Estimating Canopy Structure in an Amazon Forest from Laser Range Finder and IKONOS Satellite Observations
Gregory P. Asner, Michael Palace, Michael Keller, Rodrigo Pereira Jr., Jose N. M. Silva, and Johan C. Zweede
(Click for Abstract)
Nutrient Limitation to Primary Productivity in a Secondary Savanna in Venezuela
Nichole N. Barger, Carla M. D'Antonio, Thaura Ghneim, Keary Brink, and Elvira Cuevas
(Click for Abstract)(Resumen Haga Clic Aquí)
Composition Patterns of Caribbean Limestone Forests: Are Parsimony, Classification, and Orgination Analysis Congruent?
Jorge Carlos Trejo-Torres and James D. Ackerman
(Click for Abstract)(Resumen Haga Clic Aquí)
Distribution and Diversity of Pteridophytes and Melastomataceae along Edaphic Gradients in Yasun National Park, Ecuadorian Amazonia
Hanna Tuomisto, Kalle Ruokolainen, Axel Dalberg Poulsen, Robbin C. Moran, Catalina Quintana, Gustavo Caas, and Jorge Celi
(Click for Abstract)(Resumen Haga Clic Aquí)
Elevational Variation of Leaf Traits of Montane Rain Forest Tree Species at La Chinantla, Southern Mxico
No Velzquez-Rosas, Jorge Meave, and Sonia Vzquez-Santana
(Click for Abstract)(Resumen Haga Clic Aquí)
Herbivore-Free Time? Damage to New Leaves of Woody Plants after Hurricane Andrew
Suzanne Koptur, M. Cristina Rodriguez, Steven F. Oberbauer, Carl Weekley, and Alan Herndon
(Click for Abstract)(Resumen Haga Clic Aquí)
Spatio-temporal Variation in Post-dispersal Seed Fate
Franois Feer and Pierre-Michel Forget
(Click for Abstract)(Resumen Haga Clic Aquí)
Spatial and Temporal Variation of Macroinvertebrate Drift in Two Neotropical Streams
Luz Boyero and Jaime Bosch
(Click for Abstract)(Resumen Haga Clic Aquí)
Canopy Ferns in Lowland Dipterocarp Forest Support a Prolific Abundance of Ants, Termites, and Other Invertebrates
Martin D. F. Ellwood, David T. Jones, and William A. Foster
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Discrimination among Fish Models by Hawaiian Eleotris sandwicensis (Eleotridae)
Lynda D. Corkum
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Use of Fruiting Trees by Birds in Continuous Forest and Riparian Forest Remnants in Los Tuxtlas, Veracruz, Mexico
Catherine Graham, Jess Eduardo Martnez-Leyva, and Leticia Cruz-Paredes
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Damage and Recovery of Cycas micronesica after Typhoon Paka
Heidi Hirsh and Thomas Marler
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Staggered Flowering in Four Sympatric Varieties of Geonoma cuneata (Palmae)
Finn Borchsenius
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Spatial and Temporal Variation in Hydrochory in Amazonian Floodplain Forest
Susan M. Moegenburg
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Massive Seed Predation of Pseudobombax grandiflorum (Bombacaceae) by Parakeets Brotogeris versicolurus (Psittacidae) in a Forest Fragment in Brazil
Mercival Roberto Francisco, Vitor de Oliveira Lunardi, and Mauro Galetti
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Effects of the Tropical Freshwater Shrimp, Caridina weberi (Atyidae) on Leaf Litter Composition
Jennifer L. Williams
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Estimating Canopy Structure in an Amazon Forest from Laser Range Finder and IKONOS Satellite Observations
Gregory P. Asner (gasner@globalecolgy.stanford.edu), Michael Palace, Michael Keller, Rodrigo Pereira Jr., Jose N. M. Silva and Johan C. Zweede
Canopy structural data can be used for biomass estimation and studies of carbon cycling, disturbance, energy balance, and hydrological processes in tropical forest ecosystems. Scarce information on canopy dimensions reflects the difficulties associated with measuring crown height, width, depth, and area in tall, humid tropical forests. New field and spaceborne observations provide an opportunity to acquire these measurements, but the accuracy and reliability of the methods are unknown. We used a handheld laser range finder to estimate tree crown height, diameter, and depth in a lowland tropical forest in the eastern Amazon, Brazil, for a sampling of 300 trees stratified by diameter at breast height (DBH). We found significant relationships between DBH and both tree height and crown diameter derived from the laser measurements. We also quantified changes in crown shape between tree height classes, finding a significant but weak positive trend between crown depth and width. We then compared the field-based measurements of crown diameter and area to estimates derived manually from panchromatic 0.8 m spatial resolution IKONOS satellite imagery. Median crown diameter derived from satellite observations was 78 percent greater than that derived from field-based laser measurements. The statistical distribution of crown diameters from IKONOS was biased toward larger trees, probably due to merging of smaller tree crowns, underestimation of understory trees, and overestimation of individual crown dimensions. The median crown area derived from IKONOS was 65 percent higher than the value modeled from field-based measurements. We conclude that manual interpretation of IKONOS satellite data did not accurately estimate distributions of tree crown dimensions in a tall tropical forest of eastern Amazonia. Other methods will be needed to more accurately estimate crown dimensions from high spatial resolution satellite imagery.
