Gerardo Avalos

Allometry and stilt root structure of the neotropical palm Euterpe precatoria (Arecaceae) across sites and successional stages.

The lack of secondary meristems shapes allometric relationships of the palms, influencing species segregation according to their capacity to adjust form and function to spatial and temporal changes in environmental conditions. We examined the stem height vs. diameter allometry of Euterpe precatoria across environmental gradients and measured how terrain inclination and palm size affected stilt root structure at two sites in Costa Rica. We dissected the root cone into eight variables and used principal component analysis to summarize their correlation structure. The fit of the stem diameter-height relationship to the stress, elastic, and geometric similarity models was examined using data from 438 palms. Terrain inclination did not affect stilt roots, whose structure was determined by palm size. Palms under 1 m showed geometric similarity, whereas palms above 1 m had slope values that were one and a half times higher, independent of successional stage, and did not adjust to any mechanical model. Taller palms departed from these models when they were large because they had stilt root support. We conclude that height in E. precatoria is constrained by structural support at the base and that diameter at the base of the stem and stilt roots balances height increments over all the size ranges examined.

Illegal Palm Heart ( Geonoma edulis ) Harvest in Costa Rican National Parks: Patterns of Consumption and Extraction

Illegal Palm Heart (Geonoma edulis) Harvest in Costa Rican National Parks: Patterns of Consumption and Extraction. Illegal extraction of non-timber forest products in the tropics is widespread, and many protected areas face the challenge of balancing conservation needs with cultural practices related to the use and extraction of animals and plants. We studied the illegal wild palm heart extraction of Geonoma edulis, locally known as súrtuba, in Volcán Poás and Braulio Carrillo National Parks in Costa Rica. Through 96 questionnaires administered in three communities bordering these national parks, and by semistructured interviews with poachers and park managers, this study examined extraction and consumption motives, patterns, and frequencies. This palm is sought out by the communities for use during Holy Week to satisfy cultural traditions, for its associated nutritive value, and because of its unique bitter flavor, not comparable to domesticated palm heart. Whereas the majority of the respondents consume it during Holy Week (55.2%), a substantial number (27.1%) consume G. edulis palm heart at least once a month. The majority extract once a year (58%); however, a minority (2.1%) rely on G. edulis for economic subsistence. This accounts for 72.6% of the reported extraction (over 4,500 palms per year) and is supplying a year-round market for nontraditional use. Our results show that what most likely began as a cultural tradition has become an uncontrolled, nontraditional source of income. Additional efforts should determine the feasibility of limited extraction outside protected areas to satisfy traditional use. Such an effort entails the decentralization of biodiversity policies and innovative methods to implement protective measures, as well as incentives for community involvement in the management of this palm heart species.

Facing Shortage or Excessive Light: How Tropical and Subtropical Trees Adjust Their Photosynthetic Behavior and Life History Traits to a Dynamic Forest Environment

Light is critical for plant establishment, growth, and survival in wet tropical forests. The objective of this chapter is to analyze paradigms of photosynthetic performance and life history traits of tropical forest trees to contrasting light environments across the forest floor, gaps and upper canopy. Physiological and morphological plasticity as well as genetically fixed adaptive traits are analyzed, including leaf optical properties and photoprotection from high irradiance. Photosynthetic adaptations to contrasting light environments of closely related species are discussed. This approach has the advantage among comparative studies of adaptations across species in that genetic relationships among species are known. Species-specific variations in maximum photosynthetic rates, which reflect the degree of adaptation to growth irradiance, are shown to be gradual, suggesting that classification into two distinct functional groups in terms of light requirements is somewhat arbitrary. Trees growing in gaps or in the upper canopy rely strongly on biochemical mechanisms to dissipate excess energy and to avoid damage to the light reaction centers and photosystems. Consistent with their high photosynthetic capacity, light demanding species are capable of plastic changes in hydraulic architecture , such as increases in hydraulic conductivity under high irradiance, which makes them more competitive in open habitats.

