Absence of soil frost affects plant-soil interactions in temperate grasslands

Schuerings J., Beierkuhnlein C., Grant K., Jentsch A., Malyshev A., Penuelas J., Sardans J., Kreyling J. (2013) Absence of soil frost affects plant-soil interactions in temperate grasslands. Plant and Soil. 371: 559-572.
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Doi: 10.1007/s11104-013-1724-y

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Background and aims: Intermittently frozen ground in winter is expected to disappear over large areas in the temperate zone due to ongoing climate warming. The lack of soil frost influences plant soil interactions and needs to be studied in more detail. Methods: Winter soil frost was avoided by belowground heating wires in a field experiment over two subsequent winters in a temperate grassland. Soil respiration, soil nitrogen availability and plant performance (aboveground biomass, root length at two depth levels, greenness, nutrient content) were compared between "no-frost" and reference plots which underwent repeated freeze-thaw cycles in both winters. Results: Soil respiration increased in the "no-frost" treatment during the warming phase (+291 %). N-availability in the upper 10 cm of the soil profile was not affected, possibly due to increased plant N accumulation during winter (+163 %), increased plant N concentration (+18 %) and increased biomass production (+31.5 %) in the growing season. Translocation of roots into deeper soil layers without changes in total root length in response to the "no-frost" treatment, however, may be a sign of nutrient leaching. Conclusions: The cumulative effect on carbon cycling due to warmer soils therefore depends on the balance between increased winter carbon loss due to higher soil biotic activity and enhanced plant productivity with higher nutrient accumulation in the growing season. © 2013 Springer Science+Business Media Dordrecht.

Llegeix més

Volatile organic compounds in the western Mediterranean basin: Urban and rural winter measurements during the DAURE campaign

Seco R., Penuelas J., Filella I., Llusia J., Schallhart S., Metzger A., Muller M., Hansel A. (2013) Volatile organic compounds in the western Mediterranean basin: Urban and rural winter measurements during the DAURE campaign. Atmospheric Chemistry and Physics. 13: 4291-4306.
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Doi: 10.5194/acp-13-4291-2013

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Atmospheric volatile organic compounds (VOCs) have key environmental and biological roles, but little is known about the daily VOC mixing ratios in Mediterranean urban and natural environments. We measured VOC mixing ratios concurrently at an urban and a rural site during the winter DAURE campaign in the northeastern Iberian Peninsula, by means of PTR-MS at both locations: a PTR-Quad-MS at the urban site and a PTR-ToF-MS at the rural site. All VOC mixing ratios measured were higher at the urban site (e.g. acetaldehyde, isoprene, benzene, and toluene with averages up to 1.68, 0.31, 0.58 and 2.71 ppbv, respectively), with the exception of some short-chain oxygenated VOCs such as acetone (with similar averages of 0.7-1.6 ppbv at both sites). The average diurnal pattern also differed between the sites. Most of the VOCs at the urban location showed their highest mixing ratios in the morning and evening. These peaks coincided with traffic during rush hour, the main origin of most of the VOCs analyzed. Between these two peaks, the sea breeze transported the urban air inland, thus helping to lower the VOC loading at the urban site. At the rural site, most of the measured VOCs were advected by the midday sea breeze, yielding the highest daily VOC mixing ratios (e.g. acetaldehyde, isoprene, benzene, and toluene with averages up to 0.65, 0.07, 0.19, and 0.41 ppbv, respectively). Only biogenic monoterpenes showed a clear local origin at this site. In addition, the concentrations of fine particulate matter observed at both sites, together with the synoptic meteorological conditions and radio-sounding data, allowed the identification of different atmospheric scenarios that had a clear influence on the measured VOC mixing ratios. These results highlight the differences and relationships in VOC mixing ratios between nearby urban and rural areas in Mediterranean regions. Further research in other urban-rural areas is warranted to better understand the urban-rural influence on atmospheric VOC mixing ratios under different atmospheric conditions. © 2013 Author(s).

