The spatial level of analysis affects the patterns of forest ecosystem services supply and their relationships

Roces-Díaz, J.V., Vayreda, J., Banqué-Casanovas, M., Díaz-Varela, E., Bonet, J.A., Brotons, L., de-Miguel, S., Herrando, S., Martínez-Vilalta, J. (2018) The spatial level of analysis affects the patterns of forest ecosystem services supply and their relationships. Science of the Total Environment. 626: 1270-1283.
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Doi: 10.1016/j.scitotenv.2018.01.150

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Shock and stabilisation following long-term drought in tropical forest from 15 years of litterfall dynamics

Rowland L., da Costa A.C.L., Oliveira A.A.R., Almeida S.S., Ferreira L.V., Malhi Y., Metcalfe D.B., Mencuccini M., Grace J., Meir P. (2018) Shock and stabilisation following long-term drought in tropical forest from 15 years of litterfall dynamics. Journal of Ecology. : 0-0.
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Doi: 10.1111/1365-2745.12931

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Litterfall dynamics in tropical forests are a good indicator of overall tropical forest function, indicative of carbon invested in both photosynthesising tissues and reproductive organs such as flowers and fruits. These dynamics are sensitive to changes in climate, such as drought, but little is known about the long-term responses of tropical forest litterfall dynamics to extended drought stress. We present a 15-year dataset of litterfall (leaf, flower and fruit, and twigs) from the world's only long-running drought experiment in tropical forest. This dataset comprises one of the longest published litterfall time series in natural forest, which allows the long-term effects of drought on forest reproduction and canopy investment to be explored. Over the first 4 years of the experiment, the experimental soil moisture deficit created only a small decline in total litterfall and leaf fall (12% and 13%, respectively), but a very strong initial decline in reproductive litterfall (flowers and fruits) of 54%. This loss of flowering and fruiting was accompanied by a de-coupling of all litterfall patterns from seasonal climate variables. However, following >10 years of the experimental drought, flower and fruiting re-stabilised at levels greater than in the control plot, despite high tree mortality in the drought plot. Litterfall relationships with atmospheric drivers were re-established alongside a strong new apparent trade-off between litterfall and tree growth. Synthesis. We demonstrate that this tropical forest went through an initial shock response during the first 4 years of intense drought, where reproductive effort was arrested and seasonal litterfall patterns were lost. However, following >10 years of experimental drought, this system appears to be re-stabilising at a new functional state where reproduction is substantially elevated on a per tree basis; and there is a new strong trade-off between investment in canopy production and wood production. © 2018 The Authors.

Llegeix més

Drought stress and tree size determine stem CO2 efflux in a tropical forest

Rowland L., da Costa A.C.L., Oliveira A.A.R., Oliveira R.S., Bittencourt P.L., Costa P.B., Giles A.L., Sosa A.I., Coughlin I., Godlee J.L., Vasconcelos S.S., Junior J.A.S., Ferreira L.V., Mencuccini M., Meir P. (2018) Drought stress and tree size determine stem CO2 efflux in a tropical forest. New Phytologist. 218: 1393-1405.
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Doi: 10.1111/nph.15024

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CO2 efflux from stems (CO2_stem) accounts for a substantial fraction of tropical forest gross primary productivity, but the climate sensitivity of this flux remains poorly understood. We present a study of tropical forest CO2_stem from 215 trees across wet and dry seasons, at the world's longest running tropical forest drought experiment site. We show a 27% increase in wet season CO2_stem in the droughted forest relative to a control forest. This was driven by increasing CO2_stem in trees 10–40 cm diameter. Furthermore, we show that drought increases the proportion of maintenance to growth respiration in trees > 20 cm diameter, including large increases in maintenance respiration in the largest droughted trees, > 40 cm diameter. However, we found no clear taxonomic influence on CO2_stem and were unable to accurately predict how drought sensitivity altered ecosystem scale CO2_stem, due to substantial uncertainty introduced by contrasting methods previously employed to scale CO2_stem fluxes. Our findings indicate that under future scenarios of elevated drought, increases in CO2_stem may augment carbon losses, weakening or potentially reversing the tropical forest carbon sink. However, due to substantial uncertainties in scaling CO2_stem fluxes, stand-scale future estimates of changes in stem CO2 emissions remain highly uncertain. © 2018 The Authors New Phytologist © 2018 New Phytologist Trust

