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Tropical Forests (tropical + forest)

Distribution by Scientific Domains
Life Sciences88%
Earth and Environmental Science7%
Humanities and Social Sciences2%
3 Other Domains3%
Distribution within Life Sciences
Ecology & Organismal Biology18%
Conservation Science13%
Entomology3%
14 Other Subdomains63%

Kinds of Tropical Forests

  • dry tropical forest
  • lowland tropical forest
    		•
  • moist tropical forest
  • seasonal tropical forest
    		•
  • wet tropical forest

    • Terms modified by Tropical Forests

  • tropical forest species
    		•

    Selected Abstracts

    Effects of Conversion of Dry Tropical Forest to Agricultural Mosaic on Herpetofaunal Assemblages

    CONSERVATION BIOLOGY, Issue 2 2008
    IRERI SUAZO-ORTUÑO
    atributos de vulnerabilidad; bosque tropical seco; ensambles herpetofaunísticos; modificación del hábitat; mosaico agrícola Abstract:,We explored the impact of forest conversion to agricultural mosaic on anuran, lizard, snake, and turtle assemblages of Neotropical dry forests. Over 2 years, we sampled 6 small watersheds on the west coast of Mexico, 3 conserved and 3 disturbed. The disturbed watersheds were characterized by a mosaic of pastures and cultivated fields (corn, beans, squash) intermingled with patches of different successional stages of dry forest. In each watershed, we conducted 11 diurnal and nocturnal time-constrained searches in 10 randomly established plots. We considered vulnerability traits of species in relation to habitat modification. Eighteen anuran, 18 lizard, 23 snake, and 3 turtle species were recorded. Thirty-six species (58%) occurred in both forest conditions, and 14 (22%) and 12 species (19%) occurred only in the conserved and disturbed sites, respectively. Assemblages responded differently to disturbance. Species richness, diversity, and abundance of lizards were higher in disturbed forests. Anuran diversity and species richness were lower in disturbed forest but abundance was similar in both forest conditions. Diversity, richness, and abundance of turtles were lower in disturbed forest. The structure and composition of snake assemblages did not differ between forest conditions. We considered species disturbance sensitive if their abundance was significantly less in disturbed areas. Four anuran (22%), 2 lizard (11%), and 3 turtle (100%) species were sensitive to disturbance. No snake species was sensitive. The decline in abundance of disturbance-sensitive species was associated with the reduction of forest canopy cover, woody stem cover, roots, and litter-layer ground cover. Anuran species with small body size and direct embryonic development were especially sensitive to forest disturbance. An important goal for the conservation of herpetofauna should be the determination of species traits associated with extinction or persistence in agricultural mosaics. Resumen:,Exploramos el impacto de la conversión de bosques a mosaico agrícola sobre ensambles de lagartijas, serpientes y tortugas de bosques Neotropicales secos. Durante 2 años muestreamos 6 cuencas pequeñas, 3 conservadas y 3 perturbadas, en la costa occidental de México. Las cuencas perturbadas se caracterizaron por un mosaico de pastizales y campos cultivados (maíz, frijol, calabaza) entremezclados con parches de bosque seco en diferentes etapas sucesionales. En cada cuenca, realizamos 11 búsquedas diurnas y nocturnas en 10 parcelas establecidas aleatoriamente. Consideramos los atributos de vulnerabilidad de especies en relación con la modificación del hábitat. Registramos 18 especies de lagartijas, 23 de serpientes y 3 de tortugas. Treinta y seis especies (58%) ocurrieron en ambas condiciones de bosque, y 14 (22%) y 12 (19%) especies solo ocurrieron en los sitios conservados y perturbados, respectivamente. Los ensambles respondieron a la perturbación de manera diferente. La riqueza de especies, la diversidad y la abundancia de lagartijas fueron mayores en los bosques perturbados. La diversidad y riqueza de especies de anuros fueron menores en el bosque perturbado pero la abundancia fue similar en ambas condiciones de bosque. La diversidad, riqueza de especies y abundancia de tortugas fueron menores en el bosque perturbado. La estructura y la composición de los ensambles de serpientes no difirieron entre condiciones de bosque. Consideramos que las especies eran sensibles a la perturbación si su abundancia fue significativamente menor en las áreas perturbadas. Cuatro (22%) especies de anuros, 2 (11%) de lagartijas y 3 (100%) de tortugas fueron sensibles a la perturbación. Ninguna especie de serpiente fue sensible. La declinación en la abundancia de especies sensibles a la perturbación se asoció con la reducción en la cobertura del dosel, de tallos leñosos, raíces y hojarasca. Las especies de anuros de cuerpo pequeño y desarrollo embrionario directo fueron especialmente sensibles a la perturbación del bosque. La determinación de atributos de las especies asociadas con su extinción o persistencia en mosaicos agrícolas debería ser una meta importante para la conservación de la herpetofauna. [source]

    Biological and Cultural Anthropology of a Changing Tropical Forest: A Fruitful Collaboration across Subfields

    AMERICAN ANTHROPOLOGIST, Issue 2 2006
    REBECCA HARDIN
    In this article, we integrate approaches from biological and cultural anthropology to describe changing relationships between humans and animals in the Dzanga-Ndoki Park and Dzanga-Sangha Dense Forest Reserve (RDS), Central African Republic (CAR). Recent decades have seen a rapid proliferation of human activities, with striking tensions between logging and conservation economies. Our data suggest that certain animals and humans initially adapted successfully to these forest uses, and that local residents have crafted culturally rich new ways of living in the forest. However, our longitudinal data indicate animal declines and expanding frontiers of increasingly intensive human use. These trends are altering previous territorial arrangements and coming to undermine today's remarkably rich spectrum of human,animal encounters there. Our combined approach offers an alternative to increasingly distinct method and theory between anthropology's subfields. We sketch a research agenda for integrated anthropological attention to environmental change, especially to transformations in human,animal interactions and entanglements. [source]

    Reproductive Biology of the Epiphytic Bromeliad Werauhia gladioliflora in a Premontane Tropical Forest