Forest structure and territory size relationship in the neotropical understorey insectivore Henicorhina leucosticta

TheneotropicalterrestrialinsectivoreHenicorhinaleucosticta(Troglodytidae)maintainslong-termterritories 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.

Allometric estimation of total leaf area in the neotropical palm Euterpe oleracea at La Selva, Costa Rica

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.

Influence of light conditions on the allometry and growth of the understory palm Geonoma undata subsp. edulis (Arecaceae) of neotropical cloud forests

PREMISE OF THE STUDY Knowledge on the growth responses of understory palms to changing light conditions within neotropical cloud forests is limited. The low light regime of these environments, in addition to persistent cloudiness, low ambient temperatures, and slow nutrient cycles, imposes significant constraints on biomass accumulation. Here, we evaluate how changes in the understory light conditions influenced the allometry and growth of G. undata subsp. edulis in two cloud forests in Costa Rica. METHODS We examined the structural relationships between stem diameter, stem height, and crown area in reproductive and nonreproductive individuals. We related the variation in stem growth and crown area with allometry, leaf production and longevity, and light conditions that we measured using hemispherical photographs over 1 year. KEY RESULTS The allometric and growth pattern of G. undata subsp. edulis was characterized by its investment in crown area, which was strongly and positively related to increments in palm height and reproduction. Growth, measured as the increase in crown area and stem height, was not explained by the variation in the light regime spanning 1 year. However, reproductive individuals were generally taller, more slender, and had larger leaf areas than nonreproductive individuals. CONCLUSIONS Our results demonstrated that stem growth responses were mostly controlled by initial crown size rather than by temporal differences in the understory light regimes of cloud forests. These results suggest that cloud forest understory palms have a limited capacity to respond to light changes and rely mostly on an opportunistic strategy for biomass accumulation and reproduction.

Propagation of the Palm Flora in a Lowland Tropical Rainforest in Costa Rica: Fruit Collection and Germination Patterns:

Palms are important structural components of tropical rain forests. Nonetheless, information on their propagation potential under nursery conditions to facilitate their use in forest restoration is scarce. This article studies the propagation potential of a tropical palm assemblage focusing on seed collection and germination patterns in the rainforest of Tirimbina, Costa Rica. From October 2013 to January 2016, we evaluated palm fruit availability and analyzed the germination potential of 5,172 seeds from 21 species monitored weekly for 57 weeks. Palm fruits were available all year; the percentage germination was 65.6%, and 90% of seeds germinated in 7 to 25 weeks. Contrary to the prevalent view that palms have low germination, germination was completed relatively fast. Palm propagation is limited by low species abundance rather than by fruit availability or germination potential. To propagate palms for restoration projects, we suggest to determine the species abundance and diversity at the study site, identify propagation priorities according to the species conservation status, and collect fruits throughout the year in a systematic way to include the greatest species and habitat diversity and infer the phenological patterns that will guide future seed collection. Our results are relevant to foster palm propagation with the purpose of including palms in forest restoration and increase our understanding of palm ecology, conservation, and regeneration strategies.

Do functional diversity and trait dominance determine carbon storage in an altered tropical landscape

Altered landscapes play a major role in biodiversity conservation and carbon (C) storage in the tropics. There is increasing evidence that C storage potential is controlled by tree functional diversity, but underlying mechanisms are debated. We analyzed the effects of trait dominance (mass-ratio hypothesis), species diversity, and trait variation (species complementarity) on C storage in the soils and vegetation of 20 agroforestry systems (AFS) and seven forested sites in Costa Rica. AFS consisted of organic and conventional coffee farms and pastures with trees. We used the community weighted mean (CWM) to measure trait dominance, and functional divergence (FDvar) to evaluate trait variation of wood densities (WD) and maximum heights (Hmax) of woody plants at each site. Species richness, the number of woody plants per hectare, and slope of the terrain were also considered as independent variables. Soil organic carbon (SOC) increased with higher CWMWD and with higher variability of Hmax (

Colonization Strategies of Two Liana Species in a Tropical Dry Forest Canopy

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