Llegeix més

Zero-sum landscape effects on acorn predation associated with shifts in granivore insect community in new holm oak (Quercus ilex) forests

Ruiz-Carbayo, H., Bonal, R., Pino, J., Espelta, J.M. (2018) Zero-sum landscape effects on acorn predation associated with shifts in granivore insect community in new holm oak (Quercus ilex) forests. Diversity and Distributions. : 0-0.
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Doi: 10.1111/ddi.12701

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Anthropogenic reservoirs of various sizes trap most of the sediment in the Mediterranean Maghreb basin

Sadaoui M., Ludwig W., Bourrin F., Bissonnais Y.L., Romero E. (2018) Anthropogenic reservoirs of various sizes trap most of the sediment in the Mediterranean Maghreb basin. Water (Switzerland). 10: 0-0.
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Doi: 10.3390/w10070927

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The purpose of this study is to obtain a spatially explicit assessment of the impact of reservoirs on natural river sediment fluxes to the sea in theMediterraneanMaghreb Basin (MMB), a region where both mechanical erosion rates and the anthropogenic pressure on surface water resources are high. We combinedmodeling of riverine sediment yields (sediment fluxes divided by the drainage basin area) and water drainage intensities in a 5' × 5' grid point resolution (~10 km × 10 km) with a compilation of existing reservoirs in the area, and calculated sediment trapping based on average water residence time in these reservoirs. A total number of 670 reservoirs could be assembled from various sources (including digitization fromGooglemaps), comprising large-scale, small-scale and hillside reservoirs. 450 of them could be implemented in ourmodeling approach. Our results confirmthat natural sediment yields are clearly above the world average, with the greatest values for Morocco (506 t km-2 year-1), followed by Algeria (328 t km-2 year-1) and by Tunisia (250 t km-2 year-1). Including dams in the downstream routing of suspended sediments to the sea reduces the natural sediment flux in the entireMMB to the sea from 96 to 36Mt km-1 year-1, which corresponds to an average sediment retention of 62%. Trapping rates are highest in the Tunisian basin part, with about 72%, followed by the Algerian (63%) and the Moroccan basin parts (55%). Small reservoirs and hillside reservoirs are quantitatively important in the interception of these sediments compared to large reservoirs. If we only considered the dams included in the widely used Global Reservoir and Dam(GRanD) database which comprisesmainly large reservoirs sediment retention behind dams would account for 36% of the natural suspended particulate matter (SPM) flux to theMediterranean Sea. Our data reveal negative correlation between sediment retention and natural erosion rates among the threeMaghreb countries,which can be explained by the greater difficulties to build dams in steep terrains where natural sediment yields are high. Although the lowest sediment retention rates are found in theMoroccan part of theMMB, it is probably here where riverine sediment starvation has the greatest impacts on coastline dynamics. Understanding the impact of dams and related water infrastructures on riverine sediment dynamics is key in arid zones such as theMMB, where global warming is predicted to cause important changes in the climatic conditions and the water availability. © 2018 by the authors.

Llegeix més

Regeneration of Pinus pinaster Aiton after prescribed fires: Response to burn timing and biogeographical seed provenance across a climatic gradient

Sagra J., Ferrandis P., Plaza-Álvarez P.A., Lucas-Borja M.E., González-Romero J., Alfaro-Sánchez R., De las Heras J., Moya D. (2018) Regeneration of Pinus pinaster Aiton after prescribed fires: Response to burn timing and biogeographical seed provenance across a climatic gradient. Science of the Total Environment. 637-638: 1550-1558.
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Doi: 10.1016/j.scitotenv.2018.05.138

