Species mixing boosts root yield in mangrove trees

Lang'at J.K.S., Kirui B.K.Y., Skov M.W., Kairo J.G., Mencuccini M., Huxham M. (2013) Species mixing boosts root yield in mangrove trees. Oecologia. 172: 271-278.
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Doi: 10.1007/s00442-012-2490-x

Resum:

Enhanced species richness can stimulate the productivity of plant communities; however, its effect on the belowground production of forests has scarcely been tested, despite the role of tree roots in carbon storage and ecosystem processes. Therefore, we tested for the effects of tree species richness on mangrove root biomass: thirty-two 6 m by 6 m plots were planted with zero (control), one, two or three species treatments of six-month-old Avicennia marina (A), Bruguiera gymnorrhiza (B) and Ceriops tagal (C). A monoculture of each species and the four possible combinations of the three species were used, with four replicate plots per treatment. Above- and belowground biomass was measured after three and four years' growth. In both years, the all-species mix (ABC) had significant overyielding of roots, suggesting complementarity mediated by differences in rhizosphere use amongst species. In year four, there was higher belowground than aboveground biomass in all but one treatment. Belowground biomass was strongly influenced by the presence of the most vigorously growing species, A. marina. These results demonstrate the potential for complementarity between fast- and slow-growing species to enhance belowground growth in mangrove forests, with implications for forest productivity and the potential for belowground carbon sequestration. © 2012 Springer-Verlag Berlin Heidelberg.

Llegeix més

Short-term ecological and behavioural responses of Mediterranean ant species Aphaenogaster gibbosa (Latr. 1798) to wildfire

Lazaro-Gonzalez A., Arnan X., Boulay R., Cerda X., Rodrigo A. (2013) Short-term ecological and behavioural responses of Mediterranean ant species Aphaenogaster gibbosa (Latr. 1798) to wildfire. Insect Conservation and Diversity. 6: 627-638.
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Doi: 10.1111/icad.12018

Resum:

Fire greatly affects plant and animal biodiversity. There is an extensive body of literature on the effects of fire on insect communities, in which a large variability of responses has been observed. Very few studies, however, have addressed functional responses at the species level, information that would greatly enhance our understanding of the impact of fire at higher organisational levels. The aim of this study is to analyse the short-term ecological and behavioural responses of the Mediterranean ant Aphaenogaster gibbosa to fire-induced environmental changes. We compared aspects of the abiotic and biotic environment relevant to this species, as well as differences in colony foraging behaviour, on unburnt and burnt plots in a Mediterranean area that was affected by a wildfire. Our results showed that fire modified plant cover around nests and daily cycles of soil temperature close to the nest. Although there were no significant differences in food quantity, food quality (particularly seed composition) was different between unburnt and burnt plots. In accordance with these environmental changes, we found significant differences in the daily activity rhythms and diet composition of A. gibbosa between unburnt and burnt plots. Overall, these differences did not result in significant changes in overall foraging activity and efficiency, allowing ant colonies to maintain the same food intake regardless of the habitat they occupied. We conclude that A. gibbosa uses behavioural plasticity to modify its foraging strategy in recently burnt environments and thus survive post-fire conditions. © 2013 The Royal Entomological Society.

Llegeix més

Innovating innovation rate and its relationship with brains, ecology and general intelligence

Lefebvre L., Reader S.M., Sol D. (2013) Innovating innovation rate and its relationship with brains, ecology and general intelligence. Brain, Behavior and Evolution. 81: 143-145.
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Doi: 10.1159/000348485

Resum:

[No abstract available]

Llegeix més

Beta diversity as the variance of community data: Dissimilarity coefficients and partitioning

Legendre P., De Caceres M. (2013) Beta diversity as the variance of community data: Dissimilarity coefficients and partitioning. Ecology Letters. 16: 951-963.
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Doi: 10.1111/ele.12141

Resum:

