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Optimising long-term monitoring projects for species distribution modelling: How atlas data may help

Aizpurua O., Paquet J.-Y., Brotons L., Titeux N. (2014) Optimising long-term monitoring projects for species distribution modelling: How atlas data may help. Ecography. : 0-0.
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Doi: 10.1111/ecog.00749

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Long-term biodiversity monitoring data are mainly used to estimate changes in species occupancy or abundance over time, but they may also be incorporated into predictive models to document species distributions in space. Although changes in occupancy or abundance may be estimated from a relatively limited number of sampling units, small sample size may lead to inaccurate spatial models and maps of predicted species distributions. We provide a methodological approach to estimate the minimum sample size needed in monitoring projects to produce accurate species distribution models and maps. The method assumes that monitoring data are not yet available when sampling strategies are to be designed and is based on external distribution data from atlas projects. Atlas data are typically collected in a large number of sampling units during a restricted timeframe and are often similar in nature to the information gathered from long-term monitoring projects. The large number of sampling units in atlas projects makes it possible to simulate a broad gradient of sample sizes in monitoring data and to examine how the number of sampling units influences the accuracy of the models. We apply the method to several bird species using data from a regional breeding bird atlas. We explore the effect of prevalence, range size and habitat specialization of the species on the sample size needed to generate accurate models. Model accuracy is sensitive to particularly small sample sizes and levels off beyond a sufficiently large number of sampling units that varies among species depending mainly on their prevalence. The integration of spatial modelling techniques into monitoring projects is a cost-effective approach as it offers the possibility to estimate the dynamics of species distributions in space and over time. We believe our innovative method will help in the sampling design of future monitoring projects aiming to achieve such integration. © 2014 The Authors.

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Soil enzymes associated with carbon and nitrogen cycling in invaded and native secondary forests of northwestern Argentina

Aragon R., Sardans J., Penuelas J. (2014) Soil enzymes associated with carbon and nitrogen cycling in invaded and native secondary forests of northwestern Argentina. Plant and Soil. : 0-0.
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Doi: 10.1007/s11104-014-2192-8

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Background and aims Alien success has frequently been associated with changes in the concentrations of soil nutrients. We aim to investigate the effects of plant invasion on soil nutrients, potential enzyme activity and litter elemental composition and stoichiometry. Methods We compared stands of secondary forest invaded by Ligustrum lucidum and those dominated by natives, and performed litter chemical analyses on 3 native and 2 exotic tree species. Results Soils of invaded sites had 20 and 30 % increase in β-glucosidase and alkaline phosphatase activity, higher Olsen-phosphorus (P) and potassium (K) concentrations and lower nitrogen (N) concentration and N:P, N:K and ammonium:Olsen-P ratios. Invaded and non-invaded sites differed in their overall nutrient composition and enzyme activity. Natives and exotics differed in nine of the 16 litter elemental composition and stoichiometry variables analyzed. Conclusions The low N:P ratio in litter, the decrease in soil N in invaded stands and the low N concentration of exotics suggest that N is the limiting nutrient and that exotic success is related to higher N uptake and use efficiency. The higher investment in the acquisition of soil resources, higher nutrient uptake and use efficiency of limiting nutrients contribute to the success of exotics in this subtropical forest. © 2014 Springer International Publishing Switzerland.

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Composition and habitat use of small mammals in old-growth mountain forests

Arnan X., Comas L., Gracia M., Retana J. (2014) Composition and habitat use of small mammals in old-growth mountain forests. Journal of Natural History. 48: 481-494.
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Doi: 10.1080/00222933.2013.800611

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Old-growth mountain forests in the Pyrenees have natural gap dynamics, a well-developed shrub layer and a large amount of dead wood. Small mammal communities in two types of old-growth forests, silver fir and mountain pine, were studied in July and September in 2006 and 2007. Four species were trapped: bank vole (Myodes glareolus), wood mouse (Apodemus sylvaticus), garden dormouse (Eliomys quercinus) and common shrew (Sorex araneus). Bank voles and wood mice were most commonly trapped (78% of all captures). There were no differences in community composition in the two forest types, although the bank vole was more often captured in the silver fir than in the mountain pine forest. Mammals were more frequently captured at trap stations with high shrub cover, high tree regeneration cover and low herbaceous cover. Our results show that forest structure and, to a lesser extent, forest type determine small mammal community structure, and specifically fine-scale occurrence patterns, in these old-growth forests. © 2013 Taylor & Francis.