    PLANT BIOLOGY, Issue 2 2005
    A. Cascante-Marín
    Abstract: The floral phenology, fruit and seed production, and self-compatibility of Werauhia gladioliflora, an epiphytic bromeliad with a wide distribution, were studied in a premontane forest in the Monteverde area in Costa Rica. The species presents the pollination syndrome of chiropterophily, and it is visited by the small bats Hylonycteris underwoodi and Glossophaga commissarisi (Glossophaginae). The population flowering period extended from October to early December (end of rainy season) and seed dispersal occurred from February to April (dry season). Most plants opened a single flower per night, either every day or at one-day intervals during the flowering period. In natural conditions, the average fruit set amounted to almost half of the potential output, but individual fecundity (number of seeds) remained high. Seed number per fruit and germination capacity after artificial selfing and out-crossing treatments did not differ from natural pollination conditions. Werauhia gladioliflora exhibited high levels of autonomous self-pollination and self-compatibility at the individual and population level, characters associated with the epiphytic habitat. These reproductive traits are also associated with early colonizer species, yet life history traits, such as seed dispersal, seedling establishment success, and growth, are likely to have a major role in determining the presence of this species in the successional vegetation patches scattered over the studied premontane area. [source]

    Effects of Mycorrhizae and Nontarget Organisms on Restoration of a Seasonal Tropical Forest in Quintana Roo, Mexico: Factors Limiting Tree Establishment

    RESTORATION ECOLOGY, Issue 2 2005
    Michael F. Allen
    Abstract We initiated a study of the effects of mycorrhizal fungal community composition on the restoration of tropical dry seasonal forest trees. Tree seedlings were planted in a severely burned experimental site (1995 fire) during the growing season of 1998 at the El Edén Ecological Reserve, in north Quintana Roo, Mexico. Seedlings of Leucaena leucocephala, Guazuma ulmifolia, Caesalpinia violacea, Piscidia piscipula, Gliricidia sepium, and Cochlospermum vitifolium were germinated in steam-sterilized soil and either remained uninoculated (nonmycorrhizal at transplanting) or were inoculated with mycorrhizal fungi in soils from early-seral (recently burned) or late-seral (mature forest) inoculum. Inoculum from the early-seral soil was largely Glomus spp., whereas a diverse community of arbuscular mycorrhizal fungi were reintroduced from the mature forest including species of Scutellospora, Gigaspora, Glomus, Sclerocystis, and Acaulospora. Plants grew better when associated with the mature forest inoculum, unlike a previous experiment in which plants grew taller with the early-seral inoculum. Reasons for the different responses include a less-intense burn resulting in more residual organic matter. In addition to mycorrhizal responses, plants were severely affected by deer browsing. One tree species, C. vitifolium found in the region but not in the reserve, was eliminated by a resident fungal facultative pathogen. Several practical conclusions for restoration can be made. The common nursery practice of soil sterilization may be detrimental because it eliminates beneficial mycorrhizal fungi; species not native to the site may not survive because they may not be adapted to the local pathogens; and herbivory can be severe depending on the landscape context of the restoration. [source]

    Declines in Leaf Litter Nitrogen Linked to Rising Temperatures in a Wet Tropical Forest

    BIOTROPICA, Issue 5 2010
    Katherine Tully
    ABSTRACT In the tropics rainfall can vary by hundreds of millimeters from month to month, while mean temperatures fluctuate by only a few degrees. Nevertheless, during this 7-year study, we observed 35,52 percent declines in litter nitrogen concentrations in response to small increases in minimum temperature, with no response to the larger oscillations in rainfall. Abstract in Spanish is available at http://www.blackwell-synergy.com/loi/btp. [source]

    Assessment of Aboveground Carbon in Primary and Selectively Harvested Tropical Forest in Papua New Guinea

    BIOTROPICA, Issue 4 2010
    Julian C. Fox
    ABSTRACT Papua New Guinea (PNG) has become the focus of climate change mitigation initiatives such as reducing emissions from deforestation and forest degradation, but defensible estimates of forest carbon are lacking. Here we present a methodology for estimating aboveground forest carbon, and apply it to a large Permanent Sample Plot system maintained by Papua New Guinea Forest Research Institute. We report the first estimates of forest carbon in lowland tropical forest in PNG. Average aboveground carbon in stems >10 cm diam. for 115 selectively harvested 1-ha plots in lowland tropical forest was 66.3±3.5 Mg C/ha (95% CI) while for 10 primary forest plots the average was 106.3±16.2 Mg C/ha. We applied ratios based on field observations, in-country studies, and the literature to estimate unmeasured pools of aboveground carbon (stems <10 cm diam., fine litter and coarse woody debris). Total aboveground carbon was estimated at 90.2 and 120.8 Mg C/ha in selectively harvested and primary lowland forest, respectively. Our estimate for primary tropical forest is lower than biome averages for tropical equatorial forest, and we hypothesize that frequent disturbances from fire, frost, landslides, and agriculture are limiting carbon stock development. The methodology and estimates presented here will assist the PNG government in its preparedness for mitigation initiatives, are of interest to communities that are seeking to participate in voluntary carbon markets, and will encourage transparency and consistency in the estimation of forest carbon. [source]

    Dispersal of Desiccation-Sensitive Seeds is not Coincident with High Rainfall in a Seasonal Tropical Forest in Australia

    BIOTROPICA, Issue 3 2010
    James P. Hill
    ABSTRACT We tested the hypothesis that dispersal periods of recalcitrant seeded species were coincident with the wet season in a seasonal tropical forest in Australia. Unlike similar forests, we found no support for this pattern. Intensification of seasonal aridity may increase mortality in desiccation-sensitive seeds. [source]

    Effects of Vegetation Thinning on Above- and Belowground Carbon in a Seasonally Dry Tropical Forest in Mexico