Beta diversity can be measured in different ways. Among these, the total variance of the community data table Y can be used as an estimate of beta diversity. We show how the total variance of Y can be calculated either directly or through a dissimilarity matrix obtained using any dissimilarity index deemed appropriate for pairwise comparisons of community composition data. We addressed the question of which index to use by coding 16 indices using 14 properties that are necessary for beta assessment, comparability among data sets, sampling issues and ordination. Our comparison analysis classified the coefficients under study into five types, three of which are appropriate for beta diversity assessment. Our approach links the concept of beta diversity with the analysis of community data by commonly used methods like ordination and anova. Total beta can be partitioned into Species Contributions (SCBD: degree of variation of individual species across the study area) and Local Contributions (LCBD: comparative indicators of the ecological uniqueness of the sites) to Beta Diversity. Moreover, total beta can be broken up into within- and among-group components by manova, into orthogonal axes by ordination, into spatial scales by eigenfunction analysis or among explanatory data sets by variation partitioning. © 2013 John Wiley & Sons Ltd/CNRS.

Llegeix més

Do smart birds stress less? An interspecific relationship between brain size and corticosterone levels

Lendvai A.Z., Bokony V., Angelier F., Chastel O., Sol D. (2013) Do smart birds stress less? An interspecific relationship between brain size and corticosterone levels. Proceedings of the Royal Society B: Biological Sciences. 280: 0-0.
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Doi: 10.1098/rspb.2013.1734

Resum:

Vertebrates respond to unpredictable noxious environmental stimuli by increasing secretion of glucocorticoids (CORT). Although this hormonal stress response is adaptive, high levels of CORT may induce significant costs if stressful situations are frequent. Thus, alternative coping mechanisms that help buffer individuals against environmental stressors may be selected for when the costs of CORT levels are elevated. By allowing individuals to identify, anticipate and cope with the stressful circumstances, cognition may enable stress-specific behavioural coping. Although there is evidence that behavioural responses allowanimals to cope with stressful situations, it is unclear whether or not cognition reduces investment in the neuroendocrine stress response. Here, we report that in birds, species with larger brains relative to their body size showlower baseline and peakCORTlevels than species with smaller brains. This relationship is consistent across life-history stages, and cannot be accounted for by differences in life history and geographical latitude. Because a large brain is a major feature of birds that base their lifetime in learning new things, our results support the hypothesis that enhanced cognition represents a general alternative to the neuroendocrine stress response. © 2013 The Author(s) Published by the Royal Society. All rights reserved.

Llegeix més

Addressing a critique of the TEASI framework for invasive species risk assessment

Leung B., Roura-Pascual N., Bacher S., Heikkila J., Brotons L., Burgman M.A., Dehnen-Schmutz K., Essl F., Hulme P.E., Richardson D.M., Sol D., Vila M. (2013) Addressing a critique of the TEASI framework for invasive species risk assessment. Ecology Letters. 16: 1415-14.
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Doi: 10.1111/ele.12172

Resum:

We address criticism that the Transport, Establishment, Abundance, Spread, Impact (TEASI) framework does not facilitate objective mapping of risk assessment methods nor defines best practice. We explain why TEASI is appropriate for mapping, despite inherent challenges, and how TEASI offers considerations for best practices, rather than suggesting one best practice. © 2013 John Wiley & Sons Ltd/CNRS.

Llegeix més

Suitability of the management of habitat complexity, acorn burial depth, and a chemical repellent for post-fire reforestation of oaks

Leverkus A.B., Castro J., Puerta-Piñero C., Rey Benayas J.M. (2013) Suitability of the management of habitat complexity, acorn burial depth, and a chemical repellent for post-fire reforestation of oaks. Ecological Engineering. 53: 15-22.
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Doi: 10.1016/j.ecoleng.2013.01.003

Resum:

Acorn sowing is a reforestation technique that can potentially render high-quality oak seedlings and high seedling survival, although it is often discarded due to high rates of seed predation. Predator activity can be modified by habitat complexity due to its effects on accessibility and protection for different predators. In this study we analysed how habitat complexity generated by different post-fire management treatments, sowing depth, and capsaicin (a chemical repellent) affect acorn predation by two guilds of post-dispersal predators that differ in size and foraging behaviour. We carried out two acorn predation experiments. In Experiment #1 we buried acorns at two depths (2 and 8. cm) in two post-fire burnt-wood management treatments of different habitat complexity, namely: (1) Salvage Logging (SL), where the burnt trunks were cut and piled and the branches were masticated (lower habitat complexity), and (2) Non-Intervention (NI), with no action after the fire and 100% of the trees naturally fallen by 2009, thus leaving a habitat with lying burnt logs and branches (higher habitat complexity). In Experiment #2 we repeated Experiment #1, with the addition of capsaicin as a mammal repellent treatment. Most acorns were consumed in both years (ca. 90%), mainly by rodents. In Experiment #1 predation by boars accounted for 4.1% of overall predation, and it was about twice as high in SL than in NI, likely due to the physical difficulty for large mammals to forage in an area with a complex structure created by lying logs and branches. In contrast, rodents consumed ca. 1.4 times more acorns in NI than in SL, which led to overall greater predation in NI in both experiments. This was likely due to the protection provided by the branches for the rodent community. Deeper burial reduced predation by small percentages, although in Experiment #1 it had a negligible effect in NI. Capsaicin did not reduce predation, and it reduced seedling emergence to half. This study suggests that habitat complexity created by trunks and branches reduced predation by wild boars, but favoured rodent acorn predation. We conclude that other methods for the protection of individual acorns need to be identified to increase the success of oak reforestation via seeding. © 2013 Elsevier B.V.

Llegeix més

Plant competition and facilitation after extreme drought episodes in Mediterranean shrubland: Does damage to vegetation cover trigger replacement by juniper woodland?

Lloret F., Granzow-de la Cerda I. (2013) Plant competition and facilitation after extreme drought episodes in Mediterranean shrubland: Does damage to vegetation cover trigger replacement by juniper woodland?. Journal of Vegetation Science. 24: 1020-1032.
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Doi: 10.1111/jvs.12030

Resum:

Question: We analyse the contribution of plant-plant interactions, particularly the outcome of plant competition and plant facilitation, on vegetation dynamics as a result of extreme drought episodes. These events will likely become more frequent under climate change, can induce vegetation die-off and alter community dynamics. We study succession in a shrubland that tends to be replaced by juniper (Juniperus phoenicea) woodland. Due to drought, shrubland die-off may result in competition release favouring J. phoenicea juveniles, and accelerating shrubland replacement. Alternatively, deleterious abiotic stress may increase after loss of vegetation cover protection. Location: Mediterranean coastal shrublands, South Spain (Doñana National Park). Methods: Field estimates of plant growth, production of needle-like leaves, water-use efficiency (WUE; leaf δ13C) and N leaf content of J. phoenicea juveniles in relation to plant size, drought-induced damage, cover and habit characteristics of surrounding vegetation, and drought-induced defoliation of the surrounding vegetation. Results: Juniperus phoenicea juveniles growing beneath a dense vegetation canopy, particularly trees and large shrubs, were less damaged during the extreme drought episode. Plant size correlated negatively with damage. Post-drought growth was higher in juveniles partially released from the vegetation canopy, supporting the existence of a balance between competition and facilitation. Cover of pines, large shrubs and spiny shrubs favoured growth of juveniles. Needle-like juvenile leaves were more abundant in plants covered by the surrounding vegetation or in moderately damaged plants, but less abundant in plants without damage. Higher leaf δ13C values - indicating water stress - were measured in plants more damaged by drought and in those without canopy protection, or under vegetation strongly affected by drought. Leaf N content was lower in undamaged plants and individuals covered by surrounding vegetation. Conclusion: We did not find evidence that gaps opened by drought promoted growth of the potential replacing J. phoenicea. Thus, drought-induced enhancement of successional replacement of shrublands with woodlands was not supported; instead, our findings foresee shrubland prevalence under future climate change conditions. Plant facilitation will play a relevant role in this process. Thus, we herein extend the relevance of plant-plant interactions to extreme drought episodes related to climate change, highlighting their role as drivers of community dynamics. © 2012 International Association for Vegetation Science.