Nutrient Limitation to Primary Productivity in a Secondary Savanna in Venezuela
Nichole N. Barger (nichole@nrel.colostate.edu), Carla M. D'Antonio, Thaura Ghneim, Keary Brink, and Elvira Cuevas
We examined nutrient limitation to primary productivity in a secondary savanna in the interior branch of the Coastal Range of Venezuela, which was converted from forest to savanna more than 100 years ago. We manipulated soil nutrients by adding nitrogen (+N), phosphorus and potassium (+PK), and nitrogen, phosphorus, and potassium (+NPK) to intact savanna. Eleven months after fertilization, we measured aboveground biomass and belowground biomass as live fine roots in the top 20 cm of soil, and species and functional group composition in response to nutrient additions. Aboveground biomass was highest in the NPK treatment ([mean g/m 2 ]; control = 402, +N = 718, +PK = 490, +NPK = 949). Aboveground production, however, appeared to be limited primarily by N. Aboveground biomass increased 78 percent when N was added alone but did not significantly respond to PK additions when compared to controls. In contrast to aboveground biomass, belowground biomass increased with PK additions but showed no significant increase with N (depth 0-20 cm; [mean g/m 2 ]; control = 685, +N = 443, +PK = 827, +NPK = 832). There was also a 36 percent increase in root length with PK additions when compared to controls. Whole savanna shoot:root ratios were similar for control and +PK (0.6), while those for +N or +NPK fertilization were significantly higher (1.7 and 1.2, respectively). Total biomass response (above + belowground) to nutrient additions showed a strong N and PK co-limitation ([mean g/m 2 ]; control = 1073, +N = 1111, +PK = 1258, +NPK = 1713). Aboveground biomass of all monocots increased with N additions, whereas dicots showed no response to nutrient additions. Trachypogon spp. (T. plumosus + T. vestitus) and Axonopus canescens , the two dominant grasses, made up more than 89 percent of the total aboveground biomass in these sites. Trachypogon spp. responded to NPK, whereas A. canescens, sedges, and the remaining monocots only responded to N. Even though nutrient additions resulted in higher aboveground biomass in N and NPK fertilized plots, this had little effect on plant community composition. With the exception of sedges, which responded positively to N additions and increased from 4 to 8 percent of the plant community, no changes were observed in plant community composition after 11 months.
En este estudio se examinaron las limitaciones nutricionales en la productividad primaria de una sabana secundaria de ms de 100 aos localizada en el brazo interior de la Cordillera de la Costa de Venezuela. Se manipularon los nutrientes del suelo mediante la adicin de nitrgeno (+N), fsforo y potasio (+PK), y nitrgeno, fsforo, y potasio (+NPK) al suelo de la sabana. Despus de once meses de iniciarse los experimentos se midi la respuesta a la adicin de nutrientes en trminos de produccin de biomasa area, biomasa de races finas vivas en los primeros 20 cm de suelo, y cambios en la composicin de especies y grupos funcionales. La biomasa area fue mayor en las parcelas fertilizadas con N o en combinacin de NPK ([promedio g/m 2 ]; control = 402, +N = 718, +PK = 490, +NPK = 949) indicando que la produccin area est limitada principalmente por N. No hubo respuesta estadsticamente significativa a la adicin de PK con respecto a los controles. La biomasa de races finas aument con la adicin de PK y NPK mientras que no hubo aumento significativo con N (profundidad 0-20 cm; [promedio g/m 2 ]; control = 685, +N = 443, +PK = 827, +NPK = 832). La adicin de PK modific la arquitectura radical con un aumento de 36 por ciento en la longitud de las races con respecto al control. La relacin vstago/raz fue similar en los tratamientos control y +PK (0.6), pero significativamente mayor en +N (1.7) y +NPK (1.2) indicando nuevamente una limitacin principal por N. La respuesta de la biomasa total (vstago + races vivas) a la adicin de nutrientes refleja una colimitacin de N y PK ([promedio g/m 2 ]; control = 1073, +N = 1111, +PK = 1258, +NPK = 1713). La biomasa area de las monocotiledneas aument con la adicin de N, mientras que no hubo respuesta significativa a la adicin de nutrientes en las dicotiledneas. Trachypogon spp. (T. plumosus + T. vestitus) and Axonopus canescens , las dos gramneas dominantes, representaron ms del 89 por ciento de la biomasa total en las parcelas. Trachypogon spp. respondieron a NPK, mientras que A. canescens, ciperceas, y las otras monocotiledneas slo respondieron a N. No hubo cambios significativos en la composicin de especies como respuesta a la adicin de nutrientes, con la excepcin de las ciperceas que respondieron significativamente a la adicin de N con un aumento de 4 a 8 por ciento.