    BIOTROPICA, Issue 3 2009
    Rodrigo Vargas
    ABSTRACT Mature tropical forests are disappearing and secondary forests are becoming more abundant, thus there is an increasing need to understand the ecology and management of secondary forests. In the Yucatan Peninsula, Mexico, seasonally dry tropical forests are subject to frequent fire, and early-successional stands are extremely dense. We applied vegetation thinning (removal of all stems < 2 cm in diameter) to hasten secondary succession and open the understory to reduce the fire ladder in an 11-yr-old stand. We quantified the effect of vegetation thinning on above- and belowground carbon over 5 yr. Aboveground carbon included all standing vegetation and belowground carbon included fine roots and organic carbon in the Oi, Oe, and Oa soil horizons. Trees with diameter of 2,10 cm and > 10 cm had higher carbon accumulation rates in thinned plots than in control plots. Carbon stored in the Oi-horizon and the Oe > 2 mm fraction remained significantly higher in thinned plots even 5 yr after treatment. Carbon in fine roots was significantly higher in thinned plots, and radiocarbon (14C) data suggest that fine roots in thinned plots were recently produced in comparison with fine roots in control plots. We did not find significant differences in total ecosystem carbon after 5 yr (126 ± 6 and 136 ± 8 Mg C/ha, respectively). These results suggest rapid carbon recovery and support the hypothesis that young tropical forests thinned to hasten succession and reduce the fire hazard may have only a short-term negative impact on carbon accumulation in vegetation and soils. RESUMEN Los bosques tropicales maduros están desapareciendo y los bosques secundarios se han vuelto mas abundantes, por eso hay una creciente necesidad de entender la ecología y el manejo de los bosques secundarios. En la Península de Yucatán, México, los bosques secos de temporal están sujetos a frecuentes fuegos y los bosques secundarios son extremadamente densos. En este estudio se aplicó un aclareo de vegetación (remoción de todos los tallos < 2 cm en diámetro) para acelerar la sucesión secundaria y controlar el riesgo de fuego en un bosque de 11 años. Cuantificamos el efecto del aclaro de vegetación en el carbono arriba del suelo y el carbono bajo el suelo por cinco años. El carbono arriba del suelo incluyó toda la vegetación en pie y el carbono bajo el suelo incluyó raíces finas y el carbono orgánico de los horizontes Oi, Oe y Oa del suelo. Los árboles con diámetro entre 2,10 cm y > 10 cm tuvieron mayor acumulación de carbono en las parcelas de aclareo que en las control. El carbono guardado en el horizonte Oi y en la fracción Oe > 2 mm permaneció con niveles más altos en las parcelas de aclareo incluso cinco años después del tratamiento. El carbono en las raíces finas fue significativamente mayor en las parcelas con aclareo y los datos de radiocarbono (14C) sugieren que las raíces finas en las parcelas con aclareo fueron producidas después que las raíces finas en las parcelas control. No encontramos diferencias en el carbono total del ecosistema entre las parcelas control y las de aclareo después de cinco años (126 ± 6 and136 ± 8 Mg C/ha, respectivamente). Estos resultados sugieren una rápida recuperación del carbono y apoyan la hipótesis de que el aclareo para acelerar la sucesión y controlar el riesgo de fuego en bosques tropicales tempranos solo tiene un efecto negativo a corto plazo en la acumulación de carbono del suelo y vegetación. [source]

    Shrinking Buffers Undercut Protected Tropical Forests

    CONSERVATION, Issue 3 2005
    Article first published online: 8 MAR 200
    No abstract is available for this article. [source]

    Extent of Nontimber Resource Extraction in Tropical Forests: Accessibility to Game Vertebrates by Hunters in the Amazon Basin

    CONSERVATION BIOLOGY, Issue 2 2003
    Carlos A. Peres
    We conducted a basin-wide geographic information system analysis of the nonmotorized accessibility of Amazonian NTFP extraction and estimated the proportion of the Amazon drainage basin within Brazil ( 3.74 million km 2 ) that can be accessed on foot from the nearest navigable river or functional road. We use a long-term series of standardized line-transect vertebrate censuses conducted throughout the region to illustrate the effects of physical accessibility on wildlife densities in terms of hunting pressure as a function of distance from the nearest point of access. Population abundance in large-bodied, prime-target species preferred by game hunters tended to increase at greater distances from the access matrix, whereas small-bodied species ignored by hunters usually showed the reverse trend. In addition, we estimated the proportion of presumably inviolate core areas within nature, extractive, and indigenous reserves of Brazilian Amazonia that are prohibitively remote and unlikely to be overhunted; for instance, only 1.16% of the basin-wide area is strictly protected on paper and is reasonably safe from extractive activities targeted to game vertebrates and other valuable NTFPs. Finally, we discuss the concept of truly undisturbed wildlands in the last major tropical forest regions by distinguishing potentially overharvested areas from those that remain largely or entirely pristine and that maintain viable populations of a full complement of harvest-sensitive species. Resumen: Las actividades de extracción enfocadas en un amplio rango de productos forestales no maderables ( NTFPs ) son omnipresentes en los bosques tropicales. Sin embargo, la extensión de bosques estructuralmente intactos en una determinada región afectada por esta forma de perturbación críptica ha sido escasamente documentada. Realizamos un análisis GIS del acceso no motorizado para la extracción NTFP en el Amazonas y estimamos la proporción de la desembocadura de la cuenca amazónica ( ,3.74 millones de km2 ) a la cual se puede acceder a pie a partir del río navegable o la carretera funcional más cercana. Utilizamos series de censos de vertebrados a largo plazo empleando transectos en línea estandarizados a lo largo de la región para ejemplificar los efectos del acceso físico sobre las densidades de vida silvestre en términos de presión de caza como función de la distancia al punto de acceso más cercano. La abundancia poblacional de especies de cuerpo grande que son blancos preferidos por los cazadores tendió a crecer a mayores distancias de la matriz de acceso, mientras que las especies de cuerpo pequeño ignoradas por los cazadores generalmente muestran la tendencia inversa. Además, estimamos la proporción de áreas medulares presuntamente inviolables dentro de las reservas naturales, extractivas e indígenas del Amazonas brasileño que son prohibitivamente remotas y poco probables de ser sobreexplotadas: por ejemplo, solo el 1.16% del área de la cuenca estrictamente proyectada en papel está razonablemente a salvo de las actividades extractivas de los vertebrados de caza y otras NTFPs valiosas. Finalmente, discutimos el concepto de tierras silvestres verdaderamente no perturbadas en las grandes regiones de bosque tropical restantes diferenciando las áreas potencialmente sobreexplotadas de aquellas que son en su mayor parte o totalmente prístinas y que mantienen poblaciones viables de un complemento total de especies sensibles a la cosecha. [source]

    The Emerging Era of Novel Tropical Forests

    BIOTROPICA, Issue 5 2009
    Ariel E. Lugo
    ABSTRACT In 1966 Eugene P. Odum delivered a speech before the Ecological Society of America that transformed the way ecologists looked at succession. His comparison of mature and successional systems lead ecologists to place secondary forests in an inferior position relative to mature ones to the point that today, prominent tropical biologists argue for and against the conservation value of secondary forests. Nevertheless, we live in the era of secondary forests that is rapidly giving way to a new era of novel tropical forests. Research in Puerto Rico documents the emergence of novel forests, which are different in terms of species composition, dominance, and relative importance of species from forests that were present before the island was deforested. These novel forests emerged without assistance. They are a natural response to the new environmental conditions created by human activity. Natural processes have remixed or reassembled native and introduced plant and animal species into novel communities adapted to anthropogenic environmental conditions. Novel forests are expected to protect soils, cycle nutrients, support wildlife, store carbon, maintain watershed functions, and mitigate species extinctions. The dawn of the age of tropical novel forests is upon us and must not be ignored. [source]

