El treball de les competències científiques en les pràctiques de camp d'ecologia

En aquesta comunicació es presenta com es realitzen i avaluen les pràctiques de camp de l'assignatura d'Ecologia (troncal de 2on any) de la Llicenciatura de Biologia i Ciències Ambientals de la UAB. Aquestes pràctiques estan concebudes d'una manera, tant en la seva realització com en la seva avaluació que els hi dona un gran potencial com eina d'aprenentatge tant per continguts i competències pròpies de l'Ecologia com per competències de caràcter científic general més enllà de la pròpia disciplina. Per tant es poden readaptar fàcilment a altres assignatures o llicenciatures del campus que realitzen pràctiques de camp. En aquesta comunicació es fa un anàlisi de quines competències científiques es treballen amb aquestes pràctiques i, com algunes variants introduïdes recentment en la seva avaluació, amb la incorporació de tutories, poden millorar encara més aquest aprenentatge. Especificar l'àmbit d'aplicació El tipus de pràctiques que es presenten en aquesta comunicació i les conclusions extretes poden ser útils per diferents assignatures de diferents llicenciatures de Ciències, en especial aquelles que realitzen pràctiques de camp. Coautors: Unitat d'Ecologia de la UAB

Deposició atmosfèrica en dos alzinars (Quercus ilex L.) del Montseny sotmesos a una exposició contrastada de contaminants de l'àrea barcelonina i vallesana

Consultable des del TDXTítol obtingut de la portada digitalitzad

Incendis forestals : com es recupera la vida animal?

Científics de la UAB i del CREAF han aconseguit demostrar que els canvis que es produeixen en l'estructura vegetal d'un bosc després d'un incendi impliquen també canvis als animals que hi vivien abans de l'incendi. Per validar la seva hipòtesi, els investigadors han estudiat unes de les comunitats animals més sensibles a canvis de la coberta vegetal: les comunitats de formigues.Científicos de la UAB y del CREAF han conseguido demostrar que los cambios que se producen en la estructura vegetal de un bosque después de un incendio implican también cambios en los animales que vivían antes del fuego. Para validar su hipótesis, los investigadores han estudiado unas de las comunidades más sensibles a cambios en la cubierta vegetal: las comunidades de hormigas

És homogènia la recuperació, després del foc, de les comunitats de plantes i de formigues dels boscos de Catalunya?

Es presenten les principals conclusions de diversos estudis amb l'objectiu d'avaluar la resiliència dels boscos de Catalunya després d'un incendi. Es mostra que hi ha un ventall ampli de respostes, que inclou boscos amb una alta resiliència al foc i que recuperen ràpidament l'espècie o espècies arbòries dominants, però també altres boscos en què l'espècie dominant abans del foc no es recupera i són substituïts per altres formacions boscoses o arbustives. La substitució de les espècies dominants i estructuradores del bosc comporta que tota la comunitat de plantes i de formigues que hi viuen tinguin menor resiliència al foc que les dels boscos que mantenen les mateixes espècies dominants d'abans del foc. Aquests resultats impliquen repensar algunes idees sobre les possibles conseqüències dels focs sobre la biodiversitat i quins han de ser els objectius de la gestió de determinades zones cremades.¿Es homogénea la recuperación, tras el incendio, de las comunidades de plantas y de hormigas de los bosques de Cataluña? Se presentan las principales conclusiones de diversos estudios con el objetivo de evaluar la resiliencia de los bosques de Cataluña después de un incendio. Se muestra que existe un amplio abanico de respuestas, que incluye bosques con una alta resiliencia al fuego y que recuperan rápidamente la especie o especies arbóreas dominantes, pero también otros bosques donde la especie dominante no se recupera y son sustituidos por otras formaciones boscosas o arbustivas. La sustitución de estas especies dominantes y estructurantes del bosque supone que toda la comunidad de plantas y de hormigas que viven tengan menor resiliencia al fuego que las de los bosques que mantienen las mismas especies dominantes antes del fuego. Estos resultados implican replantear algunas ideas sobre las posibles consecuencias de los fuegos sobre la biodiversidad y cuáles deben ser los objetivos de gestión de determinadas zonas quemadas.Is homogeneous the postfire recovery of plant and ant communities in Catalan forests? We presents the main conclusions of different studies to analyze the forest resilience in Catalonia after fire. It shows how there is a sufficiently broad range of responses, which include forests with high resilience to fire and quickly recover the species or dominant tree species, but also other forests where before fire, the dominant species are not recovered and then, are replaced by other types of woodland and shrubs. In these cases, the replacement of dominant species and forest structure means that the whole community of plants and ants that live in these forests have less resilience to fire than forests that maintain the same dominant species before fire. These results imply think about the possible consequences of fires on biodiversity and also what should be the objectives of management of certain areas burned