Llegeix més

Female reproductive success in gynodioecious Thymus vulgaris: Pollen versus nutrient limitation and pollinator foraging behaviour

Arnan X., Escola A., Rodrigo A., Bosch J. (2014) Female reproductive success in gynodioecious Thymus vulgaris: Pollen versus nutrient limitation and pollinator foraging behaviour. Botanical Journal of the Linnean Society. 175: 395-408.
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Doi: 10.1111/boj.12173

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Gynodioecy is a dimorphic breeding system in which female individuals coexist with hermaphroditic individuals in the same population. Females only contribute to the next generation via ovules, and many studies have shown that they are usually less attractive than hermaphrodites to pollinators. Several mechanisms have been proposed to explain how females manage to persist in populations despite these disadvantages. The 'resource reallocation hypothesis' (RRH) states that females channel resources not invested in pollen production and floral advertisement towards the production of more and/or larger seeds. We investigated pollination patterns and tested the RRH in a population of Thymus vulgaris. We measured flower display, flower size, nectar production, visitation rates, pollinator constancy and flower lifespan in the two morphs. In addition, we measured experimentally the effects of pollen and resource addition on female reproductive success (fruit set, seed set, seed weight) of the two morphs. Despite lower investment in floral advertisement, female individuals were no less attractive to pollinators than hermaphrodites on a per flower basis. Other measures of pollinator behaviour (number of flowers visited per plant, morph preference and morph constancy) also showed that pollinators did not discriminate against female flowers. In addition, stigma receptivity was longer in female flowers. Accordingly, and contrary to most studies on gynodioecious species, reproductive success of females was not pollen limited. Instead, seed production was pollen limited in hermaphrodites, suggesting low levels of cross-pollination in hermaphrodites. Seed production was resource limited in hermaphrodites, but not in females, thus providing support for the RRH. © 2014 The Linnean Society of London.

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Interactively modelling land profitability to estimate European agricultural and forest land use under future scenarios of climate, socio-economics and adaptation

Audsley E., Trnka M., Sabate S., Maspons J., Sanchez A., Sandars D., Balek J., Pearn K. (2014) Interactively modelling land profitability to estimate European agricultural and forest land use under future scenarios of climate, socio-economics and adaptation. Climatic Change. : 0-0.
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Doi: 10.1007/s10584-014-1164-6

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Studies of climate change impacts on agricultural land use generally consider sets of climates combined with fixed socio-economic scenarios, making it impossible to compare the impact of specific factors within these scenario sets. Analysis of the impact of specific scenario factors is extremely difficult due to prohibitively long run-times of the complex models. This study produces and combines metamodels of crop and forest yields and farm profit, derived from previously developed very complex models, to enable prediction of European land use under any set of climate and socio-economic data. Land use is predicted based on the profitability of the alternatives on every soil within every 10' grid across the EU. A clustering procedure reduces 23,871 grids with 20+ soils per grid to 6,714 clusters of common soil and climate. Combined these reduce runtime 100 thousand-fold. Profit thresholds define land as intensive agriculture (arable or grassland), extensive agriculture or managed forest, or finally unmanaged forest or abandoned land. The demand for food as a function of population, imports, food preferences and bioenergy, is a production constraint, as is irrigation water available. An iteration adjusts prices to meet these constraints. A range of measures are derived at 10' grid-level such as diversity as well as overall EU production. There are many ways to utilise this ability to do rapid What-If analysis of both impact and adaptations. The paper illustrates using two of the 5 different GCMs (CSMK3, HADGEM with contrasting precipitation and temperature) and two of the 4 different socio-economic scenarios ("We are the world", "Should I stay or should I go" which have contrasting demands for land), exploring these using two of the 13 scenario parameters (crop breeding for yield and population) . In the first scenario, population can be increased by a large amount showing that food security is far from vulnerable. In the second scenario increasing crop yield shows that it improves the food security problem. © 2014 Springer Science+Business Media Dordrecht.