    Estimating Fine Root Turnover in Tropical Forests along an Elevational Transect using Minirhizotrons

    BIOTROPICA, Issue 5 2008
    Sophie Graefe
    ABSTRACT Growth and death of fine roots represent an important carbon sink in forests. Our understanding of the patterns of fine root turnover is limited, in particular in tropical forests, despite its acknowledged importance in the global carbon cycle. We used the minirhizotron technique for studying the changes in fine root longevity and turnover along a 2000-m-elevational transect in the tropical mountain forests of South Ecuador. Fine root growth and loss rates were monitored during a 5-mo period at intervals of four weeks with each 10 minirhizotron tubes in three stands at 1050, 1890, and 3060 m asl. Average root loss rate decreased from 1.07 to 0.72 g/g/yr from 1050 to 1890 m, indicating an increase in mean root longevity with increasing elevation. However average root loss rate increased again toward the uppermost stand at 3060 m (1.30 g/g/yr). Thus, root longevity increased from lower montane to mid-montane elevation as would be expected from an effect of low temperature on root turnover, but it decreased further upslope despite colder temperatures. We suggest that adverse soil conditions may reduce root longevity at high elevations in South Ecuador, and are thus additional factors besides temperature that control root dynamics in tropical mountain forests. [source]

    The Plight of Large Animals in Tropical Forests and the Consequences for Plant Regeneration

    BIOTROPICA, Issue 3 2007
    S. Joseph Wright
    ABSTRACT We introduce a special section that addresses the bushmeat or wild meat crisis, its direct impact on game species, and its indirect impact on plants in tropical forests. RESUMEN Introducimos una sección especial que trata la crisis de la carne de animales salvajes, su impacto directo sobre las especies cazadas y su impacto indirecto sobre las plantas en los bosques tropicales. [source]

    Upland Soil Charcoal in the Wet Tropical Forests of Central Guyana

    BIOTROPICA, Issue 2 2007
    David S. Hammond
    ABSTRACT A soil charcoal survey was undertaken across 60,000 ha of closed-canopy tropical forest in central Guyana to determine the occurrence, ubiquity, and age of past forest fires across a range of terra firme soil types. Samples were clustered around six centers consisting of spatially nested sample stations. Most charcoal was found between 40 and 60 cm depth with fewest samples yielding material at 0,20 cm depth. The first core yielded charcoal at most stations. Charcoal ages of a random subsample ranged from less than 200 YBP to 9500 YBP with a noticeable peak between 1000 and 1250 YBP. Results reinforce a view that most closed-canopy tropical forests in eastern Amazonia have been subject to palaeo-fire events of unknown severity with a peak in charcoal age consistently appearing between 1000 and 2000 YBP. The two samples dated to the early Holocene represent some of the oldest indicators of paleo-fire known from upland Neotropical forest soils. Ubiquitous soil charcoal in central Guyana further indicate both forest resilience to fire and the widespread propensity for regional forests to burn, particularly during anomalous periods of drought. [source]

    Why Do Some Tropical Forests Have So Many Species of Trees?

    BIOTROPICA, Issue 4 2004
    Egbert Giles Leigh Jr.
    ABSTRACT Understanding why there are so many kinds of tropical trees requires learning, not only how tree species coexist, but what factors drive tree speciation and what governs a tree clade's diversification rate. Many report that hybrid sterility evolves very slowly between separated tree populations. If so, tree species rarely originate by splitting of large populations. Instead, they begin with few trees. The few studies available suggest that reproductive isolation between plant populations usually results from selection driven by lowered fitness of hybrids: speciation is usually a response to a "niche opportunity." Using Hubbell's neutral theory of forest dynamics as a null hypothesis, we show that if new tree species begin as small populations, species that are now common must have spread more quickly than chance allows. Therefore, most tree species have some setting in which they can increase when rare. Trees face trade-offs in suitability for different microhabitats, different-sized clearings, different soils and climates, and resistance to different pests. These trade-offs underlie the mechanisms maintaining ,-diversity and species turnover. Disturbance and microhabitat specialization appear insufficient to maintain ,-diversity of tropical trees, although they may maintain tree diversity north of Mexico or in northern Europe. Many studies show that where trees grow readily, tree diversity is higher and temperature and rainfall are less seasonal. The few data available suggest that pest pressure is higher, maintaining higher tree diversity, where winter is absent. Tree a-diversity is also higher in regions with more tree species, which tend to be larger, free for a longer time from major shifts of climate, or in the tropics, where there are more opportunities for local coexistence. RESUMEN Comprender por qué hay tantos tipos de árboles tropicales, se requiere aprender no sólo cómo las especies de árboles coexisten, sino también, cuáles factores conducen a su especiación, y qué determina la velocidad de diversificación de un clado de árboles. Muchos reportan que la esterilidad hibrida evoluciona muy lentamente entre poblaciones separadas de árboles. De ser asi, las especies de árboles raramente se originarian por la separación de grandes poblaciones; más bien empezarian con pocos árboles. Los pocos estudios disponibles sugieren que el aislamiento reproductivo entre las poblaciones vegetales usualmente resulta de selección derivada del bajo éxito de los hibridos: la especiación general-mente responde a una "oportunidad de nicho". Usando la teoria neutral de Hubbell de dinámica de bosques como hipótesis nula, nosotros mostramos que si las nuevas especies de árboles comienzan como poblaciones pequeñas, especies que ahora son communes deberian haberse expandido más rápido que lo que el azar permite. Por lo tanto, la mayoria de las especies de árboles tendrian alguna condición donde sus poblaciones podrian crecer cunando son raras. Los árboles enfrentan compromises en su adecuación por diferentes microhábitats, claros de differentes tamanos, diferentes suelos y climas, y resistencia a differentes plagas. Esros compromises sirven de base para los mecanismos que mantienen la diversidad , y al reemplazo especial de especies. Los distrubios y la especialización de microhabitats parecen ser insuficiente para mantener la diversidad , de árboles tropicales, sin embargo elloss pueden mantener diversidad de árboles al norte de México o en Europa del norte. Muchos estudios muestran que en lugares donde los árboles cresen fácilmente, la diversidad de árboles es mayor donde la temperatura y la lluvia son menos estacionales. Los pocos estudios disponibles sugieren que la presión de las plagas es mayor, manteniendo asl la diversidad de árboles en lugares donde no hay invierno. La diversidad , de árboles también es más alta en regions con más especies de árboles, las culaes tienden a ser más largas, exentas por un largo periodo de tiempo de grandes cambios climáticos, oen los trópicos donde hay más oportunidades de coexistir localmente. [source]