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Prescribed fires are used as a fuel reduction tool, but heat alter microsite conditions affecting the natural regeneration of Mediterranean pine forests. Our study tested the hypothesis that implementing prescription before or after pine seed release may influence the composition of tree communities by changing the regeneration patterns of Pinus pinaster Aiton across a climatic gradient in the eastern Iberian Peninsula. We ran a seed-sowing experiment to analyse the recruitment patterns of this pine species in prescribed-burned stands, in two different biogeographical seed provenances from wetter and drier areas than the local seeding site. Survival of seedlings was through one year, until the end of the first drought and winter period, respectively. >5400 seeds were sown during the study distributed in sixty plots (30 burned, 30 unburned) per site and treatment, with 10 seeding units per plot. General linear models (GLMs) and ANOVA analyses indicated higher performance for the Drier seed provenance in burned areas, whereas a similar performance was recorded in the control area. Control areas showed higher germination and success rates for plant establishment throughout the study period. Total germination and survival after one year were slightly higher, respectively, at northern sites due to massive mortality during summer in the southern stands. At the burned sites, the mean germination time was significantly longer in those seeds sown before fire passage than those sown after fire. Total germination and successful establishment were significantly higher in the individuals sown before the passage of the fire than in those sown after fire. Most of the mortality occurred in summer for the southern stand, while winter was the most constraining period at the northern sites. The understanding of the dynamics in this species' establishment can help managers to perform a better management planning according to the species' ecology. © 2018 Elsevier B.V.

Llegeix més

Vapor–pressure deficit and extreme climatic variables limit tree growth

Sanginés de Cárcer, P., Vitasse, Y., Peñuelas, J., Jassey, V.E.J., Buttler, A., Signarbieux, C. (2018) Vapor–pressure deficit and extreme climatic variables limit tree growth. Global Change Biology. 24: 1108-1122.
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Doi: 10.1111/gcb.13973

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Reply to ‘a comment on the limitations of UAVs in wildlife research – the example of colonial nesting waterbirds’

Sardà-Palomera F., Bota G., Sardà F., Brotons L. (2018) Reply to ‘a comment on the limitations of UAVs in wildlife research – the example of colonial nesting waterbirds’. Journal of Avian Biology. 49: 0-0.
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Doi: 10.1111/jav.01902

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[No abstract available]

Llegeix més

Importance of reporting ancillary site characteristics, and management and disturbance information at ICOS stations

Saunders M., Dengel S., Kolari P., Moureaux C., Montagnani L., Ceschia E., Altimir N., López-Ballesteros A., Marańon-Jimenez S., Acosta M., Klumpp K., Gielen B., De Beeck M.O., Hörtnagl L., Merbold L., Osborne B., Grünwald T., Arrouays D., Boukir H., Saby N., Nicolini G., Papale D., Jones M. (2018) Importance of reporting ancillary site characteristics, and management and disturbance information at ICOS stations. International Agrophysics. 32: 457-469.
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Doi: 10.1515/intag-2017-0040

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There are many factors that influence ecosystem scale carbon, nitrogen and greenhouse gas dynamics, including the inherent heterogeneity of soils and vegetation, anthropogenic management interventions, and biotic and abiotic disturbance events. It is important therefore, to document the characteristics of the soils and vegetation and to accurately report all management activities, and disturbance events to aid the interpretation of collected data, and to determine whether the ecosystem either amplifies or mitigates climate change. This paper outlines the importance of assessing both the spatial and temporal variability of soils and vegetation and to report all management events, the import or export of C or N from the ecosystem, and the occurrence of biotic/abiotic disturbances at ecosystem stations of the Integrated Carbon Observation System, a pan-European research infrastructure. © 2018 Matthew Saunders et al., published by Sciendo 2018.

Llegeix més

Predictable evolution towards larger brains in birds colonizing oceanic islands

Sayol F., Downing P.A., Iwaniuk A.N., Maspons J., Sol D. (2018) Predictable evolution towards larger brains in birds colonizing oceanic islands. Nature Communications. 9: 0-0.
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Doi: 10.1038/s41467-018-05280-8

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Theory and evidence suggest that some selective pressures are more common on islands than in adjacent mainland habitats, leading evolution to follow predictable trends. The existence of predictable evolutionary trends has nonetheless been difficult to demonstrate, mainly because of the challenge of separating in situ evolution from sorting processes derived from colonization events. Here we use brain size measurements of >1900 avian species to reveal the existence of one such trend: increased brain size in island dwellers. Based on sister-taxa comparisons and phylogenetic ancestral trait estimations, we show that species living on islands have relatively larger brains than their mainland relatives and that these differences mainly reflect in situ evolution rather than varying colonization success. Our findings reinforce the view that in some instances evolution may be predictable, and yield insight into why some animals evolve larger brains despite substantial energetic and developmental costs. © 2018, The Author(s).

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