approach, which combines δ18O, Δ17O and δ15N in NO3 - and δ15N in NH4 +, were used to assess N transformations by the canopies. Generally, HN sites showed higher NH4-N and NO3-N concentrations in RF compared to the LN sites. Similar values of δ15N-NO3 - and δ18O in RF suggested similar source of atmospheric NO3 - (i.e. local traffic), while more positive values for δ15N-NH4 + at HN compared to LN likely reflected the contribution of dry NHx deposition from intensive local farming. The isotopic signatures of the N-forms changed after interacting with tree canopies. Indeed, 15N-enriched NH4 + in TF compared to RF at all sites suggested that canopies played an important role in buffering dry Ndep also at the low Ndep site. Using two independent methods, based on δ18O and Δ17O, we quantified for the first time the proportion of NO3 - in TF, which derived from nitrification occurring in tree canopies at the HN site. Specifically, for Scots pine, all the considered isotope approaches detected biological nitrification. By contrast for the beech, only using the mixing model with Δ17O, we were able to depict the occurrence of nitrification within canopies. Our study suggests that tree canopies play an active role in the N cycling within forest ecosystems. Processing of Ndep within canopies should not be neglected and needs further exploration, with the combination of multiple isotope tracers, with particular reference to Δ17O. © 2015 John Wiley & Sons Ltd.

Llegeix més

Shifts in indigenous culture relate to forest tree diversity: A case study from the Tsimane', Bolivian Amazon

Gueze M., Luz A.C., Paneque-Galvez J., Macia M.J., Orta-Martinez M., Pino J., Reyes-Garcia V. (2015) Shifts in indigenous culture relate to forest tree diversity: A case study from the Tsimane', Bolivian Amazon. Biological Conservation. 186: 251-259.
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Doi: 10.1016/j.biocon.2015.03.026

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Understanding how indigenous peoples' management practices relate to biological diversity requires addressing contemporary changes in indigenous peoples' way of life. This study explores the association between cultural change among a Bolivian Amazonian indigenous group, the Tsimane', and tree diversity in forests surrounding their villages. We interviewed 86 informants in six villages about their level of attachment to traditional Tsimane' values, our proxy for cultural change. We estimated tree diversity (Fisher's Alpha index) by inventorying trees in 48 0.1-ha plots in old-growth forests distributed in the territory of the same villages. We used multivariate models to assess the relation between cultural change and alpha tree diversity. Cultural change was associated with alpha tree diversity and the relation showed an inverted U-shape, thus suggesting that tree alpha diversity peaked in villages undergoing intermediate cultural change. Although the results do not allow for testing the direction of the relation, we propose that cultural change relates to tree diversity through the changes in practices and behaviors that affect the traditional ecological knowledge of Tsimane' communities; further research is needed to determine the causality. Our results also find support in the intermediate disturbance hypothesis, and suggest that indigenous management can be seen as an intermediate form of anthropogenic disturbance affecting forest communities in a subtle, non-destructive way. © 2015 Elsevier Ltd.

Llegeix més

Assessing impacts of land abandonment on Mediterranean biodiversity using indicators based on bird and butterfly monitoring data

HERRANDO S., BROTONS L., ANTON M., PARAMO F., VILLERO D., TITEUX N., QUESADA J., STEFANESCU C. (2015) Assessing impacts of land abandonment on Mediterranean biodiversity using indicators based on bird and butterfly monitoring data. Environmental Conservation. : 0-0.
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Doi: 10.1017/S0376892915000260

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In Europe, and particularly in the Mediterranean Basin, the abandonment of traditional land-use practices has been reported as one of the main causes of decline for open-habitat species. Data from large-scale bird and butterfly monitoring schemes in the north-east Iberian Peninsula were used to evaluate the impact that land abandonment has had on local biodiversity. Species’ habitat preferences, along a gradient from open to forest habitats, were significantly related to population trends: for both birds and butterflies, open-habitat species showed the most marked declines while forest species increased moderately. Multi-species indicators for tracking the impact of land abandonment on bird and butterfly populations were developed using habitat preference estimates and population trend indices. The patterns shown by these indicators were in line with the changes occurring in forest cover in the monitoring sites. This study reveals that multi-species indicators based on monitoring data from different taxonomic groups (here, birds and butterflies) may usefully be employed to track impacts of environmental change on biodiversity. Copyright © Foundation for Environmental Conservation 2015