    Comparing tropical forest tree size distributions with the predictions of metabolic ecology and equilibrium models

    ECOLOGY LETTERS, Issue 5 2006
    Helene C. Muller-Landau
    Abstract Tropical forests vary substantially in the densities of trees of different sizes and thus in above-ground biomass and carbon stores. However, these tree size distributions show fundamental similarities suggestive of underlying general principles. The theory of metabolic ecology predicts that tree abundances will scale as the ,2 power of diameter. Demographic equilibrium theory explains tree abundances in terms of the scaling of growth and mortality. We use demographic equilibrium theory to derive analytic predictions for tree size distributions corresponding to different growth and mortality functions. We test both sets of predictions using data from 14 large-scale tropical forest plots encompassing censuses of 473 ha and > 2 million trees. The data are uniformly inconsistent with the predictions of metabolic ecology. In most forests, size distributions are much closer to the predictions of demographic equilibrium, and thus, intersite variation in size distributions is explained partly by intersite variation in growth and mortality. [source]

    Global trends in senesced-leaf nitrogen and phosphorus

    GLOBAL ECOLOGY, Issue 5 2009
    Zhiyou Yuan
    ABSTRACT Aim, Senesced-leaf litter plays an important role in the functioning of terrestrial ecosystems. While green-leaf nutrients have been reported to be affected by climatic factors at the global scale, the global patterns of senesced-leaf nutrients are not well understood. Location, Global. Methods, Here, bringing together a global dataset of senesced-leaf N and P spanning 1253 observations and 638 plant species at 365 sites and of associated mean climatic indices, we describe the world-wide trends in senesced-leaf N and P and their stoichiometric ratios. Results, Concentration of senesced-leaf N was highest in tropical forests, intermediate in boreal, temperate, and mediterranean forests and grasslands, and lowest in tundra, whereas P concentration was highest in grasslands, lowest in tropical forests and intermediate in other ecosystems. Tropical forests had the highest N : P and C : P ratios in senesced leaves. When all data were pooled, N concentration significantly increased, but senesced-leaf P concentration decreased with increasing mean annual temperature (MAT) and mean annual precipitation (MAP). The N : P and C : P ratios also increased with MAT and MAP, but C : N ratios decreased. Plant functional type (PFT), i.e. life-form (grass, herb, shrub or tree), phylogeny (angiosperm versus gymnosperm) and leaf habit (deciduous versus evergreen), affected senesced-leaf N, P, N : P, C : N and C : P with a ranking of senesced-leaf N from high to low: forbs , shrubs , trees > grasses, while the ranking of P was forbs , shrubs , trees < grasses. The climatic trends of senesced-leaf N and P and their stoichiometric ratios were similar between PFTs. Main conclusions, Globally, senesced-leaf N and P concentrations differed among ecosystem types, from tropical forest to tundra. Differences were significantly related to global climate variables such as MAT and MAP and also related to plant functional types. These results at the global scale suggest that nutrient feedback to soil through leaf senescence depends on both the climatic conditions and the plant composition of an ecosystem. [source]

    Fruit and fibre: the nutritional value of figs for a small tropical ruminant, the blue duiker (Cephalophus monticola)

    AFRICAN JOURNAL OF ECOLOGY, Issue 4 2009
    Erin L. Kendrick
    Abstract Tropical forests throughout the world are home to a guild of small ruminants that consume fruit as a substantial portion of their diet. Because the rumen is relatively inefficient at digesting nonstructural carbohydrates and only slowly digests cellulose, the feeding adaptations of frugivorous ruminants are enigmatic. We examined the nutritional value of wild figs to blue duikers, one of the smallest and most frugivorous ruminants, through chemical analyses and a series of digestion trials with six species of wild African figs. These figs were high in fat, protein, cell wall, lignin and Ca : P ratios, low in sugar and starch, and high in unextractable, fibre-bound tannins when compared with many other fruits. The fibre-bound tannins and protein caused protein digestibility and nitrogen balance to be consistently low or negative. The high fibre content of the figs allowed duikers to only digest 30,60% of energy contained in the figs. However, duikers were able to consume enough digestible energy to maintain body mass during 4-day trials. Therefore, a ruminant digestive system is beneficial to mammals eating high fibre, high-tannin tropical fruit like figs, especially if the mammal is small enough to harvest a sufficient amount to meet its daily energy requirements and has adaptations for reducing the effects of tannins on protein digestibility. Résumé Les forêts tropicales du monde entier abritent toute une faune de petits ruminants dont les fruits constituent une part non négligeable de l'alimentation. Comme le rumen est relativement peu efficace pour digérer les hydrates de carbone non structuraux et ne digère que lentement la cellulose, les adaptations alimentaires des ruminants frugivores sont encore énigmatiques. Nous avons examiné la valeur nutritionnelle des figues sauvages pour le céphalophe bleu, un des ruminants les plus petits et parmi les plus frugivores, au moyen d'analyses chimiques et d'une série d'essais de digestion avec six espèces de figues sauvages africaines. Ces figues étaient riches en graisses, en protéines, en parois cellulaires, en lignine, et leur rapport Ca/P était élevé; elles avaient un contenu faible en sucre et en amidon, et beaucoup de tanins impossibles à extraire, liés aux fibres, comparés à de nombreux autres fruits. Les tanins liés aux fibres et les protéines faisaient que la digestibilité des protéines et l'équilibre azotéétaient en permanence faibles ou négatifs. Le contenu en fibres élevé des figues ne permettait aux céphalophes de digérer que 30 à 60% de l'énergie contenue dans les figues. Cependant, pendant les quatre jours du test, les céphalophes ont pu consommer suffisamment d'énergie digestible pour conserver leur masse corporelle. C'est pourquoi le système digestif des ruminants est bénéfique pour les mammifères qui consomment des fruits tropicaux riches en fibres et en tanins, comme les figues, spécialement si le mammifère est assez petit pour pouvoir en trouver une quantité suffisante pour répondre à ses besoins quotidiens en énergie, et qu'il possède des adaptations qui lui permettent de réduire les effets des tanins sur la digestibilité des protéines. [source]

    Determining woodpecker diversity in the sub-Himalayan forests of northern India using call playbacks