Interaction strength in plant-pollinator networks : Are we using the right measure?

Understanding how ecological networks are assembled is important because network structure reflects ecosystem functioning and stability. Quantitative network analysis incorporates measures of interaction strength as an estimate of the magnitude of the effect of interaction partners on one another. Most plant-pollinator network studies use frequency of interaction between individual pollinators and individual plants (encounter) as a surrogate of interaction strength. However, the number of flowers visited per encounter may strongly vary among pollinator and plant species, and therefore not all encounters are quantitatively equivalent. We sampled plant-pollinator interactions in a Mediterranean scrubland and tested whether using a measure of interaction strength based on the number of flowers visited resulted in changes in species (species strength, interaction species asymmetry, specialization) and network descriptors (nestedness, H2', interaction evenness, plant generality, pollinator generality) compared to the encounter-based measure. Several species (including some of the most abundant ones) showed important changes in species descriptors, notably in specialization. These changes were especially important in plant species with large floral displays, which became less specialized with the visit-based measure of interaction strength. At the network level we found significant changes in all properties analysed. With the encounter-based approach plant generality was much higher than pollinator generality (high specialization asymmetry between trophic levels). However, with the visit-based approach plant generality was greatly reduced so that plants and pollinators had similar levels of generalization. Interaction evenness also decreased strongly with the visit-based approach. We conclude that accounting for the number of flowers visited per encounter provides a more ecologically relevant measure of interaction strength. Our results have important implications for the stability of pollination networks and the evolution of plant-pollinator interactions. The use of a visit-based approach is especially important in studies relating interaction network structure and ecosystem function (pollination and/or exploitation of floral resources)

Spatial variability of hosts, parasitoids and their interactions across a homogeneous landscape

Species assemblages and their interactions vary through space, generating diversity patterns at different spatial scales. Here, we study the local-scale spatial variation of a cavity-nesting bee and wasp community (hosts), their nest associates parasitoids), and the resulting antagonistic network over a continuous and homogeneous habitat. To obtain bee/wasp nests, we placed trap-nests at 25 sites over a 32 km2 area. We obtained 1,541 nests (4,954 cells) belonging to 40 host species and containing 27 parasitoid species. The most abundant host species tended to have higher parasitism rate. Community composition dissimilarity was relatively high for both hosts and parasitoids, and the main component of this variability was species turnover, with a very minor contribution of ordered species loss (nestedness). That is, local species richness tended to be similar across the study area and community composition tended to differ between sites. Interestingly, the spatial matching between host and parasitoid composition was low. Host β-diversity was weakly (positively) but significantly related to geographic distance. On the other hand, parasitoid and host-parasitoid interaction β-diversities were not significantly related to geographic distance. Interaction β-diversity was even higher than host and parasitoid β-diversity, and mostly due to species turnover. Interaction rewiring between plots and between local webs and the regional metaweb was very low. In sum, species composition was rather idiosyncratic to each site causing a relevant mismatch between hosts and parasitoid composition. However, pairs of host and parasitoid species tended to interact similarly wherever they co-occurred. Our results additionally show that interaction β-diversity is better explained by parasitoid than by host β-diversity. We discuss the importance of identifying the sources of variation to understand the drivers of the observed heterogeneity