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Species distribution models and impact factor growth in environmental journals: Methodological fashion or the attraction of global change science

B L. (2014) Species distribution models and impact factor growth in environmental journals: Methodological fashion or the attraction of global change science. PLoS ONE. 9: 0-0.
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Doi: 10.1371/journal.pone.0111996

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In this work, I evaluate the impact of species distribution models (SDMs) on the current status of environmental and ecological journals by asking the question to which degree development of SDMs in the literature is related to recent changes in the impact factors of ecological journals. The hypothesis evaluated states that research fronts are likely to attract research attention and potentially drive citation patterns, with journals concentrating papers related to the research front receiving more attention and benefiting from faster increases in their impact on the ecological literature. My results indicate a positive relationship between the number of SDM related articles published in a journal and its impact factor (IF) growth during the period 2000-09. However, the percentage of SDM related papers in a journal was strongly and positively associated with the percentage of papers on climate change and statistical issues. The results support the hypothesis that global change science has been critical in the development of SDMs and that interest in climate change research in particular, rather than the usage of SDM per se, appears as an important factor behind journal IF increases in ecology and environmental sciences. Finally, our results on SDM application in global change science support the view that scientific interest rather than methodological fashion appears to be the major driver of research attraction in the scientific literature.

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The combined effects of a long-term experimental drought and an extreme drought on the use of plant-water sources in a Mediterranean forest

Barbeta A., Mejia-Chang M., Ogaya R., Voltas J., Dawson T.E., Penuelas J. (2014) The combined effects of a long-term experimental drought and an extreme drought on the use of plant-water sources in a Mediterranean forest. Global Change Biology. : 0-0.
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Doi: 10.1111/gcb.12785

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Vegetation in water-limited ecosystems relies strongly on access to deep water reserves to withstand dry periods. Most of these ecosystems have shallow soils over deep groundwater reserves. Understanding the functioning and functional plasticity of species-specific root systems and the patterns of or differences in the use of water sources under more frequent or intense droughts is therefore necessary to properly predict the responses of seasonally dry ecosystems to future climate. We used stable isotopes to investigate the seasonal patterns of water uptake by a sclerophyll forest on sloped terrain with shallow soils. We assessed the effect of a long-term experimental drought (12 years) and the added impact of an extreme natural drought that produced widespread tree mortality and crown defoliation. The dominant species, Quercus ilex, Arbutus unedo and Phillyrea latifolia, all have dimorphic root systems enabling them to access different water sources in space and time. The plants extracted water mainly from the soil in the cold and wet seasons but increased their use of groundwater during the summer drought. Interestingly, the plants subjected to the long-term experimental drought shifted water uptake toward deeper (10-35 cm) soil layers during the wet season and reduced groundwater uptake in summer, indicating plasticity in the functional distribution of fine roots that dampened the effect of our experimental drought over the long term. An extreme drought in 2011, however, further reduced the contribution of deep soil layers and groundwater to transpiration, which resulted in greater crown defoliation in the drought-affected plants. This study suggests that extreme droughts aggravate moderate but persistent drier conditions (simulated by our manipulation) and may lead to the depletion of water from groundwater reservoirs and weathered bedrock, threatening the preservation of these Mediterranean ecosystems in their current structures and compositions.

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Contribution of ecosystem services to air quality and climate change mitigation policies: The case of urban forests in Barcelona, Spain

Baro F., Chaparro L., Gomez-Baggethun E., Langemeyer J., Nowak D.J., Terradas J. (2014) Contribution of ecosystem services to air quality and climate change mitigation policies: The case of urban forests in Barcelona, Spain. Ambio. 43: 466-479.
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Doi: 10.1007/s13280-014-0507-x

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Mounting research highlights the contribution of ecosystem services provided by urban forests to quality of life in cities, yet these services are rarely explicitly considered in environmental policy targets. We quantify regulating services provided by urban forests and evaluate their contribution to comply with policy targets of air quality and climate change mitigation in the municipality of Barcelona, Spain. We apply the i-Tree Eco model to quantify in biophysical and monetary terms the ecosystem services "air purification," "global climate regulation,"and the ecosystem disservice "air pollution" associated with biogenic emissions. Our results show that the contribution of urban forests regulating services to abate pollution is substantial in absolute terms, yet modest when compared to overall city levels of air pollution and GHG emissions. We conclude that in order to be effective, green infrastructure-based efforts to offset urban pollution at the municipal level have to be coordinated with territorial policies at broader spatial scales. ©The Author(s) 2014.