    JOURNAL OF FIELD ORNITHOLOGY, Issue 2 2010
    Raman Kumar
    ABSTRACT Tropical forests have exceptional woodpecker diversity, but little is known about the abundance and diversity of woodpeckers in the Indian subcontinent, particularly for the Shorea robusta -dominated moist deciduous forests of northern India. Our objective was to compare the number of woodpecker species and number of individuals detected using playback surveys and visual/aural transect surveys at five sites. Each site was surveyed 5,6 times along a 2000-m transect, with woodpeckers detected using two methods: (1) visual and aural cues, and (2) playing back calls of 13 species at 400-m intervals. Both methods involved similar effort per survey (100,110 min). During surveys, we detected 11 species of woodpeckers. More species and more than twice as many individuals were detected during playback surveys than during visual/aural surveys. In addition, species accumulation curves showed that we detected the species known to be present based on previous work faster with playback surveys than with visual/aural surveys at four of the five sites. During field trials, 97% of targeted individuals (N= 269) of 12 species responded to playback, and 83% of the responses occurred within 1 min of broadcast. The number of species of woodpeckers in our study area (11 species) was typical for a structurally diverse, tropical/subtropical moist broad-leaved forest. Our results demonstrate that playback surveys are more efficient and accurate than visual/aural surveys, and that playback surveys can be useful for assessing and monitoring woodpecker diversity in tropical forests. RESUMEN Los bosques tropicales tienen una diversidad excepcional de pájaros carpinteros, pero se conoce muy poco sobre la abundancia y diversidad de estas aves en la parte norte del sub-continente de la India, particularmente en el bosque deciduo húmedo dominado por Shorea robusta. Nuestro objetivo fue comparar el número de especies y de individuos de carpinteros utilizando grabaciones para censarlos y transectos visuales/auditivos en cinco lugares. Cada lugar fue censado 5,6 veces, cada 400m, a lo largo de un transecto de 2000 m, utilizando pistas visuales y auditivas y grabaciones de 13 especies. Ambos métodos incluyeron un esfuerzo similar por censo (100,110 minutos). Durante los censos, detectamos 11 especies de pájaros carpinteros. Una cantidad mayor de especies y más del doble de los individuos fueron detectados utilizando grabaciones que en los censos visuales/auditivos. Además, las curvas de acumulación de especies mostraron que detectamos las especies que sabíamos estaban presentes (basados en trabajos previos) de forma más rápida utilizando grabaciones que con el método visual/auditivo en cuatro de las cinco localidades. Durante las pruebas de campo el 97% (N= 269) de 12 especies respondieron a las grabaciones, y el 83% de las respuestas se obtuvieron un minuto después de exponerlos a la grabación. El número de especies de pájaros carpinteros en nuestra área de estudio (11) fue el típico para un bosque tropical/subtropical húmedo de hoja ancha y estructura diversificada. Nuestros resultados demuestran que los censos en donde se usan grabaciones son más eficientes y precisos que los censos visuales/auditivos. Además que los censos en donde se usan grabaciones pueden ser útiles para determinar y monitorear la diversidad de carpinteros en bosques tropicales. [source]

    Tropical Montane Forest Restoration in Costa Rica: Overcoming Barriers to Dispersal and Establishment

    RESTORATION ECOLOGY, Issue 4 2000
    Karen D. Holl
    Abstract Tropical forests are being cleared at an alarming rate although our understanding of their ecology is limited. It is therefore essential to design restoration experiments that both further our basic knowledge of tropical ecology and inform management strategies to facilitate recovery of these ecosystems. Here we synthesize the results of research on tropical montane forest recovery in abandoned pasture in Costa Rica to address the following questions: (1) What factors limit tropical forest recovery in abandoned pasture? and (2) How can we use this information to design strategies to facilitate ecosystem recovery? Our results indicate that a number of factors impede tropical forest recovery in abandoned pasture land. The most important barriers are lack of dispersal of forest seeds and seedling competition with pasture grasses. High seed predation, low seed germination, lack of nutrients, high light intensity, and rabbit herbivory also affect recovery. Successful strategies to facilitate recovery in abandoned pastures must simultaneously overcome numerous obstacles. Our research shows that establishment of woody species, either native tree seedlings or early-successional shrubs, can be successful in facilitating recovery, by enhancing seed dispersal and shading out pasture grasses. On the contrary, bird perching structures alone are not an effective strategy, because they only serve to enhance seed dispersal but do not reduce grass cover. Remnant pasture trees can serve as foci of natural recovery and may enhance growth of planted seedlings. Our results highlight the importance of: (1) understanding the basic biology of an ecosystem to design effective restoration strategies; (2) comparing results across a range of sites to determine which restoration strategies are most generally useful; and (3) considering where best to allocate efforts in large-scale restoration projects. [source]

    Responses of squirrel monkeys to seasonal changes in food availability in an eastern Amazonian forest

    AMERICAN JOURNAL OF PRIMATOLOGY, Issue 2 2007
    Anita I. Stone
    Abstract Tropical forests are characterized by marked temporal and spatial variation in productivity, and many primates face foraging problems associated with seasonal shifts in fruit availability. In this study, I examined seasonal changes in diet and foraging behaviors of two groups of squirrel monkeys (Saimiri sciureus), studied for 12 months in Eastern Brazilian Amazonia, an area characterized by seasonal rainfall. Squirrel monkeys were primarily insectivorous (79% of feeding and foraging time), with fruit consumption highest during the rainy season. Although monkeys fed from 68 plant species, fruit of Attalea maripa palms accounted for 28% of annual fruit-feeding records. Dietary shifts in the dry season were correlated with a decline in ripe A. maripa fruits. Despite pronounced seasonal variation in rainfall and fruit abundance, foraging efficiency, travel time, and distance traveled remained stable between seasons. Instead, squirrel monkeys at this Eastern Amazonian site primarily dealt with the seasonal decline in fruit by showing dietary flexibility. Consumption of insects, flowers, and exudates increased during the dry season. In particular, their foraging behavior at this time strongly resembled that of tamarins (Saguinus sp.) and consisted of heavy use of seed-pod exudates and specialized foraging on large-bodied orthopterans near the forest floor. Comparisons with squirrel monkeys at other locations indicate that, across their geographic range, Saimiri use a variety of behavioral tactics during reduced periods of fruit availability. Am. J. Primatol. 69:1,16, 2007. © 2006 Wiley-Liss, Inc. [source]

    Fruit, Minerals, and Forest Elephant Trails: Do All Roads Lead to Rome?