Composition Patterns of Caribbean Limestone Forests: Are Parsimony, Classification, and Ordination Analyses Congruent?
Jorge Carlos Trejo-Torres (jctrejo@excite.com) and James D. Ackerman
This study presents an analysis of floristic composition patterns for limestone vegetation from three Caribbean islands: Hispaniola, Mona, and Puerto Rico. The physical setting of these communities varies from very dry to wet climates, and from ridgetops, slopes, to plateaus. Consequently, vegetation communities have variable species composition. The questions addressed were: (1) What are the patterns of species composition among limestone vegetation types based on a parsimony analysis of species assemblages (PASA) and how congruent are they with geography, climate, topography, and vegetation physiognomy? and (2) How do PASA patterns compare to floristic patterns obtained with a classification (UPGMA) and an ordination (NMS)? The main distinction of floristic categories was between communities of humid and dry climates, followed by a finer separation of communities congruent with topography; vegetation physiognomy corresponded with both. PASA, UPGMA, and NMS produced highly coincident floristic groups; however, affinities among groups were different. Advantages of PASA over UPGMA and NMS are that PASA produces groupings strictly based on the shared species and provides different measures of support for floristic groups. The three techniques indicated that the humid and dry limestone areas of Puerto Rico had floristically divergent dry-type vegetation, even when they were structurally and physiognomically convergent. Also, floristic affinities of dry communities in Puerto Rico were stronger with dry communities on other islands than to more humid communities on the same island; thus, humidity regime is stronger than geography in promoting floristic links among limestone vegetation communities of the Caribbean. Almost every conclusion obtained from UPGMA and NMS was also taken from PASA, and so all three techniques are compatible. The methodological, theoretical, and interpretive simplicity of PASA is what makes it an attractive procedure for studies that examine composition patterns.
Este estudio analiza los patrones de composicin florstica entre bosques crsticos en tres islas del Caribe: La Espaola, Mona, y Puerto Rico. El ambiente fsico de estas comunidades vara de climas muy secos a muy hmedos, y de puntas, a laderas, a valles. Consecuentemente, las comunidades vegetales tienen una composicin florstica considerablemente variable. Las preguntas abordadas son: Cules son los patrones de composicin florstica entre comunidades de vegetacin crstica obtenidos por un Anlisis Parsimonioso de Ensamblajes de Especies (APEE)? Son estos patrones congruentes con la geografa, el clima, la topografa y la fisionoma de la vegetacin? Cmo se comparan los patrones del APEE con otros obtenidos por una clasificacin (UPGMA) y una ordenacin (NMS)? La distincin principal entre las categoras florsticas fue entre comunidades de climas hmedos y secos, seguida de una separacin ms fina de las categoras congruentes con la topografa; la fisionoma de la vegetacin fue consistente con ambos factores. El APEE, UPGMA, y NMS produjeron grupos florsticos muy coincidentes. Las ventajas del APEE sobre UPGMA y NMS son que el primero produce agrupaciones basadas estrictamente en especies compartidas y provee distintas medidas del soporte de los grupos florsticos. Las tres tcnicas indicaron que las reas crsticas hmedas y secas de Puerto Rico tienen una vegetacin de tipo seco que es florsticamente divergente, an cuando es estructural y fisionmicamente convergente. Tambin, las afinidades florsticas de las comunidades secas de Puerto Rico fueron ms cercanas a las comunidades secas de las otras islas, que a las comunidades ms hmedas de la misma isla; entonces, el rgimen de humedad es ms fuerte que la geografa para definir afinidades florsticas entre estas comunidades de vegetacin crstica del Caribe. Las conclusiones basadas en UPGMA y NMS pueden tambin extraerse del APEE, de tal modo que las tres son tcnicas compatibles. La simplicidad metodolgica, terica e interpretativa del APEE lo convierte en un procedimiento atractivo para estudios que buscan patrones de composicin.