Crecimiento diametral de la encina (Quercus ilex L.) en un año de abundante precipitación estival : efecto de la irrigación previa y de la fertilización

Diameter growth of 1131 Quercus ilex stems in a closed-canopy stand in the Prades mountains (NE Spain) was measured in 1992, a year of higher than average summer rainfall, to know (i) whether increased water availability in summer resulted in increased stem diameter growth in the same year, and (ii) whether a higher light interception capacity, induced by soil fertilization or previous imgation had a positive effect on tree growth during a year when summer water stress was reduced. Twenty four experimental plots were used in a complete factorial design involving three factors each at two levels: nitrogen fertilization (O and 250 kg Nha), phosphorus fertilization (O and 125 kg P/ha), and imgation (O and 20 mm per week during the warm seasons of 1989, 1990 and 1991). Fertilizers were applied in March 1989, and the same dose repeated in March 1992. Mean stem diameter growth per plot during 1992, averaged over all plots, was 0.83 mm yr-' (k0.09 S.E. among plot means), a growth rate roughly double that of the three preceding years. Thus, Q. ilex is able to use summer rainfall to increase its stem diameter growth in the same year. When all Q. ilex stems were included in the analysis, none of the three experimental factors significantly affected stem diameter growth during 1992. For dominant stems, N fertilization significantly increased mean stem diameter growth by 42%, compared to non-fertilized stems, while P fertilization and previous inigation did not. Thus, increased light interception capacity by itself (as shown by the previously imgated plots) was not conductive to increased stem diameter growth in a year of relatively high water availability. However, increased light interception capacity of the crowns coupled with an enhanced N supply (as in the N-fertiiized plots) did so in dominant trees. This is the first time that a significant effect of N fertilization on stem diameter growth of Q. ilex is reported for the Prades experimental plots.Se midió el crecimiento diametral de 1131 pies de encina en monte bajo de vuelo cerrado en el monte de Poblet (Prades, Tarragona) durante 1992, un año con precipitación estival superior a la media, para averiguar (1) si la mayor disponibilidad estival de agua se traducia en un mayor crecimiento de 10s troncos en el mismo &o, y (2) si una mayor capacidad de intercepción de la luz, como resultado de la imgación previa o de la fertilización del suelo tenia un efecto positivo sobre el crecimiento en un año lluvioso. Se utilizaron venticuatro parcelas en un diseño factorial completo con tres factores a dos niveles cada uno: fertilización con nitrógeno (O y 250 kg N/ha), fertilización con fósforo (O y 125 kg Pha) e irrigación (O y 20 mm semanales durante las estaciones cáíidas de 1989,1990 y 1991). Los fertilizantes se aplicaron en marzo de 1989, y la misma dosis se repitió en marm de 1992. El crecimiento diametral medio durante 1992, promediado sobre todas las parcelas, fue de 0.83 mm año-' ( a . 0 9 E.E. entre parcelas), una tasa aproximadamente el doble que la media de 10s tres años anteriores. La encina es pues capaz de utilizar la precipitación estival para aumentar su crecimiento diametral en el mismo año. Analizando conjuntamente 10s datos de todas las encinas, ninguno de 10s tres factores experimentales tuvo efectos significatives sobre el crecimiento de 1992. Sin embargo, para 10s pies dominantes, la fertilizaci6n con N aumentó significativamente el crecimiento diametral medio en un 42% con respecto a las encinas dominantes que recibieron otros tratamientos, mientras que la fertilización con P y la inigación previa no tuvieron efecto significativa. Por tanto, la mayor capacidad de intercepción de luz por si misrna (como en las parcelas previamente irrigadas) no se tradujo en un mayor crecimiento diametral en un año de buena disponibilidad hídrica. En cambio, la mayor capacidad de intercepción de luz del dosel combinada con una mejor nutrición nitrogenada (como en las parcelas fertilizadas con N) si tuvo tal efecto. Esta es la primera vez que se demuestra que el N es un factor limitante del crecimiento diametral de 10s troncos de las encinas en el monte bajo de las montañas de Prades