    BIOTROPICA, Issue 3 2004
    Stephen Blake
    ABSTRACT Tropical forests are among the most heterogeneous environments on earth, and food resources for many animals are patchy both in time and space. In Africa's equatorial forest, permanent trails created and maintained by forest elephants are conspicuous features. Trails may be several meters wide and continue for tens of kilometers. Speculation on which resources determine the distribution of trails has identified fruit, browse, and mineral deposits as candidates. In this study, the relationships between these habitat variables and elephant trails were investigated. The size of individual trails and the density of the trail system increased dramatically with proximity to mineral deposits. Fruit tree basal area decreased with perpendicular distance from trails, while that of non-fruit trees did not. Fruit tree abundance and basal area were significantly higher on trail intersections than random sites and increased with intersection size. No relationship was found between monocotyledon browse abundance and elephant trail system characteristics. Clumped resources, which are at least partially reliable, provide a high nutritional payback, and are not rapidly depleted and can thus be visited repeatedly, appear to influence permanent trail formation by forest elephants. Permanent trails may allow naive individuals or those with imperfect knowledge to locate and acquire important resources. [source]

    Conservation value of degraded habitats for forest birds in southern Peninsular Malaysia

    DIVERSITY AND DISTRIBUTIONS, Issue 5 2006
    Kelvin S.-H.
    ABSTRACT Clearance of tropical forest for agricultural purposes is generally assumed to seriously threaten the survival of forest species. In this study, we quantified the conservation value, for forest bird species, of three degraded habitat types in Peninsular Malaysia, namely rubber tree plantations, oil palm plantations, and open areas. We surveyed these degraded habitats using point counts to estimate their forest bird species richness and abundance. We assessed whether richness, abundance, and activities of different avian dietary groups (i.e. insectivores and frugivores) varied among the habitats. We identified the critical habitat elements that accounted for the distribution of forest avifauna in these degraded habitats. Our results showed that these habitats harboured a moderate fraction of forest avifauna (approximately 46,76 species) and their functions were complementary (i.e. rubber tree plantations for moving; open habitats for perching; shrubs in oil palm plantations for foraging). In terms of species richness and abundance, rubber tree plantations were more important than oil palm plantations and open habitats. The relatively high species richness of this agricultural landscape was partly due to the contiguity of our study areas with extensive forest areas. Forecasts of forest-species presence under various canopy cover scenarios suggest that leaving isolated trees among non-arboreal crops could greatly attract relatively tolerant species that require tree canopy. The conservation value of degraded habitats in agricultural landscapes seems to depend on factors such as the type of crops planted and distance to primary forest remnants. [source]

    Neighbour-regulated mortality: the influence of positive and negative density dependence on tree populations in species-rich tropical forests

    ECOLOGY LETTERS, Issue 8 2003
    Halton A. Peters
    Abstract Density-dependent mortality has long been posited as a possible mechanism for the regulation of tropical forest tree density. Despite numerous experimental and phenomenological investigations, the extent to which such mechanisms operate in tropical forests remains unresolved because the demographical signature of density dependence has rarely been found in extensive investigations of established trees. This study used an individual-based demographical approach to investigate the role of conspecific and heterospecific neighbourhood crowding on tree mortality in a Panamanian and a Malayan tropical forest. More than 80% of the species investigated at each site were found to exhibit density-dependent mortality. Furthermore, most of these species showed patterns of mortality consistent with the Janzen,Connell hypothesis and the rarely explored hypothesis of species herd protection. This study presents some of the first evidence of species herd protection operating in tree communities. [source]

    Variation in leaf functional trait values within and across individuals and species: an example from a Costa Rican dry forest

    FUNCTIONAL ECOLOGY, Issue 1 2010
    Catherine M. Hulshof
    Summary 1.,Patterns of species co-existence and species diversity in plant communities remain an important research area despite over a century of intensive scrutiny. To provide mechanistic insight into the rules governing plant species co-existence and diversity, plant community ecologists are increasingly quantifying functional trait values for the species found in a wide range of communities. 2.,Despite the promise of a quantitative functional trait approach to plant community ecology, we suggest that, along with examining trait variation across species, an assessment of trait variation within species should also be a key component of a trait-based approach to community ecology. Variability within and between individuals and populations is likely widespread due to plastic responses to highly localized abiotic and biotic interactions. 3.,In this study, we quantify leaf trait variation within and across ten co-existing tree species in a dry tropical forest in Costa Rica to ask: (i) whether the majority of trait variation is located between species, within species, within individuals or within the leaves themselves; (ii) whether trait values collected using standardized methods correlate with those collected using unstandardized methods; and (iii) to what extent can we differentiate plant species on the basis of their traits? 4.,We find that the majority of variation in traits was often explained by between species differences; however, between leaflet trait variation was very high for compound-leaved species. We also show that many species are difficult to reliably differentiate on the basis of functional traits even when sampling many individuals. 5.,We suggest an ideal sample size of at least 10, and ideally 20, individuals be used when calculating mean trait values for individual species for entire communities, though even at large sample sizes, it remains unclear if community level trait values will allow comparisons on a larger geographic scale or if species traits are generally similar across scales. It will thus be critical to account for intraspecific variation by comparing species mean trait values across space in multiple microclimatic environments within local communities and along environmental gradients. Further, quantifying trait variability due to plasticity and inheritance will provide a better understanding of the underlying patterns and drivers of trait variation as well as the application of functional traits in outlining mechanisms of species co-existence. [source]

    Forced depression of leaf hydraulic conductance in situ: effects on the leaf gas exchange of forest trees

    FUNCTIONAL ECOLOGY, Issue 4 2007
    T. J. BRODRIBB
    Summary 1Recent work on the hydraulic conductance of leaves suggests that maximum photosynthetic performance of a leaf is defined largely by its plumbing. Pursuing this idea, we tested how the diurnal course of gas exchange of trees in a dry tropical forest was affected by artificially depressing the hydraulic conductance of leaves (Kleaf). 2Individual leaves from four tropical tree species were exposed to a brief episode of forced evaporation by blowing warm air over leaves in situ. Despite humid soil and atmospheric conditions, this caused leaf water potential (,leaf) to fall sufficiently to induce a 50,74% drop in Kleaf. 3Two of the species sampled proved highly sensitive to artificially depressed Kleaf, leading to a marked and sustained decline in the instantaneous rate of CO2 uptake, stomatal conductance and transpiration. Leaves of these species showed a depression of hydraulic and photosynthetic capacity in response to the ,blow-dry' treatment similar to that observed when major veins in the leaf were severed. 4By contrast, the other two species sampled were relatively insensitive to Kleaf manipulation; photosynthetic rates were indistinguishable from control (untreated) leaves 4 h after treatment. These insensitive species demonstrate a linear decline of Kleaf with ,leaf, while Kleaf in the two sensitive species falls precipitously at a critical water deficit. 5We propose that a sigmoidal Kleaf vulnerability enables a high diurnal yield of CO2 at the cost of exposing leaves to the possibility of xylem cavitation. Linear Kleaf vulnerability leads to a relatively lower CO2 yield, while providing better protection against cavitation. [source]