Distribution and Diversity of Pteridophytes and Melastomataceae along Edaphic Gradients in Yasun National Park, Ecuadorian Amazonia
Hanna Tuomisto (hantuo@utu.fi), Kalle Ruokolainen, Axel Dalberg Poulsen, Robbin C. Moran, Catalina Quintana, Gustavo Caas, and Jorge Celi
We documented the floristic composition of pteridophytes (ferns and fern allies) and Melastomataceae in Yasun National Park, Amazonian Ecuador. Our main questions were: (1) Are the density of individuals, species richness, and/or species diversity (measured with Shannon's H') of the two plant groups related to edaphic differences? and (2) How many of the pteridophyte and Melastomataceae species are non-randomly distributed in relation to a soil base content gradient within terra firme (non-inundated forest). To answe these questions, we sampled 27 line transects of 500 X 5 m distributed in an area of ca 20 X 25 km. The study area included a permanent 50 ha plot established to monitor forest dynamics; thus, our results also provide information on landscape-scale floristic variability to which results from within the plot can be compared. A total of 45,608 individuals and 140 species of pteridophytes, and 4893 individuals and 89 species of the Melastomataceae, were counted in thetransects. Both with pteridophytes and with Melastomataceae, a clear negative correlation was found between the amount of extractable bases in the soil and the number of plant individuals encountered in a transect. With Melastomataceae, species richness and species diversity also were negatively correlated with soil base content, but with pteridophytes they were not. More than 50 percent of the common species of both pteridophytes and Melastomataceae were nonrandomly distributed along the soil cation content gradient within terra firme. We conclude that while the species richness patterns observed in one plant group are not indicative of similar patterns in other plant groups, it seems likely that a substantial (but unknown) proportion of species belonging to other plant groups will be found to show distribution patterns that reflect edaphic preferences within terra firme forests.
Se estudi la composicin florstica de pteridofitas (helechos y plantas afines) y Melastomataceas en el Parque Nacional Yasun, Amazona ecuatoriana. Nuestras preguntas principales fueron: (1) estn relacionadas la densidad de individuos, la riqueza de especies y/o la diversidad (medida con la H' de Shannon) de los dos grupos de plantas con las diferencias edficas? y (2) cuntas de las especies de pteridofitas y Melastomataceas estn distribuidas en tierra firme de una manera que no sea al azar, sino en relacin a un gradiente de concentracin de cationes en el suelo? Para desarrollar estas preguntas, muestreamos 27 transectos de 500 por 5 m distribuidos en una rea de 20 por 25 km. El rea de estudio incluye una parcela permanente de 50 ha, establecida para estudiar la dinmica del bosque; por lo tanto, nuestros resultados proveen informacin sobre la variabilidad florstica en una escala del paisaje que puede compararse con la de la parcela. En total se encontraron en los transectos 45,608 individuos y 140 especies de pteridofitas, y 4893 individuos y 89 especies de Melastomataceas. Tanto las pteridofitas como las Melastomataceas, mostraron una correlacin negativa significativa entre la cantidad de cationes en el suelo y el nmero de individuos de plantas dentro de un transecto. En las Melastomataceas, la riqueza de especies y la diversidad estuvieron negativamente correlacionadas con el contenido de cationes en el suelo, pero en las pteridofitas, no existi tal correlacin. Ms de 50 por ciento de las especies comunes de pteridfitas y Melastomataceas estuvieron distribuidas dentro de la tierra firme de una manera no aleatoria en relacin con el gradiente de cationes en el suelo. Concluimos que aunque los patrones de diversidad de las especies observadas en un grupo de plantas no son indicativos de patrones similares en otros grupos, es probable que una proporcin apreciable (pero desconocida) de especies pertenecientes a otros grupos de plantas pueda mostrar patrones de distribucin que reflejen preferencias edficas dentro de los bosques de tierra firme.
Elevational Variation of Leaf Traits in Montane Rain Forest Tree Species at La Chinantla, Southern Mxico
No Velzquez-Rosas, Jorge Meave (jamdc@hp.fciencias.unam.mx), and Sonia Vzquez-Santana
Variation in leaf traits of dominant tree species in six montane rain forest communities was analyzed along an elevational gradient ranging from 1220 to 2560 m within a single basin at La Chinantla, Oaxaca, Mxico. Three groups of characters were used: morphological (leaf shape, margin, blade configuration, and phyllotaxy), morphometric (leaf area, leaf mass per area, stomatal density, and blade length/width ratio), and anatomical (thicknesses of blade, palisade [PP], and spongy [SP] parenchymae, PP/SP ratio, and epidermis and cuticle thicknesses). The variation of morphological characteristics was only evident at the highest elevations; in contrast, thickness of leaf blade, PP, SP, as well as leaf mass per area clearly increased along the gradient, whereas leaf area was the only variable that significantly decreased with elevation. Thicknesses of epidermis and of the two cuticles were not significantly correlated with elevation. A classification analysis based on a leaf trait matrix led to the distinction between low and high elevation communities, with an approximate limit between them at ca 2300 to 2400 m. The results are discussed in light of environmental changes occurring along elevational gradients. Leaf characteristics of montane rain forest plants offer important insights about the complex roles of abiotic factors operating in these environments and supplement the traditional physiognomic classification schemes for these communities.
