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Wet Tropical Forest (wet + tropical_forest)

Distribution by Scientific Domains

Life Sciences	100%

Selected Abstracts

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]

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]

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]

Mesoscale Gradients of Herb Richness and Abundance in Central Amazonia,

BIOTROPICA, Issue 6 2006
Flávia R. C. Costa
ABSTRACT There are few hypotheses to explain local understory diversity patterns. There is a consensus that climate and soil fertility affect understory density and diversity at large scales, but few studies addressed the mechanisms controlling density and diversity locally. Here, I examine patterns of abundance and diversity of three understory herb groups along gradients of soil nutrients and topography at the mesoscale (64 km2) in a wet tropical forest, and possible factors causing them. Herb richness, diversity, density, and cover were measured in fifty-nine 250 × 2 m plots systematically distributed over Reserva Ducke, Manaus. Herb groups responded differently to environmental gradients. Whereas density and cover of pteridophytes increased with altitude and slope, Marantaceae density and cover decreased. Density of sedges increased with altitude, but did not vary with slope. Density and cover of Marantaceae and sedges but not pteridophytes increased with the soil cation content. Pteridophyte richness increased with slope whereas Marantaceae richness decreased, richness of both groups increased with cation content. Diversity increased with altitude for Marantaceae and decreased for pteridophytes. Some of these patterns agree with what is expected from herbs, such as the greater abundance of Marantaceae and sedges in flat and low altitude plots, where water availability is higher and probably also light, and the greater richness of Marantaceae and pteridophytes in higher nutrient plots. The unexpected results of higher abundance and richness of pteridophytes in slopes, instead of in bottomlands, suggest that biotic or litter-mediated controls may be important to set these patterns. RESUMO Existem poucas hipóteses para explicar os padrões locais de diversidade do sub-bosque. Existe consenso de que clima e fertilidade do solo afetam a densidade e diversidade do sub-bosque em macro-escala, mas poucos estudos procuraram os mecanismos que controlam a densidade e diversidade em escala local. Neste estudo, eu examino os padrões de abundância e diversidade de 3 grupos de ervas de sub-bosque ao longo de gradients de nutrientes e topografia em uma floresta tropical úmida, e os possíveis fatores causais. A riqueza, diversidade, cobertura e densidade das ervas foram medidas em 59 parcelas de 250 × 2 m, distribuídas sobre 64 km2 na Reserva Ducke, Manaus. Os grupos de ervas responderam de forma diferente aos gradientes ambientais. Enquanto a densidade e cobertura das samambaias aumentaram com a altitude e a inclinação do terreno, a densidade e cobertura de Marantaceae diminuíram. A densidade de capins aumentou coma altitude, mas não variou com a inclinação. A densidade e cobertura de Marantaceae e capins aumentou com o conteúdo de nutrientes do solo, mas não para as pteridófitas. A riqueza de samambaias aumentou com a inclinação do terreno enquanto a riqueza de Marantaceae decresceu, e a riqueza dos dois grupos aumentou com o conteúdo de nutrientes. A diversidade aumentou com a altitude para Marantaceae e diminuiu para as samambaias. Alguns destes padrões concordam com o esperado para ervas, tais como a maior abundância de Marantaceae e capins nas parcelas planas e baixas, onde a disponibilidade de água e provavelmente de luz são maiores. Entretanto, os resultados inesperados de maior abundância e riqueza de pteridófitas nos terrenos mais inclinados, ao invés de nos baixios, sugerem que controles bióticos ou mediados pela liteira podem ser mais importantes para o estabelecimento destes padrões. [source]