    Effects of nutrient additions on ecosystem carbon cycle in a Puerto Rican tropical wet forest

    GLOBAL CHANGE BIOLOGY, Issue 2 2006
    YIQING LI
    Abstract Wet tropical forests play a critical role in global ecosystem carbon (C) cycle, but C allocation and the response of different C pools to nutrient addition in these forests remain poorly understood. We measured soil organic carbon (SOC), litterfall, root biomass, microbial biomass and soil physical and chemical properties in a wet tropical forest from May 1996 to July 1997 following a 7-year continuous fertilization. We found that although there was no significant difference in total SOC in the top 0,10 cm of the soils between the fertilization plots (5.42±0.18 kg m,2) and the control plots (5.27±0.22 kg m,2), the proportion of the heavy-fraction organic C in the total SOC was significantly higher in the fertilized plots (59%) than in the control plots (46%) (P<0.05). The annual decomposition rate of fertilized leaf litter was 13% higher than that of the control leaf litter. We also found that fertilization significantly increased microbial biomass (fungi+bacteria) with 952±48 mg kg,1soil in the fertilized plots and 755±37 mg kg,1soil in the control plots. Our results suggest that fertilization in tropical forests may enhance long-term C sequestration in the soils of tropical wet forests. [source]

    Effects of an experimental drought on soil emissions of carbon dioxide, methane, nitrous oxide, and nitric oxide in a moist tropical forest

    GLOBAL CHANGE BIOLOGY, Issue 5 2004
    Eric A. Davidson
    Abstract Changes in precipitation in the Amazon Basin resulting from regional deforestation, global warming, and El Niño events may affect emissions of carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), and nitric oxide (NO) from soils. Changes in soil emissions of radiatively important gases could have feedback implications for regional and global climates. Here we report results of a large-scale (1 ha) throughfall exclusion experiment conducted in a mature evergreen forest near Santarém, Brazil. The exclusion manipulation lowered annual N2O emissions by >40% and increased rates of consumption of atmospheric CH4 by a factor of >4. No treatment effect has yet been detected for NO and CO2 fluxes. The responses of these microbial processes after three rainy seasons of the exclusion treatment are characteristic of a direct effect of soil aeration on denitrification, methanogenesis, and methanotrophy. An anticipated second phase response, in which drought-induced plant mortality is followed by increased mineralization of C and N substrates from dead fine roots and by increased foraging of termites on dead coarse roots, has not yet been detected. Analyses of depth profiles of N2O and CO2 concentrations with a diffusivity model revealed that the top 25 cm soil is the site of most of the wet season production of N2O, whereas significant CO2 production occurs down to 100 cm in both seasons, and small production of CO2 occurs to at least 1100 cm depth. The diffusivity-based estimates of CO2 production as a function of depth were strongly correlated with fine root biomass, indicating that trends in belowground C allocation may be inferred from monitoring and modeling profiles of H2O and CO2. [source]

    Global trends in senesced-leaf nitrogen and phosphorus

    GLOBAL ECOLOGY, Issue 5 2009
    Zhiyou Yuan
    ABSTRACT Aim, Senesced-leaf litter plays an important role in the functioning of terrestrial ecosystems. While green-leaf nutrients have been reported to be affected by climatic factors at the global scale, the global patterns of senesced-leaf nutrients are not well understood. Location, Global. Methods, Here, bringing together a global dataset of senesced-leaf N and P spanning 1253 observations and 638 plant species at 365 sites and of associated mean climatic indices, we describe the world-wide trends in senesced-leaf N and P and their stoichiometric ratios. Results, Concentration of senesced-leaf N was highest in tropical forests, intermediate in boreal, temperate, and mediterranean forests and grasslands, and lowest in tundra, whereas P concentration was highest in grasslands, lowest in tropical forests and intermediate in other ecosystems. Tropical forests had the highest N : P and C : P ratios in senesced leaves. When all data were pooled, N concentration significantly increased, but senesced-leaf P concentration decreased with increasing mean annual temperature (MAT) and mean annual precipitation (MAP). The N : P and C : P ratios also increased with MAT and MAP, but C : N ratios decreased. Plant functional type (PFT), i.e. life-form (grass, herb, shrub or tree), phylogeny (angiosperm versus gymnosperm) and leaf habit (deciduous versus evergreen), affected senesced-leaf N, P, N : P, C : N and C : P with a ranking of senesced-leaf N from high to low: forbs , shrubs , trees > grasses, while the ranking of P was forbs , shrubs , trees < grasses. The climatic trends of senesced-leaf N and P and their stoichiometric ratios were similar between PFTs. Main conclusions, Globally, senesced-leaf N and P concentrations differed among ecosystem types, from tropical forest to tundra. Differences were significantly related to global climate variables such as MAT and MAP and also related to plant functional types. These results at the global scale suggest that nutrient feedback to soil through leaf senescence depends on both the climatic conditions and the plant composition of an ecosystem. [source]

    Soil moisture dynamics in an eastern Amazonian tropical forest

    HYDROLOGICAL PROCESSES, Issue 12 2006
    Rogério D. Bruno
    Abstract We used frequency-domain reflectometry to make continuous, high-resolution measurements for 22 months of the soil moisture to a depth of 10 m in an Amazonian rain forest. We then used these data to determine how soil moisture varies on diel, seasonal and multi-year timescales, and to better understand the quantitative and mechanistic relationships between soil moisture and forest evapotranspiration. The mean annual precipitation at the site was over 1900 mm. The field capacity was approximately 0·53 m3 m,3 and was nearly uniform with soil depth. Soil moisture decreased at all levels during the dry season, with the minimum of 0·38 m3 m,3 at 3 m beneath the surface. The moisture in the upper 1 m showed a strong diel cycle with daytime depletion due to evapotranspiration. The moisture beneath 1 m declined during both day and night due to the combined effects of evapotranspiration, drainage and a nighttime upward movement of water. The depth of active water withdrawal changed markedly over the year. The upper 2 m of soil supplied ,56% of the water used for evapotranspiration in the wet season and ,28% of the water used in the dry season. The zone of active water withdrawal extended to a depth of at least 10 m. The day-to-day rates of moisture withdrawal from the upper 10 m of soil during rain-free periods agreed well with simultaneous measurements of whole-forest evapotranspiration made by the eddy covariance technique. The forest at the site was well adapted to the normal cycle of wet and dry seasons, and the dry season had only a small effect on the rates of land,atmosphere water vapour exchange. Copyright © 2006 John Wiley & Sons, Ltd. [source]