Llegeix més

Relationship between projected changes in future climatic suitability and demographic and functional traits of forest tree species in Spain

Lloret F., Martinez-Vilalta J., Serra-Diaz J.M., Ninyerola M. (2013) Relationship between projected changes in future climatic suitability and demographic and functional traits of forest tree species in Spain. Climatic Change. 120: 449-462.
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Doi: 10.1007/s10584-013-0820-6

Resum:

The response of plant species to future climate conditions is probably dependent on their ecological characteristics, including climatic niche, demographic rates and functional traits. Using forest inventory data from 27 dominant woody species in Spanish forests, we explore the relationships between species characteristics and projected changes in their average climatic suitability (occurrence of suitable climatic conditions for a species in a given territory) obtained by empirical niche-based models, under a business-as-usual climate change scenario (A1, HadCM3, 2001-2100). We hypothesize that most species will suffer a decline in climatic suitability, with a less severe for species (i) currently living in more arid climates or exhibiting a broader current climatic niche; (ii) with higher current growth rates; (iii) with functional traits related to resistance to water deficits. The analysis confirm our hypothesis since apart from a few Mediterranean species, most species decrease their climatic suitability in the region under future climate, characterized by increased aridity. Also, species living in warmer locations or under a wider range of climatic conditions tend to experience less decrease in climatic suitability. As hypothesized, a positive relationship was detected between current relative growth rates and increase in future climatic suitability. Nevertheless, current tree mortality did not correlate with changes in future climatic suitability. In contrast with our hypothesis, functional traits did not show a clear relationship with changes in climate suitability; instead species often presented idiosyncratic responses that, in some cases, could reflect past management. These results suggest that the extrapolation of species performance to future climatic scenarios based on current patterns of dominance is constrained by factors other than species autoecology, particularly human activity. © 2013 Springer Science+Business Media Dordrecht.

Llegeix més

Seasonal variations in terpene emission factors of dominant species in four ecosystems in NE Spain

Llusia J., Penuelas J., Guenther A., Rapparini F. (2013) Seasonal variations in terpene emission factors of dominant species in four ecosystems in NE Spain. Atmospheric Environment. 70: 149-158.
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Doi: 10.1016/j.atmosenv.2013.01.005

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We studied the daily patterns in the rates of foliar terpene emissions by four typical species from the Mediterranean region in two days of early spring and two days of summer in 4 localities of increasing biomass cover in Northern Spain. The species studied were Thymelaea tinctoria (in Monegros), Quercus coccifera (in Garraf), Quercus ilex (in Prades) and Fagus sylvatica (in Montseny). Of the total 43 VOCs detected, 23 were monoterpenes, 5 sesquiterpenes and 15 were not terpenes. Sesquiterpenes were the main terpenes emitted from T. tinctoria. Total VOC emission rates were on average about 15 times higher in summer than in early spring. The maximum rates of emission were recorded around midday. Emissions nearly stopped in the dark. No significant differences were found for nocturnal total terpene emission rates between places and seasons. The seasonal variations in the rate of terpene emissions and in their chemical composition can be explained mainly by dramatic changes in emission factors (emission capacity) associated in some cases, such as for beech trees, with very different foliar ontogenical characteristics between spring and summer. The results show that temperature and light-standardised emission rates were on average about 15 times higher in summer than in early spring, which, corroborating other works, calls to attention when applying the same emission factor in modelling throughout the different seasons of the year. © 2013 Elsevier Ltd.

Llegeix més

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