Bees exposed to climate change are more sensitive to pesticides

Altres ajuts: acords transformatius de la UABBee populations are exposed to multiple stressors, including land-use change, biological invasions, climate change, and pesticide exposure, that may interact synergistically. We analyze the combined effects of climate warming and sublethal insecticide exposure in the solitary bee Osmia cornuta. Previous Osmia studies show that warm wintering temperatures cause body weight loss, lipid consumption, and fat body depletion. Because the fat body plays a key role in xenobiotic detoxification, we expected that bees exposed to climate warming scenarios would be more sensitive to pesticides. We exposed O. cornuta females to three wintering treatments: current scenario (2007-2012 temperatures), near-future (2021-2050 projected temperatures), and distant-future (2051-2080). Upon emergence in spring, bees were orally exposed to three sublethal doses of an insecticide (Closer, a.i. sulfoxaflor; 0, 4.55 and 11.64 ng a.i./bee). We measured the combined effects of wintering and insecticide exposure on phototactic response, syrup consumption, and longevity. Wintering treatment by itself did not affect winter mortality, but body weight loss increased with increasing wintering temperatures. Similarly, wintering treatment by itself hardly influenced phototactic response or syrup consumption. However, bees wintered at the warmest temperatures had shorter longevity, a strong fecundity predictor in Osmia. Insecticide exposure, especially at the high dose, impaired the ability of bees to respond to light, and resulted in reduced syrup consumption and longevity. The combination of the warmest winter and the high insecticide dose resulted in a 70% longevity decrease. Smaller bees, resulting from smaller pollen-nectar provisions, had shorter longevity suggesting nutritional stress may further compromise fecundity in O. cornuta. Our results show a synergistic interaction between two major drivers of bee declines, and indicate that bees will become more sensitive to pesticides under the current global warming scenario. Our findings have important implications for pesticide regulation and underscore the need to consider multiple stressors to understand bee declines

Collateral effects of beekeeping : impacts on pollen-nectar resources and wild bee communities

