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Otarola M.F.,University of Costa Rica | Avalos G.,University of Costa Rica | Avalos G.,Center for Sustainable Development Studies
American Journal of Botany | Year: 2014

• Premise of the study: Environmental heterogeneity is a strong selective force shaping adaptation and population dynamics across temporal and spatial scales. Natural and anthropogenic gradients influence the variation of environmental and biotic factors, which determine population demography and dynamics. Successional gradients are expected to influence demographic parameters, but the relationship between these gradients and the species life history, habitat requirements, and degree of variation in demographic traits remains elusive. • Methods: We used the palm Euterpe precatoria to test the effect of successional stage on plant demography within a continuous population. We calculated demographic parameters for size stages and performed matrix analyses to investigate the demographic variation within primary and secondary forests of La Selva, Costa Rica. • Key results: We observed differences in mortality and recruitment of small juveniles between primary and secondary forests. Matrix models described satisfactorily the chronosequence of population changes, which were characterized by high population growth rate in disturbed areas, and decreased growth rate in old successional forests until reaching stability. • Conclusions: Different demographic parameters can be expressed in contiguous subpopulations along a gradient of successional stages with important consequences for population dynamics. Demographic variation superimposed on these gradients contributes to generate subpopulations with different demographic composition, density, and ecological properties. Therefore, the effects of spatial variation must be reconsidered in the design of demographic analyses of tropical palms, which are prime examples of subtle local adaptation. These considerations are crucial in the implementation of management plans for palm species within spatially complex and heterogeneous tropical landscapes. © 2014 Botanical Society of America. Source

Otarola M.F.,University of Campinas | Otarola M.F.,Center for Sustainable Development Studies | Sazima M.,University of Campinas | Solferini V.N.,University of Campinas
Ecology and Evolution | Year: 2013

Reproductive strategies, sexual selection, and their relationship with the phenotype of individuals are topics widely studied in animals, but this information is less abundant for plants. Variability in flowering phenology among individuals has direct impact on their fitness, but how reproductive phenology is affected by the size of the individuals needs further study. We quantified the flowering intensity, length, and reproductive synchronization of two sympatric dioecious Wild Nutmeg tree species (Virola, Myristicaceae) in the Brazilian Atlantic forest, and analyzed its relationships with tree size. Two distinct strategies in flowering timing and intensity were found between species (annual versus biennial flowering), and among individuals in the annual flowering species (extended versus peak flowering). Only for the annual flowering species the reproductive output is related to tree size and large trees present proportionally higher flower coverage, and lower synchronization than smaller ones. Flowering is massive and highly synchronized in the biennial species. Sex ratios are not different from 1:1 in the two species, and in the two segregated reproductive subgroups in the biennial flowering species. The biennial flowering at individual level is a novelty among reproductive patterns in plants, separating the population in two reproductive subgroups. A proportional increase in the reproductive output with size exists only for the annual flowering species. A biennial flowering can allow resource storage favouring massive flowering for all the individuals diluting their relationship with size. © 2013 The Authors. Source

Hager A.,Center for Sustainable Development Studies
Agroforestry Systems | Year: 2012

Agroforestry systems can mitigate greenhouse gas (GHG) emissions, conserve biodiversity and generate income. Whereas the provision of ecosystem services by agroforestry is well documented, the functional relationships between species composition, diversity and carbon (C)-storage remain uncertain. This study aimed to analyze the effects of management (conventional vs. organic), woody plant diversity and plant composition on aboveground and belowground C-storage in coffee agroforestry systems. It was expected that organic farms would store more C, and that an increase in plant diversity would enhance C-storage due to complementarity effects. Additionally, it was expected that steep slopes decrease C-storage as a result of topsoil erosion. Woody plants were identified on 1 ha plots within 14 coffee farms (7 conventional and 7 organic). C-stocks in trees, coffee plants and roots were estimated from allometric equations. C-stocks in litter and topsoil (0-25 cm) were estimated by sampling. On average, farms stored 93 ± 29 Mg C ha -1. Soil organic carbon accounted for 69 % of total C. Total C-stocks were 43 % higher on organic farms than on conventional farms (P < 0.05). Conventional and organic farms differed in vegetation structure, but not in species diversity. It was found that the combined effect of farm type, species richness, species composition and slope explained 83 % of the variation in total C-storage across all farms (P < 0.001). Coffee agroforestry in general and organic farms in particular may contribute to GHG mitigation and biodiversity conservation in a synergistic manner which has implications for the effective allocation of resources for conservation and climate change mitigation strategies in the agricultural sector. © 2012 Springer Science+Business Media B.V. Source

Avalos G.,University of Costa Rica | Avalos G.,Center for Sustainable Development Studies | Sylvester O.,University of Costa Rica
Trees - Structure and Function | Year: 2010

We estimated the magnitude of the total leaf area of the neotropical palm Euterpe oleracea and examined its allometry relative to the variation in stem height and diameter at La Selva Biological Station in Costa Rica. The allometric relationships between frond leaf area and frond length (from tip to base), and between frond leaf area and number of leaflets, were determined by natural logarithmic regressions to estimate the total area of each frond. Palm total leaf area was then estimated by adding the area of the composing fronds. We fit 14 separate regression models that related one or more of the morphological variables (number of fronds, diameter at breast height, stem height) to the total leaf area. Our results show that palm total leaf area is directly proportional to the number of fronds and palm size as reflected in stem height and diameter. Eight out of the 14 models had r2 values of >0.90 and incorporated a diverse combination of predictor variables. Simple linear regression models were more congruent with the observed values of total leaf area, whereas natural logarithmic models overestimated the value of total leaf area for large palms. Both approaches show a high degree of association among morphological characters in E. oleracea supporting the hypothesis that palms behave like unitary organisms, and are morphologically constrained by the lack of secondary meristems. To afford attaining canopy heights, woody palms need to show a high degree of phenotypic integration, shaping their growth and allometric relationships to match spatial and temporal changes in resources. © 2010 Springer-Verlag. Source

Vargas L.E.,University of Costa Rica | Sanchez N.V.,National University of Costa Rica | Avalos G.,University of Costa Rica | Avalos G.,Center for Sustainable Development Studies
Journal of Tropical Ecology | Year: 2011

The neotropical terrestrial insectivore Henicorhina leucosticta (Troglodytidae) maintains long-term territories through vocalizations and forages among leaf litter trapped in the understorey vegetation and ground litter. The relationship between forest structure and H. leucosticta territory size was studied in La Selva Biological Station, Costa Rica, during the non-breeding season in 2009. Forest structure was measured by assessing canopy openness and leaf area index (LAI) using hemispherical photography, while territory size was estimated with the playback technique using local conspecific vocalizations. Mean territory area was 3.8±2.8 ha (mean±SD, n = 10). Territory radius length was similar in old-growth forest and abandoned agro-forest plantations. We found that H. leucosticta territory size decreased as median LAI increased. We propose that LAI is related to territory size through the amount of leaf fall and subsequent leaf litter accumulation over the understorey plants, which constitutes an important reservoir of arthropod prey and nest materials for H. leucosticta. The long-term supply of food resources is likely to affect territory size in this species, as well as other insectivorous birds with similar foraging behaviour. These results are congruent with the structural cues hypothesis. © 2010 Cambridge University Press. Source

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