Llegeix més

Geographical patterns of congruence and incongruence between correlative species distribution models and a process-based ecophysiological growth model

Serra-Diaz J.M., Keenan T.F., Ninyerola M., Sabate S., Gracia C., Lloret F. (2013) Geographical patterns of congruence and incongruence between correlative species distribution models and a process-based ecophysiological growth model. Journal of Biogeography. 40: 1928-1938.
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Doi: 10.1111/jbi.12142

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Aim: Our aim was to map the climate dependence of tree species distributions (probability of occurrence) and forest growth (net primary productivity) by comparing the congruence and incongruence between correlative and process-based modelling approaches. Location: Iberian Peninsula, south-western Europe. Methods: We used forest inventory data for three widespread tree species (Quercus ilex, Pinus halepensis and Pinus sylvestris) to model climatic suitability with an ensemble of seven correlative species distribution models (using biomod). We then simulated forest net primary productivity (NPP) as a surrogate of forest growth for forests of each species using an ecophysiological process-based model (gotilwa+) along a gradient of climatic suitability. The spatial distribution of the growth estimates was then compared with that of the suitability estimates, and robust regression was used to classify regions in terms of model congruence. Results: Quercus ilex and P. sylvestris both showed a positive relationship between forest NPP and climatic suitability. The main discrepancies were found in the north of the peninsula, where there was high potential forest growth but low climate suitability. Low forest-growth estimates in areas of high suitability only appeared for P. sylvestris in southern montane regions. Pinus halepensis always showed a negative relationship between estimated growth and climatic suitability. The analysis of other ecophysiological parameters (mean leaf life and leaf area index) suggests that this tree species has different physiological strategies that allow differential growth rates in areas of low suitability. Main conclusions: We found that the relationship between estimated growth and distribution varies strongly in different areas and species. Mapping the incongruences between the predicted climatic suitability and growth allowed us to identify regions where other factors (e.g. biotic interactions) may be more significant than the physiological limits on growth. We show that new insights into species distributions can be gained from mapping the differences between correlative and process-based models. © 2013 John Wiley & Sons Ltd.

Llegeix més

Behavioural adjustments for a life in the city

Sol D., Lapiedra O., Gonzalez-Lagos C. (2013) Behavioural adjustments for a life in the city. Animal Behaviour. 85: 1101-1112.
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Doi: 10.1016/j.anbehav.2013.01.023

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While human-induced rapid environmental changes are putting many organisms at risk of extinction, others are doing better than ever. This raises the question of why organisms differ in their tolerance to environmental alterations. Here, we ask whether and how behavioural adjustments assist animals in dealing with the urbanization process, one of the primary causes of biodiversity loss and biotic homogenization. Based on a literature review, we present both theoretical and empirical arguments to show that behavioural adjustments to urban habitats are widespread and that they may potentially be important in facilitating resource use, avoiding disturbances and enhancing communication. While a growing number of studies report behavioural differences between urban and nonurban animals, very few studies directly address the underlying mechanisms. In some cases, the changes in behaviour occur very rapidly and involve learning, and hence can be attributed to behavioural plasticity. In other cases, however, it cannot be ruled out that behavioural differences between urban and nonurban animals result from natural selection or nonrandom sorting of individuals by behavioural traits that affect dispersal, habitat selection or establishment. Because the urbanization process is expected to continue to threaten biodiversity in the near future, there is some urgency to improve our understanding of the mechanisms through which behaviour helps animals to cope with such environmental alterations. © 2013 The Association for the Study of Animal Behaviour.

