Quero JL, Sterck FJ, Martínez-Vilalta J, Villar R (2011) Summer drought dynamics in the hydraulics, gas exchange and morphology of six co-existing Mediterranean woody species. Oecologia 166: 45-57.
Ripullone F, Rivelli AR, Baraldi R, Guarini R, Guerrieri R, Magnani F, Peñuelas F, Raddi S, Borghetti M (2011) Effectiveness of the photochemical reflectance index to track photosynthetic activity over a range of forest tree species and plant water statuses. Functional Plant Biology 38: 177-186.
Peppe DJ, Royer DL, Cariglino B,Oliver SY, Newman S, Leight E, Enikolopov G, Fernandez-Burgos M, Herrera F, Adams JM, Correa E, Currano ED, Erickson JM, Hinojosa LF, Hoganson JW, Iglesias A, Jaramillo CA, Johnson KR, Jordan GJ, Kraft N (eds). (2011) Sensitivity of leaf size and shape to climate: global patterns and paleoclimatic applications. New Phytologist 190: 724-739.
Alvarez A, Gracia M, Retana J (2011) Fuel types and crown fire potential in Mediterranean pine forests. European Journal of Forest Research doi: 10.1007/s10342-011-0520-6.
Alvarez A, Gracia M, Vayreda J, Retana J (2011) Patterns of fuel types and crown fire potential in Pinus halepensis forests in the Western Mediterranean Basin. Forest Ecology and Management doi:10.1016/j.foreco.2011.01.039.
Andrés P., Salgado C., Espelta J.M. (2011) Optimizing nursery and plantation methods to grow Cedrela odorata seedlings in tropical dry agroecosystems. Agroforestry Systems. 83: 225-234.EnllaçDoi: 10.1007/s10457-011-9404-5
Cedrela odorata (Spanish cedar) is a valuable multi-purpose tree which Central American rural communities and farmers give priority to introducing in pastures and home gardens. In order to propose realistic methods for C. odorata production in local nurseries in the dry tropical region of Nicaragua, we studied: (a) the ability of locally collected C. odorata seeds to germinate, (b) seed response to storage under ambient conditions or under cold storage, (c) the effects of irradiance and watering during cultivation on seedling morphology and post-transplantation survival, and (d) the effects of competition from grasses on C. odorata seedlings transplanted to pastures. Seed germination ranged from 55 to 66% and remained constant after 6 months of storage under ambient conditions or cold storage. C. odorata seedling morphology was sensitive to irradiation and watering in the nursery growing period. Deep shade reduced seedling biomass and leafiness and increased specific leaf area and root-to-shoot ratio. Water shortage increased root mass ratio and root-to-shoot ratio and decreased leaf mass ratio. Post-transplantation success was favored by weeding, and was the highest for seedlings grown under deep shade and water restrictions. © 2011 Springer Science+Business Media B.V.
Armenteras D., Rodríguez N., Retana J., Morales M. (2011) Understanding deforestation in montane and lowland forests of the Colombian Andes. Regional Environmental Change. 11: 693-705.EnllaçDoi: 10.1007/s10113-010-0200-y
Colombian Andean forests cover nine million ha. These forests provide an informative case study of mountain deforestation in South America. They are surrounded by tropical lowland forests, and they host most of the country's human population. This study evaluates the relative importance of human and natural variables in deforestation of the Colombian Andes between 1985 and 2005 using remote sensing methods, geographic information system (GIS) technology and general linear models (GLM). The following factors affected the annual deforestation in the region positively: forced population migration, unsatisfied basic needs, economic activity, crops, pastures, illicit crops, protected areas and slope. Factors having a negative effect were tenure of small land parcels, road density, water scarcity and mean temperature. The results of this study also provide insight into the differences between the dynamics of lowland forests and those of montane forests. Montane forests had a lower annual rate of deforestation than did forests in the lowlands. Socio-economic, demographic and biophysical factors explain overall deforestation rates for the region. However, when altitude variation is taken into account, intraregional differences in the Andes become evident. Deforestation processes differ between those areas adjacent to the high Andean valleys where most of the country's population concentrates and those areas in the tropical lowlands north, west and east of the Andean chain. Differences between lowland and montane forest dynamics are due partly to the accessibility of forests and differences in wealth and economic activities. In montane forests, deforestation is positively influenced by economic activity, the presence of protected areas and higher slopes. Deforestation in montane forests is negatively affected by tenure of small land parcels, road density, water scarcity and mean temperature. Lowland deforestation rates are more closely related to rural population, pasture percentage, crops, protected areas and temperature. Our results suggest that montane forests appear to be in a more advanced stage of colonisation and economic development, whereas lowland forests are closer to the colonisation frontier and to rapidly growing colonist populations. This study reinforces the idea that although the most common tropical drivers of deforestation are found in the Andes, these drivers operate differently when intraregional differences are considered. © 2010 Springer-Verlag.