Se analiz la variacin de caractersticas foliares de las especies arbreas dominantes en seis comunidades de bosque lluvioso de montaa ubicadas a lo largo de un gradiente altitudinal comprendido entre 1220 y 2560 m s.n.m. dentro de una misma cuenca en la regin de La Chinantla, Oaxaca, Mxico. Se utilizaron tres tipos de caracteres: morfolgicos (forma de la hoja, tipo de margen, configuracin de la lmina y filotaxia), morfomtricos (rea foliar, masa foliar por unidad de rea, densidad estomtica y cociente largo/ancho de la lmina), y anatmicos (grosor de la lmina, de los parnquimas en empalizada [PEm] y esponjoso [PEs], cociente PEm/PEs y grosor de la epidermis y de la cutcula). La variacin de las caractersticas morfolgicas slo fue evidente en los sitios de mayor elevacin; por el contrario, los grosores de la lmina foliar, el PEm y el PEs, as como la masa foliar por unidad de rea aumentaron claramente a lo largo del gradiente. El rea foliar fue la nica variable que mostr un decremento significativo con la altitud. Los grosores de la epidermis y las dos cutculas no se correlacionaron significativamente con la altitud. Un anlisis de clasificacin basado en una matriz de caractersticas foliares permiti distinguir comunidades de baja y de alta altitud, cuyo lmite se ubica aproximadamente entre 2300 y 2400 m s.n.m. Los resultados son discutidos a la luz de los cambios ambientales que tienen lugar a lo largo de gradientes altitudinales. Las caractersticas foliares de los bosques montanos lluviosos proporcionan claves importantes sobre el papel relativo de los factores abiticos que operan en estos ambientes y complementan los esquemas fisonmicos de clasificacin de estas comunidades.
Herbivore-Free Time? Damage to New Leaves of Woody Plants after Hurricane Andrew
Suzanne Koptur (kopturs@flu.edu), M. Cristina Rodriguez, Steven F. Oberbauer, Carl Weekley, and Alan Herndon.
All broadleaf woody plants of pinelands and hammocks (upland areas) in the northern parts of Everglades National Park were defoliated by the strong winds of Hurricane Andrew in August 1992. Most plants re-leafed within two months of the storm, at which time we tagged newly produced leaves of eight species (five species in two hardwood hammocks and four in two pineland sites; one species was studied in both habitats), and monitored individual leaf area lost or damaged monthly for three months. We marked a second cohort of new leaves on the same individuals four months later and monitored these for three months. Herbivory rates in leaves of the first cohort were lower than observed in pre-hurricane studies on two of the species, and lower in the first cohort than in the second cohort in six of the eight species studied, indicating that most insect herbivores were virtually absent for the first few months after the storm. Additionally, most species produced significantly larger leaves in the first cohort than the second cohort, and leaves of the second cohort were not significantly different in size from pre-hurricane leaves in one species for which pre-hurricane data were available. The large disturbance of the hurricane defoliated and reduced the aboveground biomass of the plants, but apparently also eliminated most herbivores and competition for light, facilitating the recovery of the plants.
Todas las plantas de hojas anchas que se encontraban en los pinares rocosos y en los bosques de madera dura en el rea norte del Parque Nacional de los Everglades fueron defoliadas por los vientos fuertes del huracn Andrew en agosto de 1992. En muchas de estas plantas las hojas renacieron en los dos meses posteriores al huracn; durante este periodo se marcaron las hojas nuevas en ocho especies (cinco especies en dos bosques de madera dura y cuatro especies en dos sitios de pinares, una de dichas especies se estudi en los dos habitats). Se registr el rea foliar perdida o daada de cada hoja cada mes durante tres meses. Un segundo grupo de hojas nuevas se marc en los mismos individuos cuatro meses despus y se muestre durante tres meses. La tasa de herbivora en las hojas del primer grupo fue ms baja que la observada en estudios anteriores al huracn en dos de las especies, y ms baja en el primer grupo que en el segundo en seis de las ocho especies estudiadas, lo cual indica que muchos de los insectos herbvoros estuvieron ausentes en los meses posteriores al huracn. Adicionalmente en el primer grupo muchas de las especies produjeron hojas significativamente ms grandes que las del segundo. El tamao de las hojas del segundo grupo no fue significativamente diferente del de hojas previas al huracn en una de las especies de la que se tenan mediciones. La defoliacin masiva y la reduccin de biomasa causada por el huracn en las plantas elimin la mayora de insectos herbvoros y la competencia por la luz lo que ayud a la recuperacin de las plantas.