Llegeix més

Multi-generational long-distance migration of insects: Studying the painted lady butterfly in the Western Palaearctic

Stefanescu C., Páramo F., Åkesson S., Alarcón M., Ávila A., Brereton T., Carnicer J., Cassar L.F., Fox R., Heliölä J., Hill J.K., Hirneisen N., Kjellén N., Kühn E., Kuussaari M., Leskinen M., Liechti F., Musche M., Regan E.C., Reynolds D.R., Roy D.B., Ryrholm N., Schmaljohann H., Settele J., Thomas C.D., van Swaay C., Chapman J.W. (2013) Multi-generational long-distance migration of insects: Studying the painted lady butterfly in the Western Palaearctic. Ecography. 36: 474-486.
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Doi: 10.1111/j.1600-0587.2012.07738.x

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Long-range, seasonal migration is a widespread phenomenon among insects, allowing them to track and exploit abundant but ephemeral resources over vast geographical areas. However, the basic patterns of how species shift across multiple locations and seasons are unknown in most cases, even though migrant species comprise an important component of the temperate-zone biota. The painted lady butterfly Vanessa cardui is such an example; a cosmopolitan continuously-brooded species which migrates each year between Africa and Europe, sometimes in enormous numbers. The migration of 2009 was one of the most impressive recorded, and thousands of observations were collected through citizen science programmes and systematic entomological surveys, such as high altitude insect-monitoring radar and ground-based butterfly monitoring schemes. Here we use V. cardui as a model species to better understand insect migration in the Western Palaearctic, and we capitalise on the complementary data sources available for this iconic butterfly. The migratory cycle in this species involves six generations, encompassing a latitudinal shift of thousands of kilometres (up to 60 degrees of latitude). The cycle comprises an annual poleward advance of the populations in spring followed by an equatorward return movement in autumn, with returning individuals potentially flying thousands of kilometres. We show that many long-distance migrants take advantage of favourable winds, moving downwind at high elevation (from some tens of metres from the ground to altitudes over 1000 m), pointing at strong similarities in the flight strategies used by V. cardui and other migrant Lepidoptera. Our results reveal the highly successful strategy that has evolved in these insects, and provide a useful framework for a better understanding of long-distance seasonal migration in the temperate regions worldwide. © 2012 The Authors. Journal compilation © 2012 Nordic Society Oikos.

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The ecology of seed dispersal by small rodents: A role for predator and conspecific scents

Sunyer P., Muñoz A., Bonal R., Espelta J.M. (2013) The ecology of seed dispersal by small rodents: A role for predator and conspecific scents. Functional Ecology. 27: 1313-1321.
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Doi: 10.1111/1365-2435.12143

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Seed-caching rodents play a key role in the ecology of seed dispersal by not only consuming but also dispersing seeds. Rodent foraging behaviour is usually framed within optimal models, which predict that their decisions should maximize food intake and minimize foraging costs. Although predation risk and seed pilferage by conspecifics have been envisaged as two potential costs, their relevance for seed-caching behaviour and seed dispersal has barely been addressed. To test the effect of predation and pilferage risk on the patterns of seed predation/dispersal by rodents, we performed a field experiment using a tri-trophic-level model (plant-mice-carnivore; Quercus spp-Apodemus sylvaticus-Genetta genetta) and the scents of the predator and conspecifics as direct cues. The behaviour of mice was analysed with video cameras set for continuous recording on consecutive nights, and we used tagged acorns to assess the patterns of acorn predation and dispersal. Our results revealed that rodents were able to discriminate between the scents of genet and conspecifics and modified their seed dispersal behaviour accordingly. Mice spent more time 'sniffing' in rodent cages than in genet cages, where they displayed more 'vigilance and freezing' behaviours. In sites with mice scents, acorns were dispersed at shorter distances and were less predated. Conversely, in sites with genet scents acorn removal was delayed. These results show that chemosensory information on predators and conspecifics influences the foraging decisions of seed-caching rodents over short spatial and temporal scales. This might entail cascading effects on the regeneration of plants. In sites where rodents perceive the risk of predation, inefficient foraging behaviour may result in less successful seed dispersal. Conversely, the detection of conspecific scents may increase dispersal efficiency and seedling recruitment. Ultimately, the relationships between two distant levels in trophic webs (plants-carnivores) appear intricate, since carnivores may affect seed dispersal by changing the foraging behaviour of their prey (the seed disperser). This indirect relationship should be considered as a new dimension of the ecology of seed dispersal by small rodents. © 2013 British Ecological Society.