Llegeix més

Sensitivity of two Iberian lakes to North Atlantic atmospheric circulation modes

Hernandez A., Trigo R.M., Pla-Rabes S., Valero-Garces B.L., Jerez S., Rico-Herrero M., Vega J.C., Jambrina-Enriquez M., Giralt S. (2015) Sensitivity of two Iberian lakes to North Atlantic atmospheric circulation modes. Climate Dynamics. : 0-0.
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Doi: 10.1007/s00382-015-2547-8

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The North Atlantic Oscillation (NAO) exerts a major influence on the climate of the North Atlantic region. However, other atmospheric circulation modes (ACMs), such as the East Atlantic (EA) and Scandinavian (SCAND) patterns, also play significant roles. The dynamics of lakes on the Iberian Peninsula are greatly controlled by climatic parameters, but their relationship with these various ACMs has not been investigated in detail. In this paper, we analyze monthly meteorological and limnological long-term datasets (1950–2011 and 1992–2011, respectively) from two lakes on the northern and central Iberian Peninsula (Sanabria and Las Madres) to develop an understanding of the seasonal sensitivity of these freshwater systems to the NAO, EA and SCAND circulation modes. The limnological variability within Lake Sanabria is primarily controlled by fluctuations in the seasonal precipitation and wind, and the primary ACMs associated with the winter limnological processes are the NAO and the SCAND modes, whereas only the EA mode appears to weakly influence processes during the summer. However, Lake Las Madres is affected by precipitation, wind and, to a lesser extent, temperature, whereas the ACMs have less influence. Therefore, we aim to show that the lakes of the Iberian Peninsula are sensitive to these ACMs. The results presented here indicate that the lake dynamics, in some cases, have a higher sensitivity to variations in the ACMs than single local meteorological variables. However, certain local features, such as geography, lake morphology and anthropic influences, are crucial to properly record the signals of these ACMs. © 2015 Springer-Verlag Berlin Heidelberg

Llegeix més

Arthropods and novel bird habitats: do clear-cuts in spruce plantations provide similar food resources for insectivorous birds compared with farmland habitats?

Hollander F.A., Titeux N., Walsdorff T., Martinage A., Van Dyck H. (2015) Arthropods and novel bird habitats: do clear-cuts in spruce plantations provide similar food resources for insectivorous birds compared with farmland habitats?. Journal of Insect Conservation. 19: 1011-1020.
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Doi: 10.1007/s10841-015-9817-y

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Arthropods, and insects in particular, constitute important food resources for several higher trophic levels like birds. Their abundance and diversity is likely to differ between habitat types depending on the local conditions and resources. This may have important consequences for arthropod consumers that occupy structurally different habitat types. Most bird-focused studies address, however, habitats at the structural, vegetation-based level and disregard the presence of sufficient quantities and qualities of arthropod prey items. Here, we compare the quantity and quality of ground-dwelling and above-ground arthropods as food resources for early-successional birds between two structurally different human-modified habitat types sharing similar bird assemblages: low-intensity farmland areas and plantation forest clear-cut areas in the south of Belgium. Forest clear-cut patches constitute a novel habitat for so-called ‘farmland’ birds. Our results show that arthropod abundance is substantially higher in farmland than in forest clear-cuts, although arthropods are slightly larger in clear-cuts. Higher arthropod abundance is associated with higher ground-level temperature in farmland. Although both habitat types host the same spectrum of arthropod species, forest and farmland management practices induce different conditions for food quantity and, to some extent, food quality for insectivorous birds. We discuss the mechanisms behind the observed pattern of arthropod abundance and the fitness-related consequences of contrasting food availability in farmland and forest clear-cut habitats for early-successional bird species. © 2015, Springer International Publishing Switzerland.