Spatio-temporal Variations in Post-dispersal Seed Fate
Franois Feer (feer@mnhn.fr) and Pierre-Michel Forget
The post-dispersal fate of Chrysophyllum lucentifolium (a canopy tree; Sapotaceae) seeds was analyzed in French Guiana over three consecutive years. Experiments using 750 thread-marked seeds were performed to investigate seed removal, predation, and caching by terrestrial vertebrates on howler monkey (Alouatta seniculus) defecation sites, where clumps of intact C. lucentifolium seeds were observed. Year-to-year variations in seed fate during the peak fruiting period were considered in relation to overall fruit and seed resource availability estimated by a raked-trail survey. The effect of two forest areas, which differed in soil and floristic composition, was examined with conspecific fruiting tree density as a covariant. Exclosure versus open treatment was used to discriminate small rodents (not larger than a spiny rat) from other vertebrates. The presence of fresh howler dung did not affect seed fate after 20 days as shown by comparisons between defecation sites and control during the first year. There was a significant effect of year on the percentage of seeds remaining after 20 days. Low seed removal in 1995 and 1996 (compared to 1997) corresponded to higher overall fruiting and higher fruiting of C. lucentifolium , or the presence of alternative resources for rodents. An effect of forest area was observed on the seed removal rate, which varied with years and protection. Comparatively, an effect of forest area on the percentage of seeds lost was observed in 1996 and an effect of treatment on the percentage of seeds eaten was seen in 1995. The mode of seed caching suggested that spiny rats were the main seed remover. Results of this study suggest that greater seedling recruitment may occur when large fruit crop and high howler dispersal co-occur with a lower impact of rodents i.e., when rodents are saturated by abundant and diversified fruit resources such as in 1995). Such event synchrony, however, is highly unpredictable after only three years of study.
Le devenir des graines aprs dispersion de Chrysophyllum lucentifolium (Sapotaceae), un arbre de la canope, a t analys en Guyane franaise sur trois annes conscutives. Des expriences utilisant 750 graines marques avec un fil ont t menes pour valuer le taux de disparition, de prdation et de mise en rserve par les vertbrs terrestres sur les sites de dfcation de singes hurleurs roux (Alouatta seniculus), o des agrgats de graines intactes de C. lucentifolium ont t observs. Les variations annuelles du devenir des graines pendant le maximum de fructification ont t examines en fonction des disponibilits globales de fruits et de graines estimes par rcoltes sur des layons balays. L'effet li deux zones de fort distinctes par le type de sol et la composition floristique a t analys avec la densit des arbres en fruit de C. lucentifolium comme covariant. Un traitement avec ou sans exclos a permis de distinguer l'action des petits rongeurs (pas plus grand que le rat pineux) de celle des autres vertbrs. La prsence de dfcation frache de singe hurleur n'a pas affect le devenir des graines aprs 20 jours d'aprs la comparaison entre les sites de dfcation et les contrles durant la premire anne. Aprs 20 jours, des variations inter-annuelles significatives du pourcentage de graines restantes ont t observes. Une disparition des graines plus faible en 1995 et 1996 qu'en 1997 concide avec une forte fructification gnrale ainsi qu'une forte fructification de C. lucentifolium ou la prsence de ressources alternatives attractives pour les rongeurs. Un effet de la zone de fort a t observ sur la disparition des graines qui a vari avec les annes et la protection. Un effet de la zone de fort a t observ sur la proportion de graines perdues en 1996 et un effet du traitement a t observ en 1995 sur la proportion de graines consommes. Le type de cache observ suggre que le rat pineux a t le principal consommateur et disperseur des graines. Les rsultats de cette tude suggrent qu'un recrutement accru des plantules est possible sur les sites o les singes hurleurs dfquent les graines en agrgats quand de fortes productions de fruits concident avec un faible impact des rongeurs c'est dire quand ceux-ci sont saturs par des ressources en fruit abondantes et diversifies. Cette synchronisation est, pour l'instant, fortement imprvisible aprs seulement trois annes d'tudes.