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A data assimilation framework for constraining upscaled cropland carbon flux seasonality and biometry with MODIS

Sus O., Heuer M.W., Meyers T.P., Williams M. (2013) A data assimilation framework for constraining upscaled cropland carbon flux seasonality and biometry with MODIS. Biogeosciences. 10: 2451-2466.
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Doi: 10.5194/bg-10-2451-2013

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Agroecosystem models are strongly dependent on information on land management patterns for regional applications. Land management practices play a major role in determining global yield variability, and add an anthropogenic signal to the observed seasonality of atmospheric CO2 concentrations. However, there is still little knowledge on spatial and temporal variability of important farmland activities such as crop sowing dates, and thus these remain rather crudely approximated within carbon cycle studies. In this study, we present a framework allowing for spatiotemporally resolved simulation of cropland carbon fluxes under observational constraints on land management and canopy greenness. We apply data assimilation methodology in order to explicitly account for information on sowing dates and model leaf area index. MODIS 250 m vegetation index data were assimilated both in batch-calibration for sowing date estimation and sequentially for improved model state estimation, using the ensemble Kalman filter (EnKF), into a crop carbon mass balance model (SPAc). In doing so, we are able to quantify the multiannual (2000-2006) regional carbon flux and biometry seasonality of maize-soybean crop rotations surrounding the Bondville Ameriflux eddy covariance site, averaged over 104 pixel locations within the wider area. (1) Validation at the Bondville site shows that growing season C cycling is simulated accurately with MODIS-derived sowing dates, and we expect that this framework allows for accurate simulations of C cycling at locations for which ground-truth data are not available. Thus, this framework enables modellers to simulate current (i.e. last 10 yr) carbon cycling of major agricultural regions. Averaged over the 104 field patches analysed, relative spatial variability for biometry and net ecosystem exchange ranges from ∼ 7 % to ∼ 18 %. The annual sign of netbiome productivity is not significantly different from carbon neutrality. (2) Moreover, observing carbon cycling at one single field with its individual sowing pattern is not sufficient to constrain large-scale agroecosystem carbon flux seasonality. Study area average growing season length is 20 days longer than observed at Bondville, primarily because of an earlier estimated start of season. (3) For carbon budgeting, additional information on cropland soil management and belowground carbon cycling has to be considered, as such constraints are not provided by MODIS. © Author(s) 2013.

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Identification of new sources of resistance to Striga gesnerioides in cowpea germplasm

Tignegre J.-B.S., Ouedraogo J.T., Melis R., Tongoona P., Sibiya J., Makanda I., Drabo I. (2013) Identification of new sources of resistance to Striga gesnerioides in cowpea germplasm. Plant Breeding. 132: 330-336.
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Doi: 10.1111/pbr.12055

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There have been reports of breakdown of striga resistance in previously resistant cowpea cultivars in Burkina Faso. This could be attributed to new striga races emerging or to an increase in the aggressiveness of current striga races. Therefore, cowpea genotypes were evaluated in fields infested with S. gesnerioides at three striga hot spots in Burkina Faso and in pots under artificial infestation with striga races SR 1, SR 5 and SR Kp to identify new, adapted and striga-resistant sources. Cowpea genotypes showed differential reactions for striga resistance over sites and for striga races in pot experiments, indicating differences in the races involved, and SR Kp was reported as a new race. Resistant sources conferring site-specific or multiple striga-race resistance were identified. Genotypes 58-57, Sanga 2, IT84S-2049, IT98K-205-8, IT93K-693-2, KVx771-10, KVx775-33-2, KVx61-1, Gorom local, Mouride and Melakh conferred resistance to all three striga races. These genotypes are potential donor parents for breeding new, adapted and striga-resistant genotypes. Cowpea landraces including Moussa local and Niaogo local with farmers' preferred traits were susceptible and need improvement for striga resistance. © 2013 Blackwell Verlag GmbH.