Llegeix més

Long-term nitrogen deposition linked to reduced water use efficiency in forests with low phosphorus availability

Huang Z., Liu B., Davis M., Sardans J., Peñuelas J., Billings S. (2015) Long-term nitrogen deposition linked to reduced water use efficiency in forests with low phosphorus availability. New Phytologist. : 0-0.
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Doi: 10.1111/nph.13785

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The impact of long-term nitrogen (N) deposition is under-studied in phosphorus (P)-limited subtropical forests. We exploited historically collected herbarium specimens to investigate potential physiological responses of trees in three subtropical forests representing an urban-to-rural gradient, across which N deposition has probably varied over the past six decades. We measured foliar [N] and [P] and stable carbon (δ13C), oxygen (δ18O) and nitrogen (δ15N) isotopic compositions in tissue from herbarium specimens of plant species collected from 1947 to 2014. Foliar [N] and N: P increased, and δ15N and [P] decreased in the two forests close to urban centers. Consistent with recent studies demonstrating that N deposition in the region is 15N-depleted, these data suggest that the increased foliar [N] and N: P, and decreased [P], may be attributable to atmospheric deposition and associated enhancement of P limitation. Estimates of intrinsic water use efficiency calculated from foliar δ13C decreased by c. 30% from the 1950s to 2014, contrasting with multiple studies investigating similar parameters in N-limited forests. This effect may reflect decreased photosynthesis, as suggested by a conceptual model of foliar δ13C and δ18O. Long-term N deposition may exacerbate P limitation and mitigate projected increases in carbon stocks driven by elevated CO2 in forests on P-limited soils. © 2015 New Phytologist Trust.

Llegeix més

Background fish feminization effects in European remote sites

Jarque S., Quiros L., Grimalt J.O., Gallego E., Catalan J., Lackner R., Pina B. (2015) Background fish feminization effects in European remote sites. Scientific Reports. 5: 0-0.
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Doi: 10.1038/srep11292

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Human activity has spread trace amounts of chemically stable endocrine-disrupting pollutants throughout the biosphere. These compounds have generated a background level of estrogenic activity that needs to be assessed. Fish are adequate sentinels for feminization effects as male specimens are more sensitive than humans to exogenous estrogenic compounds. High mountain lakes, the most distant environments of continental areas, only receive semi-volatile compounds from atmospheric deposition. We analyzed the expression levels of estrogen-regulated genes in male fish from these mountain lakes in Europe. Incipient feminization involving expression of estrogen receptor and zona radiata genes revealed a widespread diffuse estrogenic impact. This effect was correlated with the concentrations of some organochlorine compounds in fish and was consistent with the persistent occurrence of these tropospheric pollutants in the most remote planet regions. These results should be of general concern given the increasing endocrine disruption effects in human populations. © 2015, Nature Publishing Group. All rights reserved.

Llegeix més

Social evolution. Genomic signatures of evolutionary transitions from solitary to group living

Kapheim K.M., Pan H., Li C., Salzberg S.L., Puiu D., Magoc T., Robertson H.M., Hudson M.E., Venkat A., Fischman B.J., Hernandez A., Yandell M., Ence D., Holt C., Yocum G.D., Kemp W.P., Bosch J., Waterhouse R.M., Zdobnov E.M., Stolle E., Kraus F.B., Helbing S., Moritz R.F., Glastad K.M., Hunt B.G., Goodisman M.A., Hauser F., Grimmelikhuijzen C.J., Pinheiro D.G., Nunes F.M., Soares M.P., Tanaka ED., Simoes Z.L., Hartfelder K., Evans J.D., Barribeau S.M., Johnson R.M., Massey J.H., Southey B.R., Hasselmann M., Hamacher D., Biewer M., Kent C.F., Zayed A., Blatti C., Sinha S., Johnston J.S., Hanrahan S.J., Kocher S.D., Wang J., Robinson G.E., Zhang G. (2015) Social evolution. Genomic signatures of evolutionary transitions from solitary to group living. Science (New York, N.Y.). 348: 1139-1143.
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Doi: 10.1126/science.aaa4788

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The evolution of eusociality is one of the major transitions in evolution, but the underlying genomic changes are unknown. We compared the genomes of 10 bee species that vary in social complexity, representing multiple independent transitions in social evolution, and report three major findings. First, many important genes show evidence of neutral evolution as a consequence of relaxed selection with increasing social complexity. Second, there is no single road map to eusociality; independent evolutionary transitions in sociality have independent genetic underpinnings. Third, though clearly independent in detail, these transitions do have similar general features, including an increase in constrained protein evolution accompanied by increases in the potential for gene regulation and decreases in diversity and abundance of transposable elements. Eusociality may arise through different mechanisms each time, but would likely always involve an increase in the complexity of gene networks. Copyright © 2015, American Association for the Advancement of Science.