Spatial and Temporal Variation of Macroinvertebrate Drift in Two Neotropical Streams
Luz Boyero (luz@mncn.csic.es) and Jaime Bosch
The detection of spatial variation in macroinvertebrate drift depends on the spatial scale of investigation in streams of the La Selva Biological Station, Costa Rica. Drift samples were taken in a spatially nested design, with two streams, two reaches per stream, two riffles per reach, and four replicate samples per riffle. Drift showed little variation among streams, but varied significantly at the scales of reach and riffle, with variation among samples also high. In addition, sampling took place at two temporal scales: diel and at two different periods that differed in rainfall conditions. Drift diel periodicity was a clear pattern, while only density of individuals varied among sampling periods. This is the first study of macroinvertebrate drift at multiple spatial scales, despite the recognition that multi-scale studies are essential for a more complete understanding of community patterns and processes.
La deteccin de la variacin espacial en la deriva de macroinvertebrados depende de la escala espacial de investigacin, en ros de la Estacin Biolgica La Selva, Costa Rica. Se tomaron muestras de deriva usando un diseo espacial anidado, con dos ros, dos tramos por cada ro, dos rpidos por cada tramo y cuatro rplicas por cada rpido. La deriva vari muy poco entre ros, pero su variacin result significativa en las escalas de tramo y rpido, y fue alta entre muestras dentro de cada rpido. Las muestras se tomaron en dos escalas temporales: da y noche, y dos periodos con diferentes condiciones de lluvia. Se encontr una clara periodicidad diaria en la deriva, mientras que solamente la densidad de individuos vari entre periodos. Este es el primer estudio de la deriva de macroinvertebrados en mltiples escalas espaciales, a pasar de que se ha reconocido la necesidad de realizar este tipo de estudios para entender mejor los partrones y procesos de las comunidades.
Canopy Ferns in Lowland Dipterocarp Forest Support a Prolific Abundance of Ants, Termites, and Other Invertebrates
Martin D. F. Ellwood (mdfe2@cam.ac.uk), David T. Jones (dtj@nhm.ac.uk), and William A. Foster
The epiphytic Bird's Nest Fern (Asplenium nidus complex) has a large basket-shaped rosette that accumulates leaf litter. We investigated the role of these ferns in supporting invertebrate populations in the primary lowland dipterocarp forest of Danum Valley, Sabah, Malaysia. Ferns were divided into three size classes: large (rosette diameter >60 cm), intermediate (30-60 cm), and small (<30 cm). Seven hectares of forest were surveyed: the canopy had a mean density of 30 large ferns/ha and 20 intermediate ferns/ha. Six large and five intermediate ferns were removed from the crowns of Parashorea tomentella (Dipterocarpaceae) at heights between 39 and 52 m. The largest ferns had fresh weights of ca 200 kg. The mean animal abundance in large and intermediate ferns was 41,000 and 8000, respectively. Termites and ants represented at least 90 percent of the abundance in these ferns. Of the 11 ferns, 4 contained a termite nest of Hospitalitermes rufus (Nasutitermitinae), while another contained a nest of an undescribed species of Hospitalitermes . An additional 56 small ferns were removed from the low canopy (2-6 m above the forest floor), of which only 1 contained a termite nest (Nasutitermes neoparvus). These results suggest that Bird's Nest Ferns contain ca 0.5 million termites/ha and contribute almost one ton (dry mass) of suspended soil and plant material/ha. Five of the trees containing large ferns were fogged immediately before the removal of the ferns. From these samples we were able to estimate the total number of animals in each tree crown. When each estimate was added to the abundance in each fern, the results suggested that a single large fern may contain from 7 to 93 percent of the total number of invertebrates in the crown. Although these results must be treated with caution because of the small sample size, they have important implications for studies of canopy invertebrates.
Discrimination among Fish Models by Hawaiian Eleotris sandwicensis (Eleotridae)
Lynda D. Corkum (corkum@uwindsor.ca)
I examined behavioral responses of the benthic fish Eleotris sandwicensis to painted models (dummies) of fish that Eleotris typically encounter in Hawaii. Eleotris sandwicensis were associated with coarse substrates where their mean (SE) density was 1.5 (0.30) fish/m2. I hypothesised that Eleotris would retreat from all models in open areas, but not when they were present in shelters. The five models represented Stenogobius hawaiiensis, Awaous guamensis, E. sandwicensis (female coloration), a male E. sandwicensis in breeding colors (black), and a 12 cm block of wood (control). Whether or not Eleotris held its position or retreated was not a function of body size. Differences among the responses of Eleotris to models depended on whether or not the fish was hidden or exposed on substrates. More retreats in response to models occurred when Eleotris were exposed on substrates than when fish were hidden. There were no significant differences in the response of E. sandwicensis to models when fish were exposed on substrates. In contrast, responses of E. sandwicensis to the models were not random for fish that were hidden, indicating that Eleotris discriminated among the models. The basis for discrimination among models was most likely visual. Although Eleotris are typically secretive, their presence on exposed substrates at this study site may be attributed to the lack of benthivorous fishes and few avian predators. The ability of Eleotris to distinguish among fishes when hidden as well as their tendency to retreat in response to all intruders whenever exposed on substrate surfaces could reduce potential interactions between Eleotris and other native and nonindigenous fishes.