Llegeix més

Feeding preferences of the legume pod borer Maruca vitrata (Lepidoptera: Crambidae) larvae and suitability of different flower parts for larval development

Traore F., Dabire-Binso C.L., Ba N.M., Sanon A., Pittendrigh B.R. (2013) Feeding preferences of the legume pod borer Maruca vitrata (Lepidoptera: Crambidae) larvae and suitability of different flower parts for larval development. International Journal of Tropical Insect Science. 33: 107-113.
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Doi: 10.1017/S1742758413000088

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With the advent of transgenic Bacillus thuringiensis (Bt)-cowpea, there is a need to identify the feeding preferences of Maruca vitrata Fab. to determine in which component of the plant the expression of the toxin needs to be the highest to ensure the greatest efficacy of insecticidal Bt proteins. In the current study, we examined the feeding preferences of M. vitrata larvae in a naturally infested cowpea field. We also tested, in the laboratory, the suitability of different flower components for the larval development of M. vitrata. Our results indicate that in the field, all types of flowers, regardless of their age, were infested with M. vitrata larvae. The reproductive organs, in the flowers, were the preferred feeding diet for the larvae. Laboratory bioassays confirmed that the reproductive organs were the optimal tissues for M. vitrata larval development. The implications of these findings for transgenic Bt-cowpea are discussed. Copyright © icipe 2013.

Llegeix més

Island biogeography of mutualistic interaction networks

Trojelsgaard K., Baez M., Espadaler X., Nogales M., Oromi P., Roche F.L., Olesen J.M. (2013) Island biogeography of mutualistic interaction networks. Journal of Biogeography. 40: 2020-2031.
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Doi: 10.1111/jbi.12165

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Aim: The seminal theory of island biogeography, based on changing rates of immigration and extinction, should be seen in a geological context, as an island's maturity influences the richness of its biota. Here, we develop an island biogeography of biotic interactions, recognizing that, besides species richness, biodiversity also encompasses the multitude of interactions among species. By sampling interactions between plants and pollinators across the Canarian archipelago, we illustrate how the local richness, specialization and endemism of biotic interactions vary with island age and area. Location: Canary Islands (27.62° N-29.42° N and 13.33° W-18.17° W). Methods: On five islands, covering the full age range of the archipelago, plant-pollinator interactions were catalogued and their strength estimated. Network parameters (e.g. interaction richness and specialization) and the number of single-island interactions (equivalent to single-island endemics) were estimated from interaction matrices and related to island area and age. Results: Plant species richness, interaction richness and average degree of specialization of pollinator species showed hump-shaped relationships with island age. Pollinator richness varied with island area and plant richness. Plant specialization increased with island age, and the proportion of single-island interactions (pSII) exhibited a U-shaped relationship with age. Main conclusions: The previously reported hump-shaped relationship between species richness and island age, both on the scale of islands and of habitats, was confirmed for plant species in local networks. Both plants and pollinators were more generalized on the youngest island, which may be due to a predominance of generalist colonists. Pollinator specialization peaked on mid-aged islands, whereas plants showed the highest specialization on old islands, potentially reflecting their different life histories. The U-shaped relationship between the proportion of single-island interactions and island age might be explained by (1) young islands having a high proportion of unique interactions, due to interactions between generalists, and (2) old islands having unique interactions due to an accumulation of unique pairwise interactions that have evolved through time. Thus, island age - which not only captures time per se, but also the geomorphological changes of islands - may act as a regional driver of local network structure, and so the contemporary networks we observed across the Canarian archipelago illustrate the development of a network through geological time. © 2013 John Wiley & Sons Ltd.

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