Due to the contribution of honey bees (Apis mellifera) to wild flower and crop pollination, beekeeping has traditionally been considered a sustainable practice. However, high honey bee densities may have an impact on local pollen and nectar availability, which in turn may negatively affect other pollinators. This is exacerbated by the ability of honey bees to recruit foragers to highly rewarding flower patches. We measured floral resource consumption in rosemary (Rosmarinus officinalis) and thyme (Thymus vulgaris) in 21 plots located at different distances from apiaries in the scrubland of Garraf Natural Park (Barcelona), and related these measures to visitation rates of honey bees, bumblebees (Bombus terrestris) and other pollinators. In the same plots, we measured flower density, and used pan traps to characterize the wild bee community. Flower resource consumption was largely explained by honey bee visitation and marginally by bumblebee visitation. After accounting for flower density, plots close to apiaries had lower wild bee biomass. This was due to a lower abundance of large bee species, those more likely to be affected by honey bee competition. We conclude that honey bees are the main contributors to pollen/nectar consumption of the two main flowering plants in the scrubland, and that at the densities currently occurring in the park (3.5 hives/km2) the wild bee community is being affected. Our study supports the hypothesis that high honey bee densities may have an impact on other pollinators via competition for flower resources.Wegen des Beitrages der Honigbiene (Apis mellifera) bei der Bestäubung von Wildblumen und Nutzpflanzen wurde die Bienenhaltung traditionell als eine nachhaltige Aktivität angesehen. Indessen können hohe Honigbienendichten Auswirkungen auf die lokale Verfügbarkeit von Nektar und Pollen haben, was wiederum andere Bestäuber negativ beeinflussen könnte. Dies wird verstärkt durch die Fähigkeit der Honigbiene, Sammlerinnen zu lohnenden Sammelstellen zu dirigieren. Im Buschland des Garraf-Naturparks bei Barcelona maßen wir den Verbrauch von Blütenressourcen an Rosmarin (Rosmarinus officinalis) und Thymian (Thymus vulgaris) an 21 Standorten, die unterschiedlich weit von Bienenständen entfernt lagen, und setzten diese Werte in Bezug zu den Besuchsraten von Honigbienen, Hummeln (Bombus terrestris) und sonstigen Bestäubern. An den gleichen Standorten bestimmten wir die Blütendichte und setzten Farbschalen ein, um die Wildbienengemeinschaft zu erfassen. Die Nutzung der Blüt enressou wurde weitgehend durch die Besuchsraten der Honigbiene erklärt und in geringfügigem Maße durch Hummelbesuch. Nach Berücksichtigung der Blütendichte wiesen Standorte in der Nähe von Bienenständen eine geringere Wildbienen-Biomasse auf. Dies war auf eine geringere Abundanz der großen Wildbienenarten zurückzuführen, also der Arten, die wahrscheinlich durch die Konkurrenz der Honigbiene beeinträchtigt werden. Wir schließen, dass Honigbienen den größten Beitrag zum Pollen- bzw. Nektarverbrauch bei den beiden wichtigsten Blütenpflanzen des Gebietes leisten und dass die Wildbienengemeinschaft bei den gegenwärtigen Honigbienendichten im Park (3.5 Völker/km2) beeinflusst wird. Unsere Untersuchung unterstützt die Hypothese, dass hohe Honigbienendichten durch Konkurrenz um Blütenressourcen einen Einfluss auf andere Bestäuber haben könnten

Long-term effects of changing atmospheric pollution on throughfall, bulk deposition and streamwaters in a Mediterranean forest

The abatement programs implanted in Europe to reduce SO₂, NO₂ and NH³ emissions are here evaluated by analyzing the relationships between emissions in Spain and neighboring countries and atmospheric deposition in a Mediterranean forest in the Montseny mountains (NE Spain) for the last 3decades. A canopy budget model was applied to throughfall data measured during a period of high emissions (1995-1996) and a period of lower emissions (2011-2013) to estimate the changes in dry deposition over this time span. Emissions of SO₂ in Spain strongly decreased (77%) and that was reflected in reductions for nssSO4² in precipitation (65% for concentrations and 62% for SO4²-S deposition). A lower decline was found for dry deposition (29%). Spanish NO₂ emissions increased from 1980 to 1991, remained constant until 2005, and decreased thereafter, a pattern that was paralleled by NO3(-) concentrations in bulk precipitation at Montseny. This pattern seems to be related to a higher share of renewable energies in electricity generation in Spain in recent years. However, dry deposition increased markedly between 1995 and 2012, from 1.3 to 6.7kgha¯¹year¯¹. Differences in meteorology between periods may have had a role, since the recent period was drier thus probably favoring dry deposition. Spanish NH³ emissions increased by 13% between 1980 and 2012 in Spain but NH₄⁺ concentrations in precipitation and NH₄⁺-N deposition showed a decreasing trend (15% reduction) at Montseny, probably linked to the reduction ammonium sulfate and nitrate aerosols to be scavenged by rainfall. NH₄⁺-N dry deposition was similar between the compared periods. The N load at Montseny (15-17kgha¯¹year¯¹) was within the critical load range proposed for Mediterranean sclerophyllous forests (15-17.5kgha¯¹year¯¹). The onset of N saturation is suggested by the observed increasing N export in streamwaters