Use of Fruiting Trees by Birds in Continuous Forest and Riparian Forest Remnants in Los Tuxtlas, Veracruz, Mexico
Catherine Graham (cgraham@uclink.berkeley.edu), Jess Eduardo, Martnez-Leyva, and Leticia Cruz-Paredes
The composition of plant species in fragmented landscapes may be influenced by the pattern of visitation by birds to fruiting trees and by the movement of seeds among and within fragments. We compared bird visitation patterns to two tree species (Dendropanax arboreus , Araliaceae; Bursera simaruba , Burseraceae) in continuous forest and remnants of riparian vegetation in a region dominated by pasture in Los Tuxtlas, Veracruz, Mexico. We quantified frequency of visitation, fruit consumption, consistency of visitation (percentage of total tree observation periods during which a given bird species was recorded), and species composition of birds at individuals of both tree species in continuous forest and riparian remnants. Bird visitation rate, species richness, and fruit consumption rates were similar within both tree species in the two habitats. Species assemblages at D. arboreus were different between continuous forest and remnants. Species assemblages at B. simaruba did not differ by habitat. Our results demonstrate that habitat disturbance may influence avian visitation patterns, which may in turn affect subsequent recruitment patterns in some tree species. Our results, however, were not consistent between the tree species, suggesting that it is difficult to generalize concerning the effects of forest disturbance on avian species assemblages in fruiting trees.
Damage and Recovery of Cycas micronesica after Typhoon Paka
Heidi Hirsh and Thomas Marler (tmarler@uog9.uog.edu)
Typhoon Paka passed over Guam on 16 December 1997, and caused extensive damage to the Cycas micronesica population. Defoliation reduced subsequent stem extension and leaf size, and increased synchrony of flushes. Decapitated plants developed numerous adventitious buds on damaged stems during recovery. Toppled plants were selectively browsed by feral deer and pigs. Epiphytes increased susceptibility to decapitation or toppling. Growth reduction was minimal and ephemeral, indicating that this species is highly resilient to tropical cyclone damage.
Staggered Flowering in Four Sympatric Varieties of Geonoma cuneata (Palmae)
Finn Borchsenius (finn.borchsenius@biology.au.dk)
Phenology, flowering biology, and pollination were studied for one year in four sympatric varieties of the polymorphic palm Geonoma cuneata in Ecuador. Flowering seasons of the three most common varieties were significantly staggered resulting in minimal temporal overlap. No marked differences were found with respect to flowering biology or pollination. The implication of these findings for explaining the complicated morphological variation pattern found in G. cuneata and similar species complexes is discussed.
Spatial and Temporal Variation in Hydrochory in Amazonian Floodplain Forest
Susan M. Moegenburg (moegenburgs@npz.si.gov)
The hypothesis that water depth, plant species, and the presence of submerged substrates influence seed dispersal by water was tested in a whitewater tributary of the Tocantins River of the Amazon Basin. Seed dispersal was greatest when water depth was greatest, which occurred during the new moon. Seeds of buoyant species with smaller seeds required less water for dispersal than large seeded species. Submerged objects reduced the distance dispersed but not the probability of dispersal.
Massive Seed Predation of Pseudobombax grandiflorum (Bombacaceae) by Parakeets Brotogeris versicolurus (Psittacidae) in a Forest Fragment in Brazil
Mercival Roberto Francisco (dge@power.ufscar.br), Vitor de Oliveira, and Lunardi Mauro Galetti
Here we report massive seed predation of Pseudobombax grandiflorum (Bombacaceae) by Botogeris versicolurus (Psittacidae) in a forest fragment in Brazil. The intensity of seed predation was very high when compared to other studies in continuous forest, perhaps resulting from a scarcity of resources in such areas. This scarcity may limit the range of parrot's diet to a few plant species. It suggests that studies of Psittacidae seed predation may be important for conservation of some plants in fragments.
Effects of the Tropical Freshwater Shrimp Caridina weberi (Atyidae) on Leaf Litter Decomposition
Jennifer L. Williams (jlw6@uclink4.berkeley.edu)
Effects of feeding by atyid shrimp, Caridina weberi, on the rate of decomposition of leaf litter were studied in the Opunohu River, Moorea, French Polynesia. In a laboratory feeding experiment shrimp consumed microbially conditioned Hibiscus leaves, but in a field study shrimp did not affect the rate of decomposition of leaf litter. In this system, the rate of decomposition was influenced more by water discharge or by microbial activity than by shrimp.