Armenteras-Pascual D., Retana-Alumbreros J., Molowny-Horas R., Roman-Cuesta R.M., Gonzalez-Alonso F., Morales-Rivas M. (2011) Characterising fire spatial pattern interactions with climate and vegetation in Colombia. Agricultural and Forest Meteorology. 151: 279-289.EnllaçDoi: 10.1016/j.agrformet.2010.11.002
Vegetation burning in tropical countries is a threat to the environment, causing not only local ecological, economic and social impacts, but also large-scale implications for global change. The burning is usually a result of interacting factors, such as climate, land-use and vegetation type. Satellite-derived monthly time series datasets of rainfall, burned area and active fire detections between December 2000 and 2009 were used in this study. A map of vegetation types was also used to determine these factors' spatial and temporal variability and interactions with the total amount of burned area and active fires detected in Colombia. Grasslands represented the vegetation most affected by fires every year in terms of burned area (standardised by their total area), followed by secondary vegetation, pasture and forests. Grasslands were also most affected by active fires, but followed closely by pasture, agricultural areas, secondary vegetation and forests. The results indicated strong climate and fire seasonality and marked regional difference, partly explained by climatic differences amongst regions and vegetation types, especially in the Orinoco and Caribbean regions. The incidence of fire in the Amazon and Andes was less influenced by climate in terms of burned area impacted, but the strength of the ENSO phenomenon affected the Orinoco and the Andes more in terms of burned area. Many of the active fires detected occurred in areas of transition between the submontane and lowland Andes and the Amazon, where extensive conversion to pasture is occurring. The possible high impact of small fires on the tropical rainforest present in this transition area and the Amazonian rainforest deserves more attention in Colombia due to its previous lack of attention to its contribution to global change. © 2010 Elsevier B.V.
Arnan X., Bosch J., Comas L., Gracia M., Retana J. (2011) Habitat determinants of abundance, structure and composition of flying Hymenoptera communities in mountain old-growth forests. Insect Conservation and Diversity. 4: 200-211.EnllaçDoi: 10.1111/j.1752-4598.2010.00123.x
1.Old-growth forests have features that endow them with an extraordinary ecological value. These forests are sources of habitat diversity and, consequently, biodiversity, which makes them a basic objective of conservation programs. Insects have been traditionally used as indicators of forest condition. 2.The aim of this study is to uncover patterns of Hymenoptera abundance and diversity, and their relationship with structural features in old-growth forests. We use pan traps to sample the community of flying Hymenoptera in two old-growth forest types (silver fir and mountain pine) with important structural differences. 3.Compared to other surveys of local Hymenoptera communities, our sampling yielded an extremely high number of species (630). 4.At the plot level, the two forest types showed important differences in family richness and diversity, but not in abundance or in species richness and diversity. However, variability in species richness was higher among pine than silver fir plots, leading to overall higher species richness in the former. 5.Species composition also differed between pine than silver fir forests, and these differences were related to important structural differences between the two forest types. 6.Canonical correspondence and multiple regression analysis yielded contrasting habitat requirements among Hymenoptera families and functional groups (bees, sawflies, parasitic wasps and predatory wasps). 7.We conclude that flying Hymenoptera communities can be used as good indicators of forest structure, habitat complexity and conservation status. © 2010 The Authors. Insect Conservation and Diversity © 2010 The Royal Entomological Society.
Arnan X., Ferrandiz-Rovira M., Pladevall C., Rodrigo A. (2011) Worker size-related task partitioning in the foraging strategy of a seed-harvesting ant species. Behavioral Ecology and Sociobiology. 65: 1881-1890.EnllaçDoi: 10.1007/s00265-011-1197-z
Messor bouvieri is a seed-harvesting ant species in which workers forage in trails from the nest to a search area. A previous observation of seed transfer events between workers returning to the nest suggested potential task partitioning. In this study, we describe seed transportation and analyze the role of task partitioning in the foraging strategy of this species in terms of seed intake efficiency in relation to costs and benefits based on transport speed and task reliability. We assess the harvesting efficiency of task partitioning by comparing cooperative seed transport (CST) and individual seed transport (IST) events. Our results show task partitioning in the form of a sequence of transfer events among workers going from the search area to the nest. Importantly, and despite the weak worker polymorphism of this species, this sequence involved workers of different sizes, with seeds usually being passed along from smaller to larger workers. In addition, we show that small workers are better at finding seeds (spend less time finding a seed), and large workers are better at transporting them (were faster when walking back to the nest and lost fewer seeds). However, we failed to demonstrate that workers of different sizes are specialized in performing the task in which they excel. Overall, sequential CST in M. bouvieri results in a greater seed intake because seed search time decreases and task reliability increases, compared to IST. The determinants and adaptive benefits of CST are discussed. © 2011 Springer-Verlag.
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