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Local vegetation trends in the sahel of mali and senegal using long time series FAPAR satellite products and field measurement (1982-2010)

Brandt M., Verger A., Diouf A.A., Baret F., Samimi C. (2014) Local vegetation trends in the sahel of mali and senegal using long time series FAPAR satellite products and field measurement (1982-2010). Remote Sensing. 6: 2408-2434.
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Doi: 10.3390/rs6032408

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Local vegetation trends in the Sahel of Mali and Senegal from Geoland Version 1 (GEOV1) (5 km) and the third generation Global Inventory Modeling and Mapping Studies (GIMMS3g) (8 km) Fraction of Absorbed Photosynthetically Active Radiation (FAPAR) time series are studied over 29 years. For validation and interpretation of observed greenness trends, two methods are applied: (1) a qualitative approach using in-depth knowledge of the study areas and (2) a quantitative approach by time series of biomass observations and rainfall data. Significant greening trends from 1982 to 2010 are consistently observed in both GEOV1 and GIMMS3g FAPAR datasets. Annual rainfall increased significantly during the observed time period, explaining large parts of FAPAR variations at a regional scale. Locally, GEOV1 data reveals a heterogeneous pattern of vegetation change, which is confirmed by long-term ground data and site visits. The spatial variability in the observed vegetation trends in the Sahel area are mainly caused by varying tree-and land-cover, which are controlled by human impact, soil and drought resilience. A large proportion of the positive trends are caused by the increment in leaf biomass of woody species that has almost doubled since the 1980s due to a tree cover regeneration after a dry-period. This confirms the re-greening of the Sahel, however, degradation is also present and sometimes obscured by greening. GEOV1 as compared to GIMMS3g made it possible to better characterize the spatial pattern of trends and identify the degraded areas in the study region. © 2014 by the authors; licensee MDPI, Basel, Switzerland.

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Evaluating the importance of trophobiosis in a Mediterranean ant community: a stable isotope analysis

Brewitt K., Pinol J., Werner C., Beyschlag W., Espadaler X., Perez Hidalgo N., Platner C. (2014) Evaluating the importance of trophobiosis in a Mediterranean ant community: a stable isotope analysis. Insectes Sociaux. : 0-0.
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Doi: 10.1007/s00040-014-0375-1

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Trophobiosis between aphids (Aphididae, Hemiptera) and ants (Formicidae, Hymenoptera) is considered to provide an important source of nutrition for ants by aphid honeydew and aphids themselves used as prey. However, little is known about nutrient fluxes and the relative importance of trophobiosis for different ant species. Combining direct contact observations between ants and aphids with stable isotope analyses of distinct multitrophic sample sets (soil, plant, aphid, and ant), we aimed at disentangling the importance of trophobiosis in a Mediterranean food web and possible feedbacks on the functional diversity of ants in a species-rich organic Citrus plantation. We analyzed δ13C- and δ15N-values of sample sets for fertilized and natural soil, using the fertilizer as natural isotope label. The results showed trophic relationships between 18 host plant species, 22 aphid species, and 7 ant species. Direct observation revealed at least 40 different plant–aphid combinations and 25 aphid–ant combinations with a marked range of δ15N-values. However, the δ13C and δ15N isotope ratios still reflected the trophic levels. A significant correlation occurred between the isotope ratios of aphids and their host plants. However, no relationship was found between aphids and ants or between plants and ants revealing that many ant species do not exhibit a close relationship with their trophobiotic partners. Isotopic data allowed us to separate ant species into trophic functional groups and showed the relevance of other food resources. The applied fertilizer shifted the isotopic baseline for the whole trophic system. By combining the stable isotope analysis with the exact origin of the samples, we avoided a misleading interpretation of the high isotopic range of species. Thus, we emphasize the importance of considering a baseline in stable isotope food web studies.

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