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Direct and indirect impacts of climate and socio-economic change in Europe: a sensitivity analysis for key land- and water-based sectors

Kebede A.S., Dunford R., Mokrech M., Audsley E., Harrison P.A., Holman I.P., Nicholls R.J., Rickebusch S., Rounsevell M.D.A., Sabate S., Sallaba F., Sanchez A., Savin C., Trnka M., Wimmer F. (2015) Direct and indirect impacts of climate and socio-economic change in Europe: a sensitivity analysis for key land- and water-based sectors. Climatic Change. 128: 261-277.
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Doi: 10.1007/s10584-014-1313-y

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Integrated cross-sectoral impact assessments facilitate a comprehensive understanding of interdependencies and potential synergies, conflicts, and trade-offs between sectors under changing conditions. This paper presents a sensitivity analysis of a European integrated assessment model, the CLIMSAVE integrated assessment platform (IAP). The IAP incorporates important cross-sectoral linkages between six key European land- and water-based sectors: agriculture, biodiversity, flooding, forests, urban, and water. Using the IAP, we investigate the direct and indirect implications of a wide range of climatic and socio-economic drivers to identify: (1) those sectors and regions most sensitive to future changes, (2) the mechanisms and directions of sensitivity (direct/indirect and positive/negative), (3) the form and magnitudes of sensitivity (linear/non-linear and strong/weak/insignificant), and (4) the relative importance of the key drivers across sectors and regions. The results are complex. Most sectors are either directly or indirectly sensitive to a large number of drivers (more than 18 out of 24 drivers considered). Over twelve of these drivers have indirect impacts on biodiversity, forests, land use diversity, and water, while only four drivers have indirect effects on flooding. In contrast, for the urban sector all the drivers are direct. Moreover, most of the driver–indicator relationships are non-linear, and hence there is the potential for ‘surprises’. This highlights the importance of considering cross-sectoral interactions in future impact assessments. Such systematic analysis provides improved information for decision-makers to formulate appropriate adaptation policies to maximise benefits and minimise unintended consequences. © 2015, Springer Science+Business Media Dordrecht.

Llegeix més

Linking OMI HCHO and MODIS PRI satellite data with BVOCS emissions in NE Spain

Kefauver S.C., Filella I., Zhang C., Penuelas J. (2015) Linking OMI HCHO and MODIS PRI satellite data with BVOCS emissions in NE Spain. International Geoscience and Remote Sensing Symposium (IGARSS). 2015-November: 2661-2664.
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Doi: 10.1109/IGARSS.2015.7326360

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Volatile organic compounds (VOCs) play several important roles on tropospheric chemical composition. Biogenic VOCs (BVOCs) are the largest source of NMVOCs (non-methane VOCs), accounting for the release of up to 10% of total C fixed by plants in photosynthesis. As isoprene is often the dominant source of atmospheric formaldehyde (HCHO) detected using satellite sensors, it is often correlated directly to satellite HCHO observations without accounting for other HCHO sources. Here we investigate the importance of quantifying monoterpene emissions when linking remotely sensed HCHO vertical columns to terrestrial BVOCs emissions at four different ecosystems in NE Spain where monoterpene-isoprene emissions ratios are known to be unusually high. Average HCHO yield for present monoterpenes was approximately 29% compared to 45% for isoprene. Including monoterpene HCHO yield contributions in total atmospheric HCHO concentrations improved correlations from R2 of 0.35 to 0.66 and R2 of 0.56 to 0.89 when comparing OMI HCHO and MODIS PRI satellite with HCHO field measurements, respectively. © 2015 IEEE.

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